Overexpressed miR-494 down-regulates PTEN gene expression in cells transformed by anti-benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide

Aims: We investigated the functionality of miR-494 in anti-benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide (anti-BPDE)-transformed human bronchial epithelial cell 16HBE to reveal its potential target coding-gene. Main methods: The expression of mature miR-494 in cells was detected by miRNA-specific quantitative real-time polymerase chain reaction (QRT-PCR). QRT-PCR and Western blot were used to identify the expression of phosphatase and tensin homolog (PTEN) mRNA and protein. Following activation or inhibition of mature miRNA expression with precursors or antisense inhibitors, PTEN expression, luciferase activities, cell apoptosis, cell growth in soft agar and cell motility were analyzed. Key findings: The expression of miR-494 increased while PTEN protein appeared to be lower in malignant transformed 16HBE cells. Enforced miR-494 level decreased PTEN protein expression compared to a negative precursor control group. Inhibition of miR-494 expression increased PTEN protein expression compared to negative inhibitor control group. Decreased expression of miR-494 increased caspase-3/7 activities in transformed 16HBE cells, and increased expression of miR-494 decreased this activity. Inhibition of miR-494 also decreased the malignancy of transformed cells. Significance: MiR-494 regulates the expression of PTEN post-transcriptionally and functions as a micro-oncogene in carcinogenesis induced by anti-BPDE. MiR-494 may be a useful target for gene therapy. (C) 2009 Elsevier Inc. All rights reserved.