Comparative Proteomic Profiling of Tumor-Associated Proteins in Human Gastric Cancer Cells Treated with Pectolinarigenin

Pectolinarigenin (PEC), a natural flavonoid that is present in citrus fruits, has been reported to exhibit antitumor effects in several cancers. Though the mechanism of PEC-induced cytotoxicity effects has been documented, the proteomic changes that are associated with the cellular response to this flavonoid are poorly understood in gastric cancer cells. In this study, a comparative proteomic analysis was performed to identify proteins associated with PEC-induced cell death in two human gastric cancer cell lines: AGS and MKN-28. Two-dimensional gel electrophoresis (2-DE) revealed a total of 29 and 56 protein spots with significant alteration were screened in AGS and MKN-28 cells respectively. In total, 13 (AGS) and 39 (MKN28) proteins were successfully identified by mass spectrometry from the differential spots and they are known to be involved in signal transduction, apoptosis, transcription and translation, cell structural organization, and metabolism, as is consistent with multiple effects of PEC on tumor cells. Notably, novel target proteins like Probable ATP-dependent RNA helicase DDX4 (DDX4) and E3 ubiquitin-protein ligase LRSAM1 (LRSAM1) along with the commonly differential expressed proteins on both the cell lines that are treated with PEC were confirmed by immunoblotting. The DDX4 accelerates cell cycle progression by abrogating the G2 checkpoint when overexpressed in cancer cells, while the aberrant expression of LRSAM1 may be involved in the cancer pathology. Thus, proteomic analysis provides vital information about target proteins that are important for PEC-induced cell death in gastric cancer cells.