Transforming growth factor-ß-induced lncRNA-Smad7 inhibits apoptosis of mouse breast cancer JygMC(A) cells.

ABSTRACT

Transforming growth factor (TGF)-ß exhibits both pro-apoptotic and anti-apoptotic effects on epithelial cells in a context-dependent manner. The anti-apoptotic function of TGF-ß is mediated by several downstream regulatory mechanisms, and has been implicated in the tumor-progressive phenotype of breast cancer cells. We conducted RNA sequencing of mouse mammary gland epithelial (NMuMG) cells and identified a long non-coding RNA, termed lncRNA-Smad7, which has anti-apoptotic functions, as a target of TGF-ß. lncRNA-Smad7 was located adjacent to the mouse Smad7 gene, and its expression was induced by TGF-ß in all of the mouse mammary gland epithelial cell lines and breast cancer cell lines that we evaluated. Suppression of lncRNA-Smad7 expression cancelled the anti-apoptotic function of TGF-ß. In contrast, forced expression of lncRNA-Smad7 rescued apoptosis induced by a TGF-ß type I receptor kinase inhibitor in the mouse breast cancer cell line JygMC(A). The anti-apoptotic effect of lncRNA-Smad7 appeared to occur independently of the transcriptional regulation by TGF-ß of anti-apoptotic DEC1 and pro-apoptotic Bim proteins. Small interfering RNA for lncRNA-Smad7 did not alter the process of TGF-ß-induced epithelial-mesenchymal transition, phosphorylation of Smad2 or expression of the Smad7 gene, suggesting that the contribution of this lncRNA to TGF-ß functions may be restricted to apoptosis. Our findings suggest a complex mechanism for regulating the anti-apoptotic and tumor-progressive aspects of TGF-ß signaling.