RASSF1 and lung cancer: To begin the functional characterization of some of the identified piRNAs, we first validated the expression of the two most up-regulated piRNAs (piR-34871 and piR-52200) and the two most down-regulated pi-RNAs (piR-35127 and piR-46545) in lung cancer cells that either over-express RASSF1C, RASSF1A, and in cells with knocked-down RASSF1C expression by RT-PCR (Figure 3).