Chenxia Lu1, Hanwen Lu2, Mi Chen2, Junyi Zhang2, Dan Qin2, Shenghui Liu2, Xiaodong Li3, Lisheng Zhang4. 1. The Clinical Medical College of Traditional Chinese Medicine, Hubei University of Chinese Medicine, Wuhan, 430065, China. 2. College of Veterinary Medicine/College of Biomedicine and Health, Huazhong Agricultural University, Wuhan, 430070, China. 3. Hubei Provincial Hospital of TCM, Hubei Provincial Academy of TCM, Wuhan, 430061, China. 4. College of Veterinary Medicine/College of Biomedicine and Health, Huazhong Agricultural University, Wuhan, 430070, China. lishengzhang@mail.hzau.edu.cn.
Abstract
BACKGROUND: Asymmetrical cell division (ACD) maintains the proper number of stem cells to ensure self-renewal. The rate of symmetric division increases as more cancer stem cells (CSCs) become malignant; however, the signaling pathway network involved in CSC division remains elusive. FXR (Farnesoid X receptor), a ligand-activated transcription factor, has several anti-tumor effects and has been shown to target CSCs. Here, we aimed at evaluating the role of FXR in the regulation of the cell division of CSCs. METHODS: The FXR target gene and downstream molecular mechanisms were confirmed by qRT-PCR, Western blot, luciferase reporter assay, EMAS, Chip, and IF analyses. Pulse-chase BrdU labeling and paired-cell experiments were used to detect the cell division of liver CSCs. Gain- and loss-of-function experiments in Huh7 cells and mouse models were performed to support findings and elucidate the function and underlying mechanisms of FXR-Notch1 in liver CSC division. RESULTS: We demonstrated that activation of Notch1 was significantly elevated in the livers of hepatocellular carcinoma (HCC) in Farnesoid X receptor-knockout (FXR-KO) mice and that FXR expression negatively correlated with Notch1 level during chronic liver injury. Activation of FXR induced the asymmetric divisions of Sox9+ liver CSCs and ameliorated liver injury. Mechanistically, FXR directs Sox9+ liver CSCs from symmetry to asymmetry via inhibition of Notch1 expression and activity. Deletion of FXR signaling or over-expression of Notch1 greatly increased Notch1 expression and activity along with ACD reduction. FXR inhibited Notch1 expression by directly binding to its promoter FXRE. FXR also positively regulated Numb expression, contributing to a feedback circuit, which decreased Notch1 activity and directed ACD. CONCLUSION: Our findings suggest that FXR represses Notch1 expression and directs ACD of Sox9+ cells to prevent the development of liver cancer.
BACKGROUND: Asymmetrical cell division (ACD) maintains the proper number of stem cells to ensure self-renewal. The rate of symmetric division increases as more cancer stem cells (CSCs) become malignant; however, the signaling pathway network involved in CSC division remains elusive. FXR (Farnesoid X receptor), a ligand-activated transcription factor, has several anti-tumor effects and has been shown to target CSCs. Here, we aimed at evaluating the role of FXR in the regulation of the cell division of CSCs. METHODS: The FXR target gene and downstream molecular mechanisms were confirmed by qRT-PCR, Western blot, luciferase reporter assay, EMAS, Chip, and IF analyses. Pulse-chase BrdU labeling and paired-cell experiments were used to detect the cell division of liver CSCs. Gain- and loss-of-function experiments in Huh7 cells and mouse models were performed to support findings and elucidate the function and underlying mechanisms of FXR-Notch1 in liver CSC division. RESULTS: We demonstrated that activation of Notch1 was significantly elevated in the livers of hepatocellular carcinoma (HCC) in Farnesoid X receptor-knockout (FXR-KO) mice and that FXR expression negatively correlated with Notch1 level during chronic liver injury. Activation of FXR induced the asymmetric divisions of Sox9+ liver CSCs and ameliorated liver injury. Mechanistically, FXR directs Sox9+ liver CSCs from symmetry to asymmetry via inhibition of Notch1 expression and activity. Deletion of FXR signaling or over-expression of Notch1 greatly increased Notch1 expression and activity along with ACD reduction. FXR inhibited Notch1 expression by directly binding to its promoter FXRE. FXR also positively regulated Numb expression, contributing to a feedback circuit, which decreased Notch1 activity and directed ACD. CONCLUSION: Our findings suggest that FXR represses Notch1 expression and directs ACD of Sox9+ cells to prevent the development of liver cancer.
Authors: Terence Kin Wah Lee; Antonia Castilho; Vincent Chi Ho Cheung; Kwan Ho Tang; Stephanie Ma; Irene Oi Lin Ng Journal: Cell Stem Cell Date: 2011-07-08 Impact factor: 24.633
Authors: Sista Sugiarto; Anders I Persson; Elena Gonzalez Munoz; Markus Waldhuber; Chrystelle Lamagna; Noemi Andor; Patrizia Hanecker; Jennifer Ayers-Ringler; Joanna Phillips; Jason Siu; Daniel A Lim; Scott Vandenberg; William Stallcup; Mitchel S Berger; Gabriele Bergers; William A Weiss; Claudia Petritsch Journal: Cancer Cell Date: 2011-09-13 Impact factor: 31.743