Publications by authors named "Ravikanth Maddipati"

11 Publications

  • Page 1 of 1

Calcium signaling induces a partial EMT.

EMBO Rep 2021 Sep 29;22(9):e51872. Epub 2021 Jul 29.

Abramson Family Cancer Research Institute and Department of Medicine, University of Pennsylvania, Philadelphia, PA, USA.

Epithelial plasticity, or epithelial-to-mesenchymal transition (EMT), is a well-recognized form of cellular plasticity, which endows tumor cells with invasive properties and alters their sensitivity to various agents, thus representing a major challenge to cancer therapy. It is increasingly accepted that carcinoma cells exist along a continuum of hybrid epithelial-mesenchymal (E-M) states and that cells exhibiting such partial EMT (P-EMT) states have greater metastatic competence than those characterized by either extreme (E or M). We described recently a P-EMT program operating in vivo by which carcinoma cells lose their epithelial state through post-translational programs. Here, we investigate the underlying mechanisms and report that prolonged calcium signaling induces a P-EMT characterized by the internalization of membrane-associated E-cadherin (ECAD) and other epithelial proteins as well as an increase in cellular migration and invasion. Signaling through Gαq-associated G-protein-coupled receptors (GPCRs) recapitulates these effects, which operate through the downstream activation of calmodulin-Camk2b signaling. These results implicate calcium signaling as a trigger for the acquisition of hybrid/partial epithelial-mesenchymal states in carcinoma cells.
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http://dx.doi.org/10.15252/embr.202051872DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8419705PMC
September 2021

Cancer-Associated Fibroblasts: Versatile Players in the Tumor Microenvironment.

Cancers (Basel) 2020 Sep 17;12(9). Epub 2020 Sep 17.

Division of Surgical Oncology, Department of Surgery, UT Southwestern (University of Texas Southwestern Medical Center), Dallas, TX 75390, USA.

Cancer-associated fibroblasts (CAFs) are indispensable architects of the tumor microenvironment. They perform the essential functions of extracellular matrix deposition, stromal remodeling, tumor vasculature modulation, modification of tumor metabolism, and participation in crosstalk between cancer and immune cells. In this review, we discuss our current understanding of the principal differences between normal fibroblasts and CAFs, the origin of CAFs, their functions, and ultimately, highlight the intimate connection of CAFs to virtually all of the hallmarks of cancer. We address the remarkable degree of functional diversity and phenotypic plasticity displayed by CAFs and strive to stratify CAF biology among different tumor types into practical functional groups. Finally, we summarize the status of recent and ongoing trials of CAF-directed therapies and contend that the paucity of trials resulting in Food and Drug Administration (FDA) approvals thus far is a consequence of the failure to identify targets exclusive of pro-tumorigenic CAF phenotypes that are mechanistically linked to specific CAF functions. We believe that the development of a unified CAF nomenclature, the standardization of functional assays to assess the loss-of-function of CAF properties, and the establishment of rigorous definitions of CAF subpopulations and their mechanistic functions in cancer progression will be crucial to fully realize the promise of CAF-targeted therapies.
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http://dx.doi.org/10.3390/cancers12092652DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7564346PMC
September 2020

Pancreatic cancer survival analysis defines a signature that predicts outcome.

PLoS One 2018 9;13(8):e0201751. Epub 2018 Aug 9.

School of Biomedical Engineering, Sciences, and Health Systems, Drexel University, Philadelphia, PA, United States of America.

