Overexpression of p27KIP1induced cell cycle arrest in G1 phase and subsequent apoptosis in HCC-9204 cell line

AIM We have previously reported that inducibleover-expression of Bak may prolong cell cycle inG1phase and lead to apoptosis in HCC-9204 cells.This study is to investigate whether p27KIP1playsan important role in this process.METHODS In order to elucidate the exactfunction of p27KIP1in this process,a zinc induciblep27KIP1stable transfectant and transient p27KIP1-GFP fusion transfectant were constructed.Theeffects of inducible,p27KIP1on cell growth,cellcycle arrest and apoptosis were examined in themock,control pMD vector,and pMD-KIP1transfected HCC-9204 cells.RESULTS This p27KIP1-GFP transfectant maytransiently express the fusion gene.The cellgrowth was reduced by 35% at 48 h of p27KIP1induction with zinc treatment as determined bytrypan blue exclusion assay.These differencesremained the same after 72 h of p27KIP1expression,p27KIP1caused cell cycle arrest after24 h of induction,with 40% increase in G1population.Prolonged p27KIP1expression in thiscell line induced apoptotic cell death reflected byTUNEL assay.Fourty-eight h and 72 h of p27KIP1expression showed a characteristic DNA ladder onagarose gel electrophoresis. CONCLUSION Bak may induce cell cycle arrest inG1phase through upregulating expression ofp27KIP1and subsequently lead to apoptosis inHCC-9204 cells.The p27KIP1-GFP fusion proteincan be transiently expressed in HCC-9204 cells.The inducible p27KIP1-expressing cell line providesa model to assess p27KIP1function.