Publications by authors named "Joseph R Testa"

159 Publications

Papillary Renal Neoplasm With Reverse Polarity Is Often Cystic: Report of 7 Cases and Review of 93 Cases in the Literature.

Am J Surg Pathol 2021 Aug 5. Epub 2021 Aug 5.

Departments of Pathology Surgical Oncology Cancer Signaling and Epigenetics Program, Fox Chase Cancer Center, Philadelphia, PA.

Papillary renal neoplasm with reverse polarity (PRNRP) is a newly proposed entity with distinct histology and frequent KRAS mutations. To date, 93 cases of PRNRPs have been reported. In this study, we present 7 new cases of PRNRP and review the literature. Most of the pathologic features in our 7 cases are similar to those previously reported cases. However, all 7 of our cases showed at least partial cystic changes, which was not stressed in prior studies. Single-nucleotide polymorphism-microarray based chromosomal analysis demonstrated no trisomy or other alteration of chromosomes 7 or 17; and no loss or other alteration of chromosome Y was detected in all 7 cases. Next-generation sequencing detected KRAS missense mutations in 4 of 7 cases. No fusion genes were detected. In summary, PRNRP is a small, well-circumscribed often encapsulated and cystic neoplasm with loose papillary formations. Cuboidal tumor cells always have eosinophilic cytoplasm and nuclei located at the pole opposite the basement membrane with a low World Health Organization (WHO)/International Society of Urologic Pathologists (ISUP) nuclear grade. The fibrovascular cores can be hyalinized or edematous. Macrophage aggregates and intracellular hemosiderin are uncommon, and no psammoma bodies or necrosis should be seen. Immunophenotypically, this tumor is always positive for CK7 and GATA3, and negative for CD117 and vimentin. CD10 and AMACR can be positive, but often weakly and focally. PRNRP often has KRAS mutations, however, only 32% of cases have chromosomal abnormalities in chromosomes 7, 17, and Y. No recurrences, metastases, or tumor-related deaths have been reported following complete resection.
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http://dx.doi.org/10.1097/PAS.0000000000001773DOI Listing
August 2021

Genes: Roles in Development and Cancer.

Cancers (Basel) 2021 Jun 15;13(12). Epub 2021 Jun 15.

Genomics Facility, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.

Homeobox genes control body patterning and cell-fate decisions during development. The homeobox genes consist of many families, only some of which have been investigated regarding a possible role in tumorigenesis. Dysregulation of family genes have been widely implicated in cancer etiology. homeobox genes, which belong to the NK-like family, exert dual roles in development and cancer. The genes are the key transcription factors involved in regulating the development of craniofacial structures in vertebrates. The three bigenes have overlapping expression in the branchial arches. Disruption of function has destructive consequences in organogenesis and is associated with certain congenital disorders in humans. The role of genes in oncogenesis is only beginning to emerge. DLX2 diminishes cellular senescence by regulating p53 function, whereas DLX4 has been associated with metastasis in breast cancer. In human ovarian cancer cells, DLX5 is essential for regulating AKT signaling, thereby promoting cell proliferation and survival. We previously implicated as an oncogene in murine T-cell lymphoma driven by a constitutively active form of . In this mouse model, overexpression of was caused by a chromosomal rearrangement that juxtaposed the Tcr-beta promoter region near the locus. Moreover, transgenic mice overexpressing specifically in immature T-cells, develop spontaneous thymic lymphomas. Oncogenesis in this mouse model involves binding of Dlx5 to the and gene loci to activate their transcription. Dlx5 also cooperates with Akt signaling to accelerate lymphomagenesis by activating Wnt signaling. We also discuss the fact that human DLX5 is aberrantly expressed in several human malignancies.
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http://dx.doi.org/10.3390/cancers13123005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232755PMC
June 2021

Novel LRRK2 mutations and other rare, non-BAP1-related candidate tumor predisposition gene variants in high-risk cancer families with mesothelioma and other tumors.

Hum Mol Genet 2021 Aug;30(18):1750-1761

Cancer Epigenetics and Signaling Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA.

There is irrefutable evidence that germline BRCA1-associated protein 1 gene (BAP1) mutations contribute to malignant mesothelioma (MM) susceptibility. However, BAP1 mutations are not found in all cases with evidence of familial MM or in other high-risk cancer families affected by various cancers, including MM. The goal of this study was to use whole genome sequencing (WGS) to determine the frequency and types of germline gene variants occurring in 12 MM patients who were selected from a series of 141 asbestos-exposed MM patients with a family history of cancer but without a germline BAP1 mutation. WGS was also performed on two MM cases, a proband and sibling, from a previously reported family with multiple cases of MM without the inheritance of a predisposing BAP1 mutation. Altogether, germline DNA sequencing variants were identified in 21 cancer-related genes in 10 of the 13 probands. Germline indel, splice site and missense mutations and two large deletions were identified. Among the 13 MM index cases, 6 (46%) exhibited one or more predicted pathogenic mutations. Affected genes encode proteins involved in DNA repair (ATM, ATR, BRCA2, BRIP1, CHEK2, MLH3, MUTYH, POLE, POLE4, POLQ and XRCC1), chromatin modification (ARID1B, DNMT3A, JARID2 and SETD1B) or other cellular pathways: leucine-rich repeat kinase 2 gene (LRRK2) (two cases) and MSH4. Notably, somatic truncating mutation or deletions of LRRK2 were occasionally found in MMs in The Cancer Genome Atlas, and the expression of LRRK2 was undetectable or downregulated in a majority of primary MMs and MM cell lines we examined, implying that loss of LRRK2 expression is a newly recognized tumor suppressor alteration in MM.
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http://dx.doi.org/10.1093/hmg/ddab138DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8411985PMC
August 2021

Kinetic Characterization of ASXL1/2-Mediated Allosteric Regulation of the BAP1 Deubiquitinase.

Mol Cancer Res 2021 07 17;19(7):1099-1112. Epub 2021 Mar 17.

The Wistar Institute, Philadelphia, Pennsylvania.

