Journal of Experimental & Clinical Cancer Research Research PTEN and rapamycin inhibiting the growth of K562 cells through regulating mTOR signaling pathway Zhi Y Cheng, Xiao L Guo, Xiao Y Yang, Zhi Y Niu, Shi H Li, Su Y Wang, Hao Chen and Ling Pan* BioMed Central Open Access Address: Department of Hematology and Heibei Institute of Hematology, The Second Hospital of Hebei Medical University, 215 Heping Xi Road, Shijiazhuang,050000, PR China Email: Zhi Y Cheng - dzczy@sohu.com; Xiao L Guo - linger216@163.com; Xiao Y Yang - y108108@Gmail.com; Zhi Y Niu - zhiyunniu@126.com; Shi H Li - lsh20022005@126.com; Su Y Wang - suyunwcn@163.com; Hao Chen - lovexiaoqing2004@yahoo.com.cn; Ling Pan* - lingpan20002000@yahoo.com.cn * Corresponding author Published: 30 December 2008 Journal of Experimental & Clinical Cancer Research 2008, 27:87 doi:10.1186/1756-9966-27-87 This article is available from: http://www.jeccr.com/content/27/1/87 Received: 1 October 2008 Accepted: 30 December 2008 © 2008 Cheng et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Objective: To investigate, in vitro, the regulatory effects of tumor-suppressing gene PTEN on mTOR (mammalian target of rapamycin) signaling pathway, the effects of transfected PTEN and rapamycin on the growth inhibition, and apoptosis induction for human leukemia cell line K562 cells. Methods: K562 cells were transfected with recombined adenovirus-PTEN vector containing green fluorescent protein (Ad-PTEN-GFP), followed by the treatment of the cells with or without rapamycin. The proliferation inhibition rate and apoptotic rate of these transfected and/or rapamycin treated K562 cells were measured by MTT assay and flow cytometry (FCM), the expression levels of PTEN-, mTOR-, cyclinD1- and P27kip1- mRNA were measured by real-time fluorescent relative-quantification reverse transcriptional PCR (FQ-PCR), the protein expression levels of PTEN, Akt, p-Akt were detected by western blotting. Results: The proliferation of K562 cells was inhibited by PTEN gene transfection with/without the treatment of rapamycin. The expression levels of PTEN- and P27kip1- mRNA were up-regulated, and the mTOR- and cyclinD1- mRNA were down-regulated in K562 cells after the cells transfected with wild type PTEN gene and treated with rapamycin. Conclusion: PTEN and rapamycin inhibited mTOR expression by acting as an upstream regulator of mTOR. Low dose rapamycin in combination with over-expressed PTEN might have synergistic effects on inhibiting the proliferation and promoting apoptosis of K562 cells. Background PTEN (phosphatase and tensin homology deleted on chromosome ten) is a novel tumor suppressor gene, map- ping to 10q23.3 and encoding a dual-specificity phos- phatase with sequence similar to the cytoskeletal protein tensin [1,2]. It was identified as a candidate tumor sup- pressor gene based on the presence of gene deletion or inactivating mutations in human brain, breast, and pros- tate cancers and tumor cell lines [3-6]. PTEN protein can be inactivated by post-transcriptional gene silencing, post- Page 1 of 9 (page number not for citation purposes)