Molecular profile of head and neck squamous cell carcinomas bearing p16 high phenotype.

BACKGROUND

We sought to determine biomarker expression differences in head and neck squamous cell cancers (HNSCCs) based on p16/human papillomavirus (HPV) classification. In addition, our aim was to explore how expression of biomarkers is modulated after E6/E7 repression in HPV16⁺ oropharyngeal cancer cells.

METHODS

HPV16⁺ and HPV⁻ HNSCC cells were infected with retroviruses expressing short hairpin RNA targeting HPV16 E6/E7. Components of the epidermal growth factor receptor (EGFR) pathway before and after E6/E7 gene silencing were analyzed by immunoblotting and qRT-PCR. Protein expression of 13 biomarkers was analyzed using AQUA on a tissue microarray (TMA). The HPV16 status was determined using HPV16 in situ hybridization (ISH).

RESULTS

In HPV16⁺ cells, E6/E7 silencing was associated with PTEN upregulation and reduction of phosphorylated EGFR. Tumors were classified into four categories based on the HPV and p16 status. HPV⁺/p16⁺ tumors expressed significantly higher levels of E-cadherin (P = 0.003), PTEN (P = 0.004), lower levels of PI3Kp110 and β-catenin (P = 0.07). There was a significant difference in overall survival (OS, P = 0.016) among the four subsets. The median OS was 24.83 months for p16⁻/HPV⁻ patients, 11.63 for p16⁻/HPV⁺ patients and was not reached for p16⁺/HPV⁻ and p16⁺/HPV⁺ groups.

CONCLUSIONS

Aberrant EGFR signaling contributes to malignant conversion of HPV16⁺ HNSCC cells. These results validate β-catenin as a distinct biomarker in HPV⁺/p16⁺ HNSCC. Wnt signaling inhibitors merit exploration in HPV⁺/p16⁺ HNSCC.