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Abstract

Osteosarcoma is a prevalent bone cancer in adolescents, which targets the bone remodeling process that is very active during puberty due to changes in the body’s mechanical load. Two cells facilitate this remodeling system: osteoclasts, cells that break down bone, and osteoblasts, cells that build up bone. Osteosarcoma starts inside the bone, with the unbalanced production of excess osteoclasts, allowing more bone degradation than promotion. This lack of integrity allows the cancer to leave the bone and spread. The primary cellular pathway that regulates the bone remodeling system is the OPG-RANK-RANKL pathway, where the interaction between RANK-RANKL leads to osteoclast production. OPG acts as a decoy receptor by binding to RANK and blocking osteoclast production. To inhibit excess bone degradation, OPG was administered to osteosarcoma cells named U2OS. U2OS was first treated with a cytokine, TNFα, known to induce osteoclastogenesis and model metastatic osteosarcoma. ELISA, a protein detection assay, showed a significant decrease in RANK-RANKL production, supporting a potential decrease in osteoclast production. Gene expression analysis revealed an upregulation in genes responsible for bone integrity and a downregulation of WNT6 and NPC2 – genes indicative of metastasis. OPG caused a decrease in a novel biomarker in cancer progression/metastases with a 22.3 fold decrease in TUBB – an osteoclast survival gene. Diminished metastatic capability was shown through TRAP (Tartrate Resistant Acid Phosphatase) staining which showed a significant decrease in osteoclast number and an invasion assay demonstrated reduced invasion of OPG treated cells. OPG may have therapeutic potential in controlling osteosarcoma metastasis.