Abstract 1712: A single-cell RNA atlas of innate and adaptive intratumoral immunity in triple negative breast cancer during chemo- and immunotherapies
Authors: Carpen Laura , Falvo Paolo , Orecchioni Stefania , Mitola Giulia , Hillje Roman , Mazzara Saveria , Mancuso Patrizia , Pileri Stefano , Raveane Alessandro , Bertolini Francesco 
Published: June 2022

Abstract
Checkpoint inhibitors (CIs) such as anti-PD-1 and anti PD-L1 have shown combinatorial clinical activity with chemotherapy in triple negative breast cancer (TNBC), but only in a minority of patients and only for a limited period of time. Moreover, it is currently unclear what chemotherapeutic drug is the most appropriate to combine with CIs in TNBC patients. We have investigated at the single cell level the transcriptome and the trajectories of more than 50,000 innate and adaptive intratumoral immune cells in two syngeneic, immune competent, orthotopic murine models of local and metastatic TNBC. Mice injected with 4T1 cells had a predominant lymphoid infiltrate, mice injected with EMT6 cells had a predominant myeloid infiltrate. Mice were treated with CIs and several different types of chemotherapeutics, alone or in combinations. In both models, capecitabine (alone or with CIs) was the less effective drug. Platinum, doxorubicin and taxanes showed synergy with CIs and had superimposable activity. Intermittent, medium dosage cyclophosphamide (CTX) plus vinorelbine and CIs was the most active combinatorial therapy (Falvo et al, Cancer Research 2021). Vinorelbine activated antigen presenting cells and CTX generated new T cell clones including stem cell-like TCF1+ CD8+ T cells. Treatments with most in vivo efficacy were associated to a decrease of regulatory T cells and of gamma delta T cells, which were found to have a pro-tumoral activity in these murine models, likely due to IL-17 expression in the neoplastic microenvironment. An increase of several different clusters of exhausted-like CD8+ T cells was observed in pre-clinical treatments with low efficacy; an opposite trend was found for several clusters of proliferative CD8+ T cells in treatments with high in vivo efficacy. Regarding macrophages, M2-like cells were enriched after treatments with low efficacy, while an opposite behaviour was found in M1-like macrophages. Interestingly, we observed a significant increase of an M1-like cluster with high expression of the Ly6c1/Ly6c2 gene in mice successfully treated with vinorelbine, CTX and CIs. For both cell lines the percentage of plasma B cells increased after in vivo treatments with high efficacy. In particular, the most effective treatment significantly increased the frequency of germinal B cells, which were absent in untreated tumors. These data can lead to new insights on the diagnosis and treatment of TNBC and to possible clinical applications.
Citation Format: Laura Carpen, Paolo Falvo, Stefania Orecchioni, Giulia Mitola, Roman Hillje, Saveria Mazzara, Patrizia Mancuso, Stefano Pileri, Alessandro Raveane, Francesco Bertolini. A single-cell RNA atlas of innate and adaptive intratumoral immunity in triple negative breast cancer during chemo- and immunotherapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1712.