Cancer Therapy: Preclinical mTOR as a Molecular Target in HPV-Associated Oral and Cervical Squamous Carcinomas

Purpose: The incidence of head and neck squamous cell carcinomas (HNSCC) associated with human papillomavirus (HPV) infection has increased over the past decades in the United States. We aimed at examining the global impact of HPV-associated HNSCC and whether the established key role of mTOR activation in HNSCC is also observed in HPVþHNSCC lesions, thereby providing novel treatment options for HPV-associated HNSCC patients. Experimental Design: An international HNSCC tissue microarray (TMA) was used to analyze the expression of p16, a surrogate for HPV infection, and Akt-mTOR pathway activation. Results were confirmed in a large collection of HPV and HPVþ HNSCC cases and in a cervical cancer (CCSCC) TMA. Observations were validated in HNSCC and CCSCC-derived cell lines, which were xenografted into immunodeficient mice for tumorigenesis assays. Results: Approximately 20% of all HNSCC lesions could be classified as HPVþ, irrespective of their country of origin. mTOR pathway activation was observed in most HPVþ HNSCC and CCSCC lesions and cell lines. The preclinical efficacy of mTOR inhibition by rapamycin and RAD001 was explored in HPVþ HNSCC and CCSCC tumor xenografts. Both mTOR inhibitors effectively decreased mTOR activity in vivo and caused a remarkable decrease in tumor burden. These results emphasize the emerging global impact of HPV-related HNSCCs and indicate that the activation of the mTOR pathway is a widespread event in both HPV and HPV-associated HNSCC and CCSCC lesions. Conclusions:The emerging resultsmayprovide a rationale for the clinical evaluationofmTOR inhibitors as a molecular targeted approach for the treatment of HPV-associated malignancies. Clin Cancer Res; 18(9);