BAP1 is an ubiquitin hydrolase whose deubiquitinase activity is mediated by polycomb group-like protein ASXL2. Cancer-related mutations/deletions lead to loss-of-function by targeting the catalytic ubiquitin C-terminal hydrolase (UCH) or UCH37-like domain (ULD) domains of BAP1, and the latter disrupts binding to ASXL2, an obligate partner for BAP1 enzymatic activity. However, the biochemical and biophysical properties of domains involved in forming the enzymatically active complex are unknown. Here, we report the molecular dynamics, kinetics, and stoichiometry of these interactions. We demonstrate that interactions between BAP1 and ASXL2 are direct, specific, and stable to biochemical and biophysical manipulations as detected by isothermal titration calorimetry (ITC), GST association, and optical biosensor assays. Association of the ASXL2-AB box greatly stimulates BAP1 activity. A stable ternary complex is formed, comprised of the BAP1-UCH, BAP1-ULD, and ASXL2-AB domains. Stoichiometric analysis revealed that one molecule of the ULD domain directly interacts with one molecule of the AB box. Real-time kinetic analysis of the ULD/AB protein complex to the BAP1-UCH domain, based on surface plasmon resonance, indicated that formation of the ULD/AB complex with the UCH domain is a single-step event with fast association and slow dissociation rates. experiments validated in cells that the ASXL-AB box directly regulates BAP1 activity. IMPLICATIONS: Collectively, these data elucidate molecular interactions between specific protein domains regulating BAP1 deubiquitinase activity, thus establishing a foundation for small-molecule approaches to reactivate latent wild-type BAP1 catalytic activity in -mutant cancers.
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http://dx.doi.org/10.1158/1541-7786.MCR-20-0080DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8254751PMC
July 2021

Challenging Global Waste Management - Bioremediation to Detoxify Asbestos.

Front Environ Sci 2020 Mar 4;8. Epub 2020 Mar 4.

Engineering Pathway, Unitec Institute of Technology, Auckland, New Zealand.

As the 21st century uncovers ever-increasing volumes of asbestos and asbestos-contaminated waste, we need a new way to stop 'grandfather's problem' from becoming that of our future generations. The production of inexpensive, mechanically strong, heat resistant building materials containing asbestos has inevitably led to its use in many public and residential buildings globally. It is therefore not surprising that since the asbestos boom in the 1970s, some 30 years later, the true extent of this hidden danger was exposed. Yet, this severely toxic material continues to be produced and used in some countries, and in others the disposal options for historic uses - generally landfill - are at best unwieldy and at worst insecure. We illustrate the global scale of the asbestos problem via three case studies which describe various removal and/or end disposal issues. These case studies from both industrialised and island nations demonstrate the potential for the generation of massive amounts of asbestos contaminated soil. In each case, the final outcome of the project was influenced by factors such as cost and land availability, both increasing issues, worldwide. The reduction in the generation of asbestos containing materials will not absolve us from the necessity of handling and disposal of contaminated land. Waste treatment which relies on physico-chemical processes is expensive and does not contribute to a circular model economy ideal. Although asbestos is a mineral substance, there are naturally occurring biological-mediated processes capable of degradation (such as bioweathering). Therefore, low energy options, such as bioremediation, for the treatment for asbestos contaminated soils are worth exploring. We outline evidence pointing to the ability of microbe and plant communities to remove from asbestos the iron that contributes to its carcinogenicity. Finally, we describe the potential for a novel concept of creating ecosystems over asbestos landfills ('activated landfills') that utilize nature's chelating ability to degrade this toxic product effectively.
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http://dx.doi.org/10.3389/fenvs.2020.00020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7707057PMC
March 2020

Somatic Epigenetic Silencing of Inactivates Necroptosis and Contributes to Chemoresistance in Malignant Mesothelioma.

Clin Cancer Res 2021 02 17;27(4):1200-1213. Epub 2020 Nov 17.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.

Purpose: Receptor-interacting protein kinase 3 (RIPK3) phosphorylates effector molecule MLKL to trigger necroptosis. Although RIPK3 loss is seen in several human cancers, its role in malignant mesothelioma is unknown. This study aimed to determine whether RIPK3 functions as a potential tumor suppressor to limit development of malignant mesothelioma.

Experimental Design: RIPK3 expression was examined in 66 malignant mesothelioma tumors and cell lines. Promoter methylation and siRNA studies were performed to assess the mode of silencing in RIPK3-deficient malignant mesothelioma cells. Restoration of RIPK3 expression in RIPK3-negative malignant mesothelioma cells, either by treatment with 5-aza-2'-deoxycytidine or lentiviral expression of cDNA, was performed to assess effects on cell viability, necrosis, and chemosensitization.

Results: Loss of RIPK3 expression was observed in 42/66 (63%) primary malignant mesotheliomas and malignant mesothelioma cell lines, and RT-PCR analysis demonstrated that downregulation occurs at the transcriptional level, consistent with epigenetic silencing. RIPK3-negative malignant mesothelioma cells treated with 5-aza-2'-deoxycytidine resulted in reexpression of RIPK3 and chemosensitization. Ectopic expression of RIPK3 also resulted in chemosensitization and led to necroptosis, the latter demonstrated by phosphorylation of downstream target MLKL and confirmed by rescue experiments. Mining of expression and survival outcomes among patients with malignant mesothelioma available from The Cancer Genome Atlas repository revealed that promoter methylation of is associated with reduced expression and poor prognosis.

Conclusions: These data suggest that RIPK3 acts as a tumor suppressor in malignant mesothelioma by triggering necroptosis and that epigenetic silencing of by DNA methylation impairs necroptosis and contributes to chemoresistance and poor survival in this incurable disease.
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http://dx.doi.org/10.1158/1078-0432.CCR-18-3683DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7887036PMC
February 2021

Wnt signaling mediates oncogenic synergy between Akt and Dlx5 in T-cell lymphomagenesis by enhancing cholesterol synthesis.

Sci Rep 2020 09 28;10(1):15837. Epub 2020 Sep 28.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, PA, 19111, USA.

