Abstract 312: Autophagy mediates HIF2α degradation and suppresses renal tumorigenesis

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Autophagy is a conserved process involved in lysosomal degradation of protein aggregates and damaged organelles. The role of autophagy in cancer is a topic of intense debate, and the underlying mechanism is still not clear. Here we reported that the hypoxia inducible factor 2α (HIF2α), an oncogenic transcription factor implicated in renal tumorigenesis, was in part constitutively degraded by autophagy. HIF2α interacts with autophagy protein LC3, autophagy receptor p62, and lysosome protein LAMP1. Inhibition of autophagy results in HIF2α accumulation, while induction of autophagy promotes HIF2α degradation. The E3 ubiquitin ligase activity of the von Hippel-Lindau (VHL) is required for autophagic degradation of HIF2α. There is a complementary interaction between the proteasome and autophagy in HIF2α degradation. Autophagy inactivation in ATG5 knockout cells redirects HIF2α to proteasomal degradation, while proteasome inhibition induced autophagy and favored the HIF2α-p62 interaction. Importantly, we reported that clear cell renal cell carcinoma (ccRCC) was frequently associated with mono-allelic loss and/or mutation of autophagy related gene ATG7, and low expression level of autophagy genes correlated with ccRCC progression. This study sheds light on the anticancer role for autophagy in ccRCC tumorigenesis, and reveals constitutive autophagic degradation of HIF2α as a novel tumor suppression mechanism. Citation Format: Xian-De Liu, Jun Yao, Durga N. Tripathi, Zhiyong Ding, Yi Xu, Mianen Sun, Jiangwei Zhang, Shanshan Bai, Peter German, Anh Hoang, Lijun Zhou, Xuesong Zhang, Claudio J. Conti, Eleni Efstathiou, Tony N. Eissa, Gordon B. Mills, Cheryl L. Walker, Eric Jonasch. Autophagy mediates HIF2α degradation and suppresses renal tumorigenesis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 312. doi:10.1158/1538-7445.AM2014-312