The effects of p38MAPK and HBxAg on cell proliferation and apoptosis in human hepatocarcinogenesis

Abstract

To investigate the effects of host-derived p38 mitogen-activated protein kinase subunit 38 (p38MAPK) and the hepatitis B virus X antigen (HbxAg) on cell proliferation and apoptosis in human hepatocellular carcinoma (HCC), and to study the mechanism underlying hepatocarcinogenesis. Liver tissues were biopsied from healthy individuals and patients with chronic hepatitis B (CHB), liver cirrhosis, paratumor cirrhosis, and HCC. Immunohistochemical staining was used to detect expressions of HBxAg, p38MAPK, cell cycle G2/M phase-related factors (cdc25B, p34cdc2, cyclin B1), and cell proliferation factor ki-67.The terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling method (known as TUNEL) was used to detect apoptosis. The highest rates of HBxAg were detected in CHB (65.0%) and HCC (44.4%) liver samples, and the antigen was mainly expressed in nuclei. Increasingly higher rates of p38MAPK, cdc25B, cyclin B1, and p34cdc2 expression were detected with increases in disease severity: normal liver (40.0%, 20.0%, 20.0%, and 30.0%, respectively), chronic hepatitis B (60.0%, 65.0%, 40.0%, and 50.0%, respectively), liver cirrhosis (65.0%, 75.0%, 70.0%, and 55.0%, respectively), paratumor cirrhosis (66.7%, 75.0%, 75.0%, and 63.9%, respectively), and HCC (77.8%, 80.6%, 80.6%, and 72.2%, respectively). In addition, the intracellular location of p38MAPK expression was different under different disease conditions, showing nuclear expression in CHB and liver cirrhosis samples and cytoplasmic expression in paratumor cirrhosis and HCC samples (x2 = 1.11, P more than 0.05). The proliferation index (PI) and the apoptosis index (AI) were both increased along with disease severity (normal more than CHB more than paratumor cirrhosis more than HCC) (PI: 0.0000+/-0.000, 0.0502+/-0.011, 0.0411+/-0.009, 0.0762+/-0.017; AI: 0.0351+/-0.024, 0.0607+/-0.022, 0.0562+/-0.013, 0.0716+/-0.011), with the notable exception for liver cirrhosis (PI: 0.1810+/-0.036 and AI: 0.1200+/-0.018). PI in poorly-differentiated HCC (0.2285+/-0.062) was significantly higher than in well-differentiated HCC (0.1216+/-0.032, t = 2.082, P = 0.044). AI in well-differentiated HCC (0.152+/-0.026) was significantly higher than in poorly-differentiated HCC (0.081+/-0.022, t = 2.129, P = 0.041). In the process of hepatocarcinogenesis, HBxAg may cause a series of abnormal changes in cell cycle, proliferation and apoptosis by affecting the expression of p38MAPK.