Publications by authors named "Kaisa Lehti"

50 Publications

Crosstalk Between Cancer Associated Fibroblasts and Cancer Cells in Scirrhous Type Gastric Cancer.

Front Oncol 2020 16;10:568557. Epub 2020 Oct 16.

Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.

Gastric cancer (GC) is the third leading cause among all cancer deaths globally. Although the treatment outcome of GC has improved, the survival of patients with GC at stages III and IV remains unsatisfactory. Among several types of GC, scirrhous type GC (SGC) shows highly aggressive growth and invasive activity, leading to frequent peritoneal metastasis. SGC is well known to accompany abundant stromal cells that compose the tumor microenvironment (TME) along with the produced extracellular matrix (ECM) and secreted factors. One of the main stromal components is cancer associated fibroblast (CAF). In the SGC microenvironment, CAFs are a source of various secreted factors, including fibroblast growth factors (FGFs), which mediate prominent tumor-stimulating activity. In turn, cancer cells also secrete numerous factors, which can activate and educate CAFs. Current findings suggest that cancer cells and stromal cells communicate interactively the soluble factors, the ECM, and likely also by exosomes. In this review, we focus on the soluble factors mediating communication between cancer cells and CAFs in SGC, and consider how they are related to the modulation of TME and the high rate of peritoneal metastasis. At last, we discuss the perspectives on targeting these communication pathways for improved future treatment.
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http://dx.doi.org/10.3389/fonc.2020.568557DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7596590PMC
October 2020

Adaptive RSK-EphA2-GPRC5A signaling switch triggers chemotherapy resistance in ovarian cancer.

EMBO Mol Med 2020 04 2;12(4):e11177. Epub 2020 Mar 2.

Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.

Metastatic cancers commonly activate adaptive chemotherapy resistance, attributed to both microenvironment-dependent phenotypic plasticity and genetic characteristics of cancer cells. However, the contribution of chemotherapy itself to the non-genetic resistance mechanisms was long neglected. Using high-grade serous ovarian cancer (HGSC) patient material and cell lines, we describe here an unexpectedly robust cisplatin and carboplatin chemotherapy-induced ERK1/2-RSK1/2-EphA2-GPRC5A signaling switch associated with cancer cell intrinsic and acquired chemoresistance. Mechanistically, pharmacological inhibition or knockdown of RSK1/2 prevented oncogenic EphA2-S897 phosphorylation and EphA2-GPRC5A co-regulation, thereby facilitating a signaling shift to the canonical tumor-suppressive tyrosine phosphorylation and consequent downregulation of EphA2. In combination with platinum, RSK inhibitors effectively sensitized even the most platinum-resistant EphA2 , GPRC5A cells to the therapy-induced apoptosis. In HGSC patient tumors, this orphan receptor GPRC5A was expressed exclusively in cancer cells and associated with chemotherapy resistance and poor survival. Our results reveal a kinase signaling pathway uniquely activated by platinum to elicit adaptive resistance. They further identify GPRC5A as a marker for abysmal HGSC outcome and putative vulnerability of the chemo-resistant cells to RSK1/2-EphA2-pS897 pathway inhibition.
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http://dx.doi.org/10.15252/emmm.201911177DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7136956PMC
April 2020

PTPRA Phosphatase Regulates GDNF-Dependent RET Signaling and Inhibits the RET Mutant MEN2A Oncogenic Potential.

iScience 2020 Feb 31;23(2):100871. Epub 2020 Jan 31.

Systems Biology/Pathology Research Group and Proteomics Unit, Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki 00014, Finland. Electronic address:

The RET proto-oncogene encodes receptor tyrosine kinase, expressed primarily in tissues of neural crest origin. De-regulation of RET signaling is implicated in several human cancers. Recent phosphatome interactome analysis identified PTPRA interacting with the neurotrophic factor (GDNF)-dependent RET-Ras-MAPK signaling-axis. Here, by identifying comprehensive interactomes of PTPRA and RET, we reveal their close physical and functional association. The PTPRA directly interacts with RET, and using the phosphoproteomic approach, we identify RET as a direct dephosphorylation substrate of PTPRA both in vivo and in vitro. The protein phosphatase domain-1 is indispensable for the PTPRA inhibitory role on RET activity and downstream Ras-MAPK signaling, whereas domain-2 has only minor effect. Furthermore, PTPRA also regulates the RET oncogenic mutant variant MEN2A activity and invasion capacity, whereas the MEN2B is insensitive to PTPRA. In sum, we discern PTPRA as a novel regulator of RET signaling in both health and cancer.
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http://dx.doi.org/10.1016/j.isci.2020.100871DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021549PMC
February 2020

Thermal Proteome Profiling Identifies Oxidative-Dependent Inhibition of the Transcription of Major Oncogenes as a New Therapeutic Mechanism for Select Anticancer Compounds.

Cancer Res 2020 04 4;80(7):1538-1550. Epub 2020 Feb 4.

Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.

Identification of the molecular mechanism of action (MoA) of bioactive compounds is a crucial step for drug development but remains a challenging task despite recent advances in technology. In this study, we applied multidimensional proteomics, sensitivity correlation analysis, and transcriptomics to identify a common MoA for the anticancer compounds RITA, aminoflavone (AF), and oncrasin-1 (Onc-1). Global thermal proteome profiling revealed that the three compounds target mRNA processing and transcription, thereby attacking a cancer vulnerability, transcriptional addiction. This led to the preferential loss of expression of oncogenes involved in PDGF, EGFR, VEGF, insulin/IGF/MAPKK, FGF, Hedgehog, TGFβ, and PI3K signaling pathways. Increased reactive oxygen species level in cancer cells was a prerequisite for targeting the mRNA transcription machinery, thus conferring cancer selectivity to these compounds. Furthermore, DNA repair factors involved in homologous recombination were among the most prominently repressed proteins. In cancer patient samples, RITA, AF, and Onc-1 sensitized to poly(ADP-ribose) polymerase inhibitors both and These findings might pave a way for new synthetic lethal combination therapies. These findings highlight agents that target transcriptional addiction in cancer cells and suggest combination treatments that target RNA processing and DNA repair pathways simultaneously as effective cancer therapies.
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http://dx.doi.org/10.1158/0008-5472.CAN-19-2069DOI Listing
April 2020

High tissue MMP14 expression predicts worse survival in gastric cancer, particularly with a low PROX1.

Cancer Med 2019 11 27;8(16):6995-7005. Epub 2019 Sep 27.

Translational Cancer Medicine Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.

