p16 overexpression identifies oncogenic high-risk HPV infection in non-oropharyngeal squamous cell carcinoma of the head and neck.

BACKGROUND: Human papillomavirus (HPV) is an increasing risk factor for cancer. HPV-associated oropharyngeal squamous cell carcinoma (OPSCC) is associated with a favorable outcome. Blockstaining for p16 is a surrogate marker for HPV+ OPSCC. In oral and laryngeal squamous cell carcinoma (OSCC/LSCC), the relevance of p16 immunohistochemistry, alone or in combination with other cell cycle-related proteins, to identify HPV-driven non-OPSCC is less well understood.

METHODS: We stained for p16, pRb, cyclin D1, and p53 in 327 HNSCC. In 310 OPSCC, HPV-status was assessed by HPV DNA PCR. In 119 non-OPSCC, RNA in situ hybridization was additionally performed. HPV-status was correlated with staining patterns, p53 and clinical data.

RESULTS: The OPSCC showed blockstaining for p16 in 36%, 8% were equivocal. Of these, HPV-testing was performed in 57%, and 53% were positive for HPV DNA. HPV-association correlated with absence of pRb and cyclin D1 and favorable outcome. In non-OPSCC, 18% showed p16-blockstaining, and 13% showed E6/E7 RNA. Six of seven HPV+ OSCC and 8/8 LSCC lost pRb and cyclin D1. Compared to HPV-negative counterparts, patients with HPV+ cancers had lower rates of alcohol consumption and keratinizing morphology. HPV-positive OSCC had a longer overall survival (p < 0.05). HPV subtype 16 was the most common.

CONCLUSIONS: We conclude that HPV-positive non-OPSCC are associated with p16 overexpression and low levels of pRb and cyclin D1. High expression of pRb and cyclin D1 indicates HPV-negativity.