USP29-mediated HIF1a stabilization promotes Sorafenib resistance of hepatocellular carcinoma cells by upregulating glycolysis

Understanding the mechanisms underlying evasive resistance in cancer is an unmet medical need to improve the efficacy of current therapies. In hepatocellular carcinoma (HCC), aberrant expression of hypoxia inducible factor 1 a (HIF1a) and increased aerobic glycolysis metabolism represent drivers of the development of resistance to therapy with the multi-kinase inhibitor Sorafenib. However, it has remained unknown how HIF1a is activated and how its activity and the subsequent induction of aerobic glycolysis promotes Sorafenib resistance in HCC. Here, we report the ubiquitin-specific peptidase USP29 as a new regulator of HIF1a and of aerobic glycolysis during the development of Sorafenib resistance in HCC. In particular, we have identified USP29 as a critical deubiquitylase (DUB) of HIF1a, which directly deubiquitinates and stabilizes HIF1a and, thus, promotes its transcriptional activity. Among the transcriptional targets of HIF1a is the gene encoding for hexokinase 2 (HK2), a key enzyme of the glycolytic pathway. The absence of USP29, and thus of HIF1a transcriptional activity, reduces the levels of aerobic glycolysis and reinstalls the sensitivity to Sorafenib treatment in Sorafenib-resistant HCC cells in vitro and in xenograft transplantation mouse models in vivo. Notably, the absence of USP29 and high HK2 expression levels correlate with the response of HCC patients to Sorafenib therapy. Together, the data demonstrate that, as a DUB of HIF1a, USP29 promotes Sorafenib resistance in HCC cells by upregulating glycolysis, thereby opening new avenues for therapeutically targeting Sorafenib-resistant HCC in patients. Overall design: RNA-Seq of Huh7-Parental and established Huh7-IR, Huh7-CR cell lines