Matrix metalloproteinase 14 (MMP14), a membrane-associated matrix metalloproteinase, has been shown to influence the invasion and metastasis of several solid tumors. Prospero homeobox protein 1 (PROX1), involved in the development and cell fate determination, is also expressed in malignant diseases functioning either as a tumor-suppressing or oncogenic factor. In certain cancers PROX1 appears to transcriptionally suppress MMP14 expression. This study, therefore, aimed to explore the association between MMP14 and PROX1 and understand their potential as prognostic biomarkers in gastric cancer. The cohort consisted of 313 individuals operated for gastric adenocarcinoma between 2000 and 2009 in the Department of Surgery, Helsinki University Hospital. MMP14 and PROX1 expressions were studied using immunohistochemistry in the patient sample and using immunoblotting and immunofluorescence in gastric cancer cell lines. We generated survival curves using the Kaplan-Meier method, determining significance via the log-rank test. A high MMP14 expression associated with being ≥67 years (P = .041), while a positive nuclear PROX1 expression associated with tumors of a diffuse histological type (P = .041) and a high cytoplasmic PROX1 expression (P < .001). Five-year disease-specific survival among patients with a high MMP14 expression was 35.9% (95% confidence interval [CI] 24.9-46.9), compared to 45.3% (95% CI 38.0-52.6) for patients with a low MMP14 (P = .030). Survival was worse specifically among those with a high MMP14 and absent nuclear PROX1 expression (hazard ratio [HR] 1.65; 95% CI 1.09-2.51; P = .019). Thus, this study confirms that a high MMP14 expression predicts a worse survival in gastric cancer, revealing for the first time that survival is particularly worse when PROX1 is low.
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http://dx.doi.org/10.1002/cam4.2576DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6853825PMC
November 2019

MMP14 in Sarcoma: A Regulator of Tumor Microenvironment Communication in Connective Tissues.

Cells 2019 08 28;8(9). Epub 2019 Aug 28.

Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, 17177 Stockholm, Sweden.

Sarcomas are deadly malignant tumors of mesenchymal origin occurring at all ages. The expression and function of the membrane-type matrix metalloproteinase MMP14 is closely related to the mesenchymal cell phenotype, and it is highly expressed in most sarcomas. MMP14 regulates the activity of multiple extracellular and plasma membrane proteins, influencing cell-cell and cell-extracellular matrix (ECM) communication. This regulation mediates processes such as ECM degradation and remodeling, cell invasion, and cancer metastasis. Thus, a comprehensive understanding of the biology of MMP14 in sarcomas will shed light on the mechanisms controlling the key processes in these diseases. Here, we provide an overview of the function and regulation of MMP14 and we discuss their relationship with clinical and pre-clinical MMP14 data in both adult and childhood sarcomas.
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http://dx.doi.org/10.3390/cells8090991DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770050PMC
August 2019

A novel mutation in the matrix metallopeptidase 2 coding gene associated with intrafamilial variability of multicentric osteolysis, nodulosis, and arthropathy.

Mol Genet Genomic Med 2019 08 3;7(8):e802. Epub 2019 Jul 3.

Department of Pediatrics, Kuopio University Hospital, Kuopio, Finland.

Background: MONA, which stands for a spectrum of Multicentric Osteolysis, subcutaneous Nodulosis, and Athropathia, is an ultra rare autosomal recessive disorder caused by mutations in the matrix metallopeptidase 2 (MMP2) gene. To date only 44 individuals, carrying 22 different mutations have been reported. Here we report on two brothers with identical homozygous MMP2 gene mutations, but with clearly different phenotypes.

Methods: Genomic DNA was isolated from the affected brothers and the parents. An iliac crest bone biopsy was taken from the younger patient (index case). The level of matrix metallopeptidase 2 enzyme (MMP2) in serum and synovial fluid of the younger patient was analyzed using gelatin zymography.

Results: The DNA analysis revealed a homozygous c.1188C>A transversion on exon 8 of the gene. The affected brothers had the same homozygous variant and the parents were heterozygous to this variant. This variant has been reported as a compound heterozygous mutation on one individual resulting in scleroderma like skin thickening. Bone histomorphometry indicated increased trabecular bone remodeling and turnover. The zymography revealed that the level of MMP2 was completely nonmeasurable in the serum and only a minor gelatinolytic protein band of about similar molecular weight as MMP2 was found in the synovial fluid.

Conclusions: Both the age at the onset and the phenotypic severity of the syndrome in these two brothers were different despite identical genotypes. The younger patients had corneal opacities leading to deteriorating visual acuity. For the first time in this disease, opacities were successfully treated with corneal transplantations.
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http://dx.doi.org/10.1002/mgg3.802DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6687624PMC
August 2019

Vulnerability of invasive glioblastoma cells to lysosomal membrane destabilization.

EMBO Mol Med 2019 06;11(6)

Translational Cancer Medicine Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland

The current clinical care of glioblastomas leaves behind invasive, radio- and chemo-resistant cells. We recently identified mammary-derived growth inhibitor (MDGI/) as a biomarker for invasive gliomas. Here, we demonstrate a novel function for MDGI in the maintenance of lysosomal membrane integrity, thus rendering invasive glioma cells unexpectedly vulnerable to lysosomal membrane destabilization. MDGI silencing impaired trafficking of polyunsaturated fatty acids into cells resulting in significant alterations in the lipid composition of lysosomal membranes, and subsequent death of the patient-derived glioma cells via lysosomal membrane permeabilization (LMP). In a preclinical model, treatment of glioma-bearing mice with an antihistaminergic LMP-inducing drug efficiently eradicated invasive glioma cells and secondary tumours within the brain. This unexpected fragility of the aggressive infiltrating cells to LMP provides new opportunities for clinical interventions, such as re-positioning of an established antihistamine drug, to eradicate the inoperable, invasive, and chemo-resistant glioma cells from sustaining disease progression and recurrence.
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http://dx.doi.org/10.15252/emmm.201809034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6554674PMC
June 2019

FGFR4 phosphorylates MST1 to confer breast cancer cells resistance to MST1/2-dependent apoptosis.

Cell Death Differ 2019 Dec 22;26(12):2577-2593. Epub 2019 Mar 22.

Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Stockholm, SE-171 77, Sweden.

