LSD1 Stimulates Cancer-Associated Fibroblasts to Drive Notch3-Dependent Self-Renewal of Liver Cancer Stem-like Cells

Cancer stem-like cells (CSC) in hepatocellular carcinoma (HCC) are thought to mediate therapeutic resistance and poor survival outcomes, but their intrinsic and extrinsic control is not well understood. In this study, we found that the chromatin modification factor LSD1 is highly expressed in HCC CSC where it decreases during differentiation. LSD1 was responsible for maintaining CSC self-renewal and tumorigenicity in HCC, and its overexpression was sufficient to drive self-renewal of non-CSC. Levels of acetylated LSD1 were low in CSC with high LSD1 activity, and these CSC were capable of self-renewal. Notch signaling activated LSD1 through induction of the sirtuin SIRT1, leading to deacetylation and activation of LSD1 and CSC self-renewal. Notably, we found that LSD1 expression was increased in cancer-associated fibroblasts (CAF) as an upstream driver of Notch3-mediated CSCself-renewal. In clinical specimens of HCC, the presence of CAF, LSD1, and Notch3 strongly associated with poor patient survival. Overall, our results reveal that CAF-induced expression of Notch3 is responsible for LSD1 activation in CSC, driving their self-renewal in HCC. Significance: These seminal findings illuminate a complex pathway in the tissue microenvironment of liver cancer, which is responsible for orchestrating the self-renewal of stem-like cancer cells, with potential implications to improve therapy and limit relapses. (C) 2018 AACR.