MicroRNA 133B targets pro-survival molecules MCL-1 and BCL2L2 in lung cancer

Abstract

Lung cancer is the most frequent cause of cancer-related death in this country for men and women. MicroRNAs (miRNAs) are a family of small non-coding RNAs (approximately 21–25nt long) capable of targeting genes for either degradation of mRNA or inhibition of translation. We identified aberrant expression of 41 miRNAs in lung tumor versus uninvolved tissue. MiR-133B had the lowest expression of miRNA in lung tumor tissue (28-fold reduction) compared to adjacent uninvolved tissue. We identified two members of the BCL-2 family of pro-survival molecules (MCL-1 and BCL2L2 (BCLw)) as predicted targets of miR-133B. Selective over-expression of miR-133B in adenocarcinoma (H2009) cell lines resulted in reduced expression of both MCL-1 and BCL2L2. We then confirmed that miR-133B directly targets the 3′UTRs of both MCL-1 and BCL2L2. Lastly, over-expression of miR-133B induced apoptosis following gemcitabine exposure in these tumor cells. To our knowledge, this represents the first observation of decreased expression of miR-133B in lung cancer and that it functionally targets members of the BCL-2 family.