Mass Spectrometric Detected Cancer Proteins as Resources for Cancer Research

Protein evidence derived from mass spectrometry (MS) across cancer cohorts and model systems is extensive but remains fragmented across individual studies and repositories, limiting rapid retrieval and evidence-based benchmarking of cancer-context protein detection. Here we present the Mass Spectrometric Detected Cancer Proteins (MSCP) resource, an integrated database assembled from 27 large-scale cancer proteomics sources spanning human tumor cohorts, cancer cell lines, and patient-derived xenograft (PDX) models. Protein identifications were harmonized to UniProtKB-Swiss-Prot (release 2025_01) and integrated under FDR-controlled identification outputs to generate a unified catalog of 15,964 MS-supported human proteins. Benchmarking against neXtProt PE1 identified 525 proteins newly supported by MS evidence in the integrated cancer context, including proteins previously associated with chromosome-level evidence inconsistencies. Functional interpretation of the newly identified set using GO and Reactome enrichment highlighted immune- and barrier-associated processes and chromatin- and genome-regulatory pathways, including DNA methylation and histone deacetylation. Orthogonal verification using synthetic unique peptides confirmed representative newly identified proteins by concordant precursor <i>m</i>/<i>z</i> and fragment-ion patterns. MSCP provides a provenance-aware, UniProtKB-aligned resource for cancer proteomics that supports both cohort- and model-specific querying and coverage-oriented evidence aggregation, enabling standardized comparisons to reference proteomes and facilitating downstream assay planning and translational studies.