Journal of Experimental & Clinical Cancer Research 2008, 27:87 http://www.jeccr.com/content/27/1/87 regulation of the cdk inhibitors p27kip1 and p21cip1 [9-11]. Therefore, inhibition of mTOR function represents a potential therapeutic strategy [10-13]. Our results showed that in the PTEN gene transfected K562 cells, over- expressed PTEN gene combined with the treatment of rapamycin significantly promoted the expression of P27kip1 gene but inhibited the expression of the CyclinD1. Meanwhile, the percentage of cells in S and G2/M phase decreased and the cells in G0/G1 phase increased in the PTEN gene transfected K562 cells. These results suggested that PTEN gene and protein might inhibit the expression and the function of cyclins and cyclins-CDK but promote expression of P27kip1 via down-regulating p-Akt and mTOR expression. Several published papers showed that rapamycin played key role in inhibiting tumor proliferation by targeting mTOR and had synergistic anti-tumors effects with some chemotherapeutic drugs such as arsenic trioxide in several kinds of tumors [22]. The present study showed that PTEN gene transfection, together with the treatment of low con- centration of rapamycin, had a higher growth inhibition effect and apoptosis induction effect in K562 cell, accom- panied with the increased expression of PTEN mRNA and protein but decreased expression of mTOR, suggesting that rapamycin and PTEN might have synergic effect on inhibiting proliferation, promoting apoptosis and cell cycle arrest of leukemia cells via inhibiting the activity of PI3K/Akt/mTOR pathway. These results might provide a theoretical basis for the treatment of CML with new mol- ecule targeting regimens such as PTEN transfection and the use of rapamycin. Competing interests The authors declare that they have no competing interests. Authors' contributions SYW and HC participated in the measurement of the tar- get proteins by western blotting. Cell cycle distribution assay was carried out by ZYN and SHL. ZYC, XYY carried out cell culture, transfection, measurement of growth inhibition of rapamycin, statistics and writing manu- script. LP, XLG, ZYC, XYY conceived of the study, and par- ticipated in its design and coordination. LP revised the manuscript finally. All of us showed our opinion after plenty of reading. All authors read and approved the final manuscript. Acknowledgements Project supported by the Natural Science Foundation of Hebei province (Grant No. C2008001097) and by the Health Bureau Major supervise Pro- gram of Hebei province(Grant No GL200508). References 1. Myers MP, Stolarov JP, Eng C, Li J, Wang SI, Wigler MH, Parsons R, Tonks NK: PTEN, the tumor suppressor from human chro- mosome 10q23, is a dual-specificity phosphatase. Proc Natl Acad Sci USA 1997, 94(17):9052-9057. 2. 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