Graduate Institute of Medicine, Schoolof Medicine, College of Medicine, Kaohsiung Medical University, 807 Kaohsiung, Taiwan.
Carcinogenesis. 2010 Apr;31(4):587-96. doi: 10.1093/carcin/bgq030. Epub 2010 Jan 27.
Bone is a frequent target of lung cancer metastasis, which is associated with significant morbidity and a dismal prognosis. This study analyzed the soluble factors secreted by lung cancer cells, which are responsible for increasing osteoclast differentiation. Addition of recombinant human interleukin-8 (rhIL-8), present in large amounts in A549-conditioned medium (CM) and NCI-H460-CM, mimicked the inductive effect of A549-CM and NCI-H460-CM on osteoclastogenesis. In contrast, depletion of interleukin-8 (IL-8) from A549-CM and NCI-H460-CM decreased the osteoclastogenesis-inductive properties of A549-CM and NCI-H460-CM. Induction of osteoclast differentiation by lung cancer-derived-CM and rhIL-8 was associated with increased phospholipase D (PLD) activation, and the activations of protein kinase C (PKC) alpha/betaII, extracellular signal-regulated kinase (ERK) 1/2 and AKT/the mammalian target of rapamycin (mTOR). Blocking PLD by a specific inhibitor significantly decreased osteoclast formation by inhibiting PKCs activation and subsequently attenuating the phosphorylation of ERK1/2. PLD inhibitor also completely decreased AKT and mTOR phosphorylation, whereas phosphatidylinositol-3-kinase (PI3K) inhibitor only partially decreased mTOR phosphorylation, suggesting that mTOR activation by PLD is through both PI3K/AKT-dependent and PI3K/AKT-independent manner. In addition, blocking AKT and ERK1/2 by a specific inhibitor also suppressed lung cancer-derived-CM and rhIL-8-induced osteoclast differentiation. Moreover, treatment of peripheral blood mononuclear cells with sera from invasive lung cancer patients increased the formation of osteoclasts. Our study suggests that IL-8 or IL-8-mediated PLD/PKC/ERK1/2 or PLD/AKT signaling is an attractive therapeutic target for osteolytic bone metastases in lung cancer patients.
骨骼是肺癌转移的常见靶标，这与显著的发病率和不良预后相关。本研究分析了肺癌细胞分泌的可溶性因子，这些因子负责增加破骨细胞分化。添加大量存在于 A549 条件培养基（CM）和 NCI-H460-CM 中的重组人白细胞介素-8（rhIL-8）模拟了 A549-CM 和 NCI-H460-CM 对破骨细胞生成的诱导作用。相比之下，从 A549-CM 和 NCI-H460-CM 中耗尽白细胞介素-8（IL-8）降低了 A549-CM 和 NCI-H460-CM 的破骨细胞生成诱导特性。肺癌衍生-CM 和 rhIL-8 诱导破骨细胞分化与磷脂酶 D（PLD）激活增加有关，蛋白激酶 C（PKC）alpha/betaII、细胞外信号调节激酶（ERK）1/2 和 AKT/哺乳动物雷帕霉素靶蛋白（mTOR）的激活。通过特异性抑制剂阻断 PLD 可显著减少破骨细胞形成，抑制 PKC 激活并随后减弱 ERK1/2 的磷酸化。PLD 抑制剂还完全降低了 AKT 和 mTOR 的磷酸化，而磷脂酰肌醇-3-激酶（PI3K）抑制剂仅部分降低了 mTOR 的磷酸化，表明 PLD 通过 PI3K/AKT 依赖性和 PI3K/AKT 非依赖性途径激活 mTOR。此外，通过特异性抑制剂阻断 AKT 和 ERK1/2 也抑制了肺癌衍生-CM 和 rhIL-8 诱导的破骨细胞分化。此外，用侵袭性肺癌患者的血清处理外周血单核细胞增加了破骨细胞的形成。我们的研究表明，IL-8 或 IL-8 介导的 PLD/PKC/ERK1/2 或 PLD/AKT 信号是肺癌患者溶骨性骨转移的一个有吸引力的治疗靶点。
