| Background:Cervical cancer is the second most common malignancy in women worldwide. After the application of cytological screening in 1950s, the incidence and mortality of cervical cancer decreased significantly. According to the cytological diagnosis using the bethesda system (TBS), different managements are applied. However, controversy for atypical squamous cells of undetermined significance (ASCUS) and low-grade squamous intraepithelial lesion (LSIL) has being existing so far. American Society for Colposcopy and Cervical Pathology (ASCCP) recommended 3 alternative methods of managements, namely, cytological follow-up, immediate colposcopy and triage by high risk human papillomaviruses (HPV). Overdiagnosis would be considerable if immediate colposcopy were used. Missing of cervical intraepithelial neoplasia (CIN) and losing follow-up are the main disadvantages of cytological follow-up. In order to evaluate the cost-effect ratio of above-mentioned 3 methods, ALTS test (the Atypical Squamous Cells of Undetermined Significance Low Grade Squamous Intraepithelial Lesion Triage Study) found that HPV test had a high cost-effect ratio for ASCUS, with avoidance of overuse of colposcopy, saving limited medical resources and minimized missing of CIN. But most research found that HPV test to recognize CIN from ASCUS had low specificity and positive predictive value (PPV). In addition, ALTS test also found that the rate of HPV infection of LSIL was more than 80%, which lost the triage significance. ASCCP did not recommend triage by HPV test for LSIL. Thus, it is urgent and necessary to find an appropriate biomarker to distinguish benign reactive hyperplasia and CIN, especial high grade CIN. P16INK4αgene is one of tumor suppressor genes which closely relate to cell circle regulation, located in 9p21. The P16INK4αprotein, which contains 156 amino acids and whose molecular weight is 16569ku, is a cell-cycle inhibitor that binds CDK. By the pathway of cyclin D1-CDK4/6-retinoblastoma protein (pRB)-E2F, the p16INK4αinhibits the cell circle. Many researches on genes related to cervical cancer found over expression of p16INK4αgene in all cervical cancer and precancerous lesions with HPV infection, and no expression in normal tissues or cells. In addition, the expression rates of p16INK4αgene in HSIL and cancer are significantly higher than that in LSIL. Preceding researches found that immunochemistry staining of p16INK4αin cervical cytological smear could be a triage for ASCUS. Present study aimed to evaluate the value of the triage by p16INK4αin ASCUS-LSIL by immunochemistry staining in cervical cytological smear.Objective:To investigate the p16INK4αexpression in the cervical cells of ASCUS and LSIL, and to evaluate the value of triage for ASCUS and LSIL. By comparing with HPV, we want to find an effective triage for ASCUS/LSIL.Methods:Immunocytochemical analyses were carried out in residual liquid-based cytology and specimens of 104 ASCUS and 52 LSIL were enrolled in Women's Hospital, School of Medicine, Zhejiang University from March 2008 to March 2009. All women underwent colposcopy, and biopsied histological examination, HR-HPV test by Hybrid Capture II HPV (HC2), p16INK4α(scoring by the intensity of immunochemistry staining and cell morphology).18 patients of ASCUS and 7 patients of LSIL were ruled out because the number of cells was too small. Thus, there were 86 patients of ASCUS and 45 patients of LSIL in our study.Results:1. A positive relation between the score of p16IN4αand the grade of lesions was observed both in ASCUS and LSIL by Spearman analysis (P=0.000), with rs 0.609 and 0.602, respectively. Score 2 was the cutoff by ROC. By p16INK4αscreening, the sensitivity, specificity, positive predictive valur(PPV) and negative predictive value (NPV) for>CINⅡwere 87.5%,68.6%,38.9%and 96.0%in ASCUS patients, respectively. And the sensitivity, specificity, PPV and NPV for>CINⅡwere 90.0%, 71.4%,47.4%, and 96.2%in LSIL patients, respectively. The specificity with score 2 in the cutoff of p16INK4αwas significantly higher than the specificity with score 1 (X2=5.770, P<0.05 in ASCUS, X2=4.769, P<0.05 in LSIL). There was no difference of sensitivity, PPV and NPV between cutoff of score 2 and score 1, both in ASCUS and LSIL.2. The positive rates of HPV DNA in ASCUS and LSIL were 61.6%and 77.8%, respectively. By HPV DNA screening, the sensitivity, specificity, PPV and NPV for >CINⅡwere 93.8%,45.7%,28.3%and 97.0%in ASCUS patients, respectively. And the sensitivity, specificity, PPV and NPV for>CINⅡwere 90.0%,25.7%, 25.7%, and 90.0%in LSIL patients, respectively. The specificity of p16INK4αwas significantly higher than the specificity of HPV DNA (X2=7.467, P<0.05 in ASCUS, X2=14.641, P<0.05 in LSIL). There was no difference of sensitivity, PPV and NPV between p16INK4αand HPV DNA, both in ASCUS and LSIL. 3. There were 24 patients (45.3%) with p16INK4αscore≥2 in 53 patients with positive HPV DNA in ASCUS. In the patients with positive HPV DNA in ASCUS, the sensitivity, specificity, PPV and NPV for≥CINⅡusing p16INK4αwere 86.7%, 71.0%,54.2%and 93.1%. There were 19 patients (45.3%) with p16INK4αscore≥2 in 35 patients with positive HPV DNA in LSIL. In the patients with positive HPV DNA in LSIL, the sensitivity, specificity, PPV and NPV for≥CINⅡusing p16INK4αwere 100%,61.5%,47.4%and 100%.Conclusions:These data suggested that the use of p16INK4αas a biomarker combined with nuclear scoring of p16INK4αpositive cells in cervical cytology to triage ASCUS-LSIL cases was valuable. p16INK4αscreens HGCIN in cervical lesions shows better sensitivity and better specificity than HR-HPV DNA. |
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