PIR and breast cancer: Because we found that piR-35127 and piR-46545 were down-regulated in lung cancer cells over-expressing RASSF1C and were also down-regulated in 50% of lung tumor tissues examined, we over-expressed piR-35127 and piR-46545 in lung and breast cancer cell lines and in normal lung and breast epithelial cells and assessed their impact on cell proliferation, colony formation, and apoptosis.