Expression of gap junction genes connexin32 and connexin43 mRNAs and proteins, and their role in hepatocarcinogenesis.
OBJECTIVE
To investigate the relationship between hepatocarcinogenesis and the expression of connexin32 (cx32), connexin43 (cx43) mRNAs and proteins in vitro.


METHODS
Gap junction genes cx32 and cx43 mRNA in hepatocellular carcinoma cell lines HHCC, SMMC-7721 and normal liver cell line QZG were detected by in situ hybridization (ISH) with digoxin-labeled cx32, and cx43 cDNA probes. Expression of Cx32 and Cx43 proteins in the cell lines was revealed by indirect immuno-fluorescence and flow cytometry (FCM).


RESULTS
Blue positive hybridization signals of cx32 and cx43 mRNAs detected by ISH with cx32 and cx43 cDNA probes respectively were located in cytoplasm of cells of HHCC, SMMC-7721 and QZG. No significant difference of either cx32 mRNA or cx43 mRNA was tested among HHCC, SMMC-7721 and QZG (P=2.673, HHCC vs QZG; P=1.375, SMMC-7721 vs QZG). FCM assay showed that the positive rates of Cx32 protein in HHCC, SMMC-7721 and QZG were 0.7%, 1.7% and 99.0%, and the positive rates of Cx43 protein in HHCC, SMMC-7721 and QZG were 7.3%, 26.5% and 99.1% respectively. Significant differences of both Cx32 and Cx43 protein expression existed between hepatocellular carcinoma cell lines and normal liver cell line (P=0.0069, HHCC vs QZG; P=0.0087, SMMC-7721 vs QZG). Moreover, the fluorescent intensities of Cx32 and Cx43 proteins in HHCC, SMMC-7721 were lower than that in QZG.


CONCLUSIONS
Hepatocellular carcinoma cell lines HHCC and SMMC-7721 exhibited lower positive rates and fluorescent intensities of Cx32, Cx43 proteins compared with that of normal liver cell line QZG. It is suggested that lower expression of both Cx32 and Cx43 proteins in hepatocellular carcinoma cells could play pivotal roles in the hepatocarcinogenesis. Besides, genetic defects of cx32 and cx43 in post-translational processing should be considered.
Ma
Xiang-Dong
XD
Department of Obstetrics & Gynecology, Xijing Hospital, the Fourth Military Medical University, Xi'an 710033, Shaanxi Province, China. maping@fmmu.edu.cn
Ma
Xing
X
Sui
Yan-Fang
YF
Wang
Wen-Liang
WL
D006528:Carcinoma, Hepatocellular; D018031:Connexin 43 / Q000032:analysis / Q000235:genetics*; D017630:Connexins / Q000032:analysis / Q000235:genetics; D005434:Flow Cytometry; D017629:Gap Junctions / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D017403:In Situ Hybridization; D008113:Liver Neoplasms; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000502:physiology; D000097002:Gap Junction beta-1 Protein
D018031:Connexin 43; D017630:Connexins; D012333:RNA, Messenger; D000097002:Gap Junction beta-1 Protein