Complexes between insulin-like growth factor binding proteins and alpha-2-macroglobulin in patients with tumor

The intention of this work was to systematically study the presence of insulin-like growth factor-binding protein 1 and 2 (IGFBP-1 and IGFBP-2) complexes with alpha-2-macroglobulin (α2M) in the circulation of patients with various types of cancer. Serum samples were collected from patients diagnosed with cancer and divided into eight groups according to the tumor type: liver, pancreas, colon, lung, prostate, breast, cervix and ovary. Results obtained for each cancer group were compared with results obtained for the age and gender-matched controls. Electrophoretic separation and densitometric evaluation of immunoreactive protein bands were performed. According to our results, IGFBP-1/α2M and IGFBP-2/α2M complexes did not exhibit the same presence in different tumors and were also not uniformly related to the amount of monomer forms. Variations in relative quantities of IGFBP-1 monomers and complexes in different tumor types were much more pronounced than those of IGFBP-2. The amount of IGFBP-2 monomer increased in sera from all studied patients compared to controls, whereas the amount of IGFBP-2/α2M complexes most often decreased, being significantly reduced in patients with pancreas, colon, breast or ovary tumor. Although there is still no confirmation of the physiological role of IGFBP-2/α2M complexes, their decreased concentration in the circulation provides greater amount of free IGFBP-2.