RASSF1C modulates the expression of a stem cell renewal gene, PIWIL1

Abstract

BackgroundRASSF1A and RASSF1C are two major isoforms encoded by the Ras association domain family 1 (RASSF1) gene through alternative promoter selection and mRNA splicing. RASSF1A is a well established tumor suppressor gene. Unlike RASSF1A, RASSF1C appears to have growth promoting actions in lung cancer. In this article, we report on the identification of novel RASSF1C target genes in non small cell lung cancer (NSCLC).MethodsOver-expression and siRNA techniques were used to alter RASSF1C expression in human lung cancer cells, and Affymetrix-microarray study was conducted using NCI-H1299 cells over-expressing RASSF1C to identify RASSF1C target genes.ResultsThe microarray study intriguingly shows that RASSF1C modulates the expression of a number of genes that are involved in cancer development, cell growth and proliferation, cell death, and cell cycle. We have validated the expression of some target genes using qRT-PCR. We demonstrate that RASSF1C over-expression increases, and silencing of RASSF1C decreases, the expression of PIWIL1 gene in NSCLC cells using qRT-PCR, immunostaining, and Western blot analysis. We also show that RASSF1C over-expression induces phosphorylation of ERK1/2 in lung cancer cells, and inhibition of the MEK-ERK1/2 pathway suppresses the expression of PIWIL1 gene expression, suggesting that RASSF1C may exert its activities on some target genes such as PIWIL1 through the activation of the MEK-ERK1/2 pathway. Also, PIWIL1 expression is elevated in lung cancer cell lines compared to normal lung epithelial cells.ConclusionsTaken together, our findings provide significant data to propose a model for investigating the role of RASSF1C/PIWIL1 proteins in initiation and progression of lung cancer.

Differential DNA methylation profiles of infants exposed to maternal asthma during pregnancy

“…Increased expression of PIWIL1 has been reported in asthmatic airway epithelium . Expression of PIWIL1 is regulated by RAS associated domain family (RASSF1C) which also regulates the MEK‐ERK1/2 pathway, known to be important in the pathogenesis of asthma . We observed hyper‐methylation of this locus suggesting possible down regulated expression, in contrast to the up regulation reported in the epithelium, which may relate to the tissues sampled (i.e., blood vs. airway epithelium) or the influence of developmental changes on the relationship between this gene and asthma.…”

Evidence that RASSF1C Stimulation of Lung Cancer Cell Proliferation Depends on IGFBP-5 and PIWIL1 Expression Levels

“…We have previously demonstrated that knock-down of RASSF1C expression results in down-regulation of PIWIL1 gene expression [12]. Thus we wanted to determine if PIWIL1 gene knock-down will affect β-catenin expression.…”

The significance of PIWI family expression in human lung embryogenesis and non-small cell lung cancer

“…Other mechanisms have also been shown to affect PIWIL1 expression. Reeves and coworkers found that PIWIL1 expression was higher in NSCLC cell lines (A549 and NCI-H1299) than in normal lung epithelial cells (CRL-9482) and that the expression of PIWIL1 could be activated by the oncogene RASSF1C [ 38 ].…”