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p16INK4A overexpression is frequently detected in tumour-free tonsil tissue without association with HPV

Authors


E-J M Speel, PhD, Department of Molecular Cell Biology, UNS50-17, Maastricht University Medical Centre, PO Box 616, 6200 MD Maastricht, the Netherlands. e-mail: ernstjan.speel@molcelb.unimaas.nl

Abstract

Klingenberg B, Hafkamp H C, Haesevoets A, Manni J J, Slootweg P J, Weissenborn S J, Klussmann J P & Speel E-J M
(2010) Histopathology56, 957–967
p16INK4Aoverexpression is frequently detected in tumour-free tonsil tissue without association with HPV

Aims:  Oncogenic human papillomavirus (HPV) type 16 has been strongly associated with tonsillar squamous cell carcinoma (TSCC) and appears to be of prognostic significance. Because HPV+ TSCC also accumulates p16INK4A, this cyclin-dependent kinase inhibitor has been proposed as a potential biomarker for HPV in clinical diagnosis. The aim of this study was to determine the prevalence of HPV in tumour-free tonsillar tissue and the value of p16INK4A overexpression in predicting its presence.

Methods and results:  p16INK4A overexpression was detected by immunohistochemistry in tissue sections of tumour-free tonsils of 262 patients. They were treated for non-oncological reasons (snoring or chronic/recurrent tonsillitis) consisting of tonsillectomy. Genomic DNA isolated from these tissues was subjected to HPV-specific polymerase chain reaction (PCR) analysis. p16INK4A immunoreactivity was detected in 28% of samples in both crypt epithelium (49/177) and lymphoid germinal centres (52/187), which correlated with each other (P < 0.0001). No reactivity was observed in superficial squamous cell epithelium. HPV16 and 18 were detected by PCR analysis in 2/195 cases (1%), which, however, were negative on fluorescence in situ hybridization analysis and discrepant on p16INK4A immunostaining.

Conclusions:  No proof was found for the presence of HPV in tumour-free tonsil tissue, despite increased p16INK4A expression in a quarter of tonsil cases. Other mechanisms than HPV infection are therefore implicated in p16INK4A up-regulation.

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