Background: The phosphatase and TENsin homologue (PTEN) is a tumour suppressor gene found to be deleted or mutated in a number of germ-line inherited disorders and many tumour types. PTEN modulates the cell cycle and cell survival through negative regulation of the PI3K-Akt pro-proliferative and anti-apoptotic signalling pathway. PTEN expression has been shown to be regulated at the transcriptional and post-translational levels, and, more recently, post-transcriptional regulation of PTEN by miRNAs has been described. PTEN pseudogene-1 (PTENP1) is a processed, translationally silent, pseudogene of PTEN. It is transcribed into a PTEN mRNA-mimic that has been shown to bind PTEN-targeting miRNAs within the 3’ UTR. This has identified PTENP1 as an indirect tumour suppressor that liberates the PTEN mRNA for translation.

Aims: The 3’UTR of PTENP1 has been shown to bind PTEN-targeting miRNAS and this study aimed to test for the regulatory and tumour suppressive effects of the 5’UTR and coding sequence (CDS) of PTENP1 through the potential binding of PTEN-targeting miRNAs within the respective regions.

Methods: PTEN and PTENP1 have high sequence homology and bioinformatics analyses were used to predict miRNAs that may target common regions within the 5’UTR and the CDS of PTEN and PTENP1. PTENP1-specific primers were designed to amplify the 5’UTR, CDS and 3’ UTR, for cloning into an expression vector. Expression constructs were transfected into U-2OS osteosarcoma cells that were then assayed for cell proliferation changes and quantitative changes in PTEN gene expression brought about by PTENP1 expression.

Results and Discussion: Bioinformatics analyses identified a number of miRNAs that target regions common to the 5’UTR and CDS of PTEN and PTENP1. In addition to the previously reported 3’UTR, results to date implicate the 5’UTR and the CDS of PTENP1 in an indirect regulatory, and tumour suppressive effect that is miRNA-dependent.