Prevalence of human papillomavirus types, viral load and physical status of HPV16 in head and neck squamous cell carcinoma from the South Swedish Health Care Region

Abstract

Incidence of human papillomavirus (HPV)-positive head and neck squamous cell carcinoma (HNSCC) is rising in several countries. Intriguingly, large variations of HPV16 viral load and different proportions of the physical viral status among HNSCC have been reported. We analysed fresh biopsies of 275 HNSCC patients from the South Swedish Health Care Region for HPV types with modified general primer PCR and Luminex. Seventy-eight HPV16-positive HNSCC cases were further investigated for viral DNA load and physical status using quantitative PCR for HPV E2 and E7 genes. Presence of intact E2 gene, as a surrogate marker for episomal HPV, was investigated with conventional PCR. Fifteen different HPV types were detected in HNSCC cases and HPV16 was present in 74 % of the HPV-positive cases. HPV was detected in 65 % (92/141) and 11 % (15/134) of oropharyngeal and non-oropharyngeal carcinomas, respectively (P<0.0001). HPV was detected in 73 % (75/103) of tonsillar carcinomas. The median load of HPV16 was 13 copies cell-1 (range 0.003-1080). Among HPV16-positive patients with oropharyngeal carcinoma, metastases to regional lymph nodes were observed in 100 % (17/17) and 68 % (40/58) for those with <1 HPV16 copy cell-1 and >1 HPV16 copy cell-1, respectively (P=0.007). Among HPV16 cases, purely integrated HPV16 was found in 6 %, whereas entirely episomal and mixed virus was detected in 51 and 42 % of cases, respectively. Conclusively, HPV16 viral DNA load demonstrated a large diversity among HNSCCs. Although integration of HPV16 is common (48 %), the episomal HPV16 is salient (93 %) among HPV16 HNSCCs. In addition, low amount of HPV16 was associated with lymph node metastases among oropharyngeal carcinomas.