Abstract P64: Adipose-enriched Peri-tumoral Stroma Prognosticates Poorer Survival in Breast Cancers

Abstract Background: Breast cancers display a large degree of diversity between and within tumors. Intra-tumoral heterogeneity is contributed by variations in tumor cells and non-malignant stromal and immune cells of the tumor microenvironment (TME). So far, studies on the TME have focused on intra-tumoral stroma, whereas little attention has been given to the peri-tumoral microenvironment, extending beyond the tumor margins into the surrounding histologically normal-appearing tissues. Here, we hypothesized that intrinsic intra-tumoral heterogeneity impacts the more distal peri-tumoral stroma, which may in turn affect tumor growth and development. Methods: A systematic, multi-regional transcriptomic profiling analysis of the tumor and peri-tumoral regions from 8 ER+/PR+/HER2− invasive breast carcinomas was performed using the human Clariom™ S Assay. For each patient, 5 spatially distinct tumor samples were obtained, while peri-tumoral samples were collected from 4 different sides and at varying distances up to 7 cm from tumor margins. Pathway enrichment analyses and cellular deconvolution were performed to determine their molecular characteristics and cell type compositions. Gene expression signatures identified from peri-tumoral samples were applied to tumor-adjacent normal RNA-seq samples from 50 TCGA ER+/PR+/HER2− breast cancer patients to determine their prognostic value. Results: The 8 tumors displayed varying levels of spatial diversity in their biological properties, including 3 tumors with basal-classified regions. Four peri-tumoral clusters with distinct pathway activities and cell compositions were identified, but were independent of distance and location to the tumor. Two clusters reflect the major breast peri-tumoral states – a pro-inflammatory, adipose-enriched phenotype which was significantly associated with poorer overall survival (HR=4. 28, p-value=0. 02), and an adaptive immune cell- and myofibroblast-enriched phenotype. Conclusion: This suggests that the peri-tumoral stroma may be an important determinant in cancer progression. Moreover, independent of spatially-defined patterns, the peri-tumoral phenotype appears to be driven by inter-individual variations in the proportion of fibroglandular and fat tissue of the breast. Citation Format: Hannah Si Hui Lau, Veronique Kiak Mien Tan, Benita Kiat Tee Tan, Yirong Sim, Jelmar Quist, Aye Aye Thike, Puay Hoon Tan, Shazib Pervaiz, Anita Grigoriadis, Kanaga Sabapathy. Adipose-enriched Peri-tumoral Stroma Prognosticates Poorer Survival in Breast Cancers abstract. In: Proceedings of Frontiers in Cancer Science; 2023 Nov 6-8; Singapore. Philadelphia (PA): AACR; Cancer Res 2024;84 (8Suppl): Abstract nr P64.