Abstract PD2-01: Local and lymphoid immune surveillance mechanisms in “exceptional survivors” of stage 4 cancers following standard of care chemo- and targeted therapies

Abstract

Abstract Breast cancer patients with advanced metastatic disease can exhibit rapid disease progression, disease stabilisation or partial responses of varying duration. However, for reasons that are not fully elucidated, a small fraction of patients will elicit an exceptional durable response to standard anticancer treatments or survive significantly longer than patients with clinically comparable tumours. Here, we investigate the drivers of immune surveillance mechanisms across breast cancer subtypes in stage IV exceptional survivors (n=13) with matched control cohorts of stage IV typical responders (n=6), early breast cancer patients (n=5) and healthy volunteers (n=17). Peripheral blood mononuclear cells (PBMCs) from patients were stained with 8 panels providing 241 non-redundant immune parameters for flow cytometry analysis. Principle Component Analysis (PCA) showed distinct segregation of the exceptional survivors from the other control groups with an immune signature in exceptional survivors constituting of activated NK, CD8 T cells and gamma delta (gd) T cells pointing towards higher innate immunogenicity in these individuals. Specifically, although these metastatic exceptional responder patients possessed comparable NK cell frequencies, the proportion of NKG2D+CD56dimCD16+ NK cells were significantly enriched compared to the typical responders. Additionally, proportions of CD8+ central memory (CD45RA- CD27+) and effector memory (CD45RA- CD27-) gd T cells, were also seen to be significantly increased. Functional in vitro validation of these findings along with scRNA sequencing of lymph node and tumour tissue is currently underway. To our knowledge, this work is the first to explore in depth the immune signatures in the peripheral blood of exceptional survivors with metastatic breast cancer. Elucidating the immunological reasons for favourable atypical responses alongside functional tumour microenvironment analysis offers unique insights for predictive biomarker identification and discovery of axes that could be exploited therapeutically to benefit those with less favourable responses. Written informed consent was obtained from all individuals in accordance with the Declaration of Helsinki under the following research ethics committee; London-Chelsea approved study (REC ID 13/LO/1248). Citation Format: Helen Kakkassery, Thanussuyah Alaguthurai, Rosalind Graham, Esme Carpenter, Farhana Hossain, Sean Keane, Sheeba Irshad. Local and lymphoid immune surveillance mechanisms in “exceptional survivors” of stage 4 cancers following standard of care chemo- and targeted therapies [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD2-01.