Abstract C003: Multimodal and multiplexed spatial regulation of the breast collagen proteome: Comparative analysis in Black and White women from normal breast tissue and triple-negative breast cancer

Abstract Non-Hispanic Black women (BW) are diagnosed with more aggressive breast cancer subtypes at younger ages and have higher mortality rates compared to non-Hispanic White women (WW). Within the breast microenvironment emergent data shows that stromal collagen plays a significant role in aggressiveness of breast cancer linked to ancestral traits. However, the molecular composition of collagen stroma has yet to be linked to ancestry and aggressiveness of breast cancer. The purpose of this study was to evaluate the microenvironment within ancestry-defined normal breast and triple-negative breast cancer (TNBC) to understand spatial regulation of collagen stroma that may link to ancestral differences in cancer. Multimodal, multiplexed spatial analyses were performed. Techniques included Second Harmonic Generation (SHG) to measure collagen fibers, mass spectrometry imaging to measure the collagen proteome, and mass-tagged antibody panels to investigate immune signatures in TNBC. Normal breast tissues were obtained from the Susan G. Komen Tissue Bank, African American (AA; n=20) and European American (EA; n=20) samples were annotated with risk scores, age, Body Mass Index (BMI), Breast Imaging-Reporting and Data System (BI-RADS), continental ancestry, and family history. Triple-negative breast cancer (TNBC, n=80) tissues from BW with extensive clinical annotations including age, BMI, stage, metastasis, and survival were evaluated in comparison to 20+ TNBC tissues from WW. In the normal breast cohort, evaluation of BMI (overweight and obese) within ancestry groups showed significant but opposing differences in fiber width measurements. As BMI increases, AA showed statistically thicker fibers while EA showed statistically thinner fibers. At the protein level, two types of collagens were significantly higher in EA and one type is higher in AA. Within the TNBC cohort, collagen fiber length and width measurements by SHG were significantly shorter and thinner in stage II compared to stage I but no other stage comparisons were significant. This may indicate that ECM remodeling occurs at earlier stages in TNBC. Initial analyses showed that collagen peptide intensities significantly vary by TNBC stage (75 peptides, ANOVA test FDR p-value < 0.05). In the cohort of women who survived, 90 ECM peptides significantly correlated with collagen fiber widths, indicating a relationship between collagen physical and molecular properties within a defined region. Seven immune markers defined differences in survival when grouped by high vs low expression within tumor regions. These markers include CD20 (Hazard Ratio HR = 7.99, p-value = 0.002) and PD-1 (HR = 3.68, p-value = 0.048), which have both been studied in breast cancer. Current work focuses on collagen peptide post-translational modifications that may differ in TNBC patients by vital status and are detected in normal breast at risk of cancer. These findings support that molecular composition in breast stroma contributes to aggressive ancestral traits of breast cancer risk and triple-negative breast cancer. Citation Format: Jaclyn B. Dunne, Heather Jensen-Smith, Laura Spruill, Taylor S. Hulahan, Jade K. Macdonald, George E. Sandusky, M. A. Hollingsworth, Anand S. Mehta, Richard R. Drake, Jeffrey R. Marks, Harikrishna Nakshatri, Marvella E. Ford, Peggi M. Angel. Multimodal and multiplexed spatial regulation of the breast collagen proteome: Comparative analysis in Black and White women from normal breast tissue and triple-negative breast cancer [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C003.