Role of the Hypoxia-inducible factor-1 alpha induced autophagy in the conversion of non-stem pancreatic cancer cells into CD133+ pancreatic cancer stem-like cells

Abstract

The initiation and progression of various solid tumors, including pancreatic carcinoma, are driven by a population of cells with stem cell properties, namely cancer stem cells (CSCs). Like their normal counterparts, CSCs are also believed to rely on their own microenvironment termed niches to sustain the population. Hypoxia-inducible factor-1α (HIF-1α) is a major actor in the cell survival response to hypoxia. Recently, several researchers proposed that non-stem cancer cells can convert to stem-like cells to maintain equilibrium. The present study focuses on whether non-stem pancreatic cancer cells can convert to stem-like cells and the role of HIF-1α and autophagy in modulating this conversation. The non-stem pancreatic cancer cells and pancreatic cancer stem-like cells were separated by magnetic sorting column. Intermittent hypoxia enhanced stem-like properties of non-stem pancreatic cancer cells and stimulated the levels of HIF-1α, LC3-II and Beclin. Enhanced autophagy was associated with the elevated level of HIF-1α. The conversation of non-stem pancreatic cancer cells into pancreatic cancer stem-like cells was induced by HIF-1α and autophagy. This novel finding may indicate the specific role of HIF-1α and autophagy in promoting the dynamic equilibrium between CSCs and non-CSCs. Also, it emphasizes the importance of developing therapeutic strategies targeting cancer stem cells as well as the microenvironmental influence on the tumor.