The identification of activation pathways linked to anti-tumor T-cell polyfunctionality, associated with clinical benefit, is of great relevance in the new era of immunotherapy and combined chemo-immunotherapy. Recently we have reported that Melan-A-specific CD8 T cells isolated from long-term surviving patients treated with DTIC injected in a tight window before peptide-vaccination plus IFN-α; possess higher anti-tumor reactivity and an enlarged T-cell repertoire, compared to cells isolated after vaccination alone, suggesting that DTIC before peptide-vaccination may favor a protective anti-tumor specific immune response (1).
To identify the mechanisms enhancing the immune response induced by the combined therapy, we analyzed the endogenous and treatment-induced antigen specific CD8 T-cell response in a panel of Melan-A- and gp100-specific clones from five patients. To this purpose, we analyzed the maturation/differentiation phenotype of these clones (CCR7 and CD45RA), the co-stimulatory (CD27, CD28 and ICOS) and inhibitory (TIM-3, LAG-3 and PD-1) profile, in parallel with the polyfunctionality (IFN-γ; TNF-α; and Granzyme B) and the activation of AKT (pSer473-AKT).
AKT activation was correlated with the differentiation profile (in term of CD28 and/or CD27 expression) and was associated with poor polyfunctionality and low ICOS expression in Melan-A-specific T cells isolated from the endogenous response of both treatments and from the peptide-vaccination-driven response. Conversely, in three patients the combined treatment with DTIC before peptide vaccination elicited tumor-specific CD8+ T cells displaying the hallmarks of differentiated and highly activated effector T cells. These clones are highly efficient in tumor killing, possess polyfunctional activity, up-regulate inhibitory receptors (with PD-1 expressed at the highest level), retain proliferative capability and activate an AKT pathway not-related to the expression of CD27/CD28 molecules and partially dependent on ICOS engagement. Strikingly, T-cell polyfunctionality elicited by the combined therapy was strictly dependent on this AKT activation, as demonstrated by the blockade with selective inhibitors, which occurred only in Melan-A-specific CD8+ T cells and not in cells specific for gp100, suggesting that the nature of the peptide is crucial for the activation of this pathway.
We suggest that this phenotypic and functional T-cell signature related to a highly effective tumor-specific response is fine-tuned between TCR activation, co-stimulatory and inhibitory signals critical to preserve the self-tolerance during immunotherapy treatment. Of clinical relevance, these three patients treated with chemo-immunotherapy are clinically disease-free after 9 years of follow-up.
The study represents a critical contribution for the comprehension of the mechanisms underlying the advantages of combined chemo-immunotherapy and paves the way for the identification of new biomarkers of T-cell activation that may be employed as markers of immune responsiveness.
1. Palermo B, Del Bello D, Sottini A, Serana F, Ghidini C, Gualtieri N, Ferraresi V, Catricalà C, Belardelli F, Proietti E, Natali PG, Imberti L, Nisticò P. Dacarbazine treatment before peptide vaccination enlarges T-cell repertoire diversity of melan-a-specific, tumor-reactive CTL in melanoma patients. Cancer Res. 2010 Sep 15;70(18):7084-92.
Citation Format: Ornella Franzese, Belinda Palermo, Cosmo Di Donna, Isabella Sperduti, Mariangela Panetta, Maria Laura Foddai, Angela Santoni, Paola Nisticò. Polyfunctional antitumor CD8 T cells obtained from a broad repertoire elicited by chemo-immunotherapy and preventing melanoma relapse depends on the activation of an AKT pathway sustained by ICOS. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A003.