N6-methyladenosine-induced ERR. triggers chemoresistance of cancer cells through upregulation of ABCB1 and metabolic reprogramming

Background: Drug resistance severely reduces treatment efficiency of chemotherapy and leads to poor prognosis. However, regulatory factors of chemoresistant cancer cells are largely unknown. Methods: The expression of estrogen receptor related receptors (ERRs) in chemoresistant cancer cells are checked. The roles of ERR gamma in chemoresistance are confirmed by in vitro and in vivo studies. The mechanisms responsible for ERR gamma-regulated expression of ABCB1 and CPT1B are investigated. Results: The expression of ERR gamma is upregulated in chemoresistant cancer cells. Targeted inhibition of ERR gamma restores the chemosensitivity. ERR gamma can directly bind to the promoter of ABCB1 to increase its transcription. An elevated interaction between ERR gamma and p65 in chemoresistant cells further strengthens transcription of ABCB1. Further, ERR gamma can increase the fatty acid oxidation (FAO) in chemoresistant cells via regulation of CPT1B, the rate-limiting enzyme of FAO. The upregulated ERR. in chemoresistant cancer cells might be due to increased levels of N6-methyladenosine (m(6)A) can trigger the splicing of precursor ESRRG mRNA. Conclusions: m(6)A induced ERR gamma confers chemoresistance of cancer cells through upregulation of ABCB1 and CPT1B.