202 Ann. N.Y. Acad. Sci. 1028: 202–212 (2004). © 2004 New York Academy of Sciences. doi: 10.1196/annals.1322.025 Intercellular Communication and Human Hepatocellular Carcinoma GIUSEPPE CARRUBA, a LETIZIA COCCIADIFERRO, a VINCENZO BELLAVIA, b SERGIO RIZZO, a CHRISTOS TSATSANIS, c DEMETRIOS SPANDIDOS, c PAOLA MUTI, d COLIN SMITH, e PARMENDER MEHTA, f AND LUIGI CASTAGNETTA a,b a Department of Experimental Oncology and Clinical Application, University Medical School, Palermo, Italy b Experimental Oncology Unit, Department of Clinical Oncology, ARNAS-Civico, “M. Ascoli” Cancer Hospital Center, Palermo, Italy c School of Medicine, University of Crete, Heraklion, Crete, Greece d Department of Social and Preventive Medicine, University at Buffalo, State University of New York, Buffalo, New York 14214, USA e School of Biomedical and Molecular Sciences, University of Surrey, Guildford, UK f Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA ABSTRACT: We have previously reported that gap junction–mediated inter- cellular communication (GJIC) can be restored in junctionally deficient human prostate epithelial cells, also suggesting that GJIC activity is regulated by estrogen. In the present work, we report studies on sex steroid regulation of GJIC and proliferative activity in both nontumoral (Chang liver, CL) and malignant (HepG2, Huh7) human liver cells. Junctional activity and liver cell growth were measured using the scrape-loading/dye-transfer (SL/DT) and the MTS assay, respectively. Using the SL/DT, only Huh7 cells exhibited a moderate degree of junctional activity in basic conditions, while neither CL nor HepG2 cells showed functional GJIC. Under exactly the same experimental approach used for prostate studies, we observed that, once again, both estrogen (either estradiol or estrone) and FK induce a significant increase of GJIC in Huh7 cells, while exposure of HepG2 cells to FK produces only a limited rise of junc- tional activity in this cell line. However, estrogen induced a significant increase and reduction of the proliferative activity of CL and Huh7 cells, respectively, while growth of HepG2 cells was not affected. While the above evidence suggests that estrogens are primarily implicated in growth regulation and communication of both prostate and liver epithelial cells, it also implies that compounds able to restore GJIC in junctionally deficient cells or prevent its disruption in junctionally proficient cells may be used for development of new Address for correspondence: Giuseppe Carruba, M.D., Ph.D., Department of Experimental Oncology and Clinical Application, University Medical School, c/o “M. Ascoli” Cancer Hospital Center, ARNAS-Civico, Via C. Lazzaro 2, 90127 Palermo, Italy. Voice: +39-091-666-4346; fax: +39-091-666-4352. lucashbl@unipa.it