The paper: Analysis of the plasma peptidome from pancreas cancer patients connects a peptide in plasma to overexpression of the parent protein in tumors.
Antwi K, Hostetter G, Demeure MJ, Katchman BA, Decker GA, Ruiz Y, Sielaff TD, Koep LJ, Lake DF.
J Proteome Res. 2009 Oct;8(10):4722-31. [PubMed]
It is known that differential splicing of the QSOX1 message generates shorter human QSOX forms (QSOX1b) that lack the transmembrane helix found at the C-terminus of QSOX1a. The longer form may be retained in the Golgi, or presented at the cell surface; but a significant fraction of QSOX appears to be secreted from cells. Although most of this is likely QSOX1b, some activity may be released from cells following proteolysis of the variable C-terminal region of QSOX1a.
In this interesting report, Dr. Douglas Lake and colleagues have observed a peptide from this C-terminal region (NEQE … see above) that is released into the plasma of patients with pancreatic cancer.
Antwi et al. state: “This is the first report of QSOX1 peptides in plasma from DAP (ductal adenocarcinoma of the pancreas) patients and makes the rare connection between a peptide in plasma from cancer patients and overexpression of the parent protein in tumors.´
Further studies are envisaged to evaluate the potential of this QSOX1 peptide as a biomarker in cancer of the pancreas.