Cancer cells balance with the equilibrium of cell death and growth to expand and metastasize. The activity of mammalian sterile20-like kinases (MST1/2) has been linked to apoptosis and tumor suppression via YAP/Hippo pathway-independent and -dependent mechanisms. Using a kinase substrate screen, we identified here MST1 and MST2 among the top substrates for fibroblast growth factor receptor 4 (FGFR4). In COS-1 cells, MST1 was phosphorylated at Y433 residue in an FGFR4 kinase activity-dependent manner, as assessed by mass spectrometry. Blockade of this phosphorylation by Y433F mutation induced MST1 activation, as indicated by increased threonine phosphorylation of MST1/2, and the downstream substrate MOB1, in FGFR4-overexpressing T47D and MDA-MB-231 breast cancer cells. Importantly, the specific knockdown or short-term inhibition of FGFR4 in endogenous models of human HER2 breast cancer cells likewise led to increased MST1/2 activation, in conjunction with enhanced MST1 nuclear localization and generation of N-terminal cleaved and autophosphorylated MST1. Unexpectedly, MST2 was also essential for this MST1/N activation and coincident apoptosis induction, although these two kinases, as well as YAP, were differentially regulated in the breast cancer models analyzed. Moreover, pharmacological FGFR4 inhibition specifically sensitized the HER2 MDA-MB-453 breast cancer cells, not only to HER2/EGFR and AKT/mTOR inhibitors, but also to clinically relevant apoptosis modulators. In TCGA cohort, FGFR4 overexpression correlated with abysmal HER2 breast carcinoma patient outcome. Therefore, our results uncover a clinically relevant, targetable mechanism of FGFR4 oncogenic activity via suppression of the stress-associated MST1/2-induced apoptosis machinery in tumor cells with prominent HER/ERBB and FGFR4 signaling-driven proliferation.
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http://dx.doi.org/10.1038/s41418-019-0321-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7224384PMC
December 2019

An Ex Vivo Tissue Culture Model for Fibrovascular Complications in Proliferative Diabetic Retinopathy.

J Vis Exp 2019 01 25(143). Epub 2019 Jan 25.

Research Programs Unit, Genome-Scale Biology, Biomedicum Helsinki, University of Helsinki; Department of Microbiology, Tumor, and Cell Biology (MTC), Karolinska Institutet;

Diabetic retinopathy (DR) is the most common microvascular complication of diabetes and one of the leading causes of blindness in working-age adults. No current animal models of diabetes and oxygen-induced retinopathy develop the full-range progressive changes manifested in human proliferative diabetic retinopathy (PDR). Therefore, understanding of the disease pathogenesis and pathophysiology has relied largely on the use of histological sections and vitreous samples in approaches that only provide steady-state information on the involved pathogenic factors. Increasing evidence indicates that dynamic cell-cell and cell-extracellular matrix (ECM) interactions in the context of three-dimensional (3D) microenvironments are essential for the mechanistic and functional studies towards the development of new treatment strategies. Therefore, we hypothesized that the pathological fibrovascular tissue surgically excised from eyes with PDR could be utilized to reliably unravel the cellular and molecular mechanisms of this devastating disease and to test the potential for novel clinical interventions. Towards this end, we developed a novel method for 3D ex vivo culture of surgically-excised patient-derived fibrovascular tissue (FT), which will serve as a relevant model of human PDR pathophysiology. The FTs are dissected into explants and embedded in fibrin matrix for ex vivo culture and 3D characterization. Whole-mount immunofluorescence of the native FTs and end-point cultures allows thorough investigation of tissue composition and multicellular processes, highlighting the importance of 3D tissue-level characterization for uncovering relevant features of PDR pathophysiology. This model will allow the simultaneous assessment of molecular mechanisms, cellular/tissue processes and treatment responses in the complex context of dynamic biochemical and physical interactions within the PDR tissue architecture and microenvironment. Since this model recapitulates PDR pathophysiology, it will also be amenable for testing or developing new treatments.
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http://dx.doi.org/10.3791/59090DOI Listing
January 2019

Soluble and membrane-bound adenylate kinase and nucleotidases augment ATP-mediated inflammation in diabetic retinopathy eyes with vitreous hemorrhage.

J Mol Med (Berl) 2019 03 7;97(3):341-354. Epub 2019 Jan 7.

MediCity Research Laboratory, University of Turku, Tykistökatu 6A, 20520, Turku, Finland.

ATP and adenosine are important signaling molecules involved in vascular remodeling, retinal function, and neurovascular coupling in the eye. Current knowledge on enzymatic pathways governing the duration and magnitude of ocular purinergic signaling is incompletely understood. By employing sensitive analytical assays, this study dissected ocular purine homeostasis as a complex and coordinated network. Along with previously characterized ecto-5'-nucleotidase/CD73 and adenylate kinase activities, other enzymes have been identified in vitreous fluids, including nucleoside triphosphate diphosphohydrolase (NTPDase), adenosine deaminase, and alkaline phosphatase. Strikingly, activities of soluble adenylate kinase, adenosine deaminase, ecto-5'-nucleotidase/CD73, and alkaline phosphatase, as well as intravitreal concentrations of ATP and ADP, were concurrently upregulated in patients suffering from diabetic retinopathy (DR) with non-clearing vitreous hemorrhage (VH), when compared to DR eyes without VH and control eyes operated due to macular hole or pucker. Additional histochemical analysis revealed selective distribution of key ecto-nucleotidases (NTPDase1/CD39, NTPDase2, ecto-5'-nucleotidase/CD73, and alkaline phosphatase) in the human sensory neuroretina and optic nerve head, and also in pathological neofibrovascular tissues surgically excised from patients with advanced proliferative DR. Collectively, these data provide evidence for specific hemorrhage-related shifts in purine homeostasis in DR eyes from the generation of anti-inflammatory adenosine towards a pro-inflammatory and pro-angiogenic ATP-regenerating phenotype. In the future, identifying the exact mechanisms by which a broad spectrum of soluble and membrane-bound enzymes coordinately regulates ocular purine levels and the further translation of purine-converting enzymes as potential therapeutic targets in the treatment of proliferative DR and other vitreoretinal diseases will be an area of intense interest. KEY MESSAGES: NTPDase, alkaline phosphatase, and adenosine deaminase circulate in human vitreous. Purinergic enzymes are up-regulated in diabetic eyes with vitreous hemorrhage. Soluble adenylate kinase maintains high ATP levels in diabetic retinopathy eyes. Ecto-nucleotidases are co-expressed in the human retina and optic nerve head. Alkaline phosphatase is expressed on neovascular tissues excised from diabetic eyes.
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http://dx.doi.org/10.1007/s00109-018-01734-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6394560PMC
March 2019

Integrated Molecular Analysis of Undifferentiated Uterine Sarcomas Reveals Clinically Relevant Molecular Subtypes.

Clin Cancer Res 2019 04 7;25(7):2155-2165. Epub 2019 Jan 7.

