Journal of Experimental & Clinical Cancer Research 2008, 27:87 http://www.jeccr.com/content/27/1/87 FAingtui-rpero1liferation effect of PTEN geng transfecion in K562 cells NC: Anti-proliferation effect of PTEN geng transfecion in K562 cells NC: controlled K562 cells; Ad-GFP: Ad-GFP tran- fected K562 cells; Ad-PTEN-GFP: Ad-PTEN-GFP tranfected K562 cell reached the top level on the third day and then decreased gradually in the following three days, while the expression level of mTOR mRNA decreased to the lowest level on the third day and recovered gradually in the following three days. However, the expression level of BCR/ABL fusion gene did not change significantly (P > 0.05) (Fig 2). The expression level of PTEN mRNA had negative correlation with that of mTOR mRNA (r = -0.956, P < 0.05). The result also showed that the expression level of PTEN protein increased gradually after Ad-GFP-PTEN transfection, and the top level was detected on the third day of the transfec- tion. The expression level of p-Akt but not total Akt decreased in PTEN transfected K562 cells, the lowest level appeared on the third day (Fig 3). PTEN transfection changed the cell cycle distribution in K562 cells Cell cycle analysis by FCM showed that the percentage of G2/M phase cells in Ad-PTEN-GFP transfected K562 cells decreased, while the percentage of G0/G1 cells increased at each tested time point. Cell cycle was arrested at the G0/G1 phase (Figure 4 and Table 2). PTEN transfection and rapamycin treatment affected the growth and apoptosis of K562 cells Previous studies showed that rapamycin have anti-inflam- matory, anti-tumor and immunosuppressive activities. Our results showed that the growth of K562 cells, which were transfected with PTEN and treated with RAPA (10 nmol/L) for 72 h, was significantly inhibited by 37.4%. This was significantly higher than that in K562 cells trans- fected with Ad-GFP and treated with 10 nmol/L RAPA (17.2%, P < 0.01) or that in K562 cells transfected with PTEN but without RAPA treatment (7.5%, P < 0.01). The apoptosis rate in K562 cells transfected with PTEN and treated with 10 nmol/L RAPA for 3 days was 31.5%, sig- nificantly higher than that in K562 cells transfected with Ad-GFP and treated with 10 nmol/L RAPA (6.8%, P < 0.01), or that in K562 cells transfected with Ad-PTEN-GFP but without RAPA treatment (6.1%, P < 0.01) (Fig 5). PTEN transfection and rapamycin treatment affected the expression of CyclinD1 and P27kip1 mRNA CyclinD1 and P27kip1 mRNA and proteins were the key factors in modulating cell cycle. The present study showed that the expression level of CyclinD1 mRNA decreased in K562 cells transfected with Ad-PTEN-GFP and treated with 10 nmol/L RAPA for three days (0.121 ± 0.012), which was significantly lower than that in Ad-PTEN-GFP transfected K562 cells but without RAPA treatment (0.228 ± 0.036, P < 0.01), or that in Ad-GFP transfected and 10 nmol/L RAPA treated K562 cells (0.675 ± 0.049). The expression level of P27kip1 mRNA was negatively corre- lated with that of CyclinD1 mRNA. P27kip1 mRNA expressed at the top level (0.936 ± 0.061) in K562 cells transfected with Ad-PTEN-GFP and treated with 10 nmol/ L RAPA for three days, which was significantly higher than that in K562 cells transfected with Ad-PTEN-GFP but Page 4 of 9 (page number not for citation purposes)