PIWIL1 and lung cancer: Interestingly, we found that co-expression of RASSF1C and IGFBP-5 reduced PIWIL1 mRNA and protein levels in lung cancer cell lines, while co-expression of RASSF1A-RASSF1C did not have a major effect on PIWIL1 mRNA levels compared to cells over-expressing RASSF1C (Figure 7).