Antigen-specificity and DTIC before peptide-vaccination differently shape immune-checkpoint expression pattern, anti-tumor functionality and TCR repertoire in melanoma patients

Abstract

We have recently described that DNA-damage inducing drug DTIC, administered before peptide (Melan-A and gp100)-vaccination, improves anti-tumor CD8+ Melan-A-specific T-cell functionality, enlarges the Melan-A+ TCR repertoire and impacts the overall survival of melanoma patients. To identify whether the two Ags employed in the vaccination differently shape the anti-tumor response, herein we have carried out a detailed analysis of phenotype, anti-tumor functionality and TCR repertoire in treatment-driven gp100-specific CD8+ T cells, in the same patients previously analyzed for Melan-A. We found that T-cell clones isolated from patients treated with vaccination alone possessed an Early/intermediate differentiated phenotype, whereas T cells isolated after DTIC plus vaccination were late-differentiated. Sequencing analysis of the TCRBV chains of 29 treatment-driven gp100-specific CD8+ T-cell clones revealed an oligoclonal TCR repertoire irrespective of the treatment schedule. The high anti-tumor activity observed in T cells isolated after chemo-immunotherapy was associated with low PD-1 expression. Differently, T-cell clones isolated after peptide-vaccination alone expressed a high level of PD-1, along with LAG-3 and TIM-3, and were neither tumor-reactive nor polyfunctional. Blockade of PD-1 reversed gp100-specific CD8+ T-cell dysfunctionality, confirming the direct role of this co-inhibitory molecule in suppressing anti-tumor activity, differently from what we have previously observed for Melan-A+CD8+ T cells, expressing PD-1 but highly functional. These findings indicate that the functional advantage induced by combined chemo-immunotherapy is determined by the tumor antigen nature, T-cell immune-checkpoints phenotype, TCR repertoire diversity and anti-tumor T-cell quality and highlights the importance of integrating these parameters to develop effective immunotherapeutic strategies.

Unraveling the crosstalk between melanoma and immune cells in the tumor microenvironment

“…It is becoming more apparent, however, that more than just overexpression of wildtype peptide sequences from melanoma cells is needed to induce effective anti-tumor responses from tolerant or low-affinity T cells. Hence, the use of checkpoint inhibitors, such as anti-PD1/PD-L1 and anti-CTLA-4, and adjuvants in combination with selfantigen cancer vaccines is almost requisite (76,77). Currently, identification of neo-antigens broadly expressed by melanomas is an area of intense research.…”

T cell receptor therapy against melanoma—Immunotherapy for the future?

“…While neoantigens expressed by melanoma cells would be the most immunogenic, that is most likely to expand cytotoxic T cells, self‐antigens expressed at high levels could potentially break tolerance and activate low‐affinity CD8+ T cells. To induce effective anti‐tumour responses from such tolerant or low‐affinity T cells, the use of checkpoint inhibitors or a combination with self‐antigen cancer vaccines may be necessary 100 …”

T-cell repertoire diversity: friend or foe for protective antitumor response?

“…The increased diversity of TCR repertoire was not observed in patients treated with the peptide vaccination alone [ 72 ]. Noteworthy, diversity may be related to the nature of the tumor Ags, since the TCR repertoire specific for gp100, the other peptide used in the vaccine formulation, was oligoclonal irrespective of the combined dacarbazine treatment [ 74 , 75 ]. In agreement, Stuge and co-workers observed a diversified Melan-A-specific CD8 + repertoire expanded after peptide-vaccination, although a significant proportion of these cells was unable to lyse tumor cells [ 76 ].…”