Anti-Telomerase CD4 + Th1 Immunity and Monocytic-Myeloid-Derived-Suppressor Cells Are Associated with Long-Term Efficacy Achieved by Docetaxel, Cisplatin, and 5-Fluorouracil (DCF) in Advanced Anal Squamous Cell Carcinoma: Translational Study of Epitopes-HPV01 and 02 Trials

Docetaxel, cisplatin and 5-fluorouracil (DCF) chemotherapy regimen is highly effective in advanced anal squamous cell carcinoma (SCCA), as demonstrated by the Epitopes-HPV02 study results. Here, we analyzed the impact of DCF regimen and the prognostic value of adaptive immune responses and immunosuppressive cells in SCCA patients included in two prospective studies (Epitopes-HPV01 and HPV02). The presence of T-cell responses against Human papillomavirus (HPV)16-E6/E7 and anti-telomerase (hTERT)-antigens was measured by IFNᵧ-ELISpot. Here, we showed that HPV-adaptive immune responses are increased in SCCA patients. SCCA patients also displayed enhanced circulating TH1 T-cells restricted by hTERT. Exposition to DCF increased hTERT immunity but not HPV or common viruses immune responses. Notably, the correlation of hTERT immune responses with SCCA patients' clinical outcomes highlights that hTERT is a relevant antigen in this HPV-related disease. The influence of peripheral immunosuppressive cells was investigated by flow cytometry. While both regulatory T-cells and monocytic-myeloid-derived suppressive cells (M-MDSC) accumulated in the peripheral blood of SCCA patients, only high levels of M-MDSC were negatively correlated with hTERT adaptive immune responses and predicted poor prognosis. Altogether, our results reveal that hTERT is a relevant antigen in HPV-driven SCCA disease and that M-MDSC levels influence TH1-adaptive immune responses and patients' survival.