Novel Biomarkers in the Management of HPV-Positive & -Negative Oropharyngeal Carcinoma

Human Papillomavirus (HPV)-related oropharyngeal carcinoma is considered to be in the early stages of an epidemic. A marked rise in the incidence of this sexually-transmissible cancer has captured the public interest, and much debate exists over both the prophylactic and therapeutic strategies currently employed to manage this healthcare priority. HPV-positive oropharyngeal carcinoma is associated with highly favourable oncological outcomes. Clinical attention over recent years has been paid to the potential de-escalation of therapy in order to account for the disease’s favourable prognosis, in addition to reducing therapeutic burden in a well-prognosticating, younger patient cohort, for which consequences of radical chemo-radiotherapy strategies may disproportionately impact on longer-term quality of life. Whilst optimising the management of the ever-increasing proportion of HPV-positive oropharyngeal carcinomas is desirable and highly justifiable, it appears the poorer prognosticating HPV-negative oropharyngeal carcinoma has at least in part become overlooked. Oropharyngeal carcinoma is unique in comparison to many other established HPV-related cancers inasmuch as a clear HPV-negative subset exists, to which established aetiological factors (tobacco smoking and alcohol consumption) strongly correlate. For most other HPV-related carcinomas, such as cervical, anal and penile, tumours classified as HPV-negative are either regarded as potentially-virus containing, or else cannot be correlated to a definitive aetiological agent. Comparison of HPV-positive and -negative oropharyngeal carcinoma therefore offers unprecedented insight into the biological significance of each aetiological agent, and how prognostication of each disease may relate to tumour behaviour at a molecular level. Whilst improved outcomes may be attributable in part to greater radio-sensitivity due to preservation of key wild-type genes in HPV-positive tumours, more comprehensive biological differences are likely to underpin the overall behaviour of disease – indeed, surgical outcomes are also favourable in HPV-positive disease. This thesis explores the potential for the tumour microenvironment to differ between HPV-positive and -negative disease. We hypothesised that due to the strictly epitheliotropic nature of the Human Papillomavirus, activation of the tumour microenvironment would potentially be suppressed in order to avoid host clearance of pathogen during the natural history of viral infection, whereas penetrating carcinogens linked to tobacco smoking and alcohol consumption may either directly derange the stroma or, less contentiously, induce an increased mutational load which in turn in turn may offer greater opportunity for tumour evolution towards deranged microenvironmental signalling. A 2D tissue culture model of the tumour microenvironment was created and used to test the hypothesis of a difference in microenvironmental interactions between HPV-positive versus HPV-negative disease, and normal stroma. Confirmation of an increase in migration-inducing signals from the modelled normal fibroblast stroma in HPV-negative disease led to further investigation at a molecular level using cytokine array technology. Further ELISA quantification and recombinant protein dose-response analysis ultimately identified Human Hepatocyte Growth Factor (HGF) as a primary candidate molecule for driving the additional migration observed in response to activated stroma. IL-6, co-secreted with HGF by stimulated fibroblasts, was also found to have a supporting role through the co-induction of STAT3. Final confirmation of HGF’s principal role in inducing HPV-negative tumour migration was undertaken using the clinically relevant c-Met inhibitors, foretinib & INCB28060 (recently rebranded as capmatinib).