Dexamethasone inhibits stemness maintenance and enhances chemosensitivity of hepatocellular carcinoma stem cells by inducing deSUMOylation of HIF-1α and Oct4

It has been controversial whether patients with hepatocellular carcinoma (HCC) should receive glucocorticoid therapy during chemotherapy. Recent studies have demonstrated that glucocorticoids increase the therapeutic sensitivity of tumors to some chemotherapeutic drugs, but the specific mechanism remains unclear. In the present study, dexamethasone (Dex) was used to treat HCC stem cells. The results demonstrated that Dex reduced stemness maintenance and self-renewal of HCC stem cells, promoted epithelial-to-mesenchymal transition, inhibited migration and angiogenesis and, more importantly, increased cell sensitivity to the herpes simplex virus thymidine kinase/ganciclovir drug system in vitro and in vivo. Further mechanistic analyses demonstrated that Dex inhibited small ubiquitin-like modifier (SUMO) modification of several proteins in HCC stem cells, including hypoxia-inducible factor (HIF)-1α, an important hypoxia tolerance protein, and octamer-binding transcription factor 4 (Oct4), a crucial stemness maintenance protein. Inducing deSUMOylation of HIF-1α and Oct4 reduced their accumulation in the nucleus, thereby inhibiting tumor angiogenesis and stemness maintenance. These findings provide a new perspective to the study of the mechanism underlying the anti-hepatocarcinogenesis effects of Dex. Due to the few side effects of glucocorticoids at low doses and their anti-inflammatory effects, the appropriate combination of glucocorticoids and chemotherapeutic drugs is expected to improve the survival of HCC patients and their prognosis.