1. Clinical Medicine Research Center, Xinqiao Hospital, Army Medical University, Chongqing 400037, China.
2. Department of Medical Oncology, Chongqing University Cancer Hospital, Chongqing 400030, China.
3. Department of Hepatobiliary Surgery, Xinqiao Hospital, Army Medical University, Chongqing 400037, China.
4. Department of Oncology, The Third Affiliated Hospital, Chongqing Medical University, Chongqing 401120, China.
#These authors contributed equally to this work.
Background & Aims: Liver cancer stem cells (LCSCs) mediate therapeutic resistance and correlate with poor outcomes in patients with hepatocellular carcinoma (HCC). Fibroblast growth factor (FGF)-19 is a crucial oncogenic driver gene in HCC and correlates with poor prognosis. However, whether FGF19 signaling regulates the self-renewal of LCSCs is unknown.
Methods: LCSCs were enriched by serum-free suspension. Self-renewal of LCSCs were characterized by sphere formation assay, clonogenicity assay, sorafenib resistance assay and tumorigenic potential assays. Ca2+ image was employed to determine the intracellular concentration of Ca2+. Gain- and loss-of function studies were applied to explore the role of FGF19 signaling in the self-renewal of LCSCs.
Results: FGF19 was up-regulated in LCSCs, and positively correlated with certain self-renewal related genes in HCC. Silencing FGF19 suppressed self-renewal of LCSCs, whereas overexpressing FGF19 facilitated CSCs-like properties via activation of FGF receptor (FGFR)-4 in none-LCSCs. Mechanistically, FGF19/FGFR4 signaling stimulated store-operated Ca2+ entry (SOCE) through both the PLCγ and ERK1/2 pathways. Subsequently, SOCE-calcineurin signaling promoted the activation and translocation of nuclear factors of activated T cells (NFAT)-c2, which transcriptionally activated the expression of stemness-related genes (e.g., NANOG, OCT4 and SOX2), as well as FGF19. Furthermore, blockade of FGF19/FGFR4-NFATc2 signaling observably suppressed the self-renewal of LCSCs.
Conclusions: FGF19/FGFR4 axis promotes the self-renewal of LCSCs via activating SOCE/NFATc2 pathway; in turn, NFATc2 transcriptionally activates FGF19 expression. Targeting this signaling circuit represents a potential strategy for improving the therapeutic efficacy of HCC.
Keywords: FGF19, self-renewal, SOCE, NFATc2, LCSCs