Reveromycin A Inhibits Osteolytic Bone Metastasis of Small-Cell Lung Cancer Cells, SBC-5, through an Antiosteoclastic Activity

Abstract

The purpose of this study was to determine therapeutic effect of a novel antibiotic, reveromycin A, against osteolytic bone metastasis of human small cell lung cancer (SBC-5) cells. Reveromycin A induced apoptosis specifically in osteoclasts in vitro. Although reveromycin A did not inhibit SBC-5 cell proliferation, it suppressed the expression of parathyroid hormone-related peptide. Intravenous inoculation of SBC-5 cells in natural killer cell-depleted severe combined immunodeficient mice produced experimental metastases in multiple organs, including the bone. Daily administration of reveromycin A inhibited the bone metastasis, but not visceral metastasis, in a dose-dependent manner. Histologic analyses revealed that although treatment with reveromycin A did not affect the number of proliferating tumor cells, it decreased the number of osteoclasts and increased apoptotic cells in bone lesions. These findings suggest that reveromycin A may inhibit osteolytic bone metastasis through suppression of osteoclast activity by directly inducing apoptosis and indirectly inhibiting tumor cell-derived parathyroid hormone-related peptide production. Therefore, reveromycin A may be a novel, potent therapeutic agent against osteolytic bone metastasis of lung cancer in humans.