PIWIL1 and lung carcinoma: And, it has been generally accepted that the hypermethylated status of the promoter CpG islands represents the long-term transcription-silencing state of the genes [11-13].Other researches have also offered the evidence that RASSF1 stimulation of lung cancer cell proliferation depends on IGFBP-5 and PIWIL1 expression levels [14].