Podium Presentation in Room 4 on Wednesday at 14:00 (Chair: Reid Groseclose / Aalim Weljie)
Authors: P. M. Angel1* , J. Saunders1, H. Jensen Smith2, E. Bruner1, M. E. Ford1, S. Berkhiser1, B. Boxall1, J. Bethard1, L. E. Ball1, E. S. Yeh3, M. A. Hollingsworth2, A. S. Mehta1, J. R. Marks4, H. Nakshatri3, R. R. Drake1
INTRODUCTION: Although European-American (EA) women have higher incidence of breast cancer, African-American (AA) women have higher mortality rates with increased occurrence of lethal cancers. AA women have increased breast density as a result of collagen deposition, a risk factor in promoting tumorigenesis. Furthermore, collagen gene regulation correlates to ancestry-dependent breast cancer progression and survival. Here, we use a novel extracellular matrix (ECM proteomic method to provide evidence that breast cancer originating from AA women has very specific regulation of collagen post-translational modifications (PTMs) that may promote a metastatic tumor microenvironment.
OBJECTIVE: Determine if breast cancer from African-American women has differential levels of collagen PTMs than breast cancer from European-American women.
METHODS: FFPE lumpectomies (n=17) were obtained from the Marks laboratory, sourced from the Cancer Genome Atlas; Ancestry-mapped tissue microarrays with >150 cores were from the Harikrishna Nakshatri laboratory. Tissues were analyzed with MUSC IRB approval by published ECM approaches using high resolution accurate mass imaging and chromatographic proteomics. Statistical comparisons were made between normal, normal adjacent to tumor and tumor breast tissue.
RESULTS: Our novel extracellular matrix proteomic studies on 17 patient lumpectomies depict that very specific sites on collagen protein types in breast tumor are post-translationally regulated by hydroxylation of proline (HYP) dependent on race (7 AA, 10 EA; no significant age or receptor status difference). From 16 collagen type proteins, 143 collagen peptides from all breast tumors were identified with HYP modifications (site probability ≥0.95). A total of 16% of the HYP peptides were unique to AA breast tumors. Imaging mass spectrometry (IMS) targeting collagens was multiplexed with second harmonic generation microscopy (SHG) which reports collagen fiber measurements. Imaging mass spectrometry targeting collagens that was done on the identical sample set after SHG also identified ancestry-dependent site specific collagen modification by hydroxylation of prolines. For instance, variants of COL3A1 peptide GPAGIPxGFPx showed up to a 3-fold increase in AA breast tumors compared to EA breast tumors (Mann-Whitney p-value <0.0001; area under the receiver operating curve 0.81, p-value ≤0.0001; HYP site probability of 1.00 for each proline designated Px). SHG supported significant ancestry-defined regulation of collagen fibers with significant increases in collagen fiber width and length at AA tumor borders (two-tailed student’s t-test p-value 1.9E-3 and 1.6E-2 respectively).
CONCLUSIONS: We provide the first evidence that post-translational regulation of collagen types may contribute to racial disparities in breast cancer. Current work determines ancestry-related changes in collagen fibers by breast cancer type and in healthy tissue.
|Grants||yes||Medical University of South Carolina, NIH|
|Board Member||yes||Imaging Mass Spectrometry Executive Committee; MSACL IMS SciCom|
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