Institute for Research in Dental Sciences, Faculty of Dentistry, Universidad de Chile, Santiago, Chile.
Advanced Center for Chronic Diseases (ACCDiS), Universidad de Chile, Santiago, Chile.
FASEB J. 2024 Jun 15;38(11):e23716. doi: 10.1096/fj.202400265R.
Tumor hypoxia has been associated with cancer progression, angiogenesis, and metastasis via modifications in the release and cargo composition of extracellular vesicles secreted by tumor cells. Indeed, hypoxic extracellular vesicles are known to trigger a variety of angiogenic responses via different mechanisms. We recently showed that hypoxia promotes endosomal signaling in tumor cells via HIF-1α-dependent induction of the guanine exchange factor ALS2, which activates Rab5, leading to downstream events involved in cell migration and invasion. Since Rab5-dependent signaling is required for endothelial cell migration and angiogenesis, we explored the possibility that hypoxia promotes the release of small extracellular vesicles containing ALS2, which in turn activate Rab5 in recipient endothelial cells leading to pro-angiogenic properties. In doing so, we found that hypoxia promoted ALS2 expression and incorporation as cargo within small extracellular vesicles, leading to subsequent transfer to recipient endothelial cells and promoting cell migration, tube formation, and downstream Rab5 activation. Consequently, ALS2-containing small extracellular vesicles increased early endosome size and number in recipient endothelial cells, which was followed by subsequent sequestration of components of the β-catenin destruction complex within endosomal compartments, leading to stabilization and nuclear localization of β-catenin. These events converged in the expression of β-catenin target genes involved in angiogenesis. Knockdown of ALS2 in donor tumor cells precluded its incorporation into small extracellular vesicles, preventing Rab5-downstream events and endothelial cell responses, which depended on Rab5 activity and guanine exchange factor activity of ALS2. These findings indicate that vesicular ALS2, secreted in hypoxia, promotes endothelial cell events leading to angiogenesis. Finally, these events might explain how tumor angiogenesis proceeds in hypoxic conditions.
肿瘤缺氧通过改变肿瘤细胞分泌的细胞外囊泡的释放和货物组成与癌症进展、血管生成和转移有关。事实上，缺氧细胞外囊泡通过不同的机制已知会引发各种血管生成反应。我们最近表明，缺氧通过 HIF-1α依赖性诱导鸟嘌呤交换因子 ALS2 促进肿瘤细胞内体信号转导，激活 Rab5，导致参与细胞迁移和侵袭的下游事件。由于 Rab5 依赖性信号转导是内皮细胞迁移和血管生成所必需的，我们探讨了缺氧促进包含 ALS2 的小细胞外囊泡释放的可能性，ALS2 反过来激活受体细胞中的 Rab5，从而导致促血管生成特性。在这样做的过程中，我们发现缺氧促进 ALS2 的表达和作为小细胞外囊泡的货物掺入，从而随后转移到受体内皮细胞并促进细胞迁移、管状形成和下游 Rab5 激活。因此，包含 ALS2 的小细胞外囊泡增加了受体内皮细胞中早期内体的大小和数量，随后β-连环蛋白破坏复合物的成分在内体隔室中被隔离，导致β-连环蛋白的稳定和核定位。这些事件集中在涉及血管生成的β-连环蛋白靶基因的表达上。在供体细胞中敲低 ALS2 可防止其掺入小细胞外囊泡中，从而阻止 Rab5 下游事件和内皮细胞反应，这些反应取决于 Rab5 活性和 ALS2 的鸟嘌呤交换因子活性。这些发现表明，缺氧时分泌的囊泡 ALS2 促进内皮细胞事件导致血管生成。最后，这些事件可能解释了肿瘤血管生成如何在缺氧条件下进行。