The Dlx5 homeobox gene was first implicated as an oncogene in a T-ALL mouse model expressing myristoylated (Myr) Akt2. Furthermore, overexpression of Dlx5 was sufficient to drive T-ALL in mice by directly activating Akt and Notch signaling. These findings implied that Akt2 cooperates with Dlx5 in T-cell lymphomagenesis. To test this hypothesis, Lck-Dlx5;Lck-MyrAkt2 transgenic mice were generated. MyrAkt2 synergized with Dlx5 to greatly accelerate and enhance the dissemination of T-lymphomagenesis. RNA-seq analysis performed on lymphomas from Lck-Dlx5;Lck-MyrAkt mice revealed upregulation of genes involved in the Wnt and cholesterol biosynthesis pathways. Combined RNA-seq and ChIP-seq analysis of lymphomas from Lck-Dlx5;Lck-MyrAkt mice demonstrated that β-catenin directly regulates genes involved in sterol regulatory element binding transcription factor 2 (Srebf2)-cholesterol synthesis. These lymphoma cells had high Lef1 levels and were highly sensitive to β-catenin and Srebf2-cholesterol synthesis inhibitors. Similarly, human T-ALL cell lines with activated NOTCH and AKT and elevated LEF1 levels were sensitive to inhibition of β-catenin and cholesterol pathways. Furthermore, LEF1 expression positively correlated with expression of genes involved in the cholesterol synthesis pathway in primary human T-ALL specimens. Together, these data suggest that targeting β-catenin and/or cholesterol biosynthesis, together with AKT, could have therapeutic efficacy in a subset of T-ALL patients.
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http://dx.doi.org/10.1038/s41598-020-72822-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7522078PMC
September 2020

Immortalization of human primary prostate epithelial cells via CRISPR inactivation of the CDKN2A locus and expression of telomerase.

Prostate Cancer Prostatic Dis 2021 03 1;24(1):233-243. Epub 2020 Sep 1.

Fels Institute for Cancer Research and Molecular Biology, Philadelphia, PA, USA.

Background: Immortalization of primary prostate epithelial cells (PrEC) with just hTERT expression is particularly inefficient in the absence of DNA tumor viral proteins or p16 knockdown.

Materials And Methods: Here, we describe the establishment of immortalized normal prostate epithelial cell line models using CRISPR technology to inactivate the CDKN2A locus concomitantly with ectopic expression of an hTERT transgene.

Results: Using this approach, we have obtained immortal cell clones that exhibit fundamental characteristics of normal cells, including diploid genomes, near normal karyotypes, normal p53 and pRB cell responses, the ability to form non-invasive spheroids, and a non-transformed phenotype. Based on marker expression, these clones are of basal cell origin.

Conclusions: Use of this approach resulted in the immortalization of independent clones of PrEC that retained normal characteristics, were stable, and non-transformed. Thus, this approach could be used for the immortalization of normal primary prostate cells. This technique could also be useful for establishing cell lines from prostate tumor tissues of different tumor grades and/or from patients of diverse ethnicities to generate cell line models that facilitate the study of the molecular basis of disease disparity.
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http://dx.doi.org/10.1038/s41391-020-00274-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7917161PMC
March 2021

Hypomorphic mTOR Downregulates CDK6 and Delays Thymic Pre-T LBL Tumorigenesis.

Mol Cancer Ther 2020 10 3;19(10):2221-2232. Epub 2020 Aug 3.

Laboratory of Cancer Biology and Genetics, CCR, NCI, NIH, Bethesda, Maryland.

PI3K/AKT/mTOR pathway hyperactivation is frequent in T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/LBL). To model inhibition of mTOR, pre-T-cell lymphoblastic leukemia/lymphoma (pre-T LBL) tumor development was monitored in mice with T lymphocyte-specific, constitutively active AKT (Lck-MyrAkt2) that were either crossed to mTOR knockdown (KD) mice or treated with the mTOR inhibitor everolimus. Lck-MyrAkt2;mTOR KD mice lived significantly longer than Lck-MyrAkt2;mTOR wild-type (WT) mice, although both groups ultimately developed thymic pre-T LBL. An increase in survival was also observed when Lck-MyrAkt2;mTOR WT mice were treated for 8 weeks with everolimus. The transcriptional profiles of WT and KD thymic lymphomas were compared, and Ingenuity Pathway Upstream Regulator Analysis of differentially expressed genes in tumors from mTOR WT versus KD mice identified let-7 and miR-21 as potential regulatory genes. mTOR KD mice had higher levels of let-7a and miR-21 than mTOR WT mice, and rapamycin induced their expression in mTOR WT cells. CDK6 was one of the most downregulated targets of both let-7 and miR21 in mTOR KD tumors. CDK6 overexpression and decreased expression of let-7 in mTOR KD cells rescued a G arrest phenotype. Combined mTOR (rapamycin) and CDK4/6 (palbociclib) inhibition decreased tumor size and proliferation in tumor flank transplants, increased survival in an intravenous transplant model of disseminated leukemia compared with single agent treatment, and cooperatively decreased cell viability in human T-ALL/LBL cell lines. Thus, mTOR KD mice provide a model to explore drug combinations synergizing with mTOR inhibitors and can be used to identify downstream targets of inhibition.
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http://dx.doi.org/10.1158/1535-7163.MCT-19-0671DOI Listing
October 2020

BRCA1 Mutational Complementation Induces Synthetic Viability.

Mol Cell 2020 06 30;78(5):951-959.e6. Epub 2020 Apr 30.

Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA. Electronic address:

BRCA1 promotes the DNA end resection and RAD51 loading steps of homologous recombination (HR). Whether these functions can be uncoupled, and whether mutant proteins retaining partial activity can complement one another, is unclear and could affect the severity of BRCA1-associated Fanconi anemia (FA). Here we generated a Brca1 mouse with a coiled-coil (CC) domain deletion. Brca1 mice are born at low frequencies, and post-natal mice have FA-like abnormalities, including bone marrow failure. Intercrossing with Brca1, which is homozygous lethal, generated Brca1 mice at Mendelian frequencies that were indistinguishable from Brca1 mice. Brca1 and Brca1 proteins were individually responsible for counteracting 53BP1-RIF1-Shieldin activity and promoting RAD51 loading, respectively. Thus, Brca1 and Brca1 alleles represent separation-of-function mutations that combine to provide a level of HR sufficient for normal development and hematopoiesis. Because BRCA1 activities can be genetically separated, compound heterozygosity for functional complementary mutations may protect individuals from FA.
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http://dx.doi.org/10.1016/j.molcel.2020.04.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7418109PMC
June 2020

Preclinical Models of Malignant Mesothelioma.

