Combined Blockade and Akt/Mtor Pathway Inhibits Growth of Human Hemangioma via Downregulation of Proliferating Cell Nuclear Antigen

Abstract

Protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway plays a crucial role in the tumorigenesis and progression of multiple tumors, and has been shown to be important therapeutic targets for cancer. The present study aimed to explore the role and molecular mechanisms of AKT/mTOR pathway in human hemangioma (HA). Twenty-five cases of human HA tissues were collected. The expression of AKT, mTOR and proliferating cell nuclear antigen (PCNA) proteins was evaluated using semi-quantitative immunohistochemistry in biopsy samples in different phases of HA. AKT/mTOR pathway was blocked by recombinant small hairpin RNA adenovirus vector rAd5-AKT+mTOR (rAd5-Am), used for infecting proliferating phase HA-derived endothelial cells (HDEC). The expression of AKT, mTOR and PCNA was detected by Real-time PCR and Western blot assays. Cell proliferative activities were determined by MTT assay, and cell cycle distribution and apoptosis were analyzed by flow cytometry. As a consequence, the expression of AKT, mTOR and PCNA was significantly increased in proliferative phase HA, while that was decreased in involutive phase. Combined blockade of AKT/mTOR pathway by rAd5-Am diminished cell proliferative activities, and induced cell apoptosis and cycle arrest with the decreased expression of AKT, mTOR and PCNA in proliferative phase HDEC. In conclusion, the activity of AKT/mTOR pathway was increased in proliferative phase HA, while it was decreased in involutive phase. Combined blockade of AKT/mTOR pathway might suppress cell proliferation via down-regulation of PCNA expression, and induce apoptosis and cycle arrest in proliferative phase HDEC, suggesting that AKT/mTOR pathway might represent the important therapeutic targets for human HA.