Abstract 3996: MicroRNA-96 is a posttranscriptional suppressor of anaplastic lymphoma kinase expression in human cancer

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase that is normally expressed in human neural cells at an early developmental stage. In contrast, the expression of ALK is minimal in adult human tissues. Nonetheless, ALK is aberrantly expressed in some of the most aggressive types of adults and children malignancies. For instance, the expression of ALK in the form of the chimeric proteins NPM-ALK and EML4-ALK is seen in a subset of T-cell lymphoma and non-small lung cancer, respectively. In addition, aberrant upregulation of full-length ALK occurs in a group of neuroblastoma patients. ALK has been shown to contribute significantly to the survival of cancer cells. It is not surprising, therefore, that targeting ALK is now considered a promising therapeutic strategy to be utilized for the treatment of these malignant diseases in the near future. Although the aberrant expression of ALK has been partially attributed to the occurrence of chromosomal abnormalities that induce the expression of ALK chimeric proteins, the mechanisms underlying this interesting phenomenon are not completely identified. We reasoned that one potential mechanism contributing to the aberrant expression of ALK in cancer cells is mediated through defects in the microRNA (miR) system. We performed analysis of miR predicted targets using 3 web-based algorithms including TargetScan, miRanda, and PicTars. Mir-96 was the only candidate with potential ability to bind to ALK 3′-untranslated region (3′-UTR) that was identified simultaneously by the 3 algorithms. qPCR analysis showed that the expression of miR-96 was markedly decreased in NPM-ALK-expressing T-cell lymphoma cell lines compared with normal human T lymphocytes. The expression of miR-96 was also negligible in lung cancer and neuroblastoma cell lines that express EML4-ALK and full-length ALK, respectively. Importantly, transfection of ALK-expressing cancer cell lines with miR-96 was associated with a pronounced decrease in the expression of the different forms of ALK protein, and not in ALK mRNA. There was a marked reduction in luciferase activity when miR-96 was transfected with ALK 3′-UTR containing the presumed binding site for miR-96. Transfection of ALK-expressing cell lines with miR-96 was associated with decreased phosphorylation of ALK downstream targets, including pSTAT3, pAKT, and pIGF-IR, with no effect on the basal levels of these oncogenic proteins. Furthermore, miR-96 decreased the proliferation of cancer cell lines that express ALK. The effects of miR-96 were not detected when cell lines were transfected with a control miR mimic. In conclusion, our results identify miR-96 as a novel tumor suppressor that functions by inducing posttranscriptional downregulation of ALK expression, and suggest that miR-96 could represent a potential modality to successfully treat aggressive tumors that express the different forms of ALK protein. 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 3996. doi:10.1158/1538-7445.AM2011-3996