The basement membrane (BM) is a special type of extracellular matrix and presents the major barrier cancer cells have to overcome multiple times to form metastases. Here we show that BM stiffness is a major determinant of metastases formation in several tissues and identify netrin-4 (Net4) as a key regulator of BM stiffness. Mechanistically, our biophysical and functional analyses in combination with mathematical simulations show that Net4 softens the mechanical properties of native BMs by opening laminin node complexes, decreasing cancer cell potential to transmigrate this barrier despite creating bigger pores. Our results therefore reveal that BM stiffness is dominant over pore size, and that the mechanical properties of ‘normal’ BMs determine metastases formation and patient survival independent of cancer-mediated alterations. Thus, identifying individual Net4 protein levels within native BMs in major metastatic organs may have the potential to define patient survival even before tumour formation. The ratio of Net4 to laminin molecules determines BM stiffness, such that the more Net4, the softer the BM, thereby decreasing cancer cell invasion activity.

基底膜 (BM) 是一种特殊类型的细胞外基质，是癌细胞必须多次克服才能形成转移的主要屏障。在这里，我们表明 BM 刚度是几种组织中转移形成的主要决定因素，并将 netrin-4 (Net4) 确定为 BM 刚度的关键调节因子。从机制上讲，我们的生物物理和功能分析结合数学模拟表明，Net4 通过打开层粘连蛋白节点复合物来软化天然 BMs 的机械性能，降低癌细胞迁移该屏障的潜力，尽管会产生更大的孔隙。因此，我们的研究结果表明，BM 刚度在孔径大小方面占主导地位，并且“正常”BM 的机械特性决定了转移形成和患者生存，而与癌症介导的改变无关。因此，识别主要转移器官中天然 BM 中的单个 Net4 蛋白水平可能有可能在肿瘤形成之前确定患者的存活率。Net4 与层粘连蛋白分子的比例决定了 BM 硬度，因此 Net4 越多，BM 越软，从而降低癌细胞的侵袭活性。