Studies on Multiple Forms of proGRP in Serum from Small Cell Lung Cancer Patients

To determine whether various forms of progastrin-releasing peptide (proGRP) exist in the human circulation, a panel of monoclonal antibodies was produced to construct immunometric assays for various proGRP fragments. In combination with liquid chromatography, this facilitated the determination of fragment size distribution in the sera of patients with small cell lung cancer (SCLC). Separation of proGRP peptides from SCLC cell lines and patient samples by ion exchange and gel filtration resulted in the identification of several C-terminal fragments with wide differences in the relative amounts of each cleavage product. The high specificity of our immunometric assays for the various serum proGRP fragments indicates that they are promising tools for future investigations on the relationship between fragment distribution and diagnosis and prognosis.