title: Differential mechanisms of CDKN2A (p16) alteration in oral tongue squamous cell carcinomas and correlation with patient outcome.
abstract: CDKN2A (p16) disruption is reported as a frequent event in head and neck squamous cell carcinomas that confers poor prognosis. We investigated the frequency of different potential mechanisms of CDKN2A inactivation in oral tongue squamous cell carcinomas (OTSCC) and their impact on patient outcome. From a cohort of 153 OTSCC patients, 131 formalin fixed paraffin embedded blocks of pre-treatment primary tumours were suitable for further molecular analysis. We assessed CDKN2A (p16) levels by immunohistochemistry (IHC), promoter methylation status by methylation-sensitive high resolution melting, mutation status by Sanger sequencing, gene copy number variation by fluorescence in situ hybridisation, and correlated these with patient outcome. We found that the majority of OTSCC did not overexpress p16 (110/116, 95%), assessed by IHC. The frequency of CDKN2A mutations was 20% (21/103), homozygous loss was 7% (7/97), hemizygous loss 31% (30/97), and promoter methylation was 18% (20/113). We found no evidence of these mechanisms in 24/106 (23%) p16 IHC negative tumours. No significant correlation was identified between any potential mechanism of CDKN2A inactivation and clinical features, including smoking status and age. There was a non-significant trend for worse overall survival for p16 IHC negative patients versus positive patients (HR = 1.81, 95% CI = 0.44-7.47, p = 0.40). No relationship was found between mechanisms of CDKN2A disruption and patient outcome. In conclusion, we demonstrate that CDKN2A alteration is a frequent event in OTSCC tumourigenesis. However, no correlation was identified between different potential mechanisms of CDKN2A disruption and clinical characteristics or patient outcome.
authors.affiliation: Department of Medical Oncology, Peter MacCallum Cancer Centre, East Melbourne, Australia; University of Melbourne, Australia; Research Division, Peter MacCallum Cancer Centre, East Melbourne, Australia.
authors.forename: Annette M
authors.initials: AM
authors.lastname: Lim
authors.forename: Hongdo
authors.initials: H
authors.lastname: Do
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Young
authors.forename: Stephen Q
authors.initials: SQ
authors.lastname: Wong
authors.forename: Christopher
authors.initials: C
authors.lastname: Angel
authors.forename: Marnie
authors.initials: M
authors.lastname: Collins
authors.forename: Elena A
authors.initials: EA
authors.lastname: Takano
authors.forename: June
authors.initials: J
authors.lastname: Corry
authors.forename: David
authors.initials: D
authors.lastname: Wiesenfeld
authors.forename: Stephen
authors.initials: S
authors.lastname: Kleid
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Sigston
authors.forename: Bernard
authors.initials: B
authors.lastname: Lyons
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Fox
authors.forename: Danny
authors.initials: D
authors.lastname: Rischin
authors.forename: Alexander
authors.initials: A
authors.lastname: Dobrovic
authors.forename: Benjamin
authors.initials: B
authors.lastname: Solomon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000378:metabolism*; D015331:Cohort Studies; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D019942:Genes, p16; D006720:Homozygote; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D017422:Sequence Analysis, DNA; D014062:Tongue Neoplasms / Q000378:metabolism*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm
keywords: CDKN2A; FISH; methylation; mutation; p16; “tongue cancer,” “oral cancer”