Therapeutical interference with the epigenetic landscape of germ cell tumors: a comparative drug study and new mechanistical insights

Abstract

Background Type II germ cell tumors (GCT) are the most common solid cancers in males of age 15 to 35 years. Treatment of these tumors includes cisplatin-based therapy achieving high cure rates, but also leading to late toxicities. As mainly young men are suffering from GCTs, late toxicities play a major role regarding life expectancy, and the development of therapy resistance emphasizes the need for alternative therapeutic options. GCTs are highly susceptible to interference with the epigenetic landscape; therefore, this study focuses on screening of drugs against epigenetic factors as a treatment option for GCTs. Results We present seven different epigenetic inhibitors efficiently decreasing cell viability in GCT cell lines including cisplatin-resistant subclones at low concentrations by targeting epigenetic modifiers and interactors, like histone deacetylases (Quisinostat), histone demethylases (JIB-04), histone methyltransferases (Chaetocin), epigenetic readers (MZ-1, LP99) and polycomb-repressive complexes (PRT4165, GSK343). Mass spectrometry-based analyses of the histone modification landscape revealed effects beyond the expected mode-of-action of each drug, suggesting a wider spectrum of activity than initially assumed. Moreover, we characterized the effects of each drug on the transcriptome of GCT cells by RNA sequencing and found common deregulations in gene expression of ion transporters and DNA-binding factors. A kinase array revealed deregulations of signaling pathways, like cAMP, JAK-STAT and WNT. Conclusion Our study identified seven drugs against epigenetic modifiers to treat cisplatin-resistant GCTs. Further, we extensively analyzed off-target effects and modes-of-action, which are important for risk assessment of the individual drugs.

SIN3‐HDAC complex‐associated factor, a chromatin remodelling gene located in the 12p amplicon, is a potential germ cell tumour‐specific oncogene

“…Hypermethylation and global remodelling of DNA methylation were reported to be key factors in mediating cisplatin resistance of testicular GCTs [34]. Drugs targeting these epigenetic modifications, including histone deacetylases, histone demethylases, histone methyltransferases, epigenetic readers and polycomb-repressive complexes, have been proposed as treatment options for GCTs [35,36]. The identification of SINHCAF as a potential oncogene specific to GCTs makes it a new target for treating GCTs.…”

Epigenetic Regulation of Driver Genes in Testicular Tumorigenesis

“…Treatment of the EC cell line P19 with the HDAC inhibitor trichostatin (TSA) inhibits cell progression [ 121 ]. A study compared treatment of germ cell tumor cell lines with seven epidrugs [ 156 ].…”

Recent Advances with KDM4 Inhibitors and Potential Applications

“…JIB-04 (compound 18 ) was identified as a KDM4/5 inhibitor (KDM4A–E IC 50 = 290–1100 nM; KDM5A IC 50 = 230 nM, ELISA assay) through cell-based screening of NCI’s diversity set library . JIB-04 blocked the proliferation of lung cancer, prostate cancer, rhabdomyosarcoma, and germ cell tumor cell lines, but not the normal cells, and suppressed tumor growth in lung cancer, breast cancer, Ewing sarcoma, hepatocellular carcinoma xenograft mouse models. Interestingly, JIB-04 is not a competitive inhibitor of 2-OG, though it bears a metal chelating moiety .…”