Background: Interleukin-7 receptor (IL-7R) is involved in the abnormal function of solid tumors, but the role and regulatory mechanisms of IL-7R in HBV-related hepatocellular carcinoma (HCC) are still unclear.
Methods: Gene and protein expression levels of IL-7R were examined in hepatoma cells transfected with hepatitis B virus (HBV) plasmids and in hepatoma cells transfected with the multifunctional nonstructural protein X (HBX). The expression of HBX and IL-7R was measured by immunohistochemical analysis in HBV-related HCC tissues. The role of NF-κB and Notch1 pathways in HBX-mediated expression of IL-7R in hepatoma cells was examined. Activation of IL-7R downstream of intracellular signaling proteins AKT, JNK, STAT5, and the associated molecules CyclinD1 and matrix metalloproteinase-9 (MMP)-9, was assessed in HBX-positive cells with or without treatment with IL-7R short hairpin RNA (shRNA). Additionally, the role of IL-7R in HBX-mediated proliferation and migration of hepatoma cells was investigated.
Results: The expression of IL-7R was increased in hepatoma cells transfected with HBV plasmids; HBX was responsible for the HBV-mediated upregulation of IL-7R. Compared to adjacent tissues, the expression of HBX and IL-7R was increased in HBV-related HCC tissues. Additionally, the relative expression levels of HBX were associated with IL-7R in HBV-related HCC tissues. The activation of NF-κB pathways and expression of Notch1 were increased in hepatoma cells transfected with HBX, and inhibition of NF-κB and Notch1 pathways significantly decreased HBX-mediated expression of IL-7R. The activation of AKT and JNK and the expression of CyclinD1 and MMP-9 were increased in HBX-positive cells. When cells were treated with IL-7R shRNA, the activation of AKT and JNK, as well as the expression of CyclinD1 and MMP-9, were significantly inhibited. Additionally, IL-7R was responsible for HBX-induced proliferation and migration ability of hepatoma cells.
Conclusions: Our data demonstrate that HBX can upregulate IL-7R via NF-κB and Notch1 pathways to facilitate the activation of intracellular pathways and expression of associated molecules, and contribute to proliferation and migration of hepatoma cells.
Keywords: Hepatitis B virus X protein; Hepatocellular carcinoma; Interleukin-7 receptor; Migration; Proliferation.