Lu Yi, Cai Zhong, Xiao Guozhi, Keller Evan T, Mizokami Atsushi, Yao Zhi, Roodman G David, Zhang Jian
Department of Medicine, University of Pittsburgh, University Drive, Pittsburgh, PA 15240, USA.
Cancer Res. 2007 Apr 15;67(8):3646-53. doi: 10.1158/0008-5472.CAN-06-1210.
Prostate cancer preferentially metastasizes to bone, resulting in high mortality. Strategies to inhibit prostate cancer metastasis include targeting both tumor-induced osteoblastic lesions and underlying osteoclastic activities. We and others have previously shown that blocking receptor activator of nuclear factor-kappaB ligand (RANKL) partially blocks tumor establishment and progression in bone in murine models. However, levels of RANKL in the cell lines used in these studies were very low, suggesting that soluble factors other than RANKL may mediate the cancer-induced osteoclast activity. To identify these factors, a human cytokine antibody array was used to measure cytokine expression in conditioned medium collected from primary prostate epithelial cells (PrEC), prostate cancer LNCaP and its derivative C4-2B, and PC3 cells. All prostate cancer cells produced high amounts of monocyte chemotactic protein-1 (MCP-1) compared with PrEC cells. Furthermore, levels of interleukin (IL)-6, IL-8, GROalpha, ENA-78, and CXCL-16 were higher in PC3 than LNCaP. These results were confirmed by ELISA. Finally, human bone marrow mononuclear cells (HBMC) were cultured with PC3 conditioned medium. Although both recombinant human MCP-1 and IL-8 directly stimulated HBMC differentiation into osteoclast-like cells, IL-8, but not MCP-1, induced bone resorption on dentin slices with 21 days of culture in the absence of RANKL. However, the conditioned medium-induced bone resorption was inhibited by MCP-1 neutralizing antibody and was further synergistically inhibited with IL-8 antibody, indicating that MCP-1, in addition to IL-8, mediates tumor-induced osteoclastogenesis and bone resorption. MCP-1 may promote preosteoclast cell fusion, forming multinucleated tartrate-resistant acid phosphatase-positive osteoclast-like cells. This study may provide novel therapeutic targets for treatment of prostate cancer skeletal metastasis.
前列腺癌易转移至骨骼，导致高死亡率。抑制前列腺癌转移的策略包括针对肿瘤诱导的成骨细胞病变和潜在的破骨细胞活性。我们和其他人之前已经表明，在小鼠模型中阻断核因子κB受体活化剂配体（RANKL）可部分阻断肿瘤在骨中的建立和进展。然而，这些研究中使用的细胞系中RANKL水平非常低，这表明除RANKL之外的可溶性因子可能介导癌症诱导的破骨细胞活性。为了鉴定这些因子，使用人细胞因子抗体阵列来测量从原代前列腺上皮细胞（PrEC）、前列腺癌LNCaP及其衍生物C4-2B以及PC3细胞收集的条件培养基中的细胞因子表达。与PrEC细胞相比，所有前列腺癌细胞均产生大量单核细胞趋化蛋白-1（MCP-1）。此外，PC3中白细胞介素（IL）-6、IL-8、GROα、ENA-78和CXCL-16的水平高于LNCaP。这些结果通过酶联免疫吸附测定（ELISA）得到证实。最后，用人骨髓单个核细胞（HBMC）与PC3条件培养基一起培养。尽管重组人MCP-1和IL-8均可直接刺激HBMC分化为破骨细胞样细胞，但在无RANKL的情况下培养21天时，IL-8而非MCP-1可诱导牙本质切片上的骨吸收。然而，条件培养基诱导的骨吸收被MCP-1中和抗体抑制，并被IL-8抗体进一步协同抑制，表明除IL-8外，MCP-1也介导肿瘤诱导的破骨细胞生成和骨吸收。MCP-1可能促进前破骨细胞融合，形成抗酒石酸酸性磷酸酶阳性的多核破骨细胞样细胞。本研究可能为前列腺癌骨转移的治疗提供新的治疗靶点。
