🧵2/10 Immune checkpoint blockade (ICB) improves #TNBC outcome in both metastatic and early setting (), but biological determinants of individual benefit, especially in early setting, are unknown Precision immunology in breast cancer is a major unmet need

🧵3/10 We investigated the impact of multicellular spatial organization on ICB response, and explored how ICB remodels the tumour microenvironment in longitudinal samples of the NeoTRIP trial (NCT02620280), collected before, during (after 1st cycle) and after neoadjuvant therapy

🧵4/10 43 proteins were quantified at single-cell resolution by Imaging Mass Cytometry Based on protein expression profiles, we identified 🗒️ 17 cancer cell populations 🗒️ 20 tumour microenvironment (TME) cell populations We also mapped carboplatin in situ by detecting platinum

🧵5/10 Both epithelial and TME cell phenotypes differed between TNBC subtypes (Basal-like 1, BL1; Basal-like 2, BL2; Luminal androgen receptor, LAR; Mesenchymal, M; Mesenchymal stem-like), and PD-L1 positive and negative tumors (by IHC Ventana SP142)

🧵(6/10) At baseline (pre-treatment), the presence of proliferating tumour cells expressing MHC-I and II and proliferating CD8 T cells expressing TCF1 were strongly predictive of pathological complete response (pCR) only in tumours receiving atezolizumab

🧵(7/10) In addition, a high number of close spatial interactions (direct cell-to-cell contacts) between tumour cells and specific immune cells, such as B cells and CD8 granzyme B+ cytotoxic T cells, were also associated with a high likelihood of benefit from immunotherapy

🧵8/10 Studyng on-treatment samples revealed that sensitive tumours enriched in CD8 granzyme B+ T cells (stronger in atezo arm), whereas in resistant tumours the proportion of CD15+ tumour cells increased (only atezo arm), a potential new mechanism of adaptive immune resistance

🧵9/10 Investigating overall cellular dynamics, we found that immunotherapy distinctively remodels tumour structure Immune cells increased dramatically on-treatment (greatest with atezo) and decreased after treatment, accompanied by a ⬇️ in cancer cells and ⬆️ in stromal cells

🧵10/10 Multivariate modeling revealed that TME activation and tumor structure play pivotal roles in predicting treatment responses to immunotherapy Additionally, early on-treatment biopsies enhance predictive accuracy and could thus inform adaptive treatment strategies

This would not have been possible without the collaboration between Fondazione Michelangelo and @CRUK_CI , the support by @SanRaffaeleMI and @FondazioneBona1 , funders including @AIRC_it @BCRFcure Special thanks to the terrific work done by Xiao Qian Wang and all co-authors

@BianchiniGP Congratulations! Beautiful work.

@BianchiniGP Important work! congrats!

@BianchiniGP adding my congratulations - important and timely work. now to figure out how to apply this to the individualization of treatment! @OncoAlert

@BianchiniGP Congratulations