Department of Oncology-Pathology, Karolinska Institutet, and Department of Pathology and Cytology, Karolinska University Hospital, Stockholm, Sweden.

Purpose: Undifferentiated uterine sarcomas (UUS) are rare, extremely deadly, sarcomas with no effective treatment. The goal of this study was to identify novel intrinsic molecular UUS subtypes using integrated clinical, histopathologic, and molecular evaluation of a large, fully annotated, patient cohort.

Experimental Design: Fifty cases of UUS with full clinicopathologic annotation were analyzed for gene expression ( = 50), copy-number variation (CNV, = 40), cell morphometry ( = 39), and protein expression ( = 22). Gene ontology and network enrichment analysis were used to relate over- and underexpressed genes to pathways and further to clinicopathologic and phenotypic findings.

Results: Gene expression identified four distinct groups of tumors, which varied in their clinicopathologic parameters. Gene ontology analysis revealed differential activation of pathways related to genital tract development, extracellular matrix (ECM), muscle function, and proliferation. A multivariable, adjusted Cox proportional hazard model demonstrated that RNA group, mitotic index, and hormone receptor expression influence patient overall survival (OS). CNV arrays revealed characteristic chromosomal changes for each group. Morphometry demonstrated that the ECM group, the most aggressive, exhibited a decreased cell density and increased nuclear area. A cell density cutoff of 4,300 tumor cells per mm could separate ECM tumors from the remaining cases with a sensitivity of 83% and a specificity of 94%. IHC staining of MMP-14, Collagens 1 and 6, and Fibronectin proteins revealed differential expression of these ECM-related proteins, identifying potential new biomarkers for this aggressive sarcoma subgroup.

Conclusions: Molecular evaluation of UUS provides novel insights into the biology, prognosis, phenotype, and possible treatment of these tumors.
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http://dx.doi.org/10.1158/1078-0432.CCR-18-2792DOI Listing
April 2019

Lymphatic Vascular Structures: A New Aspect in Proliferative Diabetic Retinopathy.

Int J Mol Sci 2018 Dec 13;19(12). Epub 2018 Dec 13.

Research Programs Unit, Genome-Scale Biology, Biomedicum Helsinki, University of Helsinki, FI-00014 Helsinki, Finland.

Diabetic retinopathy (DR) is the most common diabetic microvascular complication and major cause of blindness in working-age adults. According to the level of microvascular degeneration and ischemic damage, DR is classified into non-proliferative DR (NPDR), and end-stage, proliferative DR (PDR). Despite advances in the disease etiology and pathogenesis, molecular understanding of end-stage PDR, characterized by ischemia- and inflammation-associated neovascularization and fibrosis, remains incomplete due to the limited availability of ideal clinical samples and experimental research models. Since a great portion of patients do not benefit from current treatments, improved therapies are essential. DR is known to be a complex and multifactorial disease featuring the interplay of microvascular, neurodegenerative, metabolic, genetic/epigenetic, immunological, and inflammation-related factors. Particularly, deeper knowledge on the mechanisms and pathophysiology of most advanced PDR is critical. Lymphatic-like vessel formation coupled with abnormal endothelial differentiation and progenitor cell involvement in the neovascularization associated with PDR are novel recent findings which hold potential for improved DR treatment. Understanding the underlying mechanisms of PDR pathogenesis is therefore crucial. To this goal, multidisciplinary approaches and new ex vivo models have been developed for a more comprehensive molecular, cellular and tissue-level understanding of the disease. This is the first step to gain the needed information on how PDR can be better evaluated, stratified, and treated.
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http://dx.doi.org/10.3390/ijms19124034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6321212PMC
December 2018

Liprin-α1 modulates cancer cell signaling by transmembrane protein CD82 in adhesive membrane domains linked to cytoskeleton.

Cell Commun Signal 2018 07 13;16(1):41. Epub 2018 Jul 13.

Research Programs Unit, Genome-Scale Biology Program and Medicum, Biochemistry and Developmental Biology, University of Helsinki, Helsinki, Finland.

Background: PPFIA1 is located at the 11q13 region commonly amplified in cancer. The protein liprin-α1 encoded by PPF1A1 contributes to the adhesive and invasive structures of cytoskeletal elements and is located at the invadosomes in cancer cells. However, the precise mechanism of liprin-α1 function in cancer progression has remained elusive.

Methods: Invasion regulating activity of liprin-α1 was examined by analyzing the functions of squamous cell carcinoma of head and neck (HNSCC) cell lines in three-dimensional collagen I after RNAi mediated gene knockdown. Transcriptome profiling and Gene Set Enrichment Analysis from HNSCC and breast cancer cells were used to identify expression changes relevant to specific cellular localizations, biological processes and signaling pathways after PPFIA1 knockdown. The significance of the results was assessed by relevant statistical methods (Wald and Benjamini-Hochberg). Localization of proteins associated to liprin-α1 was studied by immunofluorescence in 2D and 3D conditions. The association of PPFIA1 amplification to HNSCC patient survival was explored using The Cancer Genome Atlas data.

Results: In this study, we show that liprin-α1 regulates biological processes related to membrane microdomains in breast carcinoma, as well as protein trafficking, cell-cell and cell-substrate contacts in HNSCC cell lines cultured in three-dimensional matrix. Importantly, we show that in all these cancer cells liprin-α1 knockdown leads to the upregulation of transmembrane protein CD82, which is a suppressor of metastasis in several solid tumors.

Conclusions: Our results provide novel information regarding the function of liprin-α1 in biological processes essential in cancer progression. The results reveal liprin-α1 as a novel regulator of CD82, linking liprin-α1 to the cancer cell invasion and metastasis pathways.
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http://dx.doi.org/10.1186/s12964-018-0253-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6045882PMC
July 2018

PROX1 is a transcriptional regulator of MMP14.

Sci Rep 2018 06 22;8(1):9531. Epub 2018 Jun 22.

Research Programs Unit, Translational Cancer Biology, University of Helsinki, Helsinki, Finland.

The transcription factor PROX1 is essential for development and cell fate specification. Its function in cancer is context-dependent since PROX1 has been shown to play both oncogenic and tumour suppressive roles. Here, we show that PROX1 suppresses the transcription of MMP14, a metalloprotease involved in angiogenesis and cancer invasion, by binding and suppressing the activity of MMP14 promoter. Prox1 deletion in murine dermal lymphatic vessels in vivo and in human LECs increased MMP14 expression. In a hepatocellular carcinoma cell line expressing high endogenous levels of PROX1, its silencing increased both MMP14 expression and MMP14-dependent invasion in 3D. Moreover, PROX1 ectopic expression reduced the MMP14-dependent 3D invasiveness of breast cancer cells and angiogenic sprouting of blood endothelial cells in conjunction with MMP14 suppression. Our study uncovers a new transcriptional regulatory mechanism of cancer cell invasion and endothelial cell specification.
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http://dx.doi.org/10.1038/s41598-018-27739-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6015061PMC
June 2018

Fibroblasts in the Tumor Microenvironment: Shield or Spear?

