Abstract 5035A: Intratumoral HPV16-specific T-cells determine clinical outcome of HPV16+ oropharyngeal carcinomas

Abstract

Abstract Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer. While the number of HNSCC cases is decreasing, the number of oropharyngeal SCC (OSCC) is rising, especially in young adults. OSCC are increasingly (45-90%) caused by human papillomavirus type 16 (HPV16). Intriguingly, patients with HPV-induced OSCC respond better to therapy than HPV-negative OSCC. This is independent of nodal status, age, stage, tumor differentiation or gender. We hypothesized that the expression of the viral antigens E6 and E7 in HPV16+ OSCC equips the immune system with two strong tumor-specific antigens resulting in the development of a type 1 T-cell immune contexture supporting the better response of HPV+ OSCC to standard therapy. To test our hypothesis we studied 87 patients with OSCC. The tumors of these patients were tested for the presence of HPV by GP5+/6+ PCR and the expression of p16 by immunohistochemistry. Moreover, fresh tumor tissue was dispersed, cryopreserved and subsequently used for in-depth analyses regarding the composition of the leukocyte infiltrates using a large set of antibodies either by CyTOF or BD Fortessa. In addition, T-cell reactivity was tested directly ex vivo and after a short-term culture period. 57% of OSCC patients were HPV16+ and they showed the best overall survival (p<0.0001, HR 6.9). Whereas none of 37 HPV-negative patients displayed intratumoral HPV16 E6/E7-specific T-cell reactivity this was detected in 25 of 40 (63%) HPV16+ OSCC. Notably, for most patients these T-cells were already detectable directly ex vivo, indicative for their activity in vivo. The presence of intratumoral HPV16-specific T-cell reactivity for the response of patients to therapy was extremely important for a better clinical outcome (p = 0.0003, HR 23.9) as estimated by Kaplan-Meier curves and log-rank analysis. Division of HPV16+ patients on the basis of p16 expression revealed that p16+ patients had a much better clinical outcome (p<0.0001, HR 11.8). In line with the notion that overexpression of p16 is directly associated with expression of the HPV16 E6 and E7 oncogenes, a strong association between p16 expression and HPV16-specific TIL reactivity was found (p<0.0001). Mechanistically, we found that OSCC cell lines promoted the differentiation of monocytes to M2 macrophages. In vitro experiments showed that the presence of HPV-specific T-cell secreted cytokines prevented this and was even able to redifferentiate macrophages into better antigen-presenting cells, both phenotypically (including co-stimulatory molecules) and functionally (more IL-12 and less IL-10 production). In addition, these cytokines mediated a direct effect on the tumor cell proliferation and metabolism, thereby slowing down tumor growth as well as changing their impact on myeloid cells in the tumor microenvironment. In conclusion, HPV-specific T cells elicited by HPV+ OSCC are highly predictive for response to therapy. Citation Format: Marij J. Welters, Lilly-Ann van der Velden, Vanessa J. van Ham, Ilina Ehsan, Renske Goedemans, Saskia J. Santegoets, Sjoerd H. van der Burg. Intratumoral HPV16-specific T-cells determine clinical outcome of HPV16+ oropharyngeal carcinomas. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5035A.