Correlations Of HR-HPV Infection To P16～(INK4A) And PTEN Expression In Cervical Cancer And CIN

Background and ObjectiveHigh-risk human papillomavirus (HR-HPV) is the most important etiologic factor for cervical cancer. Now, the new technology of HR-HPV DNA test and liquid-based Thinprep cytology test (TCT) have increased the detection rate of cervical cancer and cervical intraepithelial neoplasias(CIN), But, both the positive predictive value(PPV) of HR-HPV and the sensitive of TCT for high-grade squamous intereapithelial lesion(HSIL) are low, so that the efficiency of cervical cancer screening is limited. Recent studies had revealed that there were the abnormal expression of tumor suppressor gene p16^INK4A and PTEN in cervical cancer tissues, in addition , the abnormal function of p16^INK4A was closely correlated to HR-HPV infection and the combined detection of HR-HPV and P16^INK4A would increase PPV for HSIL. In our study, p16^INK4A and PTEN and HR-HPV were detected together in the epithelial tissues and shedding cells of cervix, which was never reported in China. We aimed to investigate the correlations of HR-HPV infection to p16^INK4A and PTEN expression in the carcinogenesis of cervical epithelium, then to explore their molecular mechanism in the pathogenesis of cervical cancer and clinical application value of p16^INK4A to cytopathologic diagnosis.Materials and methodsThe paraffin-embedded tissue samples from 134 patients included 30 cases of normal cervix tissue, 23cases of CIN I , 26 cases of CIN II, 31 cases of CIN III, 24 cases of invasive cervical cancer (22 cases of squamous cell carcinoma and 2 cases of adenocarcinoma), in the Department of Obstetrics and Gynecology, the First Affiliated Hospital, Zhengzhou University , between October 2003 and December 2005. The age of the patients ranged from 21 to 65 years, with a mean of 35 years. 89 specimens of TCT- atypical squamous cells of undetermined significance (ASCUS) were collected from the outpatients in the Department of Obstetrics and Gynecology, the First Affiliated Hospital, Zhengzhou University , between January 2006 and October 2006. The age of the patients ranged from 21 to 65 years, with a mean of 33 years. HR-HPV test specimens of All patients in this study were sampled by sampler from the cervical os and endocervix before collecting specimens of tissue and cell. All patients were not treated with any therapy before collecting specimen. All specimens of tissue and cell were diagnosed by two pathologists.Immunohistochemical method was used to detected the expression of p16^INK4A and PTEN in 134 cases of cervical tissues and immunocytochemical method was used to detect the expression of p16^INK4A in 89 cases of TCT-ASCUS. By Hybrid Capture 2 (HC-2), we detected each case's HR-HPV DNA of 13 types.By using software package SPSS11.0, Chi-Square Test and Spearman Correlation were performed, Sensitivity(Se) and Specificity(Sp) and Positive Predictive Value(PPV) and Negative Predictive Value(NPV) were also involved. Significant level was considered as "alpha equals 0.05".Results1. p16^INK4A overexpression (moderate or strong expression) was observed in the groups of CIN II /III and cervical cancer, negative or weak expression in the groups of CIN I and normal cervix. The positive rates of p16^INK4A were significantly higher in CIN II / III and cervical cancer than in normal cervix and CIN I respectively (P<0.01), and staining intensity of p16^INK4A strengthened gradually from CIN I to cancer, with the rates of its strong expression increasing progressively.2. PTEN moderate or strong expression was mainly in the normal cervix and CIN I , and the positive rates of PTEN were significantly higher in the normal cervix and CIN I than in CIN II /III and cervical cancer respectively (P<0.01).3. The positive rates of HR-HPV were significantly higher in the groups of CIN and cervical cancer than in normal cervix respectively (P<0.01). The difference in the positive rates of HR-HPV among four groups (CIN I / II /III and cervical cancer) was not statistically significant (P>0.05).4. Overexpression of p16^INK4A was closely correlated to HR-HPV infection in cervical cancer and HSIL(CIN II/III)(r_s=0.572, P<0.001), while no obvious relationship between PTEN and HR-HPV was found (r_s =-0.119, P=0.171).5. In the low-grade squamous intereapithelial lesion (LSIL)-CIN I , the positive rate of p16^INK4A was significantly lower than that of HR-HPV (P<0.01).6. In 89 cases of TCT-ASCUS, there were 22 cases of CIN II /III(HSIL)and 2 cases of cervical cancer (26.97%, 24/89) diagnosed histopathologically.7. The positive expression of p16^INK4A in TCT-ASCUS was closely correlated to HSIL diagnosed histopathologically (r_s =0.835, P=0.000). HR-HPV positive was correlated to HSIL diagnosed histopathologically (r_s =0.323, P=0.002).8. In ASCUS, PPV(84.62%) and Sp(93.85%) of P16^INK4A for HSIL was significantly higher than PPV(35.94%) and Sp(36.92%) of HR-HPV.Conclusions1. p16^INK4A overexpression is observed in HR-HPV-infected cervical cancer and HSIL, and the intensity of p16^INK4A expression reflects the degree of cervical carcinogenesis induced by HR-HPV.2. During the cervical tumorigenesis, PTEN expression is lost or decreases through HR-HPV-independent mechanism, which suggests that there are multi-factors and multi-pathways to cause carcinogenesis of cervix.3. In TCT-ASCUS, p16^INK4A immunocytochemical staining is more accurate to differentiate the malignant diseases from the benign diseases of cervix than HC-2 HR-HPV DNA test, moreover, it avoids subjectivity of morphologic diagnosis and may improve the technology of cytological diagnose.