Co-transfection of p16(INK4a) and p53 genes into the K562 cell line inhibits cell proliferation.

BACKGROUND AND OBJECTIVES: The tumor suppressor genes p53 and p16(INK4a), both of which act in tumor surveillance, are homozygously deleted in the human leukemia cell line K562. This study was performed to assess whether co-transfection of the p16(INK4a) and p53 genes could inhibit K562 cell proliferation. DESIGN AND METHODS: p16(INK4a) and p53 genes were co-transfected into K562 cells with liposome, and the expression of the transfected genes was detected by Western-immunoblotting and immunocytochemistry. The effect of the p16(INK4a) and p53 transfected cell culture was quantified by trypan blue staining, and the number of recovered viable cells was assessed every day after transfection. Cells were analyzed for expression of annexin V in order to detect apoptosis. Differentiation of transfected K562 cells was measured by the benzidine oxidation test, and the cell cycle was analyzed by flow cytometry. RESULTS: After co-transfection, there were 23% and 28% p53 and p16(INK4a) positive cells respectively. Co-transfection with p16(INK4a) and p53 genes significantly inhibited cell proliferation when compared to transfection with either p16(INK4a) or p53 gene. The percentage of cells expressing the apoptosis-related cell surface antigen annexin V was significantly higher in p53 and p16(INK4a) transfected cells than in p53 or p16(INK4a) transfected cells (6.24+/-0.37% vs 4.88+/- 0.17%, p<0.05 and vs 2.78+/-0.26%, p<0.05, respectively). p16(INK4a) and p53 co-transfection significantly increased the number of cells in G1 phase and decreased that in S phase. INTERPRETATION AND CONCLUSIONS: Expression of wild-type p16(INK4a) and p53 genes in K562 cells results in reduced proliferation and apoptosis. Introduction of exogenous p16(INK4a) and p53 genes into K562 cells might contribute to the clinical treatment of leukemia.