LC-MS/MS-based terminomics unravels carboxypeptidase B1 role in luminal A breast tumor progression
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| Year of publication | 2025 |
| Type | Conference abstract |
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| Description | Carboxypeptidase B1 (CPB1) is a metalloprotease which cleaves arginine and lysine residues from protein C-termini. Elevated CPB1 expression was previously associated with lymph node metastasis in low-grade luminal A breast tumors [1]. Here we aim to better understand the molecular role of CPB1 in breast cancer development. To identify CPB1 protein substrates, we analyzed lysates of lymph node positive luminal A breast tumors with CPB1 (vs. CPB1 negative control) via trypsin digestion and timsTOF Pro 2 LC-MS/MS system. The data were processed in Spectronaut software with semispecific search settings and in Fragterminomics package in R. Among 76,368 peptides identified in terminomics experiment (FDR=0.01), 17,748 peptides possessed a C-terminal non tryptic cleavage, including a set of top 23 proteins with C-terminal peptides with max. 2 arginine or lysine residues removed from the C-terminus specifically in CPB1-cleaved samples. These CPB1 substrates, including PDXDC1, GANAB and NID2 proteins, were associated mainly with extracellular localization, cytoskeleton and cell motility. To functionally confirm CPB1 role in metastatic potential of cancer cells, a 3D invasion assay was performed, showing increased volumes of spheroids formed by MCF7 cells overexpressing CPB1 compared to CPB1 negative control. To further analyze CPB1 association with clinical-pathological parameters, CPB1 immunohistochemistry was performed in the set of 441 breast tumors. CPB1 staining was significantly associated with lymph node status and relapse in patients of all subtypes, and specifically also with relapse of luminal A tumors (n=251; p?0.05). CPB1 histoscore was connected with a shorter relapse-free (RFS) and distant metastasis free survival in the set of 441 breast cancer patients. Multivariable Cox analysis confirmed CPB1 as the most significant factor associated with RFS in luminal A breast cancer patients. In conclusion, CPB1 seems to play a significant role in the progression of luminal A breast tumors which could be mediated by cleavage of specific protein substrates. Supported by the National Institute for Cancer Research (Program EXCELES, ID LX22NPO5102) – Next generation EU. References 1. P. Bouchal, et al. Mol Cell Proteomics, 14(7):1814-30 (2015) |
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