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Downregulation of polycomb repressive complex 2 mediates cisplatin acquired resistant in testicular germ cell tumors

ABSTRACT: A greater understanding of the hypersensitivity and curability of testicular germ cell tumors (TGCTs) has the potential to inform strategies to sensitize other solid tumors to conventional chemotherapies. More than 80% of metastatic TGCT patients are cured with cisplatin-based chemotherapy. However, resistance can occur, which results in poor outcomes. The mechanisms of cisplatin hypersensitivity and resistance in these tumors and embryonal carcinoma (EC), the stem cells of TGCTs, remain largely undefined. To study the mechanisms of cisplatin acquired resistance we generated a large panel of independently derived, acquired resistant clones from three distinct parental EC models employing a protocol designed to match standard of care regimens of TGCT patients. Transcriptomics revealed highly significant alterations shared between resistant cells regardless of their parental origin. This included a highly significant enrichment of genes normally repressed by H3K27 methylation and the polycomb repressive complex 2 (PRC2) which correlated with a substantial decrease in global H3K27me3, H2AK119 ubiquitination and expression of BMI1. Importantly repression of H3K27 methylation with the EZH2 inhibitor GSK-126 conferred cisplatin resistance to parental cells while induction of H3K27 methylation with the histone lysine demethylase inhibitor GSK-J4 resulted in increased cisplatin sensitivity to resistant cells. A gene signature based on H3K27me gene enrichment was associated with an increased rate of recurrent/progressive disease in testicular cancer patients. Our data indicates that repression of H3K27 methylation may be a mechanism of cisplatin acquired resistance in TGCTs and that restoration of PRC2 complex function could be a viable approach to overcome treatment failure.

ORGANISM(S): Homo sapiens

PROVIDER: GSE129696 | GEO | 2019/11/11

REPOSITORIES: GEO

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Project description:The development of chemo-resistance has dramatically limited the clinical efficiency of platinum-based therapy. Although many resistant mechanisms have been demonstrated, genetic/molecular alterations responsible for drug resistance in the majority of clinical cases has not been identified. We analyzed three pairs of testicular germ cell tumor (TGCT) cell lines using Affymetrix expression microarrays to identify differential expressed genes. Then the expression of CCND1/CyclinD1, selected from the microarray analysis, was determined in cisplatin sensitive and resistance cancer samples including TGCTs, ovarian and prostate cancers by quantitative reverse transcription PCR analysis (qRT-PCR). Finally, we determined the gene knocked-down effect of CyclinD1. Expression microarray study revealed a limited number of differentially expressed genes across all three cell lines when comparing the parental and resistant cells. Among them, CyclinD1 was the most significantly differentially expressed gene. Importantly, we found that, in clinical TGCT samples, the overall expression level of cyclinD1 is higher in resistant cases compared to those sensitive samples (9/12 in the resistant group and only 3/8 in the sensitive group). We also found that cyclinD1 expressed dozens of fold higher in the resistant than in the sensitive ovarian cancer cell lines and dramatically overexpressed in prostate cancer. We re-sensitized the resistant cells by knocking-down cyclinD1. We demonstrated that deregulation of cyclinD1 is the major cause of TGCT cisplatin resistance and it may also be commonly involved in other human cancers. Combined cyclinD1 inhibition and cisplatin chemotherapy may be used clinically to treat the large number of cyclinD1 deregulated resistant tumors. RNA from three paired parental and cisplatin-resistant TGCT cell lines was extracted and analysed by Affymetrix gene expression microarray profiling (Human Genome U133 plus 2.0 arrays). Expression changes associated with the resistant phenotype were identified by comparing the three cisplatin-resistant derivatives to their parental counterparts.

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Downregulation of polycomb repressive complex 2 mediates cisplatin acquired resistant in testicular germ cell tumors

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