Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) cell lines treated with triptolide for 6h - RNA-seq

Small cell carcinoma of the ovary-hypercalcemic type (SCCOHT) is a rare form of ovarian cancer affecting young women and girls. Survival rates remain poor despite aggressive treatment of these patients with high-dose chemotherapy and radiation. SCCOHT is driven by loss of both SWI/SNF ATPases SMARCA4 and SMARCA2. Loss of SWI/SNF complex activity alters chromatin state, particularly at enhancers, which is believed to be crucial for oncogenesis. Super-enhancers are a distinct subset of enhancer clusters frequently associated with oncogenes in cancer. Here we discovered key distinctions between SWI/SNF binding following SMARCA4 restoration at enhancer vs. super-enhancer sites and characterized putative oncogene expression driven by super-enhancer activity. We found high sensitivity of SCCOHT cell lines to triptolide, a small molecule derived from the naturally occurring "thunder god vine" (Tripterygium wilfordii) that targets the XPB subunit of the transcription factor II H (TFIIH) complex, found at super-enhancers. Triptolide inhibits expression of many super-enhancer associated genes, and in particular, oncogenes. Notably, SALL4 expression, which is high in SCCOHT relative to other ovarian cancers and normal cell types, is significantly decreased following short triptolide treatment. In SCCOHT patient-derived xenograft models, triptolide and its prodrug derivative minnelide are particularly effective in inhibiting tumor growth. These results demonstrate the key oncogenic role of super-enhancer activity following epigenetic dysfunction in SCCOHT, which can be effectively targeted through inhibition of its functional components, such as TFIIH inhibition with triptolide.