HBO1 determines epithelial-mesenchymal transition and promotes immunotherapy resistance in ovarian cancer cells.

PURPOSE: Epithelial-mesenchymal transition (EMT) plays critical roles in tumor progress and treatment resistance of ovarian cancer (OC), resulting in the most deadly gynecological cancer in women. However, the cell-intrinsic mechanism underlying EMT in OC remains less illuminated. METHOD: SKOV3, the OC cell line, was treated with TGF-β to induce EMT or with SB431542, an inhibitor of the TGF-β signaling pathway, to reduce migration. The function of HBO1 in EMT was confirmed by knock-down or overexpression of HBO1 in SKOV3 cells. The role of HBO1 in cell proliferation and apoptosis of SKOV3 cells was analyzed by flow cytometry. The whole-genome transcriptome was used to compare significantly different genes in control and HBO1-KD SKOV3 cells. T-cell cytotoxicity assays were measured by an IVIS spectrum. The chromatin binding of HBO1 was investigated using CUT&Tag-seq. RESULTS: Here, we show that HBO1, a MYST histone acetyltransferase (HAT), is a cell-intrinsic determinant for EMT in OC cells. HBO1 is greatly elevated during TGF-β-triggered EMT in SKOV3 OC cells as well as in later stages of clinical OC samples. HBO1 Knock-down (KD) in SKOV3 cells blocks TGF-β-triggered EMT, migration, invasion and tumor formation in vivo. Interestingly, HBO1 KD in SKOV3 cells suppresses their resistance to CAR-T cells. Mechanistically, HBO1 co-binds the gene sets responsible for EMT with SMAD4 and orchestrates a gene regulatory network critical for tumor progression in SKOV3 cells. CONCLUSION: HBO1 plays an essential onco-factor to drive EMT and promote the immunotherapy resistance in ovarian cancer cells. Together, we reveal a critical role of HBO1 mediated epigenetic mechanism in OC progression, providing an insight into designing new therapy strategies.