Over-expression of p27^kip1 affects cell cycle of hepatocellular carcinoma cell lines

Purpose: To study the effects of P27 protein, encoded by p27 ^kip1, a crucial tumor suppression gene, on hepatocellular carcinoma(HCC) cell lines HepG2 and Hep3B, when it is over-expressed. Methods: We constructed mutant P27-expressing plasmids, pEYFP-P27 (S10A), pEYFP-P27 (T157A) and pEYFP-P27(T187A), by site-mutation technique from pEYFP-P27(WT) which encodes wild type P27 protein. HCC cell lines, HepG2 and Hep3B, were transfected with pEYFP-P27(WT) as well as pEYFPK-P27(mutant). Innate and over-expressed P27 protein were examined using Western blot, and their effects on cell cycle were analyzed by FACS, respectively. Results: It was found that overexpression of all P27 fusion proteins could strengthen G1 phase arrest in HepG2 and Hep3B cells; T157A mutant beared stronger activity of G0/G1 arrest than wild type or other mutant in HepG2, while in Hep3B no remarkable differences were detected between 3 mutants and wild type P27. Conclusions: Overexpression of P27 protein can remarkably strengthen G0/G1 phase arrest in HCC cell lines.