Abstract
Abstract Most of cancer patients die, not because of the tumor in the primary site, but because of spreading to other site. In particular, bone metastasis is relatively common in patients with breast, prostate, and lung cancer. Many breast cancer patients suffer from bone metastasis with bone pain and pathological fractures. These metastases are predominantly osteolytic and develop when tumor cells interact with bone. Tumor and bone interact in a vicious cycle, where tumor-secreted factors stimulate bone cells, which in turn release growth factors and cytokines that act back on the tumor cells. Within the vicious cycle are many potential therapeutic targets for treatment of bone metastatic disease. Nelumbo nucifera (Lotus) has been known as a medicinal herb for treatment of cough, fever and hyperdipsia. Betulinic acid (BA) is a naturally occurring triterpenoid present in lotus. In this study, we found that BA reduced mRNA expressions of osteolytic factors in MDA-MB-231 human metastatic breast cancer cells. In particular, mRNA level of parathyroid hormone-related protein (PTHrP), the major component of vicious cycle within bone, was significantly inhibited by BA. Treatment with BA decreased receptor activator of nuclear factor kappa-B ligand (RANKL) /osteoprotegerin (OPG) ratio in PTHrP-treated human osteoblasts. In addition, BA dose-dependently inhibited the RANKL-induced osteoclast differentiation and bone resorption by reducing the secretion of matrix metalloproteinases (MMPs) and cathepsin K derived from osteoclasts, without any evidence of cytotoxicity. We further examined the effect of BA on ovariectomy-induced osteoporosis in mice. Serum levels of tartrate-resistant acid phosphatase isoform 5b, alkaline phosphate, calcium, osteocalcin and C-terminal telopeptide of type I collagen were significantly increased in ovariectomized (OVX) mice than in sham mice. BA inhibited increases in the serum levels of these osteoporotic markers in OVX mice. We analyzed bone volume, trabecular bone thickness, trabecular number and trabecular separation by micro-computer tomography (μ-CT) scanning. Taken together, BA may reduce the expression of PTHrP in MDA-MB-231 human metastatic breast cancer cells, RANKL/OPG ratio in PTHrP-stimulated human osteoblasts, and RANKL-induced osteoclastogenesis in bone marrow macrophages. BA may also prevent osteoporotic bone loss in OVX mice. Thus, BA can be beneficial agents for patients with secondary bone lesions associated with breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 34. doi:1538-7445.AM2012-34
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