Journal
BLOOD
Volume 120, Issue 9, Pages 1877-1887Publisher
AMER SOC HEMATOLOGY
DOI: 10.1182/blood-2011-12-396853
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Funding
- National Institutes of Health [RO-1 50947, PO1-78378, P50CA100707]
- Lebow Fund to Cure Myeloma
- DF/HCC Myeloma SPORE Career Development Award
- Pharmacyclics
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Bruton tyrosine kinase (Btk) has a well-defined role in B-cell development, whereas its expression in osteoclasts (OCs) further suggests a role in osteoclastogenesis. Here we investigated effects of PCI-32765, an oral and selective Btk inhibitor, on osteoclastogenesis as well as on multiple myeloma (MM) growth within the BM microenvironment. PCI-32765 blocked RANKL/M-CSF-induced phosphorylation of Btk and downstream PLC-gamma 2 in OCs, resulting in diminished TRAP5b (ED50 = 17nM) and bone resorption activity. PCI-32765 also inhibited secretion of multiple cytokines and chemokines from OC and BM stromal cell cultures from both normal donors (ED50 = 0.5nM) and MM patients. It decreased SDF-1-induced migration of MM cells, and down-regulated MIP1-alpha/CCL3 in MM cells. It also blocked MM cell growth and survival triggered by IL-6 or coculture with BM stromal cells or OCs in vitro. Importantly, PCI-32765 treatment significantly inhibits in vivo MM cell growth (P < .03) and MM cell-induced osteolysis of implanted human bone chips in SCID mice. Moreover, PCI-32765 prevents in vitro colony formation by stem-like cells from MM patients. Together, these results delineate functional sequelae of Btk activation mediating osteolysis and growth of MM cells, supporting evaluation of PCI-32765 as a novel therapeutic in MM. (Blood. 2012;120(9):1877-1887)
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