Department of Natural Sciences, Lebanese American University, Beirut 1102 2801, Lebanon.
Cells. 2019 Feb 18;8(2):171. doi: 10.3390/cells8020171.
Angiogenesis is a hallmark of cancer cell malignancy. The role of the RHO family GTPase RHOG in angiogenesis in vascular endothelial cells has recently been elucidated. However, the regulation of RHOG during this process, as well as its cross-talk with other RHO GTPases, have yet to be fully examined. In this study, we found that siRNA-mediated depletion of RHOG strongly inhibits tube formation in vascular endothelial cells (ECV cells), an effect reversed by transfecting dominant active constructs of CDC42 or RAC1 in the RHOG-depleted cells. We also found CDC42 to be upstream from RAC1 in these cells. Inhibiting either Phosphatidyl inositol (3) kinase (PI3K) with Wortmannin or the mitogen-activated protein kinase extracellular-regulated kinase (MAPK ERK) with U0126 leads to the inhibition of tube formation. While knocking down either RHO, GTPase did not affect p-AKT levels, and p-ERK decreased in response to the knocking down of RHOG, CDC42 or RAC1. Recovering active RHO GTPases in U0126-treated cells also did not reverse the inhibition of tube formation, placing ERK downstream from PI3K-RHOG-CDC42-RAC1 in vascular endothelial cells. Finally, RHOA and the Rho activated protein kinases ROCK1 and ROCK2 positively regulated tube formation independently of ERK, while RHOC seemed to inhibit the process. Collectively, our data confirmed the essential role of RHOG in angiogenesis, shedding light on a potential new therapeutic target for cancer malignancy and metastasis.
血管生成是癌细胞恶性的标志。最近已经阐明了 RHO 家族 GTPase RHOG 在血管内皮细胞血管生成中的作用。然而，在这个过程中 RHOG 的调节以及与其他 RHO GTPases 的串扰尚未得到充分研究。在这项研究中，我们发现 RHOG 的 siRNA 介导的耗竭强烈抑制血管内皮细胞（ECV 细胞）中的管形成，这一效应可通过在 RHOG 耗竭细胞中转染 CDC42 或 RAC1 的显性激活构建体来逆转。我们还发现，在这些细胞中，CDC42 在 RAC1 的上游。用 Wortmannin 抑制磷脂酰肌醇（3）激酶（PI3K）或用 U0126 抑制丝裂原激活的蛋白激酶细胞外调节激酶（MAPK ERK）会导致管形成的抑制。虽然敲低 RHO，GTPase 不会影响 p-AKT 水平，但敲低 RHOG、CDC42 或 RAC1 会导致 p-ERK 减少。在 U0126 处理的细胞中恢复活性的 RHO GTPases 也不能逆转管形成的抑制作用，从而将 ERK 置于 PI3K-RHOG-CDC42-RAC1 下游的血管内皮细胞中。最后，RHOA 和 Rho 激活蛋白激酶 ROCK1 和 ROCK2 独立于 ERK 正向调节管形成，而 RHOC 似乎抑制了这一过程。总之，我们的数据证实了 RHOG 在血管生成中的重要作用，为癌症恶性肿瘤和转移的潜在新治疗靶点提供了依据。
