Proteolytic cascades are deeply involved in critical stages of cancer progression. During the course of peptide-wise analysis of shotgun proteomic data sets representative of colon adenocarcinoma (AC) and ulcerative colitis (UC), we detected a cancer-specific proteolytic fingerprint composed of a set of numerous protein fragments cleaved C-terminally to V, I, A, T, or C residues, significantly overrepresented in AC. A peptide set linked by a common VIATC cleavage consensus was the only prominent cancer-specific proteolytic fingerprint detected. This sequence consensus indicated neutrophil elastase as a source of the fingerprint. We also found that a large fraction of affected proteins are RNA processing proteins associated with the nuclear fraction and mostly cleaved within their functionally important RNA-binding domains. Thus, we detected a new class of cancer-specific peptides that are possible markers of tumor-infiltrating neutrophil activity, which often correlates with the clinical outcome. Data are available via ProteomeXchange with identifiers: PXD005274 (Data set 1) and PXD004249 (Data set 2). Our results indicate the value of peptide-wise analysis of large global proteomic analysis data sets as opposed to protein-wise analysis, in which outlier differential peptides are usually neglected.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.