title: p16 INK4A overexpression is frequently detected in tumour-free tonsil tissue without association with HPV.
abstract: 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.
authors.affiliation: Department of Molecular Cell Biology, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, the Netherlands.
authors.forename: Boris
authors.initials: B
authors.lastname: Klingenberg
authors.forename: Harriët C
authors.initials: HC
authors.lastname: Hafkamp
authors.forename: Annick
authors.initials: A
authors.lastname: Haesevoets
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: Manni
authors.forename: Pieter J
authors.initials: PJ
authors.lastname: Slootweg
authors.forename: Soenke J
authors.initials: SJ
authors.lastname: Weissenborn
authors.forename: Jens P
authors.initials: JP
authors.lastname: Klussmann
authors.forename: Ernst-Jan M
authors.initials: EJ
authors.lastname: Speel
mesh_terms: 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
chemical_list: D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004279:DNA, Viral