title: Human papillomavirus (HPV) 16 E6 variants in tonsillar cancer in comparison to those in cervical cancer in Stockholm, Sweden.
abstract: BACKGROUND
  Human papillomavirus (HPV), especially HPV16, is associated with the development of both cervical and tonsillar cancer and intratype variants in the amino acid sequence of the HPV16 E6 oncoprotein have been demonstrated to be associated with viral persistence and cancer lesions. For this reason the presence of HPV16 E6 variants in tonsillar squamous cell carcinoma (TSCC) in cervical cancer (CC), as well as in cervical samples (CS), were explored.
  
  
  METHODS
  HPV16 E6 was sequenced in 108 TSCC and 52 CC samples from patients diagnosed 2000-2008 in the County of Stockholm, and in 51 CS from young women attending a youth health center in Stockholm.
  
  
  RESULTS
  The rare E6 variant R10G was relatively frequent (19%) in TSCC, absent in CC and infrequent (4%) in CS, while the well-known L83V variant was common in TSCC (40%), CC (31%), and CS (29%). The difference for R10G was significant between TSCC and CC (p = 0.0003), as well as between TSCC and CS (p = 0.009). The HPV16 European phylogenetic lineage and its derivatives dominated in all samples (>90%).
  
  
  CONCLUSIONS
  The relatively high frequency of the R10G variant in TSCC, as compared to what has been found in CC both in the present study as well as in several other studies in different countries, may indicate a difference between TSCC and CC with regard to tumor induction and development. Alternatively, there could be differences with regard to the oral and cervical prevalence of this variant that need to be explored further.
authors.affiliation: Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden. juan.du@ki.se
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.forename: Cecilia
authors.initials: C
authors.lastname: Nordfors
authors.forename: Anders
authors.initials: A
authors.lastname: Näsman
authors.forename: Michal
authors.initials: M
authors.lastname: Sobkowiak
authors.forename: Mircea
authors.initials: M
authors.lastname: Romanitan
authors.forename: Tina
authors.initials: T
authors.lastname: Dalianis
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Ramqvist
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000821:virology; D016022:Case-Control Studies; D005260:Female; D052162:Human papillomavirus 16 / Q000145:classification / Q000235:genetics* / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009856:Oncogene Proteins, Viral / Q000235:genetics*; D010802:Phylogeny; D011110:Polymorphism, Genetic; D012097:Repressor Proteins / Q000235:genetics*; D015203:Reproducibility of Results; D013548:Sweden; D014067:Tonsillar Neoplasms / Q000821:virology*; D002583:Uterine Cervical Neoplasms / Q000821:virology*
chemical_list: C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins