ABSTRACT
BACKGROUND: The phosphatidylinositol 3-kinase (PI3K)-AKT pathway is activated in many cancers. Mutational hotspots in AKT1 and in the regulatory and catalytic subunits of PI3K have been detected in multiple tumour types. In AKT1, the E17K substitution leads to a PI3K-independent activation of AKT1. METHODS: A mutational profiling of AKT1 and of the mutational hotspots in PIK3CA and PIK3R1 was carried out in samples from primary and recurrent prostate tumours. RESULTS: We show that, in prostate cancer, AKT1(E17K) had a prevalence of 1.4%. The mutation seemed to be associated with a favourable clinical course but it was not associated with a specific tumour growth pattern. Activating mutations in PIK3CA or PIK3R1 were not found in prostate cancer. CONCLUSION: The E17K substitution in AKT1 is rare in prostate cancer. It seems associated with a favourable clinical outcome but not with a specific histology of the tumour.
Subject(s)
Prostatic Neoplasms/genetics , Proto-Oncogene Proteins c-akt/genetics , Aged , DNA Mutational Analysis , Gene Expression , Gene Expression Profiling , Humans , Male , Middle Aged , Polymerase Chain Reaction , PrognosisABSTRACT
BACKGROUND: The tumor suppressor PTEN regulates many biological processes. A well-known downstream effector of PTEN is phospho-Akt. Although PTEN is the most frequently inactivated gene in prostate cancer, its mode of action is not fully understood. We studied the association of regulated PTEN expression with changes in biological function and gene expression profiles. METHODS: PTEN-negative LNCaP cells were stably transfected with wild-type PTEN cDNA under inducible control, resulting in LNCaP/PTEN cells. Microarray analysis was used to monitor gene expression changes upon induction of PTEN. Expression of selected individual genes was studied in Q-PCR and siRNA experiments. Cell-cycle distribution was analyzed by flow cytometry. RESULTS: Induced expression of PTEN in LNCaP/PTEN cells significantly inhibited cell proliferation, at least partly due to cell-cycle arrest at the G1 phase. Expression profiling combined with pathway analysis revealed that PTEN-dependent G1 growth arrest was associated with an altered mRNA expression of the G1 cell-cycle regulators Cdc25a, E2F2, cyclin G2, and RBL2/p130. Specific inhibition of Akt signaling by siRNA resulted in downregulation of both E2F2 and Cdc25a mRNA expression and upregulation of the FOXO target cyclin G2, similar to the effect observed by PTEN induction. However, Akt did not mediate the PTEN-dependent RBL2/p130 mRNA expression in LNCaP/PTEN cells. CONCLUSIONS: The results indicate that PTEN dependent gene expression is important in cell-cycle regulation and is mediated by both Akt-dependent and -independent mechanisms.
