In HeLa, SiHa, and CaSki cervical cancer cell lines, which contain an integrated HR-HPV genome of type 18, 16, or both, respectively, Piwil2 expression was observed; however, in the C33a cell line, which is negative for HR-HPV DNA and RNA, no expression was detectable (Figure 1d). This evidence concerns the gene PIWIL2 and cervical cancer.