Signal transduction of gap junctional genes, connexin32, connexin43 in human hepatocarcinogenesis

AIM: To investigate gap junctional intercellular communication (GJIC) in hepatocellular carcinoma cell lines, and signal transduction mechanism of gap junction genes connexin32(CX32), connexin43(CX43) in human hepatocarcinogenesis. METHODS: Scarped loading and dye transfer (SLDT) was employed with Lucifer Yellow (LY) to detect GJIC function in hepatocellular carcinoma cell lines HHCC, SMMC-7721 and normal control liver cell line QZG. After Fluo-3AM loading, laser scanning confocal microscope (LSCM) was used to measure concentrations of intracellular calcium [Ca2+]i in the cells. The phosphorylation on tyrosine of connexin proteins was examined by immunoblot. RESULTS: SLDT showed that ability of GJIC function was higher in QZG cell than that in HHCC and SMMC-7721 cell lines. By laser scanning confocal microscopy, concentrations of intracellular free calcium [Ca2+]i was much higher in QZG cell line (108.37 nmol/L) than those in HHCC (35.13 nmol/L) and SMMC-7721 (47.08 nmol/L) cells. Western blot suggested that only QZG cells had unphosphorylated tyrosine in CX32 protein of 32 ku and CX43 protein of 43 ku; SMMC-7721 cells showed phosphorylated tyrosine CX43 protein. CONCLUSION: The results indicated that carcinogenesis and development of human hepatocellular carcinoma related with the abnormal expression of CX genes and disorder of its signal transduction pathway, such as decrease of [Ca2+]i, post-translation phosphorylation on tyrosine of CX proteins which led to a dramatic disruption of GJIC.