Decreased hepatocyte membrane potential differences and GABAa-β3 expression in human hepatocellular carcinoma

Authors


  • Potential conflict of interest: Nothing to report.

Abstract

To determine whether hepatocyte membrane potential differences (PDs) are depolarized in human HCC and whether depolarization is associated with changes in GABAA receptor expression, hepatocyte PDs and γ-aminobutyric acid (GABA)A receptor messenger RNA (mRNA) and protein expression were documented in HCC tissues via microelectrode impalement, real-time reverse-transcriptase polymerase chain reaction, and Western blot analysis, respectively. HCC tissues were significantly depolarized (−19.8 ± 1.3 versus −25.9 ± 3.2 mV, respectively [P < 0.05]), and GABAA-β3 expression was down-regulated (GABAA-β3 mRNA and protein expression in HCC; 5,693 ± 1,385 and 0.29 ± 0.11 versus 11,046 ± 4,979 copies/100 mg RNA and 0.62 ± 0.16 optical density in adjacent tumor tissues, respectively [P = 0.002 and P < 0.0001, respectively]) when compared with adjacent nontumor tissues. To determine the physiological relevance of the down-regulation, human malignant hepatocytes deficient in GABAA-β3 receptor expression (Huh-7 cells) were transfected with GABAA-β3 complementary DNA (cDNA) or vector alone and injected into nu/nu nude mice (n = 16-17 group). Tumors developed after a mean (± SD) of 51 ± 6 days (range: 41-60 days) in 7/16 (44%) mice injected with vector-transfected cells and 70 ± 12 days (range: 59-86 days) in 4/17 (24%) mice injected with GABAA-β3 cDNA-transfected cells (P < 0.005). Conclusion: The results of this study indicate that (1) human HCC tissues are depolarized compared with adjacent nontumor tissues, (2) hepatic GABAA-β3 receptor expression is down-regulated in human HCC, and (3) restoration of GABAA-β3 receptor expression results in attenuated in vivo tumor growth in nude mice. (HEPATOLOGY 2007;45:735–745.)

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