Abstract #1391: MiR-221&222 enhance migration and invasiveness of NSCLC and hepatocarcinoma cells by targeting PTEN tumor suppressor

Lung and liver cancer are among the most deadly type of cancer. Despite improvements in treatment over the past few decades, survival in patients remains poor. MicroRNAs (miRNA) represent a novel class of small RNAs that function as negative regulators of gene expression, deeply involved in the pathogenesis and progression of several types of cancers. In our previous work we found that miR-221 and miR-222, are markedly upregulated in TRAIL-resistant and downregulated in TRAIL-sensitive non small cell lung cancer (NSCLC) cells. Our data indicated that miR-221 and -222 modulate TRAIL sensitivity in NSCLC mainly by interfering with p27 kip1 expression and TRAIL-induced caspase machinery. Here, we show that miR-221 and miR-222, are overexpressed in aggressive NSCLC and Hepatocarcinoma cells (Calu-1 and Snu-387 cells) as compared with less invasive (H460 and Sk-Hep1 cells) and/or normal lung and liver cell lines. In all 20 different cell lines tested we found an inverse relationship between the expression of miR-221 and miR-222 and the tumor suppressor PTEN. By bioinformatic analysis, we identified one binding site for miR-221&222 in the 39 untranslated region of the tumor suppressors PTEN mRNA, and we demonstrated, by luciferase assay and by western blot, that PTEN is a direct targets of miR-221/222. Besides modulating AKT pathway, and thus cell survival, PTEN down-regulation enhances invasiveness and cellular migration as assessed by migration and invasion assays,through the activation,evidenced by western blot, of the ERKs pathway. Moreover, by MTT, Annexin-FITC assay and caspase 3/7 activity, we found that miR-221&222 overexpression induce cell survival and TRAIL resistance both in NSCLC and Hepatocarcinoma cells through the down-regulation of PTEN protein and activation of Akt pathway. In vitro and in vivo functional studies such as the use of anti-miRs oligonucleotides, immunohistochemistry and in situ hybridization on 20 primary lung and liver tumor specimens, suggest that miR-221/222 can be regarded as oncogenes in those types of cancer, because they directly target and down-regulate the tumor suppressor PTEN. Furthermore, their overexpression might be an important factor contributing to TRAIL resistance and to invasiveness of NSCLC and Hepatocarcinoma cells. Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 1391.