Deregulation Of Gata6 Defines Stem Cell-like Properties In Hepatocellular Carcinoma

Abstract

Background: Stem cell-like properties in hepatocellular carcinoma (HCC) have been demonstrated to play a major role in contributing to tumor recurrence, metastasis and chemoresistance. Accumulating evidence has highlighted the plasticity of mature hepatocytes through dedifferentiation in HCC model. Hereby we studied the role of GATA6, a member of the GATA transcription factors, in liver cancer. GATA6 is essential for maintaining hepatocyte differentiation. Aberrant expression of GATA6 had been reported in human cancers particularly from endoderm-derived organs. However knowledge on GATA6 in hepatocarcinogenesis is scarce. Methods: GATA6 expression was examined by qPCR assay and immunofluorescent staining. Cell proliferation, transwell migratory and matrigel invasion assays were employed to study the cancer properties in vitro. Self-renewal ability in vitro was assessed by tumorsphere formation assay. In vivo tumorigenicity and self-renewal was investigated by a subcutaneous inoculation model with NOD/SCID mice. Transcription regulatory mechanism was elucidated by ChIP-qPCR and luciferase reporter assays. Results: GATA6 expression was significantly downregulated in HCC tissues versus non-tumoral liver tissues in our clinical cohort. The downregulation, as observed in 46% HCC cases, was associated with poorer tumor cell differentiation and poorer disease-free survival. Silencing of GATA6 in HCC cells by a lentiviral-based approach decreased the expression of HNF4α and functionally augmented proliferation, self-renewal, migration and invasion of HCC cells in vitro. Consistently, suppression of GATA6 enhanced in vivo tumorigenicity and self-renewal on serial transplantation. On the metabolic phenotype, knockdown of GATA6 promoted glycolysis in HCC cells as evidenced by upregulation of glycolytic markers and increased glucose uptake. The opposite effects were observed upon overexpression of GATA6 in HCC cells. Mechanistically, pyruvate kinase M2 (PKM2), a key glycolytic enzyme, was demonstrated to be a direct transcriptional target of GATA6. Conclusion: Our findings show that downregulation of GATA6 promotes the reprogramming of HCC cells to a less differentiated state and the acquisition of stem cell-like properties including rewiring of cancer cell metabolism. In addition, GATA6 is a potential prognosticator and therapeutic target for HCC.