AIM: We have previously reported that inducible over-expression of Bak may prolong cell cycle in G 1 phase and lead to apoptosis in HCC-9204 cells. This study is to investigate whether p27 KIP1 plays an important role in this process.

METHODS: In order to elucidate the exact function of p27 KIP1 in this process, a zinc inducible p27 KIP1 stable transfectant and transie nt p27 KIP1-GFP fusion transfectant were constructed. The effects of inducible p27 KIP1 on cell growth, cell cycle arrest and apoptosis were examined in the mock, control pMD vector, and pMD-KIP1 transfected HCC-9204 cells.

RESULTS: This p27 KIP1-GFP transfectant may transiently express the fusion gene. The cell growth was reduced by 35% at 48 h of p27 KIP1 induction with zinc treatment as determined by trypan blue exclusion assay. These differences remained the same after 72 h of p27 KIP1 expression. p27 KIP1 caused cell cycle arrest after 24 h of induction, with 40% inc rease in G 1 population. Prolonged p27 KIP1 expression in this cell line induced apoptotic cell death reflected by TUNEL assay. Fourty-eighth and 72 h of p27 KIP1 expression showed a characteristic DNA ladder on agarose gelelec trophoresis.

CONCLUSION: Bak may induce cell cycle arrest in G 1 phase through upregul ating expression of p27 KIP1 and subsequently lead to apoptosis in HCC-9204 cells. The p27 KIP1-GFP fusion protein can be transiently expr essed in HCC-9204 cells. The inducible p27 KIP1 expressing cell line provides a model to assess p27 KIP1 function.