p16 INK4A overexpression is frequently detected in tumour-free tonsil tissue without association with HPV.
OBJECTIVE
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 p16(INK4A), 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 p16(INK4A) overexpression in predicting its presence.


RESULTS
p16(INK4A) 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. p16(INK4A) 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 p16(INK4A) immunostaining.


CONCLUSIONS
No proof was found for the presence of HPV in tumour-free tonsil tissue, despite increased p16(INK4A) expression in a quarter of tonsil cases. Other mechanisms than HPV infection are therefore implicated in p16(INK4A) up-regulation.
Klingenberg
Boris
B
Department of Molecular Cell Biology, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, the Netherlands.
Hafkamp
Harriët C
HC
Haesevoets
Annick
A
Manni
Johannes J
JJ
Slootweg
Pieter J
PJ
Weissenborn
Soenke J
SJ
Klussmann
Jens P
JP
Speel
Ernst-Jan M
EJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D016009:Chi-Square Distribution; D002648:Child; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D004279:DNA, Viral / Q000235:genetics; D005260:Female; D052162:Human papillomavirus 16 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D014066:Palatine Tonsil / Q000378:metabolism* / Q000821:virology; D030361:Papillomavirus Infections / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D016133:Polymerase Chain Reaction; D014067:Tonsillar Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D015854:Up-Regulation
D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004279:DNA, Viral