talabostat and Multiple-Myeloma

Dipeptidyl peptidase (DPP) IV activity and/or structure homologues (DASH) are serine proteases implicated in tumourigenesis. We previously found that a DASH protease, fibroblast activation protein (FAP), was involved in osteoclast-induced myeloma growth. Here we further demonstrated expression of various adhesion molecules in osteoclasts cultured alone or cocultured with myeloma cells, and tested the effects of DASH inhibitor, PT-100, on myeloma cell growth, bone disease, osteoclast differentiation and activity, and expression of adhesion molecules in osteoclasts. PT-100 had no direct effects on viability of myeloma cells or mature osteoclasts, but significantly reduced survival of myeloma cells cocultured with osteoclasts. Real-time PCR array for 85 adhesion molecules revealed upregulation of 17 genes in osteoclasts after coculture with myeloma cells. Treatment of myeloma/osteoclast cocultures with PT-100 significantly downregulated 18 of 85 tested genes in osteoclasts, some of which are known to play roles in tumourigenesis and osteoclastogenesis. PT-100 also inhibited osteoclast differentiation and subsequent pit formation. Resorption activity of mature osteoclasts and differentiation of osteoblasts were not affected by PT-100. In primary myelomatous severe combined immunodeficient (SCID)-hu mice PT-100 reduced osteoclast activity, bone resorption and tumour burden. These data demonstrated that DASH proteases are involved in myeloma bone disease and tumour growth.

Topics: Alkaline Phosphatase; Animals; Biomarkers, Tumor; Bone Density; Bone Resorption; Boronic Acids; Cell Adhesion Molecules; Cell Differentiation; Coculture Techniques; Dipeptides; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; Gene Expression; Gene Expression Profiling; Humans; Immunoglobulin Light Chains; Immunohistochemistry; Mice; Mice, SCID; Multiple Myeloma; NF-kappa B; Oligonucleotide Array Sequence Analysis; Osteoclasts; p38 Mitogen-Activated Protein Kinases; Phosphorylation