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Osteosarcoma is the most common primary malignant bone tumor in children and adolescents, and lung metastasis is the major cause of death. Highly metastatic osteosarcoma cells are mechanically softer than low-metastatic cells, and calcium ions are known to regulate cytoskeletal organization and cell stiffness. We tested whether clinically available ion channel blockers could increase the stiffness of LM8 osteosarcoma cells and prevent lung metastasis in vivo.

We evaluated the actin cytoskeletal structure and polymerization in ion channel blocker-treated LM8 cells using actin staining. Cell stiffness was measured using atomic force microscopy. Metastasis-related cellular functions were analyzed using cell proliferation, wound healing, and cell adhesion assays. Furthermore, lung metastasis and tumor volume were measured in LM8-bearing mice treated with an ion channel blocker.

Treatment with ion channel blockers significantly increased actin staining intensity and stiffness in LM8 cells compared to that in untreated LM8 cells (p<0.05). The proliferation potential was significantly lower in the amlodipine-treated group (p<0.05). The ion channel blockers treatment group demonstrated significantly higher adhesion than the control group (p<0.05). The migration potential of the disopyramide- and lidocaine-treated groups were lower than that of the control group. Daily intraperitoneal administration of 20 mg/kg amlodipine for five weeks in LM8-bearing mice significantly reduced lung metastasis compared to that in the control group (p<0.05). No significant differences in tumor volume were observed after amlodipine administration.

Amlodipine could increase tumor cell stiffness and significantly reduce lung metastasis.