Abstract P2-21-03: Unique Collagen Peptide Signatures between Ductal Carcinoma in Situ and Invasive Breast Cancer by Mass Spectrometry Tissue Imaging

Ductal carcinoma in situ (DCIS) is characterized by inter-tumor heterogeneity that poses a therapeutic challenge due to its unpredictable recurrence and progression to invasive breast cancer (IBC). Recent publications have implicated the crucial role of the tumor microenvironment particularly stromal differences between DCIS patients who progress to IBC (progressors) and those that do not (non-progressors). However, spatial regulation of the collagen proteome has yet to be investigated in the context of disease progression in DCIS. In this study, we hypothesized that the collagen proteome was significantly altered between DCIS and IBC and that differentiating collagen peptide signatures could be related to clinical outcomes. Our initial studies investigated collagen peptide signatures in lumpectomies (n=13) annotated as DCIS, DCIS and invasive ductal carcinoma (IDC), or IDC only. We leveraged our previously published method for spatial imaging of collagen proteomics on tissue to report collagen types and collagen post-translational modifications including 40 other extracellular matrix (ECM) proteins involved in the regulation of collagen fibers. Over 1000 peaks were found to be linked to annotated pathologies or adjacent regions. Initial comparison of DCIS to IDC lesions demonstrated 63 differentially expressed peaks between these regions by unpaired, two-tailed t-test (p< 0.001). Image segmentation of the 315,541 pixels demonstrated 16 high-level hierarchical groups designating unique spatially localized ECM proteomic groups. Notably, these groups overlaid with histopathological features and pathological annotations. Next, we investigated collagen peptide signatures in a subset of DCIS samples from the Resource of Archival Breast Tissue (RAHBT) (n=37). Samples were histologically diverse within the tissue microarrays, with cribriform, micropapillary, papillary, solid, and comedo necrosis architectural patterns. In our preliminary analysis, we found two peptide peaks that could distinguish the solid subtype (n=22) from comedo necrosis (n=4) and one peak that could discriminate between the cribriform (n=8) and solid subtype (n=22) by area under the receiver operating curve (AUROC)≥0.75 and Wilson/Brown t-test (p< 0.05). Evaluated per clinical outcome, four ECM peptides showed significantly different peak intensities in progressors with IBC recurrence (n=7) compared to non-progressors (n=26) (AUROC≥0.75; Wilson/Brown t-test p< 0.05). One peptide had significantly different peak intensities between progressors with contralateral IBC recurrence and DCIS recurrence (n=5) and non-progressors (n=26) (AUROC≥0.75; Wilson/Brown t-test p< 0.05). Overall, the data suggest that unique collagen signatures in DCIS could be useful for understanding recurrence and progression to IBC. Further investigation of the spatial distribution of the collagen proteome within DCIS pathologies and relative to clinical outcome is warranted. Citation Format: Taylor S. Hulahan, Elizabeth N. Wallace, Siri H. Strand, Graham A. Colditz, E Shelley Hwang, Robert West, Laura Spruill, Jeffrey Marks, Richard R. Drake, Peggi M. Angel. Unique Collagen Peptide Signatures between Ductal Carcinoma in Situ and Invasive Breast Cancer by Mass Spectrometry Tissue Imaging [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-21-03.