33P - Tumor-specific CD4 Th1 responses in long-term responder melanoma patients treated with immune checkpoint inhibitors.

Background

Evidence highlights the critical role of CD4 T cells in antitumor immunity and immunotherapy. We previously reported that baseline or post-treatment hTERT-specific CD4 Th1 response in blood is associated with the efficacy of immune checkpoint inhibitors (ICI) therapy in patients with advanced melanoma and colorectal cancer (Nardin et al, 2021; Thibaudin et al, 2022). Here, we investigated the involvement of peripheral tumor reactive CD4 Th1 response in durable response to ICI in melanoma patients.

Methods

Blood samples were collected in three groups of advanced melanoma (AJCC8 stage III/IV) patients (pts) according to response to ICI: 50 pts with prolonged disease control (>1 year) (CD[FA1]), 22 pts with primary resistance (R1) defined as no response after 3 months of ICI, and 35 pts with relapsed disease after treatment discontinuation for initial disease control (>1 year) (R2). Multiparametric immunologic analyses were performed using IFN-γ ELISpot, flow cytometry on PBMC and Bulk RNA sequencing on circulating sorted CD4 T cells.

Results

A high frequency of circulating tumor-specific CD4 Th1 response, i.e response against at least one of the 3 antigens tested (hTERT, MAGE-A3 and KK-LC1), was found in all 3 groups (76%, 63%, 68% in CD, R1, R2, respectively). Among the 3 antigens tested, the circulating hTERT-specific CD4 Th1 response frequency was higher in CD compared to R1 and R2 : 70% vs 25% vs 40% positive response (**, p<0.01). Furthermore, CD4 Th1 polyspecific responses, i.e against at least 2 of the 3 antigens tested were more detected in CD pts (31 pts, 62%) compared to 15 (42%) and 7 (32%) pts in R2 and R1 respectively. hTERT-specific CD4 Th1 exhibits cytotoxic phenotype and a modified memory profile compared to non-specific CD4 T cells. Transcriptomic analyses of CD4 T cells revealed 669 genes upregulated and 52 down-regulated in CD pts, mainly enriched in Th1-associated pathways such as IFN-γ response, TNF-α signaling via NF-κB and IL-2-STAT5 signaling compared to healthy donors. Analyses of immune-related genes showed upregulation of cytotoxic markers in CD pts compared to R1 and R2.

Conclusions

In conclusion, our data demonstrated that cytotoxic hTERT-specific CD4 Th1 response is involved in the long-term response to ICI.

Legal entity responsible for the study

CHRU Besançon.

Funding

La ligue contre le cancer; Bourse Chrysalide.

Disclosure

All authors have declared no conflicts of interest.