Overexpression of p16INK4A as a specific marker for dysplastic and neoplastic epithelial cells of the cervix uteri

Abstract

Cytological screening for cervical cancer or its precursors using Papanicolaou's smear test (Pap test) has been highly efficient to reduce the morbidity and mortality of cervical cancer. However, evaluation of the Pap test relies on subjective diagnostic parameters and is affected by a high rate of false-positive and false-negative results. More objective diagnostic parameters to identify truly dysplastic or neoplastic cells in cervical smears as well as in cervical biopsy samples would therefore avoid insecurity for many patients and the high screening costs associated with repeated testing. Cervical dysplasia is induced by persistent infections through highrisk types of human papillomaviruses (HPVs). Outgrowth of dysplastic lesions is triggered by increasing expression of two viral oncogenes, E6 and E7, which both interact with various cell cycle-regulating proteins. Among these is the retinoblastoma gene product pRB, which is inactivated by E7. pRB inhibits transcription of the cyclin-dependent kinase inhibitor gene p16 INK4a . Increasing expression of the viral oncogenes in dysplastic cervical cells might thus be reflected by increased expression of p16 INK4a . In line with this hypothesis, we observed marked overexpression of p16 INK4a in all cervical intraepithelial neoplasm (CIN) I lesions (n ‫؍‬ 47) except those associated with low-risk HPV types (n ‫؍‬ 7), all CIN II lesions (n ‫؍‬ 32), all CIN III lesions (n ‫؍‬ 60) and 58 of 60 invasive cervical cancers. In contrast, no detectable expression of p16 INK4a was observed in normal cervical epithelium (n ‫؍‬ 42), inflammatory lesions (n ‫؍‬ 48) and low-grade cervical lesions (CIN I) associated with low-risk HPV types (n ‫؍‬ 7). Dysplastic cells could also be identified in cervical smears using a specific p16 INK4a monoclonal antibody. These data demonstrate that p16 INK4a is a specific biomarker to identify dysplastic cervical epithelia in sections of cervical biopsy samples or cervical smears.

P16INK4A immunostaining is a strong indicator for high‐risk‐HPV‐associated oropharyngeal carcinomas and dysplasias, but is unreliable to predict low‐risk‐HPV‐infection in head and neck papillomas and laryngeal dysplasias

“…14 The proportion of positive cells is the primary parameter, with the intensity as a secondary scoring parameter. All cases scored as 2 and 3 showed a strong immunostaining intensity, while few cases scored as 1 stained less intensely positive.…”

Detection of cancer‐related gene expression profiles in severe cervical neoplasia

“…Consecutive sections of 5 m thickness were stained by immunohistochemistry (ABC detection system) for p16 expression. Overexpression of p16 is recognized as a surrogate marker for HR HPV infection 24 and was ideal to define areas containing predominantly neoplastic and tumor cells. Microdissection was performed using an inverted microscope (Axiovert; Zeiss, Oberkochen, Germany) and an extended glass needle fixed to an electronically controlled micromanipulator (Märzhäuser, Wetzlar, Germany).…”

“…p16 is invariably overexpressed in HR HPV-positive CIN and cervical cancer as a consequence of viral E7 oncogene expression. 24 The quality of microdissection was controlled by HE staining of the remaining tissue. The homogeneity of dysplastic and tumor cells was estimated to be Ͼ90% (Fig.…”

Biological activity of probable/possible high‐risk human papillomavirus types in cervical cancer

“…19,21,22 These HPV actions influence expression of other tumor suppressor proteins such as p16 INK4a within pRb pathway. 23 Therefore, these cellular proteins, i.e., pRb, p53 and p16 INK4a are considered surrogate markers for HPV involvement. Their expression in HPV-infected tumor cells can be measured by in situ methods such as immunohistochemistry (IHC).…”