Lack of evidence of human papillomavirus-induced squamous cell carcinomas of the oral cavity in southern Germany

Abstract

Objectives: The aim of the present study was to identify HPV-attributable SCC of the oral cavity (OSCC) in a cohort of patients from southern Germany.

Materials and methods: A sensitive PCR-enzyme immunoassay (EIA) was followed by a more specific in situ hybridization (ISH) to detect high risk human papillomavirus (HPV). An immunohistochemical dual-staining for p16(INK4a) and the proliferation marker Ki-67 was used to assess whether co-expression of p16(INK4a)/Ki-67 is a better surrogate marker for HPV in OSCC than p16(INK4a) alone, based on the hypothesis that combined p16(INK4a) and Ki-67 expression might specifically discriminate oncogene-induced p16(INK4a) expression from cell-cycle arrest-inducing senescence-associated p16(INK4a) expression.

Results: HPV-DNA by PCR-EIA could be detected in 25.1% (69/275) of the tumors, but ISH was negative in all of them. Diffuse p16(INK4a) overexpression was detected in 11 HPV PCR-positive tumors, but also in 6 HPV PCR-negative tumors. p16(INK4a)-expressing cells in diffusely positive tumors co-expressed Ki-67, irrespective of the HPV status. Neither the sole HPV status nor combined HPV/p16(INK4a) status nor the sole p16(INK4a) status was significantly associated with disease free or overall survival, however a trend towards better overall survival of patients whose tumor expressed p16(INK4a) in a focal pattern (=p16(INK4a)-positive/Ki-67-negative cells) compared to no p16(INK4a) expression (p=0.09) was observed.

Conclusion: Viral DNA can be detected in some tumors by a sensitive PCR, but absence of ISH signals indicates that the HPV-attributable fraction is smaller than estimated from PCR positivity. p16(INK4a)/Ki-67 co-expression is detectable in a fraction of OSCC irrespective of the HPV status.

Keywords: DFS; EIA; HPV; HR-HPV; Human papillomavirus; ISH; Ki-67; OS; OSCC; Oral cavity; PCR; SCC; Squamous cell cancer; disease-free survival; enzyme immunoassay; high-risk human papillomavirus; human papillomavirus; in situ hybridization; overall survival; p16(INK4a); polymerase chain reaction; squamous cell cancer; squamous cell cancer of the oral cavity.