ORIGINAL ARTICLEEfficiency of immunohistochemical p16 expression and HPV typing in cervical squamous intraepithelial lesion grading and review of the p16 literature☆
Introduction
Occasionally, it is challenging to render an accurate histopathologic diagnosis of cervical cancer precursors, which is an essential determiner in prognosis and survival. In particular, the differential diagnosis between reactive states and LSIL, and LSIL and HSIL may be difficult [6], [7], [9], [20]. At this point, the need for objective and reliable diagnostic tools cannot be ignored.
p16, a tumor suppressor protein and also a cyclin-dependent kinase inhibitor, whose overexpression has repeatedly been reported to be typical of dysplastic and neoplastic epithelium of cervix [29], [1], [15], slows down the cell cycle by inactivating the cyclin-dependent kinases that phosphorylate retinoblastoma protein (pRb) [26], [16]. The viral oncogenes E6 and E7 of HPV, whose expression is associated with malignant transformation of the cervical epithelial cells [27], [31], have the ability to bind and inactivate pRb. The pRb status has a remarkable influence on the expression of p16. p16 expression in cervical lesions is hypothesized to be caused by the functional inactivation of pRb by HPV-E6 and E7 proteins.
Many studies have proposed that p16 is a useful biomarker especially for HR (high risk)-HPV type-related cervical neoplasia [16, 18, 33, 35, 39, 45, 56, 58], and also for predicting SIL progression [13], [22], [10]. Moreover, a few other studies have recently concluded that there exists a significant association between cervical lesion grade and p16 staining distribution and intensity [17], [12], [11]. As for the localization of p16 staining, there are studies that report predominant cytoplasmic staining [15] as well as predominant nuclear staining [30], and a combination of both [23].
In this study, we used immunohistochemistry to investigate the staining pattern of p16 on the basis of distribution and intensity, and the presence of HPV in squamous intraepithelial lesions of the cervix. In this way, it was expected to define the role of p16 expression and HPV typing in the diagnosis and grading of the precursor lesions of the cervix.
Section snippets
Materials and methods
Hematoxylin-eosin stained slides from formalin-fixed, paraffin-embedded tissue sections from cervical loop excision materials, formerly diagnosed as LSIL and HSIL, were reviewed by the same pathologist. From the group of cases with confirmed diagnosis, we selected a LSIL group of 15 cases and a HSIL group of 20 cases. From each chosen paraffin-embedded tissue block, three serial sections were taken.
Results
All HSIL cases (20/20) and 80% of LSIL cases (12/15) were positive with p16. Staining distribution in the HSIL cases was as follows: 50% full thickness, 45% basal, and 5% rare (Fig. 1k, l). The staining intensity of the same cases was strong in 70%, variable in 20%, and weak in 10%, accordingly. Of p16-positive LSIL cases, staining distribution was basal in 58.3% and rare in 41.7%. None of the LSIL cases showed full thickness of p16 positivity (Fig. 1m, n). The staining intensity of the same
Discussion
Despite extensive studies of cervical cancer precursors, the interobserver variation in the histopathologic interpretation of cervical biopsy specimens still constitutes a dilemma [14], [28]. The search for a specific diagnostic biomarker to solve the problem of lack of interobserver reproducibility in the histologic diagnosis of cervical intraepithelial lesions revealed p16, a tumor supressor protein, whose overexpression has been frequently shown in cervical cancers and its precursors: Klaes
Acknowledgements
The authors would like to thank to Ünal Şeref for technical support and to Lokman Kale for archival assistance.
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2015, Experimental and Molecular PathologyCitation Excerpt :The 3 year follow-up results indicated that the expression of p16 protein was negatively correlated with the survival rates of patients with cervical cancer suggesting that p16 protein also could be a prognostic biomarker for cervical cancer patients. As mentioned in the Introduction section, p16 is known as a tumor suppressor and a CDK inhibitor, which could slow down the cell cycle; its overexpression has been documented to be representative of neoplastic and dysplastic epithelium of cervix (Yildiz et al., 2007). The expression of viral oncogenes HPV (E6 and E7) has the capability to bind and inactivate pRb, whose status has a notable effect on the p16 expression, and also is correlated with the malignant transformation of cervical epithelial cells (van de Putte et al., 2003).
Methylated ZNF582 gene as a marker for triage of women with Pap smear reporting low-grade squamous intraepithelial lesions - A Taiwanese Gynecologic Oncology Group (TGOG) study
2014, Gynecologic OncologyCitation Excerpt :With the addition of Ki67, the use of p16/Ki67 dual-stain cytology has been shown to have an improved performance with high specificity without compromising sensitivity compared to HC2 [13,14]. Although p16 with or without Ki67 staining provides excellent results in the triage of women with LSILs, substantial inter-observer variability regarding the interpretation of positive p16 cytological tests has been reported due to the various criteria proposed [16–23]. Furthermore, p16 overexpression may also be detected in a fraction of non-dysplastic cells.
P16 <sup>INK4a</sup> immunocytochemistry/immunohistochemistry: Need for scoring uniformization to be clinically useful in gynecological pathology
2012, Annals of Diagnostic PathologyCitation Excerpt :This may be an important point because a statistically significant association between the p16 score and the degree of CIN has been reported [37,40–42]. As summarized in the Table, literature data show that 2-, 3-, and 4-tier systems of scoring are used [4,7,27,29,38,43–50]. Others implement a histoscore [36,37,51,52].
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This study was presented as a poster in the 20th European Congress of Pathology on 7 September 2005.