Front Oncol 2020 11;10:101. Epub 2020 Feb 11.

Division of Molecular Genetics, The Netherlands Cancer Institute, Amsterdam, Netherlands.

Rodent models of malignant mesothelioma help facilitate the understanding of the biology of this highly lethal cancer and to develop and test new interventions. Introducing the same genetic lesions as found in human mesothelioma in mice results in tumors that show close resemblance with the human disease counterpart. This includes the extensive inflammatory responses that characterize human malignant mesothelioma. The relatively fast development of mesothelioma in mice when the appropriate combination of lesions is introduced, with or without exposure to asbestos, make the autochthonous models particularly useful for testing new treatment strategies in an immunocompetent setting, whereas Patient-Derived Xenograft models are particularly useful to assess effects of inter- and intra-tumor heterogeneity and human-specific features of mesothelioma. It is to be expected that new insights obtained by studying these experimental systems will lead to new more effective treatments for this devastating disease.
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http://dx.doi.org/10.3389/fonc.2020.00101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7026500PMC
February 2020

Overall tumor genomic instability: an important predictor of recurrence-free survival in patients with localized clear cell renal cell carcinoma.

Cancer Biol Ther 2020 05 1;21(5):424-431. Epub 2020 Mar 1.

Genomics Facility, Fox Chase Cancer Center, Philadelphia, PA, USA.

Measurement of a tumor's overall genomic instability has gathered recent interest over the identification of specific genomic imbalances, as it may provide a more robust measure of tumor aggressiveness. Here we demonstrate the association of tumor genomic instability in the prediction of disease recurrence in patients with clinically localized clear cell renal cell carcinoma (ccRCC). Genomic copy number analysis was performed using SNP-based microarrays on tumors from 103 ccRCC patients. The number of copy number alterations (CNAs) for each tumor was calculated, and a genomic imbalance threshold (GIT) associated with high stage and high-grade disease was determined. Cox proportional hazards regression analyzes were performed to assess the effect of GIT on recurrence-free survival adjusting for known confounders. In the cohort, copy number losses in chromosome arms 3p, 14q, 6q, 9p, and 1p and gains of 5q and 7p/q were common. CNA burden significantly increased with increasing stage ( < .001) and grade ( < .001). The median CNA burden associated with patients presenting with advanced stage (IV) and high-grade (III/IV) tumors was ≥9, defining the GIT. On regression analysis, GIT was a superior predictor of recurrence (Hazard Ratio 4.44 [CI 1.36-14.48], = .01) independent of stage, with similar results adjusting for grade. These findings were confirmed using an alternative measure of genomic instability, weighted Genomic Integrity Index. Our data support a key role for genomic instability in ccRCC progression. More importantly, we have identified a GIT (≥ 9 CNAs) that is a superior and independent predictor of disease recurrence in high-risk ccRCC patients.
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http://dx.doi.org/10.1080/15384047.2020.1721251DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7515487PMC
May 2020

Application of Chromosome Microarray Analysis for the Differential Diagnosis of Low-grade Renal Cell Carcinoma With Clear Cell and Papillary Features.

Appl Immunohistochem Mol Morphol 2020 02;28(2):123-129

Department of Pathology.

Clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC) are the 2 most common RCCs. However, some RCCs can have both clear cell and papillary features, including clear cell papillary RCC (ccpRCC). They can be a diagnostic challenge in daily practice. Accurate diagnosis of these tumors is important for both patient prognosis and appropriate treatment. Fourteen RCCs with papillary architecture, clear cytoplasm and low Fuhrman grade were analyzed by SNP-based chromosome microarray (CMA). Seven cases had pathologic features of ccpRCC, and all had normal genomic profiles except one that had copy neutral loss of heterozygosity (cnLOH) of chromosome 3 and loss of one copy of the X chromosome. The remaining 7 cases also had papillae and clear cytoplasm. Two of these cases showed losses of chromosome 3 which are typically found in ccRCC. One had a gain of chromosome 7, which is commonly seen in pRCC. The remaining 4 had no alterations of chromosome 3 or 7. However, 3 of these 4 had monosomy 8, which are consistent with RCC with monosomy 8. The remaining case had no copy number alterations. This study shows that low-grade RCC with papillae and clear cell phenotype represents a heterogeneous group, including ccpRCC, ccRCC, pRCC, and RCC with monosomy 8. CMA analysis can be useful for the differential diagnosis of these neoplasms.
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http://dx.doi.org/10.1097/PAI.0000000000000704DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8434675PMC
February 2020

PBRM1 acts as a p53 lysine-acetylation reader to suppress renal tumor growth.

Nat Commun 2019 12 20;10(1):5800. Epub 2019 Dec 20.

Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, 19107, USA.

p53 acetylation is indispensable for its transcriptional activity and tumor suppressive function. However, the identity of reader protein(s) for p53 acetylation remains elusive. PBRM1, the second most highly mutated tumor suppressor gene in kidney cancer, encodes PBRM1. Here, we identify PBRM1 as a reader for p53 acetylation on lysine 382 (K382Ac) through its bromodomain 4 (BD4). Notably, mutations on key residues of BD4 disrupt recognition of p53 K382Ac. The mutation in BD4 also reduces p53 binding to promoters of target genes such as CDKN1A (p21). Consequently, the PBRM1 BD4 mutant fails to fully support p53 transcriptional activity and is defective as a tumor suppressor. We also find that expressions of PBRM1 and p21 correlate with each other in human kidney cancer samples. Our findings uncover a tumor suppressive mechanism of PBRM1 in kidney cancer and provide a mechanistic insight into the crosstalk between p53 and SWI/SNF complexes.
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http://dx.doi.org/10.1038/s41467-019-13608-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6925188PMC
December 2019

Monosomy of Chromosome 9 Is Associated With Higher Grade, Advanced Stage, and Adverse Outcome in Clear-cell Renal Cell Carcinoma.

Clin Genitourin Cancer 2020 02 26;18(1):56-61. Epub 2019 Sep 26.

Department of Pathology, Fox Chase Cancer Center, Temple Health System, Philadelphia, PA.

