Abstract
Epithelial to mesenchymal transition (EMT) is a key process during embryonic development and disease development and progression. During EMT, epithelial cells lose epithelial features and express mesenchymal cell markers, which correlate with increased cell migration and invasion. Transforming growth factor-β (TGF-β) is a multifunctional cytokine that induces EMT in multiple cell types. The TGF-β pathway is regulated by microRNAs (miRNAs), which are small non-coding RNAs regulating the translation of specific messenger RNAs.Herein, we identified mir-99a and mir-99b as two novel TGF-β target miRNA genes, the expression of which increased during TGF-β induced EMT of NMUMG cells. Mir-99a and mir-99b inhibition decreased TGF-β activity by inhibiting SMAD3 phosphorylation, resulting in decreased migration and increased proliferation in response to TGF-β. However, mir-99a and mir-99b inhibition was insufficient to block TGF-β induced EMT of NMUMG cells.Mir-99a and mir-99b over-expression in epithelial NMUMG cells resulted in increased proliferation, migration and fibronectin expression, while E-cadherin and ZO-1 expression were negatively regulated.In conclusion, we identified mir-99a and mir-99b as two novel modulators of TGF-β pathway that alter SMAD3 phosphorylation, in turn altering cell migration and adhesion of mesenchymal NMUMG cells. The effect of mir-99a and mir-99b over-expression on NMUMUG proliferation is dependent upon the epithelial or mesenchymal status of the cells. Our study suggests that mir-99a and mir-99b may function as modulators within a complex network of factors regulating TGF-β induced breast epithelial to mesenchymal transition, as well as proliferation and migration of breast cancer cells, providing a possible target for future translationally oriented studies in this area.
Highlights
Epithelial to mesenchymal transition (EMT) is a complex process, which involves cytoskeletal remodeling and cell–cell and cell–matrix adhesion as well as transcriptional regulation, leading to the transition from a polarized epithelial phenotype to an elongated fibroblast-like phenotype
Mir-99a and mir-99b expression increased during Transforming growth factor-b (TGF-b) induced EMT in normal mouse mammary gland (NMUMG) cells
When stimulated by TGF-b, NMUMG cells undergo EMT by showing visible morphological changes within 24 hours, and the EMT process can be considered complete in 3 days [31] (Figure 1A,B): mesenchymal NMUMG cells adopted a spindlelike shape which was correlated with actin reorganization, decreased E-cadherin expression and increased a-SMA expression
Summary
Epithelial to mesenchymal transition (EMT) is a complex process, which involves cytoskeletal remodeling and cell–cell and cell–matrix adhesion as well as transcriptional regulation, leading to the transition from a polarized epithelial phenotype to an elongated fibroblast-like phenotype. In turn mTOR negatively regulates TGF-b signaling through SMAD3 inhibition. Mirnas are regulatory genes that inhibit gene expression of specific target genes, primarily by binding to the 39 UTR of the specific mRNA [4,5,6,7]. They have important roles in many biological processes such as cell proliferation, differentiation and embryonic development as well as in the development and progression of diseases [8,9,10,11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
