Decreased hepatocyte membrane potential differences and GABAA-beta3 expression in human hepatocellular carcinoma.
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 gamma-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-beta3 expression was down-regulated (GABAA-beta3 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-beta3 receptor expression (Huh-7 cells) were transfected with GABAA-beta3 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-beta3 cDNA-transfected cells (P<0.005).


CONCLUSIONS
The results of this study indicate that (1) human HCC tissues are depolarized compared with adjacent nontumor tissues, (2) hepatic GABAA-beta3 receptor expression is down-regulated in human HCC, and (3) restoration of GABAA-beta3 receptor expression results in attenuated in vivo tumor growth in nude mice.
Minuk
Gerald Y
GY
Section of Hepatology, Department of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada. gminuk@cc.umanitoba.ca
Zhang
Manna
M
Gong
Yuewen
Y
Minuk
Leonard
L
Dienes
Hans
H
Pettigrew
Norman
N
Kew
Michael
M
Lipschitz
Jeremy
J
Sun
Dongfeng
D
D000293:Adolescent; D000328:Adult; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology*; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D022781:Hepatocytes / Q000502:physiology*; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D012333:RNA, Messenger / Q000378:metabolism; D011963:Receptors, GABA-A / Q000235:genetics / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
C546273:GABRB3 protein, human; C546270:Gabrb3 protein, mouse; D012333:RNA, Messenger; D011963:Receptors, GABA-A; D000254:Sodium-Potassium-Exchanging ATPase