The MT1-MMP/RANKL/RANK Axis in Prostate Cancer Bone Metastasis

骨转移是前列腺癌(PC)患者发病率和死亡率的主要原因。MT1-MMP1(膜型1-MMP4，又称MMP14)在人PC骨转移瘤细胞中高表达。MT1-MMP已被证明可以促进转移沉积的扩张和骨反应的溶骨侧。MT1-MMP还负责RANKL(核因子-kappa B受体激活剂配体)的释放(脱落)，RANKL是一种破骨因子，对启动破骨反应至关重要。然而，MT1-MMP释放RANKL的生化机制以及肿瘤细胞中RANKL信号促进转移沉积进展的程度尚未确定。此外，肿瘤细胞来源的RANKL与骨细胞来源的RANKL的相对作用尚不清楚。在此，我们假设肿瘤来源的MT1-MMP裂解肿瘤细胞上的膜结合RANKL(MRANKL)。这种脱落事件产生了一种可溶性形式的RANKL(SRANKL)，它通过激活癌细胞和骨细胞中特定的RANKL相关信号通路而促进转移沉积的进展。为了进一步了解这一过程，我们建议(1)研究mRANKL的MT1-MMP脱落的结构基础，并鉴定PC细胞表面的MT1-MMP/mRANKL复合体；(2)研究前列腺癌细胞中MT1-MMP-RANKL-RANK信号轴；(3)确定肿瘤来源的RANKL和RANK在MT1-MMP驱动的肿瘤骨内生长和骨重建中的作用。这项建议将使用各种生化和细胞方法，以及骨转移的动物模型。

Bone metastasis is the leading cause of morbidity and mortality in prostate cancer (pc) patients. MT1-MMP (membrane type 1-MMP, also known as MMP-14) is highly expressed in tumor cells in human pc bone metastases. MT1-MMP has been shown to promote expansion of the metastatic deposit and the osteolytic side of the bone response. MT1-MMP is also responsible for the release (shedding) of RANKL (receptor activator of nuclear factor-kappa B ligand), an osteoclastogenic factor which is crucial for the initiation of the osteoclastic response. However, the biochemical mechanisms by which MT1-MMP releases RANKL and the extent to which RANK signaling in tumor cells promotes progression of the metastatic deposit have not been characterized. Also, the relative effects of RANKL derived from tumor cells vs. bone cells is unknown. Herein, we hypothesize that tumor-derived MT1-MMP cleaves membrane-bound RANKL (mRANKL) on tumor cells. This shedding event yields a soluble form of RANKL (sRANKL) that contributes to the progression of the metastatic deposit by activating specific RANK-associated cell signaling pathways in cancer cells and bone cells. To further understand this process, we propose to (1) investigate the structural basis of MT1-MMP shedding of mRANKL and identify MT1-MMP/mRANKL complexes at the surface of pc cells; (2) investigate the MT1-MMP – RANKL – RANK signaling axis in prostate cancer cells; and (3) define the contributions of tumor-derived RANKL and RANK to intraosseous tumor growth and bone remodeling in MT1-MMP-driven tumors. This proposal will use a variety of biochemical and cellular approaches as well as animal models of bone metastasis.