RASSF1C functions as an oncogene in
lung cancer cells by stimulating proliferation and migration, and reducing apoptosis. Further, RASSF1C up-regulates important
protein-coding and non-coding genes involved in
lung cancer cell growth, including the stem cell self-renewal gene, piwil1, and small noncoding PIWI-interacting RNAs (
piRNAs). In this article, we report the identification of
microRNAs (
miRNAs) that are modulated in
lung cancer cells over-expressing RASSF1C. A
lung cancer-specific
miRNA PCR array screen was performed to identify RASSF1C target
miRNA-coding genes using
RNA isolated from the
lung cancer cell line H1299 stably over-expressing RASSF1C and corresponding control. Several modulated
miRNA genes were identified that are important in
cancer cell proliferation and survival. Among the
miRNAs down-regulated by RASSF1C is miRNA-33a-5p (miRNA-33a), which functions as a
tumor suppressor in
lung cancer cells. We validated that over-expression of RASSF1C down-regulates miR-33a expression and RASSF1C knockdown up-regulates miR-33a expression. We found that RASSF1C over-expression also increases β-
catenin,
vimentin, and snail
protein levels in cells over-expressing miR-33a. In addition, we found that RASSF1C up-regulates the expression of ABCA1
mRNA which is a known target of miR-33a. Our findings suggest that RASSF1C may promote lung epithelial mesenchymal transition (EMT), resulting in the development of a
lung cancer stem cell phenotype, progression, and
metastasis, in part, through modulation of miR-33a expression. Our findings reveal a new mechanistic insight into how RASSF1C functions as an oncogene.