SENP1/HIF-1α feedback loop modulates hypoxia-induced cell proliferation, invasion, and EMT in human osteosarcoma...

Hypoxia is an element intrinsic to most solid-tumor microenvironments, including that of osteosarcoma (OS), and is associated with resistance to therapy, poor survival, and a malignant phenotype. The purpose of the present study was to investigate the role and underlying mechanism of SUMO-specific protease 1 (SENP1)/hypoxia-inducible factor-1α (HIF-1α) feedback loop in hypoxic microenvironment of OS. We observed that the expression of SENP1 was remarkably upregulated in OS cells. Additionally, there was a concomitant high expression of HIF-1α and SENP1 in MG-63 cells under a hypoxic microenvironment. Interestingly, blockage of HIF-1α repressed the enhancement of SENP1. Moreover, knockdown of SENP1 with siRNA notably inhibited cell viability and accelerated cell apoptosis accompanied by a decrease in the expression of Bcl-2 and an increase in the expression of Bax in MG-63 cells following exposure to hypoxia. Furthermore, repression of SENP1 dramatically suppressed cell invasive ability through modulating epithelial-mesenchymal transition (EMT) marked genes as reflected by the upregulation of E-cadherin, as well as the downregulation of vimentin and N-cadherin under hypoxic conditions. Most importantly, SENP1 positively regulated HIF-1α expression level in the setting of hypoxic; subsequently, depletion of SENP1 expression markedly ameliorated vascular endothelial growth factor (VEGF) production triggered by hypoxia. Taken together, positive feedback loop between HIF-1α and SENP1 in the regulating of the process of cell proliferation, invasion, and EMT in OS cells under hypoxic conditions, suggesting that the SENP1/HIF-1α axis may serve as a new potential therapeutic agent for OS treatments.