HBx/WDR5 enhances IGF-1 transcription in hepatocellular carcinoma cells and promotes recruitment, infiltration, and activity of Treg cells

HBV X protein (HBx), the smallest open reading frame in the hepatitis B virus (HBV) genome, can promote hepatocellular carcinoma (HCC) tumorigenesis by activating the expression of multiple oncogenes through inducing epigenetic alterations and interacting with the underlying transcriptional machinery. HBV non-infected HepG2 and Huh7 cells were transfected with HBx expression plasmids. The transcriptional, protein expression, and secretion levels of IGF-1 were detected by RT-qPCR, western blot, and ELISA, respectively. ChIP-qPCR was used to analyze the binding proteins on the IGF-1 gene. A co-culture system of HCC and Treg cells was designed using Transwell chambers. IGF-1 mRNA, protein, and secretion levels were increased in HepG2 and Huh7 cells exogenously expressing HBx. HBx was able to enter the nucleus and interact with the enhancer region of the IGF-1 gene. Levels of WDR5 and H3K4me1, which bind to the enhancer region of the IGF-1 gene, were also increased in HepG2 and Huh7 cells ectopically expressing HBx. Knockdown of WDR5 counteracted the upregulation of IGF-1 mRNA and protein levels by HBx. In the cell co-culture system, HBx/IGF-1 signaling in HCC cells promoted Treg cells expansion, IL-10 secretion, and infiltration, which was blocked by the IGF-1R inhibitor picropodophyllin. HBx/WDR5 promoted IGF-1 transcription in HCC cells through enhancers. HBx could promote Treg cell recruitment, infiltration, and activity by enhancing IGF-1 expression. IGF-1/IGF-1R signaling plays an important role in the communication between HCC cells and Treg cells. Targeting WDR or IGF-1/IGF-1R would be beneficial for the treatment of HCC.