Overexpression of klotho suppresses growth and pulmonary metastasis of osteosarcoma in vivo.

Klotho is originally discovered as an anti-aging gene and knock-out of klotho accelerates aging in mice. Subsequent studies support the anti-carcinogenesis role of klotho in a variety of human malignancies. The present study investigated the role of klotho on growth and metastasis of osteosarcoma cells. The osteosarcoma cells were transduced with lentivirus particles encoding klotho or scramble control. The reconstructed osteosarcoma cells were injected into the femoral medullary cavity of nude mice to establish a xenograft animal model. The anti-tumor properties of klotho were evaluated in terms of tumor growth, apoptosis, glycogen production, and pulmonary metastasis. Lentivirus-mediated overexpression of klotho significantly decreased tumor volume and weight in osteosarcoma mice. Determination of PCNA and Ki67 expression revealed that overexpression of klotho inhibited cell proliferation in tumor tissues obtained from osteosarcoma xenografts. PAS staining also showed that overexpression of klotho significantly decreased the production of glycogen in osteosarcoma. Moreover, TUNEL positive cells were significantly increased after lentivirus-mediated overexpression of klotho. Furthermore, lentivirus-mediated upregulation of klotho reduced the number of pulmonary metastatic lesions in mice compared to control mice. These findings demonstrated that elevated klotho could inhibit osteosarcoma cell growth and pulmonary metastasis in vivo, suggesting that klotho may be a valuable therapeutic target for osteosarcoma.