Data from Rapalogs Efficacy Relies on the Modulation of Antitumor T-cell Immunity

The rapalogs everolimus and temsirolimus that inhibit mTOR signaling are used as antiproliferative drugs in several cancers. Here we investigated the influence of rapalogs-mediated immune modulation on their antitumor efficacy. Studies in metastatic renal cell carcinoma patients showed that everolimus promoted high expansion of FoxP₃⁺Helios⁺Ki67⁺ regulatory CD4 T cells (T_regs). In these patients, rapalogs strongly enhanced the suppressive functions of T_regs, mainly in a contact-dependent manner. Paradoxically, a concurrent activation of spontaneous tumor-specific Th1 immunity also occurred. Furthermore, a high rate of Eomes⁺CD8⁺ T cells was detected in patients after a long-term mTOR inhibition. We found that early changes in the T_regs/antitumor Th1 balance can differentially shape the treatment efficacy. Patients presenting a shift toward decreased T_regs levels and high expansion of antitumor Th1 cells showed better clinical responses. Studies conducted in tumor-bearing mice confirmed the deleterious effect of rapalogs-induced T_regs via a mechanism involving the inhibition of antitumor T-cell immunity. Consequently, the combination of temsirolimus plus CCR4 antagonist, a receptor highly expressed on rapalogs-exposed T_regs, was more effective than monotherapy. Altogether, our results describe for the first time a dual impact of host adaptive antitumor T-cell immunity on the clinical effectiveness of rapalogs and prompt their association with immunotherapies. Cancer Res; 76(14); 4100–12. ©2016 AACR.