Tumor development and progression have a series of complex process involving multiple changes in gene expression. Progressive tumor cells acquire an invasive and metastatic phenotype that is the main cause of death for cancer patients. Therefore, for early diagnosis and effective therapeutic intervention, we need to detect the alterations associated with transition from benign to malignant tumor cells on a molecular basis. To unravel these alterations concerned with tumor progression, a proteome approach attracts great attention because it can identify of qualitative and quantitative changes in protein composition, including their post-translational modifications.
The progressive and regressive tumor models of murine fibrosarcoma cells (QR32 clone and QRsP clone) have been established by our group. The QR clones are weakly tumorigenic and non-metastatic. QR32 cells regress spontaneously after injection of up to 2 x 105 cells subcutaneously or 1 x 106 cells intravenously in normal syngeneic mice. The QRsP clones are more highly tumorigenic and metastatic malignant tumor cells derived from QR32 cells.
The aim of this study is to identify proteins expressed differently between these two clone cells, QR32 and QRsP11. The comparison of the differential expression of proteins between single-cell-originated benign tumor cells and its derived malignant tumor cells would be of benefit for detecting important factors on tumor progression because of their very close genetic backgrounds. In this study, we performed two-dimensional gel electrophoresis and identified some proteins that showed more highly overexpression in QRsP11 than in QR32 by mass spectrometry of LC/MS/MS. It was suggested that these proteins are associated with tumor progression.