Effects of all-trans retinoic acid on expression of connexin genes and gap junction communication in hepatocellular carcinoma cell lines

Abstract

To investigate the effect of all-trans retinoic acid (ATRA) on the expression of connexin 26, 32 and 43 genes and the alteration of gap junction communication function in human hepatocellular carcinoma cells. Human hepatocellular carcinoma cell of the lines SMMC-7721 and BEL-7404 were cultured in normal medium and medium containing ATRA at a concentration of 10(-5) mol/L for 24, 48 and 72 hours respectively. RT-PCR procedure was adopted to detect the mRNA expression of CX 26, 32 and 43. Scrape-loading and dye transfer procedure was performed to examine the gap junction communication function. CX26 mRNA and CX32 mRNA were not expressed in the cell lines SMMC-7721, however, expression of CX26 mRNA and expression of CX32 mRNA were found 48 and 72 hours after being induction by ATRA respectively. CX26 mRNA and CX32 mRNA were not expressed in the cell lines BEL-7404, however, expression of CX26 mRNA and expression of CX32 mRNA were found 48 hours after induction by ATRA. Expression of CX43 mRNA was found in all cells, whether being induced by ATRA or not. Scrape-loading and dye transfer procedure showed that lucifer yellow was seen in only 1-2 lines by the delimited mark in the untreated SMMC-7721 cells and in 3-4 lines by the delimited mark in the SMMC-7721 cells treated by ATRA. But no dye transfer phenomenon was found in the BEL-7404 cells whether they were ATRA-treated or not. ATRA is able to affect the expression of CX26 and CX32 in HCC cell lines SMMC-7721 and BEL-7404 by acting at the transcription level. Reinforcement of gap junction communication function is found in the SMMC-7721 cells and not in the BEL-7404 cells, which shows that ATRA modulates the gap junction intercellular communication, by acting in different mechanisms.