Invited Presentation 36th Lorne Cancer Conference 2024

The immune infiltrate in breast cancer and relevance for prognosis and checkpoint inhibition. (#25)

Sherene Loi 1
  1. Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia

The quantity of tumor-infiltrating lymphocytes (TILs) in breast cancer is a robust prognostic factor for improved patient survival, particularly in triple-negative and HER2- overexpressing breast cancer subtypes. Although T cells are the predominant TIL population, there are qualitative differences in the T cells: in particular we have shown the importance of a tissue resident memory T cell (TRM) phenotype. We have used a syngeneic mammary tumor murine model to understand the relevance of this T cell sub-population in breast cancer control and immunotherapy responses. Treatment with T cell checkpoint inhibitors in this model resulted in the expansion of intratumoral T cells with a TRM-like subset demonstrating enhanced cytotoxic capacity as well as could provide protection against secondary tumor rechallenge. Our data suggests that CD8+ TRM cells contribute to breast cancer immunosurveillance as well as T cell immunotherapy driven breast cancer control. Further understanding of the development, maintenance and regulation of TRM cells will be crucial for successful immunotherapeutic development in breast cancer.