2-D DIGE and MALDI-TOF-MS analysis of the serum proteome in human osteosarcoma

We performed 2-D DIGE on proteins prepared from serum obtained from patients with osteosarcoma (OS) and controls, to identify differentially expressed proteins that might serve as serum biomarkers for OS prognosis. Proteins found to be differentially expressed were identified by MALDI-TOF mass spectrometric analysis, coupled with database interrogation. We compared serum samples from four individuals with OS to four age- and sex-matched healthy controls. We identified 24 protein spot-features that were significantly increased, and 34 that were significantly decreased in serum from patients with OS relative to the controls. The MS analysis revealed 18 unique proteins that were increased, and 25 unique proteins that were decreased in OS serum samples. Western blot and ELISA analysis confirmed increased levels of amyloid-related serum protein (SAA) in the OS serum samples. The increased expression levels of SAA were decreased after using MTX and cisplatin combination chemotherapy, and were further decreased after operation. Moreover, increased expression levels of sera SAA were seen in the relapsed patients. Our results suggested that the determination of serum SAA in OS patients might be utilized as a marker for relapse and in evaluation of the efficacy of therapy.