Sestrin2 inhibits hypoxia-inducible factor-1α accumulation via AMPK-mediated prolyl hydroxylase regulation

Abstract

Sestrin2 (SESN2) is an antioxidant protein that modulates cellular redox homeostasis through regeneration of peroxiredoxins. It has beneficial effects in oxidative or metabolic stress conditions as an upstream regulator of AMP-activated protein kinase (AMPK). Since hypoxia causes oxidative and metabolic stress, this study investigated the effect of SESN2 on signaling pathways altered by hypoxia in colon cancer cells. SESN2 overexpression in HEK293 cells inhibited hypoxia-inducible factor-1α (HIF-1α), which plays a crucial role in tumor growth and development in hypoxia. Moreover, infection with adenovirus-SESN2 (Ad-SESN2) decreased hypoxia or CoCl₂-induced HIF-1α accumulation in colorectal cancer cells. Ad-SESN2 also reduced CoCl₂-induced hypoxia response element (HRE)-luciferase activity and mRNA level of HIF-1α-driven genes. Furthermore, Ad-SESN2 infected cells showed anti-metastatic effects in serum-induced cell migration and invasion in vitro. Ad-SESN2 facilitated the ubiquitination of HIF-1α protein and increased hydroxyl-HIF-1α (OH-HIF-1α) level. In contrast, treatment with dimethyloxalylglycine (DMOG), an inhibitor of prolyl hydroxylase (PHD), reversed Ad-SESN2-induced OH-HIF-1α and subsequently suppressed HIF-1α level. The inhibitory effects of SESN2 on the serum-induced in vitro cell migration and invasion were also abrogated by DMOG treatment. Furthermore, knockdown of AMPKα reversed Ad-SESN2-mediated increase of OH-HIF-1α and inhibition of HIF-1α. Dominant-negative form of AMPK also restored the Ad-SESN2 mediated decrease in HIF-1α accumulation. Lastly, Ad-SESN2 suppressed tumor growth in a mouse xenograft model. Taken together, these results suggest that SESN2 increases degradation of HIF-1α via AMPK-PHD regulation that contributes to inhibition of in vitro and in vivo tumorigenesis.

Keywords: AMP-activated protein kinase; Colorectal cancer; Hypoxia-inducible factor-1α; Prolyl hydroxylase; Sestrin2.