The Role of MMP13 in Multiple Myeloma Bone Disease

摘要 多发性骨髓瘤（MM）的特征是破骨细胞（OCL）活性增加，导致骨破坏。 约80%的患者为破坏性病变和单纯溶解性病变。过度的骨吸收由OCL介导， 其由MM细胞分泌的因子及其微环境激活。都支持这一看法 发现MM细胞总是位于与活跃的骨吸收部位密切相关的位置。 基质金属蛋白酶13（MMP 13）属于能够降解和 重塑所有细胞外基质（ECM）成分。我们最近发现MM细胞分泌MMP 13， 比其他基质金属蛋白酶高400倍。初步组织芯片分析显示MMP 13是高表达的。 在MM细胞中表达，而在正常浆细胞中不表达。MM患者血清的ELISA显示100%相关性 MMP 13蛋白的检测与骨疾病之间存在显著性差异，而MMP 13在健康供体中检测不到。在 体外MMP 13增加骨吸收，其增强作用与骨吸收显著相关。 增加的OCL尺寸和核数/OCL，表明MMP 13诱导OCL前体的融合。 此外，从Mmp 13-/-小鼠产生的OCL显示出显著减少的细胞核数量和平均细胞周期。 与WT小鼠相比，OCL细胞大小和骨吸收能力。加入MMP 13逆转了融合 Mmp 13-/- MNCs的缺陷。此外，MMP 13在MM细胞中响应于IL-6而强烈上调， EMSA显示IL-6介导的AP-1激活促进MMP 13的转录。树突状细胞特异性 跨膜蛋白（DC-STAMP）是破骨细胞前体细胞-细胞融合所必需的， 外源性MMP 13。 综上所述，我们假设骨髓瘤细胞来源的MMP 13在MM诱导的细胞凋亡中起关键作用。 骨质破坏我们认为MM微环境上调IL-6触发了IL-6的分泌， MMP 13在MM细胞中的表达。反过来，MMP 13诱导DC-STAMP，导致OCL活性增加，骨密度增加。 再吸收和ECM降解。因此，靶向MMP 13可能代表了一种有效的新方法， 治疗骨髓瘤骨病（MMBD）。为了验证这些假设，我们将1）研究自分泌和 探讨MMP 13诱导MM细胞凋亡的旁分泌机制; 2）探讨MMP 13增强OCL的机制 MMP 13的形成和活性，以及3）在体内证实了MMP 13在骨髓瘤发展中的作用。 诱导溶骨性骨病变。这项工作的成功完成对实现我们的目标至关重要。 总体目标是确定骨髓瘤骨病的新疗法。

Abstract Multiple myeloma (MM) is characterized by increased osteoclast (OCL) activity that results in bone destruction and purely lytic lesions in ~80% patients. The excessive bone resorption is mediated by OCLs, which are activated by factors secreted by MM cells and their microenvironment. This is supported by the finding that MM cells are always located in close association with sites of active bone resorption. Matrix metalloproteinase 13 (MMP13) belongs to a family of endopeptidases capable of degrading and remodeling all extracellular matrix (ECM) components. We recently found that secretion of MMP13 by MM cells is up to 400-fold higher than other MMPs. Primary tissue array analysis showed that MMP13 is highly expressed in MM cells, but not in normal plasma cells. ELISA of MM patient sera revealed a 100% correlation between detection of MMP13 protein and bone disease while MMP13 was undetectable in healthy donors. In vitro MMP13 increased bone resorption, where its enhancing effects were associated with dramatically increased OCL size and nuclear number/OCL, suggesting that MMP13 induces fusion of OCL precursors. Further, OCL generated from Mmp13-/- mice showed a significantly decreased number of nuclei and average OCL cell size and bone resorption capacity compared to WT mice. Addition of MMP13 reversed the fusion defect of Mmp13-/- MNCs. Further, MMP13 was strongly upregulated in MM cells in response to IL-6 and EMSA revealed that IL-6-mediated AP-1 activation promoted MMP13 transcription. Dendritic cell-specific transmembrane protein (DC-STAMP), essential for cell-cell fusion of preosteoclasts, was upregulated by exogenous MMP13 . Taken together, we hypothesize that myeloma cell-derived MMP13 plays a pivotal role in MM-induced bone destruction. We contend that the upregulation of IL-6 by the MM microenvironment triggers the secretion of MMP13 in MM cells. In turn, MMP13 induces DC-STAMP, resulting in increased OCL activity, bone resorption and ECM degradation. As such, targeting MMP13 may represent an effective and new approach to treat myeloma bone disease (MMBD). To test these hypotheses, we will 1) investigate the autocrine and paracrine mechanisms of MMP13 induction in MM cells, 2) investigate the mechanisms of enhancing of OCL formation and activity by MMP13 and 3) confirm in vivo the role of MMP13 in the development of myeloma- induced osteolytic bone lesions. A successful completion of this work will be crucial for the achievement of our overall goal to identify novel therapies for myeloma bone disease.