Unravelling the biology of human papillomavirus (HPV) related tumours to enhance their radiosensitivity

HPV infection is associated with most squamous cell carcinomas (SCC) of the uterine cervix and many head and neck SCC. While recent understanding of the mechanisms of HPV-induced carcinogenesis has lead to the development of prophylactic vaccines, the principal modality of treatment is radiotherapy and despite concurrent chemotherapy, outcomes remain suboptimal. Improving the radiotherapeutic index thus remains an important challenge as well as defining predictive assays for treatment outcome of HPV-related tumours. Therefore elucidating the influence of the HPV virus on tumour radiosensitivity is of major interest due to the prevalence of HPV-related tumours worldwide and due to evidence that head and neck HPV-tumours have markedly different clinical outcomes compared to non-HPV-related tumours. This difference may allow for different treatment strategies to be developed. The present review aims to summarize the current understanding of radiosensitivity and HPV-related tumour biology in order to subsequently develop new approaches to enhance the therapeutic index. This review also emphasizes the relevance of E6 and E7 oncoproteins to tumour cell response to radiotherapy suggesting that specific targeted approaches such as concomitant modulation of additional pathways using targeted therapies should offer new therapeutic avenues.