Abstract 3944: PTEN is not directly regulated by miRNA-21 in non-small cell lung cancer

Abstract

Abstract Introduction: PTEN is a well known tumor suppressor gene that plays a crucial role in the regulation of many normal biological processes. Among the mechanisms taking part in its regulation has been demonstrated being miR-21 action, as it has been reported that PTEN consists one of miR-21 target genes. In this study, we speculated on the effect of miR-21 expression levels in non small cell lung cancer tissues towards: a) PTEN mRNA expression levels and b) PTEN protein levels. Materials and Methods: Thirty pairs of NSCLC fresh-frozen tissues and their corresponding noncancerous tissues were analyzed for the expression of mature miR-21 as well as for the expression of PTEN transcript using RT-qPCR. PBGD was used as a reference gene and for the evaluation of RNA quality in our samples. In parallel, PTEN protein levels were evaluated by immunohistochemistry in the same samples. Deparaffinized sections cut from paraffin-embedded tissue samples were stained with a specific anti-PTEN antibody. Tumor types and stages were determined according to the WHO classification. All samples were analyzed histologically to access the amount of tumor component (at least 70% of tumor cells) and the quality of material. Results: In 26/30 NSCLC tissues studied (86.7%), PTEN mRNA expression was decreased when compared to adjacent noncancerous tissues, while overexpression of PTEN transcript was perceived in only 4 samples (13.3%). Evaluation of PTEN protein level in these specimens revealed that in 28/30 samples (93.3%), PTEN protein was detected, while in only 2/30 samples (6.7%) PTEN protein loss was observed. The respective data for miR-21 expression levels indicated that PTEN mRNA as well as protein levels were independent of miR-21 expression status in non small cell lung cancer samples. Conclusion: Our data indicate for the first time that in NSCLC miR-21 expression levels do not directly regulate PTEN protein levels. PTEN protein was detected by IHC in the vast majority of NSCLC tissues despite the fact that PTEN mRNA expression levels were lower in cancerous tissues than in the corresponding noncancerous tissues. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3944. doi:10.1158/1538-7445.AM2011-3944