Gene expression in both healthy and cancerous tissues is controlled by a wide array of regulatory molecules including a group of small RNA molecules known as microRNAs. New research, performed by Ethan Dmitrovsky and colleagues, at Dartmouth Medical School, Hanover, now provides evidence that the microRNA miR-31 promotes lung cancer by repressing the expression of a number of tumor suppressor genes (i.e., genes that generate proteins that suppress the development of cancer).
The initial series of experiments conducted in the study indicated that miR-136, miR-376a, and miR-31 were all overexpressed in mouse and human malignant lung tissue compared with paired normal tissue. Importantly, knockdown of miR-31 expression repressed the in vitro growth of mouse and human lung cancer cell lines and reduced the in vivo tumorigenicity of mouse lung cancer cell lines.
Further analysis provided a potential mechanism by which modulation of miR-31 expression levels could affect lung cancer cell growth: miR-31 repressed expression of the tumor-suppressor genes LATS2 and PPP2R2A. As miR-31 and these target genes were inversely expressed in human lung cancers, the authors conclude that their data has clinical relevance and that miR-31 promotes lung cancer by repressing expression of specific tumor suppressors.