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 in which calcium phosphate, produced by bone-forming cells, was 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 and related phospholipase C (PLC) enzymes. Objectives: Our aim was to search for common patterns of expression in osteoblasts, as well as in ES and SS. Methods: We analysed the PLC enzymes in human osteoblasts and osteosarcoma cell lines MG-۶۳ and SaOS-۲. We compared the obtained results to the expression of PLCs in samples of patients affected with Ewing sarcoma (ES) and synovial sarcoma (SS). Results: In osteoblasts, MG-۶۳ cells and SaOS-۲ significant differences were identified in the expression of PLC δ۴ and PLC η subfamily isoforms. Differences were also identified regarding the expression of PLCs in ES and SS. Most ES and SS did not express PLCB۱, which was expressed in most osteoblasts, MG-۶۳ and SaOS-۲ cells. Conversely, PLCB۲, unexpressed in the cell lines, was expressed in some ES and SS. However, PLCH۱ was expressed in SaOS-۲ 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 ε and PLC η isoforms. Conclusion: MG-۶۳ and SaOS-۲ osteosarcoma cell lines might represent an inappropriate experimental model for studies about the analysis of signal transduction in osteoblasts