The Actin Targeting Compound Chondramide Inhibits Breast Cancer Metastasis via Reduction of Cellular Contractility

BackgroundA major player in the process of metastasis is the actin cytoskeleton as it forms key structures in both invasion mechanisms, mesenchymal and amoeboid migration. We tested the actin binding compound Chondramide as potential anti-metastatic agent.MethodsIn vivo, the effect of Chondramide on metastasis was tested employing a 4T1-Luc BALB/c mouse model. In vitro, Chondramide was tested using the highly invasive cancer cell line MDA-MB-231 in Boyden-chamber assays, fluorescent stainings, Western blot and Pull down assays. Finally, the contractility of MDA-MB-231 cells was monitored in 3D environment and analyzed via PIV analysis.ResultsIn vivo, Chondramide treatment inhibits metastasis to the lung and the migration and invasion of MDA-MB-231 cells is reduced by Chondramide in vitro. On the signaling level, RhoA activity is decreased by Chondramide accompanied by reduced MLC-2 and the stretch induced guanine nucleotide exchange factor Vav2 activation. At same conditions, EGF-receptor autophosphorylation, Akt and Erk as well as Rac1 are not affected. Finally, Chondramide treatment disrupted the actin cytoskeleton and decreased the ability of cells for contraction.ConclusionsChondramide inhibits cellular contractility and thus represents a potential inhibitor of tumor cell invasion.

**背景**：肿瘤转移过程中的关键参与者为肌动蛋白细胞骨架（actin cytoskeleton），其在间充质迁移与阿米巴样迁移这两种侵袭机制中均形成了核心结构。我们将肌动蛋白结合化合物软骨酰胺（Chondramide）作为潜在抗转移药物开展了相关实验。

**方法**：体内实验中，我们采用4T1-Luc BALB/c小鼠模型测试了软骨酰胺对肿瘤转移的影响；体外实验则选用高侵袭性癌细胞系MDA-MB-231，通过博登小室（Boyden-chamber）实验、荧光染色、蛋白质印迹（Western blot）以及下拉（Pull down）实验对软骨酰胺的作用进行了评估。最后，我们在三维培养环境中监测了MDA-MB-231细胞的收缩能力，并通过粒子图像测速（Particle Image Velocimetry, PIV）分析完成了量化分析。

**结果**：体内实验结果显示，软骨酰胺处理可抑制肿瘤向肺部转移；体外实验证实，软骨酰胺可降低MDA-MB-231细胞的迁移与侵袭能力。在信号通路层面，软骨酰胺可下调RhoA活性，同时伴随肌球蛋白轻链2（Myosin Light Chain 2, MLC-2）水平下调以及牵张诱导的鸟苷酸交换因子Vav2的激活受到抑制。在相同实验条件下，表皮生长因子受体（EGF-receptor）的自磷酸化水平、Akt、Erk以及Rac1均未受到显著影响。此外，软骨酰胺处理会破坏肌动蛋白细胞骨架，并削弱细胞的收缩能力。

**结论**：软骨酰胺可抑制细胞收缩能力，因此有望成为肿瘤细胞侵袭的潜在抑制剂。