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer death in the US. Despite multiple large-scale genetic sequencing studies, identification of predictors of patient survival remains challenging. We performed a comprehensive assessment and integrative analysis of large-scale gene expression datasets, across multiple platforms, to enable discovery of a prognostic gene signature for patient survival in pancreatic cancer. PDAC RNA-Sequencing data from The Cancer Genome Atlas was stratified into Survival+ (>2-year survival) and Survival-(<1-year survival) cohorts (n = 47). Comparisons of RNA expression profiles between survival groups and normal pancreatic tissue expression data from the Gene Expression Omnibus generated an initial PDAC specific prognostic differential expression gene list. The candidate prognostic gene list was then trained on the Australian pancreatic cancer dataset from the ICGC database (n = 103), using iterative sampling based algorithms, to derive a gene signature predictive of patient survival. The gene signature was validated in 2 independent patient cohorts and against existing PDAC subtype classifications. We identified 707 candidate prognostic genes exhibiting differential expression in tumor versus normal tissue. A substantial fraction of these genes was also found to be differentially methylated between survival groups. From the candidate gene list, a 5-gene signature (ADM, ASPM, DCBLD2, E2F7, and KRT6A) was identified. Our signature demonstrated significant power to predict patient survival in two distinct patient cohorts and was independent of AJCC TNM staging. Cross-validation of our gene signature reported a better ROC AUC (≥ 0.8) when compared to existing PDAC survival signatures. Furthermore, validation of our signature through immunohistochemical analysis of patient tumor tissue and existing gene expression subtyping data in PDAC, demonstrated a correlation to the presence of vascular invasion and the aggressive squamous tumor subtype. Assessment of these genes in patient biopsies could help further inform risk-stratification and treatment decisions in pancreatic cancer.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0201751PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6084949PMC
January 2019

Regulation of Epithelial Plasticity Determines Metastatic Organotropism in Pancreatic Cancer.

Dev Cell 2018 06;45(6):696-711.e8

Division of Gastroenterology, Perelman School of Medicine, University of Pennsylvania, 900 Biomedical Research Building II/III, 415 Curie Boulevard, Philadelphia, PA 19104, USA; Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Abramson Cancer Center, Perelman School of Medicine, University of Pennsylvania, 900 Biomedical Research Building II/III, 415 Curie Boulevard, Philadelphia, PA 19104, USA. Electronic address:

The regulation of metastatic organotropism in pancreatic ductal a denocarcinoma (PDAC) remains poorly understood. We demonstrate, using multiple mouse models, that liver and lung metastatic organotropism is dependent upon p120catenin (p120ctn)-mediated epithelial identity. Mono-allelic p120ctn loss accelerates Kras-driven pancreatic cancer formation and liver metastasis. Importantly, one p120ctn allele is sufficient for E-CADHERIN-mediated cell adhesion. By contrast, cells with bi-allelic p120ctn loss demonstrate marked lung organotropism; however, rescue with p120ctn isoform 1A restores liver metastasis. In a p120ctn-independent PDAC model, mosaic loss of E-CADHERIN expression reveals selective pressure for E-CADHERIN-positive liver metastasis and E-CADHERIN-negative lung metastasis. Furthermore, human PDAC and liver metastases support the premise that liver metastases exhibit predominantly epithelial characteristics. RNA-seq demonstrates differential induction of pathways associated with metastasis and epithelial-to-mesenchymal transition in p120ctn-deficient versus p120ctn-wild-type cells. Taken together, P120CTN and E-CADHERIN mediated epithelial plasticity is an addition to the conceptual framework underlying metastatic organotropism in pancreatic cancer.
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http://dx.doi.org/10.1016/j.devcel.2018.05.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6011231PMC
June 2018

EMT Subtype Influences Epithelial Plasticity and Mode of Cell Migration.

Dev Cell 2018 06;45(6):681-695.e4

Department of Medicine, Gastroenterology Division, Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, 421 Curie Blvd, 512 BRB II/III, Philadelphia, PA 19104, USA; Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address:

Epithelial-mesenchymal transition (EMT) is strongly implicated in tumor cell invasion and metastasis. EMT is thought to be regulated primarily at the transcriptional level through the repressive activity of EMT transcription factors. However, these classical mechanisms have been parsed out almost exclusively in vitro, leaving questions about the programs driving EMT in physiological contexts. Here, using a lineage-labeled mouse model of pancreatic ductal adenocarcinoma to study EMT in vivo, we found that most tumors lose their epithelial phenotype through an alternative program involving protein internalization rather than transcriptional repression, resulting in a "partial EMT" phenotype. Carcinoma cells utilizing this program migrate as clusters, contrasting with the single-cell migration pattern associated with traditionally defined EMT mechanisms. Moreover, many breast and colorectal cancer cell lines utilize this alternative program to undergo EMT. Collectively, these results suggest that carcinoma cells have different ways of losing their epithelial program, resulting in distinct modes of invasion and dissemination.
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http://dx.doi.org/10.1016/j.devcel.2018.05.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6014628PMC
June 2018

KLF4 Initiates Acinar Cell Reprogramming and Is Essential for the Early Stages of Pancreatic Carcinogenesis.

