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Background: Migration and invasion enhancer 1 (MIEN1) is a novel gene found to be abundantly expressed in breast tumor tissues and functions as a critical regulator of tumor cell migration and invasion to promote systemic metastases. Previous studies have identified post-translational modifications by isoprenylation at the C-terminal tail of MIEN1 to favor its translocation to the inner leaflet of plasma membrane and its function as a membrane-bound adapter molecule. However, the exact molecular events at the membrane interface activating the MIEN1-driven tumor cell motility are vaguely understood. Methods: MIEN1 was first studied using in-silico analysis on available RNA sequencing data of human breast tissues and its expression was ascertained in breast cells. We performed several assays including co-immunoprecipitation, wound healing, western blotting and immunofluorescence to decipher the molecular events involved in MIEN1-mediated tumor cell migration. Results: Clinically, MIEN1 is predominantly overexpressed in Her-2 and luminal B subtypes of breast tumors, and its increased expression correlates with poor disease free survival. Molecular studies identified a phosphorylationdependent activation signal in the immunoreceptor tyrosine based activation motif (ITAM) of MIEN1 and the phosphorylation-deficient MIEN1-mutants (Y39F/50 F) to regulate filopodia generation, migration and invasion. We found that ITAM-phosphorylation of MIEN1 is significantly impaired in isoprenylation-deficient MIEN1 mutants indicating that prenylation of MIEN1 and membrane association is required for cross-phosphorylation of tyrosine residues. Furthermore, we identified MIEN1 as a novel interactor of Annexin A2 (AnxA2), a Ca2+ -dependent phospholipid binding protein, which serves as an extracellular proteolytic center regulating plasmin generation. Fluorescence resonance energy transfer (FRET) confirmed that MIEN1 physically interacts with AnxA2 and functional studies revealed that they mutually cooperate to accentuate tumor cell motility. Interestingly, our study identified that ectopic overexpression of MIEN1 significantly enhances Tyr23-phosphorylation on AnxA2, thereby stimulating cell surface translocation of AnxA2 and catalyzing the activation of its proteolytic activity. Conclusion: Our data show that the presence and interaction of both MIEN1 and AnxA2 in breast tumors are crucial drivers of cell motility. Our study has now deciphered a novel regulatory network governing the vicious process of breast tumor cell invasion-metastasis, and findings suggest MIEN1-AnxA2 as prospective targets to counter the deadly disease. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are crucial molecules that regulate gene expression and hence pathways that are key to prostate cancer progression. These non-coding RNAs are highly deregulated in prostate cancer thus facilitating progression of the disease. Among the many genes that have gained importance in this disease, Migration and invasion enhancer 1 (MIEN1), a novel gene located next to HER2/neu in the 17q12 amplicon of the human chromosome, has been shown to enhance prostate cancer cell migration and invasion, two key processes in cancer progression. MIEN1 is differentially expressed between normal and cancer cells and tissues. Understanding the regulation of MIEN1 by microRNA may enable development of better targeting strategies. Methods The miRNAs that could target MIEN1 were predicted by in silico algorithms and microarray analysis. The validation for miRNA expression was performed by qPCR and Northern blotting in cells and by in situ hybridization in tissues. MIEN1 and levels of other molecules upon miRNA regulation was determined by Western blotting, qPCR, and immunofluorescence. The functional effects of miRNA on cells were determined by wound healing cell migration, Boyden chamber cell invasion, clonal and colony formation assays. For knockdown or overexpression of the miRNA or overexpression of MIEN1 3'UTR, cells were transfected with the oligomiRs and plasmids, respectively. Results A novel miRNA, hsa-miR-940 (miR-940), identified and validated to be highly expressed in immortalized normal cells compared to cancer cells, is a regulator of MIEN1. Analysis of human prostate tumors and their matched normal tissues confirmed that miR-940 is highly expressed in the normal tissues compared to its low to negligible expression in the tumors. While MIEN1 is a direct target of miR-940, miR-940 alters MIEN1 RNA, in a quantity as well as cell dependent context, along with altering its downstream effectors. The miR-940 inhibited migratory and invasive potential of cells, attenuated their anchorage-independent growth ability, and increased E-cadherin expression, implicating its role in mesenchymal-toepithelial transition (MET). Conclusions These results, for the first time, implicate miR-940, a regulator of MIEN1, as a promising novel diagnostic and prognostic tool for prostate cancer. [ABSTRACT FROM AUTHOR]