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Molecular characterization of p16‐immunopositive but HPV DNA‐negative oropharyngeal carcinomas
Author(s) -
Rietbergen Michelle M.,
Snijders Peter J.F.,
Beekzada Derakshan,
Braakhuis Boudewijn J.M.,
Brink Arjen,
Heideman Daniëlle A.M.,
Hesselink Albertus T.,
Witte Birgit I.,
Bloemena Elisabeth,
BaatenburgDe Jong Robert J.,
René Leemans C.,
Brakenhoff Ruud H.
Publication year - 2013
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.28580
Subject(s) - immunohistochemistry , biology , loss of heterozygosity , polymerase chain reaction , cancer research , microbiology and biotechnology , gene , immunology , genetics , allele
Recent studies have reported that p16 protein overexpression qualifies as a surrogate marker identifying an oncogenic human papillomavirus (HPV) infection in oropharyngeal squamous cell carcinoma (OPSCC). However, there is still a percentage of OPSCCs that are positive for p16 immunohistochemistry (p16 IHC) but lack HPV DNA. The objective of this study was to characterize this group at the molecular level by performing sensitive HPV DNA‐ and RNA‐based PCR methods and genetic profiling. All patients diagnosed with an OPSCC in the period 2000–2006 in two Dutch university medical centers were included ( n = 841). The presence of HPV in a tumor sample was tested by p16 IHC followed by an HPV DNA GP5+/6+ PCR. p16 IHC scored positive in 195 samples, of which 161 were HPV DNA‐positive and 34 (17%) HPV DNA‐negative. In the latter group, a SPF 10 ‐LiPA25 assay, an HPV16 type‐specific E7 PCR and an E6 mRNA RT‐PCR were performed. Next, ten of these cases were further analyzed for loss of heterozygosity (LOH) of 15 microsatellite markers at chromosome arms 3p, 9p and 17p. Of the 34 p16‐positive but PCR‐negative OPSCCs, two samples tested positive by SPF 10 assay, HPV16 E7 PCR and HPV16 E6 mRNA RT‐PCR. Three samples tested positive by SPF 10 assay but negative by the HPV16‐specific assays. Nine of ten cases that were tested for LOH showed a genetic pattern comparable to that of HPV‐negative tumors. This study categorizes p16‐positive but HPV DNA‐negative OPSCCs as HPV‐negative tumors based on genetic profiling. This study highlights the importance of performing HPV testing in addition to p16 IHC for proper identification of HPV‐associated OPSCCs.