Background: Clear-cell renal cell carcinoma (ccRCC) is one of the most common malignancies in humans and is usually associated with poor outcomes. Cancers are considered to be genetic diseases. Therefore, a better understanding of genetic alterations that are related to disease progression or poor prognosis can help to more precisely identify high-risk patients and treat them more effectively. The aim of this study was to examine the frequency of whole chromosome 9 loss (monosomy of chromosome 9) and its prognostic value in patients with ccRCC.

Materials And Methods: Single nucleotide polymorphism-based chromosome microarray (CMA) analysis was performed on 103 resected specimens from patients with ccRCC who had undergone partial or radical nephrectomy between January 2002 and March 2017 at Fox Chase Cancer Center. Monosomy 9 was correlated with clinicopathologic parameters and recurrence-free survival.

Results: Chromosome 9 loss was detected in 31 (30%) of 103 tumors. Tumors with chromosome 9 loss had higher histologic grade (3 and 4; P < .001) and pathologic stage (P < .001). In 59 patients with non-metastatic ccRCC, chromosome 9 loss was also associated with higher recurrence rate and shorter recurrence-free survival (RFS) (12-month RFS, 77.8%; 95% confidence interval, 36.5%-93.9% for chromosome 9 loss vs. 95.7%; 95% confidence interval, 84.0%-98.9% for no loss; P = .002).

Conclusions: Chromosome 9 loss was found in 30% of patients with ccRCC and correlated with higher grade, advanced stage, and shorter RFS in patients with Stage I to III ccRCC.
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http://dx.doi.org/10.1016/j.clgc.2019.09.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7781234PMC
February 2020

RPL22L1 induction in colorectal cancer is associated with poor prognosis and 5-FU resistance.

PLoS One 2019 3;14(10):e0222392. Epub 2019 Oct 3.

Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA, United States of America.

We have previously demonstrated that loss of the tumor suppressive activity of ribosomal protein (RP) RPL22 predisposes to development of leukemia in mouse models and aggressive disease in human patients; however, the role of RPL22 in solid tumors, specifically colorectal cancer (CRC), had not been explored. We report here that RPL22 is either deleted or mutated in 36% of CRC and provide new insights into its mechanism of action. Indeed, Rpl22 inactivation causes the induction of its highly homologous paralog, RPL22L1, which serves as a driver of cell proliferation and anchorage-independent growth in CRC cells. Moreover, RPL22L1 protein is highly expressed in patient CRC samples and correlates with poor survival. Interestingly, the association of high RPL22L1 expression with poor prognosis appears to be linked to resistance to 5-Fluorouracil, which is a core component of most CRC therapeutic regimens. Indeed, in an avatar trial, we found that human CRC samples that were unresponsive to 5-Fluorouracil in patient-derived xenografts exhibited elevated expression levels of RPL22L1. This link between RPL22L1 induction and 5-Fluorouracil resistance appears to be causal, because ectopic expression or knockdown of RPL22L1 in cell lines increases and decreases 5-Fluorouracil resistance, respectively, and this is associated with changes in expression of the DNA-repair genes, MGMT and MLH1. In summary, our data suggest that RPL22L1 might be a prognostic marker in CRC and predict 5-FU responsiveness.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0222392PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6776433PMC
March 2020

Clinical application of RNA sequencing in sarcoma diagnosis: An institutional experience.

Medicine (Baltimore) 2019 Jun;98(25):e16031

Department of Pathology.

Accurate diagnoses of sarcoma are sometimes challenging on conventional histomorphology and immunophenotype. Many specific genetic aberrations including chromosomal translocations have been identified in various sarcomas, which can be detected by fluorescence in situ hybridization and polymerase chain reaction analysis. Next-generation sequencing-based RNA sequencing can screen multiple sarcoma-specific chromosome translocations/fusion genes in 1 test, which is especially useful for sarcoma without obvious differentiation. In this report, we utilized RNA sequencing on formalin-fixed paraffin-embedded (FFPE) specimens to investigate the possibility of diagnosing sarcomas by identifying disease-specific fusion genes. Targeted RNA sequencing was performed on 6 sarcoma cases. The expected genetic alterations (clear cell sarcoma/EWSR1-ATF1, Ewing sarcoma/EWSR1-FLI1, myxoid liposarcoma/DDIT3-FUS) in four cases were detected and confirmed by secondary tests. Interestingly, three SS18 fusion genes (SS18-SSX2B, SS18-SSX2, and SS18-SSX4) were identified in a synovial sarcoma case. A rare fusion gene (EWSR1-PATZ1) was identified in a morphologically challenging case; which enabled us to establish the diagnosis of low grade glioneural tumor. In conclusion, RNA sequencing on FFPE specimen is a reliable method in establishing the diagnosis of sarcoma in daily practice.
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http://dx.doi.org/10.1097/MD.0000000000016031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6636967PMC
June 2019

Inactivation of Cooperates with Losses of and to Drive the Development of Pleural Malignant Mesothelioma in Conditional Mouse Models.

Cancer Res 2019 08 31;79(16):4113-4123. Epub 2019 May 31.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.

Pleural malignant mesothelioma is a therapy-resistant cancer affecting the serosal lining of the thoracic cavity. Mutations/deletions of , and are the most frequent genetic lesions in human malignant mesothelioma. We introduced various combinations of these deletions in the pleura of conditional knockout (CKO) mice, focusing on the contribution of loss. While homozygous CKO of , or alone gave rise to few or no malignant mesotheliomas, inactivation of cooperated with loss of either or to drive development of malignant mesothelioma in approximately 20% of double-CKO mice, and a high incidence (22/26, 85%) of malignant mesotheliomas was observed in (triple)-CKO mice. Malignant mesothelioma onset was rapid in triple-CKO mice, with a median survival of only 12 weeks, and malignant mesotheliomas from these mice were consistently high-grade and invasive. Adenoviral-Cre treatment of normal mesothelial cells from CKO mice, but not from mice with knockout of one or any two of these genes, resulted in robust spheroid formation , suggesting that mesothelial cells from mice have stem cell-like potential. RNA-seq analysis of malignant mesotheliomas from triple-CKO mice revealed enrichment of genes transcriptionally regulated by the polycomb repressive complex 2 (PRC2) and others previously implicated in known Bap1-related cellular processes. These data demonstrate that somatic inactivation of , and results in rapid, aggressive malignant mesotheliomas, and that deletion of contributes to tumor development, in part, by loss of PRC2-mediated repression of tumorigenic target genes and by acquisition of stem cell potential, suggesting a potential avenue for therapeutic intervention. SIGNIFICANCE: Combinatorial deletions of , and result in aggressive mesotheliomas, with loss contributing to tumorigenesis by circumventing PRC2-mediated repression of oncogenic target genes.
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http://dx.doi.org/10.1158/0008-5472.CAN-18-4093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6697648PMC
August 2019

Detecting MYB and MYBL1 fusion genes in tracheobronchial adenoid cystic carcinoma by targeted RNA-sequencing.

