Hypoxia-inducible factor-2α (HIF-2α) is a transcription factor that frequently accumulates in clear cell renal cell carcinoma (ccRCC), resulting in constitutive activation of genes involved in carcinogenesis. Belzutifan (MK-6482) has been developed as a potent and selective small molecule antagonist of HIF-2α, but resistance to this has been reported. We identified target gene that induce resistance to the HIF-2α antagonist and evaluated the mechanism and anticancer effect in ccRCC.

First, we produced a belzutifan-resistant ccRCC cell lines (786-O and A498) by gradually increasing the concentration of belzutifan (0.1μM ~ 10μM) for 3 months. The prepared belzutifan- resistant cell lines were confirmed for resistance using immunoprecipitation (IP) and proximity ligation assay (PLA). A xenograft models were produced by subcutaneously injecting belzutifan-sensitive (plain cell lines) and resistant cell lines, and belzutifan was orally administered 3 mg/kg every day for 3 weeks. To find the target that induces resistance to belzutifan, we performed RNA sequencing (RNA-seq) with tumor tissue of xenograft. Small molecule inhibitor of target gene was used to confirm the anticancer effect.

In an experiment using IP and PLA, the binding of HIF-2α and HIF-1β was reduced by belzutifan treatment in plain 786-O and A498 cells, but this binding was not reduced by belzutifan treatment in belzutifan resistance 786-O and A498 cells. Also, in animal models, the size of tumors injected with plain cell lines was reduced by belzutifan, but the size of tumors injected with resistant cell lines did not appear to be reduced by belzutifan administration. Through RNA-seq analysis, we found that SREBP1, a transcription factor involved in lipid metabolism, was associated with belzutifan-resistance. Overexpression of SREBP1 protein and lipids was confirmed in belzutifan-resistance xenograft models. in vitro and in vivo mouse model, we confirmed that the combined treatment of the SREBP1 inhibitors fatostatin and belzutifan had an anti-tumor effect.

In this study, we found the gene SREBP1, which is involved in inducing resistance to HIF-2α antagonists in ccRCC, and confirmed that co-administration of its inhibitors fatostatin and belzutifan has an anticancer effect.