Deciphering the molecular effects of romidepsin on germ cell tumors: DHRS2 involved in cell cycle arrest but not apoptosis or induction of romidepsin effectors

Testicular germ cell tumors mostly affect young men at age 17 – 40. Although high cure rates can be achieved by orchiectomy and chemotherapy, germ cell tumors can still be a lethal threat to young patients with metastases or therapy resistance. Thus, alternative treatment options are needed. Based on studies utilizing germ cell tumor cell lines, the histone deacetylase inhibitor romidepsin is a promising therapeutic option, showing high toxicity at very low doses towards cisplatin-resistant germ cell tumor cells, but not fibroblasts or Sertoli cells.
In this study, we extended our analysis of the molecular effects of romidepsin to deepen our understanding of the underlying mechanisms. Patients will benefit from these analyses, since detailed knowledge of the romidepsin effects allows for a better risk and side-effect assessment.
We screened for changes in histone acetylation of specific lysine residues and analyzed changes in the DNA methylation landscape after romidepsin treatment of the germ cell tumor proxy cell lines TCam-2, 2102EP, NCCIT and JAR, while human fibroblasts were used as controls. Additionally, we focused on the role of the dehydrogenase/reductase DHRS2, which was strongly upregulated in romidepsin treated cells, by generating DHRS2-deficient TCam-2 cells using CRISPR/Cas9 gene editing. We show that DHRS2 is dispensable for upregulation of romidepsin effectors (GADD45B,DUSP1, ZFP36, ATF3, FOS, CDKN1A,ID2) but contributes to induction of cell cycle arrest. Finally, we show that a combinatory treatment of romidepsin plus the gluccocorticoid dexamethasone further boosts expression of the romidepsin effectors and reduces viability of germ cell tumor cells more strongly than under single agent treatment. Thus, romidepsin and dexamethasone might represent a new combinatorial approach for treatment of GCT.