Prevalence, distribution, and viral load of human papillomavirus 16 DNA intonsillar carcinomas

Background. Oncogenic human papillomaviruses (HPV) DNA have repeatedly been observed in many head and neck carcinomas (HNSCCs), and HPV infections are currently considered a possible factor in the etiology of these tumors. Ho wever, the reported prevalences of HPV-DNA in HNSCC are variable. In the cu rrent study the authors used highly sensitive polymerase chain reactions (P CRs) to analyze the occurrence of viral sequences in 98 carefully stratifie d HNSCCs. The authors determined the load and localization of HPV DNA in a subset of tonsillar carcinomas and their metastases. Methods. Nested PCR and an HPV16 specific single step PCR were used to scre en 98 HNSCCs for HPV DNA for genital- and Epidermodysplasia verruciformis ( EV)associated HIVs. Typing was performed by direct sequencing and/or sequen cing of cloned amplimers. In two patients HPV16 subtypes in tonsillar carci nomas and their metastases were compared by amplification and sequencing of the long control region of the virus. In a subset of HPV16 positive tonsil lar carcinomas and their metastases, localization and viral load were deter mined using laser assisted microdissection and real time fluorescent PCR, r espectively. Results. Altogether 25 HNSCCs (26%) were found to be HPV positive. Stratifi ed according to the tumor localization, the frequency of HPV positive lesio ns was 18% in the oral cavity, 45% for oropharynx, 25% for hypopharynx, 8% for nasopharynx, and 7% for larynx. The highest HPV DNA prevalence (58%) wa s found in tonsillar carcinomas. The high risk HPV type 16 was found in 84% of positive HNSCCs, in 14% of which EV-associated HPVs were detected. Huma n papillomavirus sequences were detected in 64% of biopsies with normal muc osa from 11 patients with positive carcinomas. As a control group, 14 tumor free tonsils were analyzed. In none of these specimens were HPV sequences detected. Viral long transcriptional control region sequences in homologous metastases were identical with those in primary tumors and the load values in both locations were roughly comparable. Viral loads differed substantia lly in different areas of one tumor. Statistical evaluation of data related to clinicopathologic parameters showed a significant linkage of HPV with t onsillar carcinomas compared to other locations. Furthermore, a significant correlation of HPV status of tonsillar carcinomas with tumor grading and a lcohol consumption was found. Conclusions. Our study shows a preferential association of HPV-DNA with ton sillar carcinomas. The data support the view of HPV negative and positive t onsillar carcinomas being different tumor entities and conventional cancer risk factors being of less importance in HPV-infected individuals. The HPV genome is located in the cancer cells, whereas the infection of normal muco sa is a rare event. Data on quantification of HPV16 in tonsillar tumors and their metastases showed mean. viral loads comparable to other HPV associat ed malignancies. Cancer 2001;92: 2875-84. (C) 2001 American Cancer Society.