Abstract B033: Targeting acquired resistance to HIF2α inhibition in kidney cancer

Abstract

Abstract Recently, a HIF-2α inhibitor MK-6482 was developed and approved by FDA to treat certain patients with VHL disease-associated RCC. However, in preclinical studies, both intrinsic and adaptive resistance to this drug was reported, which highlights the necessity of uncovering the mechanisms underlying drug resistance and developing alternative treatments for HIF-2α inhibitor-resistant patients. To this end, we established several 786-O cell lines that are resistant to PT2399 (analog of MK-6482) treatment. To characterize the differences between sensitive and resistant cell lines, we performed RNA sequencing, Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) and CUT&RUN sequencing experiments. Through integrative analyses of all sequencing data, we identified a series of candidate genes which might contribute to the acquirement of drug resistance for further validation. We identified 2'-5'-oligoadenylate synthetase 2 (OAS2) as one of the candidate genes exhibiting both significant upregulation in RNA level and dramatically increased chromatin accessibility in the promoter region in resistant lines comparing to sensitive lines. We further validated the upregulation of OAS2 mRNA level as well as protein level in all resistant clones by RT-qPCR and western blot, respectively. OAS2 belongs to 2-5A synthetase family, which is involved in the activation of latent RNase L and degradation of viral RNA during innate immune response to viral infection. Interestingly, the other 3 members in this protein family, OAS1, OAS3 and OASL, are also significantly upregulated at RNA level in resistant cell lines, although the upregulation of chromatin accessibility is modest. Furthermore, OAS2, along with the other 3 family members, all show increased expression levels in ccRCC tumor tissues comparing to normal tissues. Therefore, we hypothesize that OAS2 protein promotes ccRCC cell proliferation under HIF-2α inhibitor treatment, thus contributing to the adaptive resistance to HIF-2α inhibitor. We will test this hypothesis through a series of loss-of-function and gain-of-function experiments, while continuing to investigate other candidate genes. Citation Format: Fangzhou Zhao, Jeremy Simon, Qing Zhang. Targeting acquired resistance to HIF2α inhibition in kidney cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr B033.