Abstract 1187: Sensitization to chemo-immunotherapy by targeting TGF-β in preclinical triple negative breast cancer models

Abstract Metastatic triple-negative breast cancer (mTNBC) is refractory to anti-PD- (L) 1 immunotherapy. In order to sensitize it, preclinical data show the value of adding chemotherapy treatment for its ability to induce immunogenic cancer cell death (Kroemer et al, 2013). This would enable the recruitment of cytotoxic T-CD8+ lymphocytes (CTL) and thus initiate an antitumor immune response to sensitize tumors to immunotherapy. Nevertheless, the results of clinical trials using chemo-immunotherapy combinations are divergent (IMpassion 130 and 131). The IMpassion 130 trial demonstrated the efficacy of nab-paclitaxel and atezolizumab (anti-PD-L1) in PD-L1+ patients, but unfortunately, IMpassion 131 with paclitaxel did not replicate these results. The choice of chemotherapy to combine with immunotherapy appears to be crucial for inducing an antitumor immune response. Optimizing chemo-immunotherapy combinations is a major challenge in the management of TNBC. The initial aim of this project was to evaluate the immune effects of an experimental chemotherapy doublet, based on two drugs used in mTNBC: cisplatin (CDDP) and eribulin. The idea was to find an alternative to the use of taxanes in combination with anti-PD- (L) 1. The effect of the two molecules, alone or in combination, was evaluated on immunogenic death stigmata, modulation of effector or immunosuppressive immune populations and stromal populations, and sensitization to anti-PD-L1 immunotherapy in the immunologically "cold" model: 4T1. The in vivo studies has been realized by generation of orthotopic 4T1 tumors, the analysis of the immune infiltration was performed by RT-qPCR, IHC and flow cytometry. In vitro, our results indicate that CDDP, and more intensely in combination with eribulin, significantly induces the various immunogenic death stigmas. In vivo, the therapeutic effect of chemotherapies is limited, with a superior effect of CDDP and the combination. Nevertheless, CTL recruitment and functionality induced by CDDP are significantly enhanced by eribulin. Despite these data pointing to a potential therapeutic synergy with anti PD-L1 immunotherapy, chemo-immunotherapy treatment fails to induce a superior treatment effect. The significant increase in a TGF-β signature induced by the combination in parallel with CTL recruitment explains this resistance. The results show that inhibition of TGF-β, combined with chemo-immunotherapy in the 4T1 model, leads to a reduction in tumor immunosuppression and intratumoral fibrosis, as well as an increase in CTL infiltration and cytotoxicity, enabling tumor sensitization. Overall, this project highlights the benefits of using an experimental doublet of CDDP and eribulin-based chemotherapies. This project demonstrates that management of chemo-induced immunosuppression mechanisms is necessary to overcome tumor resistance to immunotherapy. Citation Format: Laura Kalfeist, Fanny Ledys, Stacy Petit, Samia Kada-Mohammed, Mickael Rialland, François Ghiringhelli, Emeric Limagne, Sylvain Ladoire. Sensitization to chemo-immunotherapy by targeting TGF-β in preclinical triple negative breast cancer models abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 1187.