Uveal melanomas (UM) are malignant cancers arising from the pigmented layers of the eye. UM cells spread through the bloodstream, and circulating UM cells are detectable in patients before metastases appear. Extravasation of UM cells is necessary for formation of metastases, and transendothelial migration (TEM) is a key step in extravasation. UM cells execute TEM via a stepwise process involving the actin-based processes of ameboid blebbing and mesenchymal lamellipodial protrusion. UM cancers are driven by oncogenic mutations that activate Gαq/11, and this activates TRIO, a guanine nucleotide exchange factor (GEF) for RhoA and Rac1. We found that pharmacologic inhibition of Gαq/11 in UM cells reduced TEM. Inhibition of the RhoA pathway blocked amoeboid motility but led to enhanced TEM; in contrast, inhibition of the Rac1 pathway decreased mesenchymal motility and reduced TEM. Inhibition of Arp2/3 complex allowed cells to transmigrate without intercalation, a direct mechanism similar to the one often displayed by immune cells. BAP1-deficient (+/-) UM subclones displayed motility behaviors and increased levels of TEM, similar to the effects of RhoA inhibitors. We conclude that RhoA and Rac1 signaling pathways, downstream of oncogenic Gαq/11, combine with pathways regulated by BAP1 to control the motility and transmigration of UM cells.

葡萄膜黑色素瘤 (UM) 是源自眼睛色素层的恶性癌症。UM 细胞通过血流扩散，并且在转移出现之前，可以在患者体内检测到循环的 UM 细胞。UM 细胞的外渗是形成转移所必需的，而跨内皮迁移 (TEM) 是外渗的关键步骤。UM 细胞通过逐步过程执行 TEM，该过程涉及基于肌动蛋白的阿米巴起泡和间充质 lamellipodial 突起的过程。UM 癌症是由激活 Gαq/11 的致癌突变驱动的，这会激活 TRIO，一种 RhoA 和 Rac1 的鸟嘌呤核苷酸交换因子 (GEF)。我们发现 UM 细胞中 Gαq/11 的药理学抑制降低了 TEM。RhoA 通路的抑制阻断了变形虫的运动，但导致 TEM 增强；相比之下，Rac1 通路的抑制降低了间充质运动并降低了 TEM。Arp2/3 复合物的抑制允许细胞在没有嵌入的情况下进行迁移，这是一种类似于免疫细胞经常表现出的直接机制。BAP1 缺陷 (+/-) UM 亚克隆显示运动行为和增加的 TEM 水平，类似于 RhoA 抑制剂的影响。我们得出结论，致癌 Gαq/11 下游的 RhoA 和 Rac1 信号通路与 BAP1 调节的通路相结合，以控制 UM 细胞的运动和迁移。类似于 RhoA 抑制剂的作用。我们得出结论，致癌 Gαq/11 下游的 RhoA 和 Rac1 信号通路与 BAP1 调节的通路相结合，以控制 UM 细胞的运动和迁移。类似于 RhoA 抑制剂的作用。我们得出结论，致癌 Gαq/11 下游的 RhoA 和 Rac1 信号通路与 BAP1 调节的通路相结合，以控制 UM 细胞的运动和迁移。