Cancer Cell 2016 Mar;29(3):247-248

Division of Gastroenterology, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104-4863, USA. Electronic address:

Pancreatic ductal adenocarcinoma (PDA) has a dismal prognosis and is minimally responsive to current chemotherapies. In this issue of Cancer Cell, Xie et al. (2016) identify the transcription factor KLF4 as essential for the early stages of pancreatic carcinogenesis, expanding the repertoire of targets for early intervention strategies.
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http://dx.doi.org/10.1016/j.ccell.2016.02.019DOI Listing
March 2016

Pancreatic Cancer Metastases Harbor Evidence of Polyclonality.

Cancer Discov 2015 Oct 24;5(10):1086-97. Epub 2015 Jul 24.

Department of Medicine, Gastroenterology Division, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania. Abramson Family Cancer Research Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania. Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania.

Unlabelled: Studies of the cancer genome have demonstrated that tumors are composed of multiple subclones with varied genetic and phenotypic properties. However, little is known about how metastases arise and evolve from these subclones. To understand the cellular dynamics that drive metastasis, we used multicolor lineage-tracing technology in an autochthonous mouse model of pancreatic cancer. Here, we report that precursor lesions exhibit significant clonal heterogeneity but that this diversity decreases during premalignant progression. Furthermore, we present evidence that a significant fraction of metastases are polyclonally seeded by distinct tumor subclones. Finally, we show that clonality during metastatic growth-leading to either monoclonal or polyclonal expansion-differs based on the site of metastatic invasion. These results provide an unprecedented window into the cellular dynamics of tumor evolution and suggest that heterotypic interactions between tumor subpopulations contribute to metastatic progression in native tumors.

Significance: Studies of tumor heterogeneity indicate that distinct tumor subclones interact during cancer progression. Here, we demonstrate by lineage tracing that metastases often involve seeding by more than one clone and that subsequent cellular outgrowth depends on the metastatic site. These findings provide insight into clonal diversity and evolution in metastatic disease.
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http://dx.doi.org/10.1158/2159-8290.CD-15-0120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4657730PMC
October 2015

Hippo signaling regulates differentiation and maintenance in the exocrine pancreas.

Gastroenterology 2013 Jun 27;144(7):1543-53, 1553.e1. Epub 2013 Feb 27.

Gastroenterology Division, Department of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.

Background & Aims: The Hippo signaling pathway is a context-dependent regulator of cell proliferation, differentiation, and apoptosis in species ranging from Drosophila to humans. In this study, we investigated the role of the core Hippo kinases-Mst1 and Mst2-in pancreatic development and homeostasis.

Methods: We used a Cre/LoxP system to create mice with pancreas-specific disruptions in Mst1 and Mst2 (Pdx1-Cre;Mst1(-/-);Mst2(fl/fl) mice), the mammalian orthologs of Drosophila Hippo. We used a transgenic approach to overexpress Yap, the downstream mediator of Hippo signaling, in the developing pancreas of mice.

Results: Contrary to expectations, the pancreatic mass of Pdx1-Cre;Mst1(-/-);Mst2(fl/fl) mice was reduced compared with wild-type mice, largely because of postnatal de-differentiation of acinar cells into duct-like cells. Development of this phenotype coincided with postnatal reactivation of YAP expression. Ectopic expression of YAP during the secondary transition (a stage at which YAP is normally absent) blocked differentiation of the endocrine and exocrine compartments, whereas loss of a single Yap allele reduced acinar de-differentiation. The phenotype of Pdx1-Cre;Mst1(-/-);Mst2(fl/fl) mice recapitulated cellular and molecular changes observed during chemical-induced pancreatitis in mice.

Conclusions: The mammalian Hippo kinases, and YAP, maintain postnatal pancreatic acinar differentiation in mice.
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http://dx.doi.org/10.1053/j.gastro.2013.02.037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3665616PMC
June 2013

Mitochondrial reactive oxygen species promote production of proinflammatory cytokines and are elevated in TNFR1-associated periodic syndrome (TRAPS).

J Exp Med 2011 Mar 31;208(3):519-33. Epub 2011 Jan 31.

Immunoregulation Section, Autoimmunity Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutesof Health, Bethesda, MD 20892, USA.