Int J Mol Sci 2018 May 21;19(5). Epub 2018 May 21.

Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Biomedicum, Solnavägen 9, SE-17177 Stockholm, Sweden.

Tumorigenesis is a complex process involving dynamic interactions between malignant cells and their surrounding stroma, including both the cellular and acellular components. Within the stroma, fibroblasts represent not only a predominant cell type, but also a major source of the acellular tissue microenvironment comprising the extracellular matrix (ECM) and soluble factors. Normal fibroblasts can exert diverse suppressive functions against cancer initiating and metastatic cells via direct cell-cell contact, paracrine signaling by soluble factors, and ECM integrity. The loss of such suppressive functions is an inherent step in tumor progression. A tumor cell-induced switch of normal fibroblasts into cancer-associated fibroblasts (CAFs), in turn, triggers a range of pro-tumorigenic signals accompanied by distraction of the normal tissue architecture, thus creating an optimal niche for cancer cells to grow extensively. To further support tumor progression and metastasis, CAFs secrete factors such as ECM remodeling enzymes that further modify the tumor microenvironment in combination with the altered adhesive forces and cell-cell interactions. These paradoxical tumor suppressive and promoting actions of fibroblasts are the focus of this review, highlighting the heterogenic molecular properties of both normal and cancer-associated fibroblasts, as well as their main mechanisms of action, including the emerging impact on immunomodulation and different therapy responses.
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http://dx.doi.org/10.3390/ijms19051532DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5983719PMC
May 2018

A Functional Homologous Recombination Assay Predicts Primary Chemotherapy Response and Long-Term Survival in Ovarian Cancer Patients.

Clin Cancer Res 2018 09 1;24(18):4482-4493. Epub 2018 Jun 1.

Genome-Scale Biology, Research Programs Unit, University of Helsinki, Helsinki, Finland.

Homologous recombination deficiency (HRD) correlates with platinum sensitivity in patients with ovarian cancer, which clinically is the most useful predictor of sensitivity to PARPi. To date, there are no reliable diagnostic tools to anticipate response to platinum-based chemotherapy, thus we aimed to develop an functional HRD detection test that could predict both platinum-sensitivity and patient eligibility to targeted drug treatments. We obtained a functional HR score by quantifying homologous recombination (HR) repair after ionizing radiation-induced DNA damage in primary ovarian cancer samples ( = 32). Samples clustered in 3 categories: HR-deficient, HR-low, and HR-proficient. We analyzed the HR score association with platinum sensitivity and treatment response, platinum-free interval (PFI) and overall survival (OS), and compared it with other clinical parameters. In parallel, we performed DNA-sequencing of HR genes to assess if functional HRD can be predicted by currently offered genetic screening. Low HR scores predicted primary platinum sensitivity with high statistical significance ( = 0.0103), associated with longer PFI (HR-deficient vs. HR-proficient: 531 vs. 53 days), and significantly correlated with improved OS (HR score <35 vs. ≥35, hazard ratio = 0.08, = 0.0116). At the genomic level, we identified a few unclear mutations in HR genes and the mutational signature associated with HRD, but, overall, genetic screening failed to predict functional HRD. We developed an assay that detects tumor functional HRD and an HR score able to predict platinum sensitivity, which holds the clinically relevant potential to become the routine companion diagnostic in the management of patients with ovarian cancer. .
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http://dx.doi.org/10.1158/1078-0432.CCR-17-3770DOI Listing
September 2018

Lymphatic endothelium stimulates melanoma metastasis and invasion via MMP14-dependent Notch3 and β1-integrin activation.

Elife 2018 05 1;7. Epub 2018 May 1.

Research Programs Unit, Translational Cancer Biology, University of Helsinki, Helsinki, Finland.

Lymphatic invasion and lymph node metastasis correlate with poor clinical outcome in melanoma. However, the mechanisms of lymphatic dissemination in distant metastasis remain incompletely understood. We show here that exposure of expansively growing human WM852 melanoma cells, but not singly invasive Bowes cells, to lymphatic endothelial cells (LEC) in 3D co-culture facilitates melanoma distant organ metastasis in mice. To dissect the underlying molecular mechanisms, we established LEC co-cultures with different melanoma cells originating from primary tumors or metastases. Notably, the expansively growing metastatic melanoma cells adopted an invasively sprouting phenotype in 3D matrix that was dependent on MMP14, Notch3 and β1-integrin. Unexpectedly, MMP14 was necessary for LEC-induced Notch3 induction and coincident β1-integrin activation. Moreover, MMP14 and Notch3 were required for LEC-mediated metastasis of zebrafish xenografts. This study uncovers a unique mechanism whereby LEC contact promotes melanoma metastasis by inducing a reversible switch from 3D growth to invasively sprouting cell phenotype.
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http://dx.doi.org/10.7554/eLife.32490DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5929907PMC
May 2018

The microenvironment of proliferative diabetic retinopathy supports lymphatic neovascularization.

J Pathol 2018 06 6;245(2):172-185. Epub 2018 Apr 6.

Research Programmes Unit, Genome-Scale Biology, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland.

Proliferative diabetic retinopathy (PDR) is a major diabetic microvascular complication characterized by pathological angiogenesis. Several retinopathy animal models have been developed to study the disease mechanisms and putative targets. However, knowledge on the human proliferative disease remains incomplete, relying on steady-state results from thin histological neovascular tissue sections and vitreous samples. New translational models are thus required to comprehensively understand the disease pathophysiology and develop improved therapeutic interventions. We describe here a clinically relevant model, whereby the native multicellular PDR landscape and neo(fibro)vascular processes can be analysed ex vivo and related to clinical data. As characterized by three-dimensional whole-mount immunofluorescence and electron microscopy, heterogeneity in patient-derived PDR neovascular tissues included discontinuous capillaries coupled with aberrantly differentiated, lymphatic-like and tortuous endothelia. Spatially confined apoptosis and proliferation coexisted with inflammatory cell infiltration and unique vascular islet formation. Ex vivo-cultured explants retained multicellularity, islet patterning and capillary or fibrotic outgrowth in response to vitreoretinal factors. Strikingly, PDR neovascular tissues, whose matched vitreous samples enhanced lymphatic endothelial cell sprouting, contained lymphatic-like capillaries in vivo and developed Prox1 capillaries and sprouts with lymphatic endothelial ultrastructures ex vivo. Among multiple vitreal components, vascular endothelial growth factor C was one factor found at lymphatic endothelium-activating concentrations. These results indicate that the ischaemia-induced and inflammation-induced human PDR microenvironment supports pathological neolymphovascularization, providing a new concept regarding PDR mechanisms and targeting options. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/path.5070DOI Listing
June 2018

Gremlin-1 is a key regulator of the invasive cell phenotype in mesothelioma.

