E-Poster Presentation 34th Lorne Cancer Conference 2022

Stromal mediators of immune dysfunction in triple negative breast cancer (#119)

Julia Chen 1 2 3 , Sunny Wu 1 , Iveta Slapetova 4 , Ewan Millar 5 , Elgene Lim 1 2 3 , Alex Swarbrick 1 3
  1. Garvan Institute of Medical Research & Kinghorn Cancer Centre, Sydney, NSW, Australia
  2. Department of Medical Oncology, St Vincent's Hospital, Darlinghurst, NSW, Australia
  3. St Vincent Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW , Australia
  4. Biomedical Imaging Facility, Mark Wainwright Analytical Centre, University of New South Wales, Kensington, NSW, Australia
  5. Department of Anatomical Pathology, NSW Health Pathology, St George Hospital, Kogarah, NSW, Australia

Stromal cells have emerged as important mediators of immune function in solid tumours. Recent multi-omics studies from our group and others have elucidated the heterogeneity of stromal cells and their interactions with immune cells in cancers. However, the clinical relevance of these relationships remain poorly explored, limiting the development of effective targeted therapies. Our previous work revealed functionally distinct subpopulations of stromal cells associated with immune evasion and dysfunction in triple negative breast cancers: inflammatory-like cancer-associated fibroblasts (iCAFs) associated with the dysfunction of cytotoxic T-cells; and differentiated perivascular-like cells (dPVLs) associated with the exclusion of T-cells.

 

We explored the clinical relevance of these stromal subpopulations and their association with immune evasion in a large independent breast cancer cohort. Using markers derived from our single-cell multi-omics studies, we performed multiplex immunofluorescence on a cohort of 450 early breast cancer patients with mixed molecular subtypes to mark myofibroblast-like CAFs (myCAFs), iCAFs, dPVLs, endothelial cells, CD8 and/or PD1 positive T-cells. Digital imaging analysis in QuPath revealed a significant difference in both stromal composition and immune infiltration between different molecular subtypes. The abundance of dPVL is associated with decreased abundance of CD8 T-cells in triple-negative breast cancers, supporting the role of dPVL cells in T-cell exclusion. In line with previous clinical observations, a high abundance of CD8 T-cells predicts better overall survival in the iCAF-low subset of patients. However, in the iCAF-high subpopulation, CD8 did not predict survival, consistent with the predicted role of iCAFs in driving dysfunctional CD8 T-cells.

 

Using ex vivo co-culture models of primary CAFs and T-cells, we applied flow cytometry and scRNA-Seq to show that CAFs suppress the proliferative capability of T-cells and drive them towards a LAG3+ exhausted state. Our findings suggest that co-targeting stromal subpopulations could elicit a more effective immune response in a subset of patients through inhibiting T-cell dysfunction and exclusion.