Relationship between HPV typing and abnormality of G1 cell cycle regulators in cervical neoplasm

In tumorigenesis, loss of function of the G1 pathway (p16-CDK4/cyclinD1-pRB pathway (RB pathway) and p14-MDM2-p53 pathway (p53 pathway)) is a theoretically essential event. The simultaneous analysis of all components of the RB and p53 pathway may be able to explain cervical tumorigenesis. However, there are no reports in which all components of the G1 pathway and HPV typing were examined simultaneously in cervical cancer.

We examined HPV typing and the status of the G1 pathways simultaneously by PCR-SSCP, multiplex PCR, methylation-specific PCR, and immunohistochemical techniques in cervical neoplasia. A total of 105 samples (normal, 10; cervical intraepithelial neoplasm (CIN), 42; invasive cancer (IC), 53) were included.

Abnormality of the RB pathway tended to be more frequent in ICs (60.4%) than in CINs (31.0%) (P = 0.069). The primary target was p16 (CIN, 14.3%; IC, 43.4%; P = 0.032). Abnormality of the p53 pathway was detected in ICs (56.6%) and in CINs (40.5%) (P = 0.1494). In particular, strong expression of MDM2 was higher in ICs (32.1%) than in CINs (7.1%) (P = 0.0045). Abnormalities of the RB and p53 pathways were higher in low-risk and negative HPV than in high-risk HPV (81.3% vs 51.4%, P = 0.0657; 81.3% vs 45.9%, P = 0.0328). Seven HPV-negative cases had abnormalities in the RB or p53 pathways.

In conclusion, abnormality of the G1 pathway may be one of the important mechanisms for carcinogenesis of low-risk and negative HPV cases.