Mod Pathol 2019 10 25;32(10):1416-1420. Epub 2019 Apr 25.

Department of Pathology, Fox Chase Cancer Center, Philadelphia, USA.

Primary tracheobronchial adenoid cystic carcinoma is rare, accounting for less than 1% of all lung tumors. Many adenoid cystic carcinomas have been reported to have a specific chromosome translocation t(6;9)/MYB-NFIB. More recently, t(8;9)/MYBL1-NFIB gene fusion was reported in salivary gland adenoid cystic carcinomas which lacked a t(6;9)/MYB-NFIB. Two prior studies showed t(6;9)/MYB-NFIB in tracheobronchial adenoid cystic carcinoma; however, only rare cases of MYBL1 rearrangement have been reported in this carcinoma. In this study, we used targeted RNA sequencing to investigate fusion genes in tracheobronchial adenoid cystic carcinoma at our institution. Fusions of either MYB or MYBL1 genes were detected in 7 of 7 carcinomas. Three cases had MYB-NFIB, and 3 had MYBL1-NFIB. The remaining case showed a rare MYBL1-RAD51B fusion. These findings suggest that rearrangement involving MYB or MYBL1 is a hallmark of tracheobronchial adenoid cystic carcinoma.
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http://dx.doi.org/10.1038/s41379-019-0277-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6763356PMC
October 2019

Thymine DNA glycosylase as a novel target for melanoma.

Oncogene 2019 05 23;38(19):3710-3728. Epub 2019 Jan 23.

Cancer Epigenetics Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA, 19111, USA.

Melanoma is an aggressive neoplasm with increasing incidence that is classified by the NCI as a recalcitrant cancer, i.e., a cancer with poor prognosis, lacking progress in diagnosis and treatment. In addition to conventional therapy, melanoma treatment is currently based on targeting the BRAF/MEK/ERK signaling pathway and immune checkpoints. As drug resistance remains a major obstacle to treatment success, advanced therapeutic approaches based on novel targets are still urgently needed. We reasoned that the base excision repair enzyme thymine DNA glycosylase (TDG) could be such a target for its dual role in safeguarding the genome and the epigenome, by performing the last of the multiple steps in DNA demethylation. Here we show that TDG knockdown in melanoma cell lines causes cell cycle arrest, senescence, and death by mitotic alterations; alters the transcriptome and methylome; and impairs xenograft tumor formation. Importantly, untransformed melanocytes are minimally affected by TDG knockdown, and adult mice with conditional knockout of Tdg are viable. Candidate TDG inhibitors, identified through a high-throughput fluorescence-based screen, reduced viability and clonogenic capacity of melanoma cell lines and increased cellular levels of 5-carboxylcytosine, the last intermediate in DNA demethylation, indicating successful on-target activity. These findings suggest that TDG may provide critical functions specific to cancer cells that make it a highly suitable anti-melanoma drug target. By potentially disrupting both DNA repair and the epigenetic state, targeting TDG may represent a completely new approach to melanoma therapy.
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http://dx.doi.org/10.1038/s41388-018-0640-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6563616PMC
May 2019

NEAT1-TFE3 and KAT6A-TFE3 renal cell carcinomas, new members of MiT family translocation renal cell carcinoma.

Mod Pathol 2019 05 8;32(5):710-716. Epub 2019 Jan 8.

Department of Pathology, Fox Chase Cancer Center, Philadelphia, PA, 19111, USA.

Microphthalmia-associated transcription factor (MiT) family translocation renal cell carcinoma harbors variable gene fusions involving either TFE3 or TFEB genes. Multiple 5' fusion partners for TFE3 have been reported, including ASPSCR1, CLTC, DVL2, LUC7L3, KHSRP, PRCC, PARP14, NONO, SFPQ1, MED15, and RBM10. Each of these fusion genes activates TFE3 transcription which can be detected by immunostaining. Using targeted RNA-sequencing, TFE3 fusion gene partners were identified in 5 cases of TFE3 immunohistochemistry positive translocation renal cell carcinoma. Three cases demonstrated known fusions: ASPSCR1-TFE3, MED15-TFE3 and RBM10-TFE3. However, two cases showed unreported NEAT1-TFE3 and KAT6A-TFE3 fusion transcripts. The NEAT1-TFE3 RCC arose in a 59-year-old male; which demonstrated overlapping morphological features seen in NEAT2(MALAT1)-TFEB t(6;11) renal cell carcinoma, including biphasic alveolar/nested tumor cells with eosinophilic cytoplasm. The KAT6A-TFE3 renal cell carcinoma demonstrated typical morphological features of TFE3/Xp11 renal cell carcinoma including papillae, eosinophilic cytoplasm with focal clearing and abundant psammoma bodies. KAT6A gene fusion was reported in some cases of acute myeloid leukemia, which has not been previously reported in solid tumors. This report highlights the genetic complexity of TFE3 translocation renal cell carcinoma; and RNA-sequencing is a powerful approach for elucidating the underlying genetic alterations.
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http://dx.doi.org/10.1038/s41379-018-0191-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6486435PMC
May 2019

Comprehensive Study of the Clinical Phenotype of Germline BAP1 Variant-Carrying Families Worldwide.

J Natl Cancer Inst 2018 12;110(12):1328-1341

Medical Oncology Unit, Ospedale Policlinico San Martino, Genoa, Italy.

