Peptidomics-based approach reveals the secretion of the 29-residue COOH-terminal fragment of the putative tumor suppressor protein DMBT1 from pancreatic adenocarcinoma cell lines.

Deleted in malignant brain tumors 1 is a putative tumor suppressor protein in brain, lung, esophageal,gastric, and colorectal cancer. Here we report the mass spectrometric identification of a 3335 Da peptide, which was found in serum-free conditioned medium from 5 of 15 pancreatic adenocarcinoma cell lines but not from 35 carcinoma cell lines and 2 nonmalignant pancreatic duct cell lines. The peptide was the 29 COOH-terminal amino acids from deleted in malignant brain tumors 1. It is suggested that the peptide is generated inside the cells by limited proteolysis and extracellularly secreted. Our peptidomics-based approach will help screen candidate marker peptides for a particular type of cancer.