Over expression of integrin alpha 5 beta 1 in human hepatocellular carcinoma cell line suppresses cell proliferation in vitro and tumorigenicity in nude mice

Integrin alpha 5 beta 1 and alpha 2 beta 1 are the major integrin receptors in human hepatocytes. However, in human hepatocellular carcinoma cells it was found that the expression of integrin alpha 5 beta 1 was decreased and another integrin alpha 6 beta 1 increased. In this study, the SMMC7721 huma n hepatocellular carcinoma cells cotransfected or singlely transfected with integrin alpha 5 and/or beta 1 cDNAs were established, and designated alph a 5 beta 1.6-7721, alpha 5.3-7721, and beta 1.6-7721 cell lines, respective ly. Transfection with cDNAs of integrin alpha 5 and beta 1 subunits resulte d in the overexpression of each integrin and modified biological properties , including a slowed growth rate, changes in the cell cycle from 15.5% of c ontrol cells in the G2/M phase to 12.1%, 9.6% and 9.4% in alpha 5.3-7721, b eta 1.6-7721, alpha 5 beta 1.6-7721, respectively, and a decrease in the Ce ll Mitosis Index from 1.6 in controls to 0.96, 0.95, and 0.72, and 34%, 28% and 52% derived from colony forming ability, respectively. Tumorigenicity was also tested in nude mice with inoculation of cells subcutaneously. Tumo r masses growing in nude mice following inoculation with beta 1.6-7721,and alpha 5 beta 1.6-7721 cells weighed only 52% or 31% those of control cells. These results indicated that deletion or low expression of integrin alpha 5 beta 1 may play an important role in the development of hepatocellular ca rcinoma. Therefore, induction of expression of the integrin alpha 5 beta 1 in malignant cells could be a potential means of treating hepatocellular ca rcinoma.