Background: The BRCA1-associated protein-1 (BAP1) tumor predisposition syndrome (BAP1-TPDS) is a hereditary tumor syndrome caused by germline pathogenic variants in BAP1 encoding a tumor suppressor associated with uveal melanoma, mesothelioma, cutaneous melanoma, renal cell carcinoma, and cutaneous BAP1-inactivated melanocytic tumors. However, the full spectrum of tumors associated with the syndrome is yet to be determined. Improved understanding of the BAP1-TPDS is crucial for appropriate clinical management of BAP1 germline variant carriers and their families, including genetic counseling and surveillance for new tumors.

Methods: We collated germline variant status, tumor diagnoses, and information on BAP1 immunohistochemistry or loss of somatic heterozygosity on 106 published and 75 unpublished BAP1 germline variant-positive families worldwide to better characterize the genotypes and phenotypes associated with the BAP1-TPDS. Tumor spectrum and ages of onset were compared between missense and null variants. All statistical tests were two-sided.

Results: The 181 families carried 140 unique BAP1 germline variants. The collated data confirmed the core tumor spectrum associated with the BAP1-TPDS and showed that some families carrying missense variants can exhibit this phenotype. A variety of noncore BAP1-TPDS -associated tumors were found in families of variant carriers. Median ages of onset of core tumor types were lower in null than missense variant carriers for all tumors combined (P < .001), mesothelioma (P < .001), cutaneous melanoma (P < .001), and nonmelanoma skin cancer (P < .001).

Conclusions: This analysis substantially increases the number of pathogenic BAP1 germline variants and refines the phenotype. It highlights the need for a curated registry of germline variant carriers for proper assessment of the clinical phenotype of the BAP1-TPDS and pathogenicity of new variants, thus guiding management of patients and informing areas requiring further research.
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http://dx.doi.org/10.1093/jnci/djy171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6292796PMC
December 2018

Multiple tumor suppressors regulate a HIF-dependent negative feedback loop via ISGF3 in human clear cell renal cancer.

Elife 2018 10 25;7. Epub 2018 Oct 25.

Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Pennsylvania, United States.

Whereas inactivation is a primary event in clear cell renal cell carcinoma (ccRCC), the precise mechanism(s) of how this interacts with the secondary mutations in tumor suppressor genes, including , /, , and/or , remains unclear. Gene expression analyses reveal that VHL, PBRM1, or KDM5C share a common regulation of interferon response expression signature. Loss of HIF2α, PBRM1, or KDM5C in cells reduces the expression of interferon stimulated gene factor 3 (ISGF3), a transcription factor that regulates the interferon signature. Moreover, loss of SETD2 or BAP1 also reduces the ISGF3 level. Finally, ISGF3 is strongly tumor-suppressive in a xenograft model as its loss significantly enhances tumor growth. Conversely, reactivation of ISGF3 retards tumor growth by PBRM1-deficient ccRCC cells. Thus after inactivation, HIF induces ISGF3, which is reversed by the loss of secondary tumor suppressors, suggesting that this is a key negative feedback loop in ccRCC.
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http://dx.doi.org/10.7554/eLife.37925DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234029PMC
October 2018

BRCA1 Mutation-Specific Responses to 53BP1 Loss-Induced Homologous Recombination and PARP Inhibitor Resistance.

Cell Rep 2018 09;24(13):3513-3527.e7

Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA. Electronic address:

BRCA1 functions in homologous recombination (HR) both up- and downstream of DNA end resection. However, in cells with 53BP1 gene knockout (KO), BRCA1 is dispensable for the initiation of resection, but whether BRCA1 activity is entirely redundant after end resection is unclear. Here, we found that 53bp1 KO rescued the embryonic viability of a Brca1 mouse model that harbors a stop codon in the coiled-coil domain. However, Brca1;53bp1 mice were susceptible to tumor formation, lacked Rad51 foci, and were sensitive to PARP inhibitor (PARPi) treatment, indicative of suboptimal HR. Furthermore, BRCA1 mutant cancer cell lines were dependent on truncated BRCA1 proteins that retained the ability to interact with PALB2 for 53BP1 KO induced RAD51 foci and PARPi resistance. Our data suggest that the overall efficiency of 53BP1 loss of function induced HR may be BRCA1 mutation dependent. In the setting of 53BP1 KO, hypomorphic BRCA1 proteins are active downstream of end resection, promoting RAD51 loading and PARPi resistance.
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http://dx.doi.org/10.1016/j.celrep.2018.08.086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6219632PMC
September 2018

Inactivation of Tp53 and Pten drives rapid development of pleural and peritoneal malignant mesotheliomas.

J Cell Physiol 2018 11 15;233(11):8952-8961. Epub 2018 Jun 15.

Cancer Biology Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania.

Malignant mesothelioma (MM) is a therapy-resistant cancer arising primarily from the lining of the pleural and peritoneal cavities. The most frequently altered genes in human MM are cyclin-dependent kinase inhibitor 2A (CDKN2A), which encodes components of the p53 (p14ARF) and RB (p16INK4A) pathways, BRCA1-associated protein 1 (BAP1), and neurofibromatosis 2 (NF2). Furthermore, the p53 gene (TP53) itself is mutated in ~15% of MMs. In many MMs, the PI3K-PTEN-AKT-mTOR signaling node is hyperactivated, which contributes to tumor cell survival and therapeutic resistance. Here, we demonstrate that the inactivation of both Tp53 and Pten in the mouse mesothelium is sufficient to rapidly drive aggressive MMs. Pten ;Tp53 mice injected intraperitoneally or intrapleurally with adenovirus-expressing Cre recombinase developed high rates of peritoneal and pleural MMs (92% of mice with a median latency of 9.4 weeks and 56% of mice with a median latency of 19.3 weeks, respectively). MM cells from these mice showed consistent activation of Akt-mTor signaling, chromosome breakage or aneuploidy, and upregulation of Myc; occasional downregulation of Bap1 was also observed. Collectively, these findings suggest that when Pten and Tp53 are lost in combination in mesothelial cells, DNA damage is not adequately repaired and genomic instability is widespread, whereas the activation of Akt due to Pten loss protects genomically damaged cells from apoptosis, thereby increasing the likelihood of tumor formation. Additionally, the mining of an online dataset (The Cancer Genome Atlas) revealed codeletions of PTEN and TP53 and/or CDKN2A/p14ARF in ~25% of human MMs, indicating that cooperative losses of these genes contribute to the development of a significant proportion of these aggressive neoplasms and suggesting key target pathways for therapeutic intervention.
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http://dx.doi.org/10.1002/jcp.26830DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168364PMC
November 2018

The correlation between gain of chromosome 8q and survival in patients with clear and papillary renal cell carcinoma.

