A novel role for CCL3 (MIP-1α) in myeloma-induced bone disease via osteocalcin downregulation and inhibition of osteoblast function

Abstract

Upregulation of cytokines and chemokines is a frequent finding in multiple myeloma (MM). CCL3 (also known as MIP-1α) is a pro-inflammatory chemokine whose levels in the MM microenvironment correlate with osteolytic lesions and tumor burden. CCL3 and its receptors, CCR1 and CCR5, contribute to the development of bone disease in MM by supporting tumor growth and regulating osteoclast (OC) differentiation. Here, we identify inhibition of osteoblast (OB) function as an additional pathogenic mechanism in CCL3-induced bone disease. MM-derived and exogenous CCL3 represses mineralization and osteocalcin production by primary human bone marrow stromal cells and HS27A cells. Our results suggest that CCL3 effects on OBs are mediated by ERK activation and subsequent downregulation of the osteogenic transcription factor osterix. CCR1 inhibition reduced ERK phosphorylation and restored both osterix and osteocalcin expression in the presence of CCL3. Finally, treating SCID-hu mice with a small molecule CCR1 inhibitor suggests an upregulation of osteocalcin expression along with OC downregulation. Our results show that CCL3, in addition to its known catabolic activity, reduces bone formation by inhibiting OB function and therefore contributes to OB/OC uncoupling in MM.

Bone Anabolic Agents for the Treatment of Multiple Myeloma

“…CCL3 suppresses OB mineralization activity by impairing osterix expression and osteocalcin secretion via ERK signaling activation. These effects are at least partly mediated by CCR1, since a trend for increased osteocalcin levels is observed with CCR1 antagonists both in vitro and in vivo [64].…”

“…In addition, OC number per bone area was reduced and trabecular bone area increased. Notably, for the first time this study suggests a positive effect of CCR1 inhibition on OB function, by showing an upregulation of osteocalcin expression [64]. Several CCR1 antagonists have been clinically assessed in the context of inflammatory diseases without significant effects, presumably due to redundancy of signaling in the chemokine family and suboptimal pharmacokinetic properties of the inhibitors used [105].…”

“…Low dose bortezomib (0.7 mg/m2) will Increases bone formation markers, decreases pain. Decreases tumor burden BHQ880 [33] Neutralizing anti-DKK1 antibody Increases bone volume and OBn NA Decreases tumor burden MLN3897 [64] Small molecule CCR1 antagonists Trend for increase in osteocalcin expression NA Decreases OCn and tumor burden Teriparatide [109] Recombinant parathyroid hormone Increases BMD NA Decreases tumor burden AMG775…”

“…Neutralizing antibodies against CCL3 and small molecule CCR1 antagonists consistently reverse bone loss in murine models of MM [63,64,[101][102][103]. Orally available, specific, small molecule CCR1 antagonists include CCX721 (ChemoCentryx), BX471 (Berlex) [104] and MLN3897 (Millennium Pharmaceuticals).…”

Impaired osteogenic differentiation of mesenchymal stem cells derived from multiple myeloma patients is associated with a blockade in the deactivation of the Notch signaling pathway

“…[7][8][9][10] As we have cultured and expanded MM-hMSCs in vitro in the absence of MM cells, the impaired osteogenic differentiation of MM-hMSCs seems not to result from the factors produced by MM cells directly, but might be due to intrinsic abnormalities in cellular signaling pathways or gene expression. Notch signaling has a key role in the development and differentiation during embryogenesis and in postnatal life.…”