Oncotarget 2017 Nov 6;8(58):98280-98297. Epub 2017 Oct 6.

Research Programs Unit, Translational Cancer Biology, University of Helsinki, Helsinki, Finland.

Malignant mesothelioma originates from mesothelial cells and is a cancer type that aggressively invades into the surrounding tissue, has poor prognosis and no effective treatment. Gremlin-1 is a cysteine knot protein that functions by inhibiting BMP-pathway activity during development. BMP-independent functions have also been described for gremlin-1. We have previously shown high gremlin-1 expression in mesothelioma tumor tissue. Here, we investigated the functions of gremlin-1 in mesothelioma cell migration and invasive growth. Gremlin-1 promoted mesothelioma cell sprouting and invasion into three dimensional collagen and Matrigel matrices. The expression level of gremlin-1 was linked to changes in the expression of SNAI2, integrins, matrix metalloproteinases (MMP) and TGF-β family signaling - all previously associated with a mesenchymal invasive phenotype. Small molecule inhibitors of MMPs completely blocked mesothelioma cell invasive growth. In addition, inhibitors of TGF-β receptors significantly reduced invasive growth. This was associated with reduced expression of MMP2 but not SNAI2, indicating that gremlin-1 has both TGF-β pathway dependent and independent mechanisms of action. Results of mesothelioma xenograft experiments indicated that gremlin-1 overexpressing tumors were more vascular and had a tendency to send metastases. This suggests that by inducing a mesenchymal invasive cell phenotype together with enhanced tumor vascularization, gremlin-1 drives mesothelioma invasion and metastasis. These data identify gremlin-1 as a potential therapeutic target in mesothelioma.
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http://dx.doi.org/10.18632/oncotarget.21550DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5716729PMC
November 2017

Membrane-type matrix metalloproteases as diverse effectors of cancer progression.

Biochim Biophys Acta Mol Cell Res 2017 Nov 5;1864(11 Pt A):1974-1988. Epub 2017 Apr 5.

Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Nobels väg 16, SE-17177 Stockholm, Sweden; Research Programs Unit, Genome-Scale Biology and Haartman Institute, University of Helsinki, and Helsinki University Hospital, P.O. Box 63, FI-00014 Helsinki, Finland; K. Albin Johansson Foundation, Finnish Cancer Institute, P.O. Box 63, FI-00014, Helsinki, Finland. Electronic address:

Membrane-type matrix metalloproteases (MT-MMP) are pivotal regulators of cell invasion, growth and survival. Tethered to the cell membranes by a transmembrane domain or GPI-anchor, the six MT-MMPs can exert these functions via cell surface-associated extracellular matrix degradation or proteolytic protein processing, including shedding or release of signaling receptors, adhesion molecules, growth factors and other pericellular proteins. By interactions with signaling scaffold or cytoskeleton, the C-terminal cytoplasmic tail of the transmembrane MT-MMPs further extends their functionality to signaling or structural relay. MT-MMPs are differentially expressed in cancer. The most extensively studied MMP14/MT1-MMP is induced in various cancers along malignant transformation via pathways activated by mutations in tumor suppressors or proto-oncogenes and changes in tumor microenvironment including cellular heterogeneity, extracellular matrix composition, tissue oxygenation, and inflammation. Classically such induction involves transcriptional programs related to epithelial-to-mesenchymal transition. Besides inhibition by endogenous tissue inhibitors, MT-MMP activities are spatially and timely regulated at multiple levels by microtubular vesicular trafficking, dimerization/oligomerization, other interactions and localization in the actin-based invadosomes, in both tumor and the stroma. The functions of MT-MMPs are multifaceted within reciprocal cellular responses in the evolving tumor microenvironment, which poses the importance of these proteases beyond the central function as matrix scissors, and necessitates us to rethink MT-MMPs as dynamic signaling proteases of cancer. This article is part of a Special Issue entitled: Matrix Metalloproteinases edited by Rafael Fridman.
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http://dx.doi.org/10.1016/j.bbamcr.2017.04.002DOI Listing
November 2017

RhoA knockout fibroblasts lose tumor-inhibitory capacity in vitro and promote tumor growth in vivo.

Proc Natl Acad Sci U S A 2017 02 7;114(8):E1413-E1421. Epub 2017 Feb 7.

Department of Microbiology, Tumour, and Cell Biology, Karolinska Institutet, 17177 Stockholm, Sweden;

Fibroblasts are a main player in the tumor-inhibitory microenvironment. Upon tumor initiation and progression, fibroblasts can lose their tumor-inhibitory capacity and promote tumor growth. The molecular mechanisms that underlie this switch have not been defined completely. Previously, we identified four proteins overexpressed in cancer-associated fibroblasts and linked to Rho GTPase signaling. Here, we show that knocking out the Ras homolog family member A () gene in normal fibroblasts decreased their tumor-inhibitory capacity, as judged by neighbor suppression in vitro and accompanied by promotion of tumor growth in vivo. This also induced PC3 cancer cell motility and increased colony size in 2D cultures. RhoA knockout in fibroblasts induced vimentin intermediate filament reorganization, accompanied by reduced contractile force and increased stiffness of cells. There was also loss of wide F-actin stress fibers and large focal adhesions. In addition, we observed a significant loss of α-smooth muscle actin, which indicates a difference between RhoA knockout fibroblasts and classic cancer-associated fibroblasts. In 3D collagen matrix, RhoA knockout reduced fibroblast branching and meshwork formation and resulted in more compactly clustered tumor-cell colonies in coculture with PC3 cells, which might boost tumor stem-like properties. Coculturing RhoA knockout fibroblasts and PC3 cells induced expression of proinflammatory genes in both. Inflammatory mediators may induce tumor cell stemness. Network enrichment analysis of transcriptomic changes, however, revealed that the Rho signaling pathway per se was significantly triggered only after coculturing with tumor cells. Taken together, our findings in vivo and in vitro indicate that Rho signaling governs the inhibitory effects by fibroblasts on tumor-cell growth.
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http://dx.doi.org/10.1073/pnas.1621161114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5338371PMC
February 2017

Somatic MED12 Nonsense Mutation Escapes mRNA Decay and Reveals a Motif Required for Nuclear Entry.

