Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Sci Signal. 2023 Dec 19;16(816):eadg5289. doi: 10.1126/scisignal.adg5289.
Cancer-associated mutations in the guanosine triphosphatase (GTPase) RHOA are found at different locations from the mutational hotspots in the structurally and biochemically related RAS. Tyr-to-Cys (Y42C) and Leu-to-Val (L57V) substitutions are the two most prevalent RHOA mutations in diffuse gastric cancer (DGC). RHOA exhibits a gain-of-function phenotype and is an oncogenic driver in DGC. Here, we determined how RHOA promotes DGC growth. In mouse gastric organoids with deletion of , which encodes the cell adhesion protein E-cadherin, the expression of RHOA, but not of wild-type RHOA, induced an abnormal morphology similar to that of patient-derived DGC organoids. RHOA also exhibited a gain-of-function phenotype and promoted F-actin stress fiber formation and cell migration. RHOA retained interaction with effectors but exhibited impaired RHOA-intrinsic and GAP-catalyzed GTP hydrolysis, which favored formation of the active GTP-bound state. Introduction of missense mutations at KRAS residues analogous to Tyr and Leu in RHOA did not activate KRAS oncogenic potential, indicating distinct functional effects in otherwise highly related GTPases. Both RHOA mutants stimulated the transcriptional co-activator YAP1 through actin dynamics to promote DGC progression; however, RHOA additionally did so by activating the kinases IGF1R and PAK1, distinct from the FAK-mediated mechanism induced by RHOA. Our results reveal that RHOA and RHOA drive the development of DGC through distinct biochemical and signaling mechanisms.
在结构和生化上与 RAS 相关的 RHOA 鸟嘌呤三磷酸酶 (GTPase) 中发现的癌症相关突变位于不同于突变热点的位置。酪氨酸到半胱氨酸 (Y42C) 和亮氨酸到缬氨酸 (L57V) 取代是弥漫性胃癌 (DGC) 中最常见的两种 RHOA 突变。RHOA 表现出功能获得表型，是 DGC 的致癌驱动因素。在这里，我们确定了 RHOA 如何促进 DGC 生长。在编码细胞黏附蛋白 E-钙黏蛋白的缺失的小鼠胃类器官中，RHOA 的表达，但不是野生型 RHOA 的表达，诱导出类似于患者来源的 DGC 类器官的异常形态。RHOA 还表现出功能获得表型，并促进 F-肌动蛋白应力纤维形成和细胞迁移。RHOA 保留了与效应物的相互作用，但表现出 RHOA 内在和 GAP 催化的 GTP 水解受损，这有利于活性 GTP 结合状态的形成。在 RHOA 中类似于 Tyr 和 Leu 的 KRAS 残基引入错义突变不会激活 KRAS 致癌潜力，表明在 otherwise 高度相关的 GTPases 中具有不同的功能效应。两种 RHOA 突变体通过肌动蛋白动力学刺激转录共激活因子 YAP1 促进 DGC 进展；然而，RHOA 还通过激活激酶 IGF1R 和 PAK1 来实现这一点，这与 RHOA 诱导的 FAK 介导的机制不同。我们的结果表明，RHOA 和 RHOA 通过不同的生化和信号机制驱动 DGC 的发展。