Ther Adv Urol 2018 Jan 31;10(1):3-10. Epub 2017 Oct 31.

Divisions of Pathology and Cancer Biology, Fox Chase Cancer Center-Temple Health System, Philadelphia, PA, USA.

Background: The proto-oncogene , located on chromosome 8q, can be upregulated through gain of 8q, causing alteration in biology of renal cell carcinoma (RCC). The aim of this study was to evaluate the prevalence of through chromosome 8q gain and to correlate findings with cancer-specific mortality (CSM), and overall survival (OS).

Methods: Cytogenetic analysis by conventional or Chromosomal Genomic Microarray Analysis (CMA) was performed on 414 renal tumors. Nonclear and nonpapillary RCC were excluded. Impact of gain in chromosome 8q status on CSM, OS, and its correlation with clinicopathological variables were evaluated. CSM and OS were assessed using log-rank test and the Cox proportional hazards model.

Results: A total of 297 RCC tumors with cytogenetic analysis were included. Gain of 8q was detected in 18 (6.1%) tumors (9 clear cell and 9 papillary RCC), using conventional method ( 11) or CMA ( 7). Gain of 8q was associated with higher T stage ( < 0.001), grade ( < 0.001), nodal involvement ( = 0.005), and distant metastasis ( < 0.001). No association between gain of 8q and age ( = 0.23), sex ( = 0.46), and Charlson comorbidity index (CCI, = 0.59) were seen. Gain of 8q was associated with an 8.38-fold [95% confidence interval (CI), 3.83-18.34, < 0.001] and 3.31-fold (95% CI, 1.56-7.04, = 0.001) increase in CSM and decrease in OS, respectively, at a median follow up of 56 months.

Conclusion: Chromosome 8q harbors the proto-oncogene , which can be upregulated by gain of 8q. Our findings suggest that gain of 8q, can predict aggressive tumor phenotype and inferior survival in RCC.
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http://dx.doi.org/10.1177/1756287217732660DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5761913PMC
January 2018

Familial and Somatic Mutations Inactivate ASXL1/2-Mediated Allosteric Regulation of BAP1 Deubiquitinase by Targeting Multiple Independent Domains.

Cancer Res 2018 03 28;78(5):1200-1213. Epub 2017 Dec 28.

Wistar Institute, Philadelphia, Pennsylvania.

Deleterious mutations of the ubiquitin carboxy-terminal hydrolase BAP1 found in cancers are predicted to encode inactive truncated proteins, suggesting that loss of enzyme function is a primary tumorigenic mechanism. However, many tumors exhibit missense mutations or in-frame deletions or insertions, often outside the functionally critical UCH domain in this tumor suppressor protein. Thus, precisely how these mutations inactivate BAP1 is unknown. Here, we show how these mutations affect BAP1 interactions with the Polycomb group-like protein, ASXL2, using combinations of computational modeling technology, molecular biology, and reconstitution biochemistry. We found that the BAP1-ASXL2 interaction is direct and high affinity, occurring through the ASXH domain of ASXL2, an obligate partner for BAP1 enzymatic activity. The ASXH domain was the minimal domain for binding the BAP1 ULD domain, and mutations on the surfaces of predicted helices of ASXH abolished BAP1 association and stimulation of BAP1 enzymatic activity. The BAP1-UCH, BAP1-ULD, and ASXH domains formed a cooperative stable ternary complex required for deubiquitination. We defined four classes of alterations in BAP1 outside the UCH domain, each failing to productively recruit ASXH to the wild-type BAP1 catalytic site via the ULD, resulting in loss of BAP1 ubiquitin hydrolase activity. Our results indicate that many BAP1 mutations act allosterically to inhibit ASXH binding, thereby leading to loss of enzyme activity. Small-molecule approaches to reactivate latent wild-type UCH activity of these mutants might be therapeutically viable. Combined computational and biochemical approaches demonstrate that the BAP1-ASXL2 interaction is direct and high affinity and that many mutations act allosterically to inhibit BAP1-ASXL2 binding. .
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http://dx.doi.org/10.1158/0008-5472.CAN-17-2876DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6167014PMC
March 2018

Targeting MYC sensitizes malignant mesothelioma cells to PAK blockage-induced cytotoxicity.

Am J Cancer Res 2017 1;7(8):1724-1737. Epub 2017 Aug 1.

Cancer Biology Program, Fox Chase Cancer CenterPhiladelphia, Pennsylvania, USA.

Clinical management of malignant mesothelioma (MM) is very challenging due to marked resistance of this tumor to chemotherapy. Various mechanisms lead to a less than ideal drug concentration inside of MM cells, diminishing cytotoxicity. Consequently, single cytotoxic drugs achieve very modest response rates in MM patients, and combination regimens using standard and novel therapies have achieved only limited improvement in overall survival. Here, we demonstrate that MYC has either proliferative or pro-survival effects in MM cells during normal or stressed conditions, respectively. A MYC inhibitor 10058-F4 reduced MM cell proliferation via down regulation of cyclin D. Under serum starvation conditions, MM cells became quiescent, and the addition of MYC inhibitors triggered apoptosis in the resting MM cells. We also found that high concentrations of the PAK inhibitor PF3758309 killed MM cells, but the drug had only cytostatic effects at lower concentrations. These quiescent cells underwent apoptosis upon pharmacological inhibition of MYC. A novel MYC inhibitor KJ-Pyr-9 and a newer PAK inhibitor, FRAX597, also demonstrated marked cytotoxic cooperativity. Collectively, these findings demonstrate that targeting of MYC can sensitize MM cells and provide rationale for inhibition of MYC and PAK as a novel combinatory regimen for the treatment of this otherwise therapy-resistant, clinically incurable malignancy.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5574944PMC
August 2017
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