Hum Mutat 2017 03 11;38(3):269-274. Epub 2017 Jan 11.

Research Programs Unit, Genome-Scale Biology, University of Helsinki, Helsinki, Finland.

MED12 is a key component of the transcription-regulating Mediator complex. Specific missense and in-frame insertion/deletion mutations in exons 1 and 2 have been identified in uterine leiomyomas, breast tumors, and chronic lymphocytic leukemia. Here, we characterize the first MED12 5' end nonsense mutation (c.97G>T, p.E33X) identified in acute lymphoblastic leukemia and show that it escapes nonsense-mediated mRNA decay (NMD) by using an alternative translation initiation site. The resulting N-terminally truncated protein is unable to enter the nucleus due to the lack of identified nuclear localization signal (NLS). The absence of NLS prevents the mutant MED12 protein to be recognized by importin-α and subsequent loading into the nuclear pore complex. Due to this mislocalization, all interactions between the MED12 mutant and other Mediator components are lost. Our findings provide new mechanistic insights into the MED12 functions and indicate that somatic nonsense mutations in early exons may avoid NMD.
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http://dx.doi.org/10.1002/humu.23157DOI Listing
March 2017

Liprin-α1 is a regulator of vimentin intermediate filament network in the cancer cell adhesion machinery.

Sci Rep 2016 Apr 14;6:24486. Epub 2016 Apr 14.

Research Programs Unit, Genome-Scale Biology Research Program and Institute of Biomedicine, Medical Biochemistry and Developmental Biology, 00014 University of Helsinki, Finland.

PPFIA1 is located at the 11q13 region, which is one of the most commonly amplified regions in several epithelial cancers including head and neck squamous cell carcinoma and breast carcinoma. Considering the location of PPFIA1 in this amplicon, we examined whether protein encoded by PPFIA1, liprin-α1, possesses oncogenic properties in relevant carcinoma cell lines. Our results indicate that liprin-α1 localizes to different adhesion and cytoskeletal structures to regulate vimentin intermediate filament network, thereby altering the invasion and growth properties of the cancer cells. In non-invasive cells liprin-α1 promotes expansive growth behavior with limited invasive capacity, whereas in invasive cells liprin-α1 has significant impact on mesenchymal cancer cell invasion in three-dimensional collagen. Current results identify liprin-α1 as a novel regulator of the tumor cell intermediate filaments with differential oncogenic properties in actively proliferating or motile cells.
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http://dx.doi.org/10.1038/srep24486DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4830931PMC
April 2016

Proactive for invasion: Reuse of matrix metalloproteinase for structural memory.

J Cell Biol 2016 Apr;213(1):11-3

Research Programs Unit, Genome-Scale Biology and Haartman Institute, University of Helsinki, Helsinki University Hospital and Finnish Cancer Institute, Helsinki FI-00014, Finland Department of Microbiology, Tumor, and Cell Biology, Karolinska Institute, Stockholm SE-17165, Sweden

Migratory cells translocate membrane type-1 matrix metalloproteinase (MT1-MMP) to podosomes or invadosomes to break extracellular matrix barriers. In this issue, El Azzouzi et al. (2016.J. Cell. Biol.http://dx.doi.org/10.1083/jcb.201510043) describe an unexpected function for the MT1-MMP cytoplasmic domain in imprinting spatial memory for podosome reformation via assembly in membrane islets.
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http://dx.doi.org/10.1083/jcb.201603066DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4828696PMC
April 2016

Quantitative Proteomics Analysis of Vitreous Humor from Diabetic Retinopathy Patients.

J Proteome Res 2015 Dec 30;14(12):5131-43. Epub 2015 Oct 30.

Molecular Systems Biology Research Group, Institute of Biotechnology, University of Helsinki , FI-00014 Helsinki, Finland.

Initial triggers for diabetic retinopathy (DR) are hyperglycemia-induced oxidative stress and advanced glycation end-products. The most pathological structural changes occur in retinal microvasculature, but the overall development of DR is multifactorial, with a complex interplay of microvascular, neurodegenerative, genetic/epigenetic, immunological, and secondary inflammation-related factors. Although several individual factors and pathways have been associated with retinopathy, a systems level understanding of the disease is lacking. To address this, we performed mass spectrometry based label-free quantitative proteomics analysis of 138 vitreous humor samples from patients with nonproliferative DR or the more severe proliferative form of the disease. Additionally, we analyzed samples from anti-VEGF (vascular endothelial growth factor) (bevacizumab)-treated patients from both groups. In our study, we identified 2482 and quantified the abundancy of 1351 vitreous proteins. Of these, the abundancy of 230 proteins was significantly higher in proliferative retinopathy compared with nonproliferative retinopathy. This specific subset of proteins was linked to inflammation, complement, and coagulation cascade proteins, protease inhibitors, apolipoproteins, immunoglobulins, and cellular adhesion molecules, reflecting the multifactorial nature of the disease. The identification of the key molecules of the disease is critical for the development of new therapeutic molecules and for the new use of existing drugs.
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http://dx.doi.org/10.1021/acs.jproteome.5b00900DOI Listing
December 2015

A Case of Abnormal Lymphatic-Like Differentiation and Endothelial Progenitor Cell Activation in Neovascularization Associated with Hemi-Retinal Vein Occlusion.

Case Rep Ophthalmol 2015 May-Aug;6(2):228-38. Epub 2015 Jul 17.

Genome-Scale Biology Research Program, Research Programs Unit, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland.

Purpose: Pathological vascular differentiation in retinal vein occlusion (RVO)-related neovessel formation remains poorly characterized. The role of intraocular lymphatic-like differentiation or endothelial progenitor cell activity has not been studied in this disease.

Methods: Vitrectomy was performed in an eye with hemi-RVO; the neovessel membrane located at the optic nerve head was removed and subjected to immunohistochemistry. Characterization of the neovascular tissue was performed using hematoxylin and eosin, α-smooth muscle actin, and the pan-endothelial cell (EC) adhesion molecule CD31. The expression of lymphatic EC markers was studied by lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), podoplanin (PDPN), and prospero-related homeobox protein 1 (Prox-1). Potential vascular stem/progenitor cells were identified by active cellular proliferation (Ki67) and expression of the stem cell marker CD117.

