These three cervical cancer cell lines are known to contain high-risk serotype human papilloma virus (HPV) sequences in their DNA and expressed the E6 and E7 oncoproteins [34,35] It is very likely that the HPV-originated E6 and E7 resulted in defective cell cycle regulations that rendered the cells unable to be arrested at G0/1 phase via inactivation of the retinoblastoma protein (Rb) and p53 [35,36]. This evidence concerns the gene RB1 and cervical cancer.