Reactive oxygen species (ROS) have an established role in inflammation and host defense, as they kill intracellular bacteria and have been shown to activate the NLRP3 inflammasome. Here, we find that ROS generated by mitochondrial respiration are important for normal lipopolysaccharide (LPS)-driven production of several proinflammatory cytokines and for the enhanced responsiveness to LPS seen in cells from patients with tumor necrosis factor receptor-associated periodic syndrome (TRAPS), an autoinflammatory disorder caused by missense mutations in the type 1 TNF receptor (TNFR1). We find elevated baseline ROS in both mouse embryonic fibroblasts and human immune cells harboring TRAPS-associated TNFR1 mutations. A variety of antioxidants dampen LPS-induced MAPK phosphorylation and inflammatory cytokine production. However, gp91(phox) and p22(phox) reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits are dispensable for inflammatory cytokine production, indicating that NADPH oxidases are not the source of proinflammatory ROS. TNFR1 mutant cells exhibit altered mitochondrial function with enhanced oxidative capacity and mitochondrial ROS generation, and pharmacological blockade of mitochondrial ROS efficiently reduces inflammatory cytokine production after LPS stimulation in cells from TRAPS patients and healthy controls. These findings suggest that mitochondrial ROS may be a novel therapeutic target for TRAPS and other inflammatory diseases.
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http://dx.doi.org/10.1084/jem.20102049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3058571PMC
March 2011

Concerted action of wild-type and mutant TNF receptors enhances inflammation in TNF receptor 1-associated periodic fever syndrome.

Proc Natl Acad Sci U S A 2010 May 10;107(21):9801-6. Epub 2010 May 10.

Inflammatory Biology Section, Laboratory of Clinical Investigation and Immunoregulation Section, Autoimmunity Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.

TNF, acting through p55 tumor necrosis factor receptor 1 (TNFR1), contributes to the pathogenesis of many inflammatory diseases. TNFR-associated periodic syndrome (TRAPS, OMIM 142680) is an autosomal dominant autoinflammatory disorder characterized by prolonged attacks of fevers, peritonitis, and soft tissue inflammation. TRAPS is caused by missense mutations in the extracellular domain of TNFR1 that affect receptor folding and trafficking. These mutations lead to loss of normal function rather than gain of function, and thus the pathogenesis of TRAPS is an enigma. Here we show that mutant TNFR1 accumulates intracellularly in peripheral blood mononuclear cells of TRAPS patients and in multiple cell types from two independent lines of knockin mice harboring TRAPS-associated TNFR1 mutations. Mutant TNFR1 did not function as a surface receptor for TNF but rather enhanced activation of MAPKs and secretion of proinflammatory cytokines upon stimulation with LPS. Enhanced inflammation depended on autocrine TNF secretion and WT TNFR1 in mouse and human myeloid cells but not in fibroblasts. Heterozygous TNFR1-mutant mice were hypersensitive to LPS-induced septic shock, whereas homozygous TNFR1-mutant mice resembled TNFR1-deficient mice and were resistant to septic shock. Thus WT and mutant TNFR1 act in concert from distinct cellular locations to potentiate inflammation in TRAPS. These findings establish a mechanism of pathogenesis in autosomal dominant diseases where full expression of the disease phenotype depends on functional cooperation between WT and mutant proteins and also may explain partial responses of TRAPS patients to TNF blockade.
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http://dx.doi.org/10.1073/pnas.0914118107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2906866PMC
May 2010

Peptide-conjugated quantum dots activate neuronal receptors and initiate downstream signaling of neurite growth.

Nano Lett 2005 Apr;5(4):603-7

Department of Biomedical Engineering, 44 Cummington St., Room 701, Boston University, Boston, Massachusetts 02215, USA.

Quantum dots (QDs) could serve as fluorescent scaffolds for effecting specific physiological and pharmacological responses in cells. Here, we conjugate the peptide ligand betaNGF to QD surfaces, and confirm surface modification and single QD nanostructure using AFM. We show that betaNGF-QDs retain bioactivity, activate TrkA receptors, and initiate neuronal differentiation in PC12 cells. Receptor-evoked activity of QD-immobilized ligands has wide-ranging implications for the development of molecular tools and therapeutics targeted at understanding and regulating cell function.
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http://dx.doi.org/10.1021/nl047977cDOI Listing
April 2005
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