Results: The specimen contained blood vessels lined by ECs and surrounded by pericytes. Immunoreactivity for LYVE-1 and Prox-1 was detected, with Prox-1 being more widely expressed in the active Ki67-positive lumen-lining cells. PDPN expression was instead found in the cells residing in the extravascular tissue. Expression of the stem cell markers CD117 and Ki67 suggested vascular endothelial progenitor cell activity.

Conclusions: Intraocular lymphatic-like differentiation coupled with progenitor cell activation may be involved in the pathology of neovessel formation in ischemia-induced human hemi-RVO.
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http://dx.doi.org/10.1159/000437254DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4553915PMC
September 2015

Indications of lymphatic endothelial differentiation and endothelial progenitor cell activation in the pathology of proliferative diabetic retinopathy.

Acta Ophthalmol 2015 Sep 21;93(6):512-23. Epub 2015 Apr 21.

Research Programs Unit, Genome-Scale Biology, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland.

Purpose: Proliferative diabetic retinopathy (PDR) is characterized by ischaemia- and inflammation-induced neovascularization, but the pathological vascular differentiation in PDR remains poorly characterized. Here, endothelial progenitor and growth properties, as well as potential lymphatic differentiation, were investigated in the neovascular membrane specimens from vitrectomized patients with PDR.

Methods: The expression of pan-endothelial CD31 (PECAM-1), ETS-related gene (ERG), α-smooth muscle actin (α-SMA), and stem/progenitor cell marker CD117 (c-kit) and cell proliferation marker Ki67 was investigated along with the markers of lymphatic endothelial differentiation (vascular endothelial growth factor receptor (VEGFR)-3; prospero-related homeobox gene-1 (Prox-1), lymphatic vessel endothelial receptor [LYVE)-1 and podoplanin (PDPN)] by immunohistochemistry. Lymphocyte antigen CD45 and pan-macrophage marker CD68 were likewise investigated.

Results: All specimens displayed CD31, ERG and α-SMA immunoreactivity in irregular blood vessels. Unexpectedly, VEGFR3 and Prox-1 lymphatic marker positive vessels were also detected in several tissues. Prox-1 was co-expressed with CD117 in lumen-lining endothelial cells and adjacent cells, representing putative endothelial stem/progenitor cells and pro-angiogenic perivascular cells. Immunoreactivity of CD45 and CD68 was detectable in all investigated diabetic neovessel specimens. PDPN immunoreactivity was also detected in irregular lumen-forming structures, but these cells lacked CD31 and ERG that mark blood and lymphatic endothelium.

Conclusions: Although the inner part of human eye is physiologically devoid of lymphatic vessels, lymphatic differentiation associated with endothelial stem/progenitor cell activation may be involved in the pathogenesis of human PDR. Further studies are warranted to elucidate whether targeting lymphatic factors could be beneficial in the treatment of patients with the sight-threatening forms of DR.
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http://dx.doi.org/10.1111/aos.12741DOI Listing
September 2015

MMP16 Mediates a Proteolytic Switch to Promote Cell-Cell Adhesion, Collagen Alignment, and Lymphatic Invasion in Melanoma.

Cancer Res 2015 May 25;75(10):2083-94. Epub 2015 Mar 25.

Research Programs Unit, Genome-Scale Biology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland. Pathology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland. Finnish Cancer Institute, Helsinki, Finland.

Lymphatic invasion and accumulation of continuous collagen bundles around tumor cells are associated with poor melanoma prognosis, but the underlying mechanisms and molecular determinants have remained unclear. We show here that a copy-number gain or overexpression of the membrane-type matrix metalloproteinase MMP16 (MT3-MMP) is associated with poor clinical outcome, collagen bundle assembly around tumor cell nests, and lymphatic invasion. In cultured WM852 melanoma cells derived from human melanoma metastasis, silencing of MMP16 resulted in cell-surface accumulation of the MMP16 substrate MMP14 (MT1-MMP) as well as L1CAM cell adhesion molecule, identified here as a novel MMP16 substrate. When limiting the activities of these trans-membrane protein substrates toward pericellular collagen degradation, cell junction disassembly, and blood endothelial transmigration, MMP16 supported nodular-type growth of adhesive collagen-surrounded melanoma cell nests, coincidentally steering cell collectives into lymphatic vessels. These results uncover a novel mechanism in melanoma pathogenesis, whereby restricted collagen infiltration and limited mesenchymal invasion are unexpectedly associated with the properties of the most aggressive tumors, revealing MMP16 as a putative indicator of adverse melanoma prognosis.
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http://dx.doi.org/10.1158/0008-5472.CAN-14-1923DOI Listing
May 2015

Actin-associated protein palladin promotes tumor cell invasion by linking extracellular matrix degradation to cell cytoskeleton.

Mol Biol Cell 2014 Sep 2;25(17):2556-70. Epub 2014 Jul 2.

Research Programs Unit, Genome-Scale Biology, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland Department of Pathology, Haartman Institute, FIN-00014, University of Helsinki, Helsinki, Finland

Basal-like breast carcinomas, characterized by unfavorable prognosis and frequent metastases, are associated with epithelial-to-mesenchymal transition. During this process, cancer cells undergo cytoskeletal reorganization and up-regulate membrane-type 1 matrix metalloproteinase (MT1-MMP; MMP14), which functions in actin-based pseudopods to drive invasion by extracellular matrix degradation. However, the mechanisms that couple matrix proteolysis to the actin cytoskeleton in cell invasion have remained unclear. On the basis of a yeast two-hybrid screen for the MT1-MMP cytoplasmic tail-binding proteins, we identify here a novel Src-regulated protein interaction between the dynamic cytoskeletal scaffold protein palladin and MT1-MMP. These proteins were coexpressed in invasive human basal-like breast carcinomas and corresponding cell lines, where they were associated in the same matrix contacting and degrading membrane complexes. The silencing and overexpression of the 90-kDa palladin isoform revealed the functional importance of the interaction with MT1-MMP in pericellular matrix degradation and mesenchymal tumor cell invasion, whereas in MT1-MMP-negative cells, palladin overexpression was insufficient for invasion. Moreover, this invasion was inhibited in a dominant-negative manner by an immunoglobulin domain-containing palladin fragment lacking the dynamic scaffold and Src-binding domains. These results identify a novel protein interaction that links matrix degradation to cytoskeletal dynamics and migration signaling in mesenchymal cell invasion.
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http://dx.doi.org/10.1091/mbc.E13-11-0667DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4148246PMC
September 2014