Human papillomavirus (HPV) is a necessary cause of cervical cancer and its precursors. Increased expression of high-risk hrHPV viral oncogenes in abnormal cells might increase the expression of p16INK4a. We aimed to determine the role of p16INK4a in detecting hrHPV-transformed epithelial cells in liquid-based cervical cytology, and compared the results with hrHPV DNA testing by realtime polymerase chain reaction (RT-PCR). Fifty-seven cytological samples were tested for p16INK4a immunomarker and hrHPV DNA. Test performance of both tests was determined by comparing sensitivity, specificity and predictive values using available histological follow-up data as gold standard. Of 57 samples, 36 (63.2%) showed immunoreactivity for p16INK4a and 43 (75.4%) were hrHPV-infected. A fairly low concordance rate (k = 0.504) between p16INK4a immunolabelling and hrHPV DNA status was noted. For prediction of cervical intraepithelial neoplasia (CIN) II and worse lesions, p16INK4a had a sensitivity and specificity of 93.5% and 60%; whereas hrHPV DNA testing had a sensitivity and specificity of 100% and 20%. Dual testing by combining p16INK4a and hrHPV showed sensitivity and specificity of 100% and 33.3%. In conclusion, p16INK4a is useful in predicting severity of the cytological abnormalities. Although p16INK4a is more specific but less sensitive than hrHPV in detecting high-grade cervical lesions, a combination of both tests failed to demonstrate significant improvement in diagnostic sensitivity, specificity and predictive value. Larger-scale prospective studies are required to assess further whether this biomarker should be routinely used as primary screening tool independently or in combination with hrHPV testing to improve diagnostic accuracy in cervical cytology.
Cervical cancer is the second most common cancer affecting Malaysian women. Despite the implementation of pap smear screening, many women are still diagnosed only in the advanced stage of cervical cancer. This could partly be due to failure of detection of its precursor lesions; hence the need to search for novel biomarkers to assist in the screening and diagnosis of cervical neoplasia. This study aims to determine the expression of p16INK4A and survivin as possible predictive biomarkers in cervical squamous neoplasm.
On integration into the host cervical keratinocyte genome, human papillomavirus (HPV) E7 protein binds pRB,releasing E2F from normally incompetent pRB-E2F complexes and allowing propagation of G1-S transition by the E2F. p16(INK4a), a tumour suppressor protein, increases in reflex response to counter this. 29 histologically re-confirmed low-grade squamous intraepithelial lesions (LSIL), 27 high-grade squamous intraepithelial lesions (HSIL) and 30 invasive cervical squamous carcinoma (SCC) were immunohistochemically stained for p16(INK4a) expression using the CINtec Histology Kit (REF 9511, mtm laboratories AG, Heidelberg, Germany) to re-affirm the notion that integration of HPV occurs predominantly in SCC and possibly HSIL and less in LSIL and normal squamous epithelium (NSqE). Implicit was also the attempt to understand the role of E2F, as indicated by p16(INK4a), in evolution of SCC from HSIL. No ethnic predilection was noted for LSIL, HSIL or SCC. Patients with SCC were significantly older by about 14-years compared with HSIL (p < 0.05) while there was no significant age difference between HSIL and LSIL. p16(INK4a) expression was significantly increased (p < 0.05) in both HSIL (88.9%) and SCC (83.3%) compared with LSIL (3.4%) and NSqE (0%); the NSqE being normal squamous epithelium noted in 17 of the LSIL, 19 HSIL and 5 SCC. From these findings there is suggestion that fundamental upstream events viz HPV integration, E7 upregulation followed by E2F activation occurs at point of transformation to HSIL and continues unrelentingly for another one to two decades before hitherto unclear factors convert a non-invasive lesion into an overtly invasive malignant counterpart. Interestingly, the occurrence of HSIL and LSIL in almost the same age group could mean that alteration from episomal to integrated form of HPV may not incur a prolonged incubation period, unlike from HSIL to SCC.