Tu1676 Role of Sprouty-2 and MicroRNA in Colon Cancer

Abstract

Introduction: We earlier established that sprouty-2 is overexpressed in human colon cancer and up-regulates c-met and thereby increases the growth phenotype and metastatic potential of colon cancer cells (Oncogene, 29: 5241-53, 2010). To our knowledge, this was the first study to demonstrate the tumor oncogene phenotype of sprouty-2 in colon cancer metastasis. On the contrary, cancer protective role of sprouty-2 was noted in breast, liver and prostate cancers. However, a recent report on non-small cell lung cancer (NSCLC) discovered that silencing of sprouty-2 reduced c-met expression and thus confirmed our findings in colorectal cancer (PNAS, 110: 8573-78, 2013). We further extended our studies to demonstrate that this pathway modulates gastrointestinal specific microRNAs (miRNAs) and regulates various oncogenes and tumor suppressor genes in colon cancer cells. Methods: RNA from control and shRNA sprouty-2 transfected cells were labeled with Hy5 and Hy3 respectively and hybridized to miRCURY LNA arrays. Unsupervised miRNA clustering was carried out and a heat map prepared with Java TreeView. MicroRNA targets were identified by Real-time PCR, western blotting and 3'UTR luciferase assays. Migratory phenotype of colon cancer cells was confirmed by cell migration and invasion assays in trans-well chambers. Cancer cells were transfected by miRNA mimics to assess the expression levels of target genes. Human colon cancer tissue microarrays were utilized to assess the expression of miRNA target genes. Human tumor sections were evaluated by immunofluorescence and immunohistochemical staining. Results: Sprouty-2 shRNA transfected stable cell lines demonstrated upregulation of tumor suppressive miRNAs and down-regulation of oncogenic miRNAs. Transfection of miRNA mimics regulated AKT, p21, N-cadherin and E-cadherin expression in western blotting and RTPCR experiments. Both shRNA sprouty-2 and miRNA mimics blocked cell migration and invasion in cancer cells. AKT was upregulated whereas E-cadherin was downregulated at the invasive fronts in human colon tumors. Conclusion: Sprouty-2/ AKT/E-cadherin expression levels could be used to risk-stratify patients for CRC recurrence and sprouty-2 axis regulation may lead to the development of therapeutics in colon and lung cancer.