Different expression and localization of phosphoinositide specific phospholipases C in human osteoblasts, osteosarcoma cell lines, Ewing sarcoma and synovial sarcoma

Background: bone hardness and strength depends on mineralization, which involves a complex process where calcium phosphate, produced by bone-forming cells, were shed around the fibrous matrix. This process is strictly regulated, and a number of signal transduction systems were interested in calcium metabolism, such as the Phosphoinositide (PI) pathway, including the Phospholipase C (PLC) enzymes. Methods: we analysed the PLC enzymes in human osteoblasts and osteosarcoma cell lines MG-63 and SaOS-2. We compared the results to the expression of PLCs in samples of patients affected with Ewing Sarcoma (ES) and Synovial Sarcoma (SS). Results: In osteoblasts, MG-63 cells and SaOS-2 significant differences were identified in the expression of PLC 4 and PLC subfamily isoforms. Differences were also identified regarding the expression of PLCs in ES and SS. Most ES and SS did not express PLCB1, which was expressed in most osteoblasts, MG-63 and SaOS-2 cells. Conversely, PLCB2, unexpressed in the cell lines, was expressed in some ES and SS. However, PLCH1 was expressed in SaOS-2 and inconstantly expressed in osteoblasts, while it was expressed in ES and unexpressed in SS. The most relevant difference observed in ES compared to SS regarded PLC and PLC isoforms. Conclusion: MG-63 and SaOS-2 osteosarcoma cell lines probably do not represent the appropriate experimental model for studies about the analysis of signal transduction in osteoblasts