Histone variant macroH2A1 rewires carbohydrate and lipid metabolism of hepatocellular carcinoma cells towards cancer stem cells

We recently described the phenotype of HepG2 and Huh-7 hepatocellular carcinoma cells deleted for histone variant macroH2A1, which acquire cancer stem cell phenotype (Lo Re O et al., Hepatology 2017, PMID: 28913935). We found that short hairpin RNA-mediated macroH2A1 knockdown induces acquisition of CSC-like features, including the growth of significantly larger and less differentiated tumors when injected into nude mice. MacroH2A1-depleted HCC cells also exhibited reduced proliferation, resistance to chemotherapeutic agents, and stem-like metabolic changes consistent with enhanced hypoxic responses and increased glycolysis. As macroH2A1 is a potent transcriptional modifier we asked how KD of this histone variant might affect patterns of gene expression, and whether we could identify potential mechanistic links to the observed in vitro and in vivo HCC phenotypes. We obtained and validated an RNA-Seq dataset (Borghesan M et al., Cancer Res 2016, PMID: 26772755; Lo Re O et al., Hepatology 2017, PMID: 28913935), to conduct an unbiased comparison of the transcriptional profiles of HepG2 macroH2A1 KD cells and controls. Using a cut-off of 2 fold change, assessment of differentially expressed genes for macroH2A1 KD versus CTL showed no transcriptional overlap between the different HepG2 cell lines. Considering all differentially-expressed genes, there was significant enrichment (–log(p-value) > 1.3) in several functions and pathways that regulate pluripotency of human embryonic stem cells.