Moores Cancer Center, Department of Obstetrics, Gynecology and Reproductive Science, UC San Diego Health, La Jolla, CA, 92093, USA.
Biomedical Sciences Graduate Program, UC San Diego Health, La Jolla, CA, 92093, USA.
Oncogene. 2019 Sep;38(36):6323-6337. doi: 10.1038/s41388-019-0881-8. Epub 2019 Jul 15.
Ovarian cancer is the fifth-leading cause of cancer death among women. The dissemination of ovarian tumors and growth as spheroids accompanies late-stage disease. In cell culture, ovarian tumor cell spheroids can exhibit elevated resistance to environmental stressors, such as reactive oxygen species. Homeostatic balance of the antioxidant response is a protective mechanism that prevents anoikis, a form of programmed cell death. Signaling pathways activated by integrin receptors suppress anoikis. Rgnef (ARHGEF28/p190RhoGEF) is a guanine nucleotide exchange factor that is activated downstream of integrins. We find that Rgnef protein levels are elevated in late-stage serous ovarian cancer, high Rgnef mRNA levels are associated with decreased progression-free and overall survival, and genomic ARHGEF28 loss is associated with increased patient survival. Using transgenic and transplantable Rgnef knockout mouse models, we find that Rgnef is essential for supporting three-dimensional ovarian spheroid formation in vitro and tumor growth in mice. Using RNA-sequencing and bioinformatic analyses, we identify a conserved Rgnef-supported anti-oxidant gene signature including Gpx4, Nqo1, and Gsta4; common targets of the NF-kB transcription factor. Antioxidant treatment enhanced growth of Rgnef-knockout spheroids and Rgnef re-expression facilitated NF-κB-dependent tumorsphere survival. These studies reveal a new role for Rgnef in ovarian cancer to facilitate NF-κB-mediated gene expression protecting cells from oxidative stress.
卵巢癌是女性癌症死亡的第五大主要原因。卵巢肿瘤的扩散和球体生长伴随着晚期疾病。在细胞培养中，卵巢肿瘤细胞球体可以表现出对环境应激物（如活性氧）的更高抗性。抗氧化反应的动态平衡是一种保护机制，可防止细胞凋亡，即程序性细胞死亡的一种形式。整合素受体激活的信号通路抑制细胞凋亡。Rgnef（ARHGEF28/p190RhoGEF）是一种鸟嘌呤核苷酸交换因子，可被整合素激活。我们发现 Rgnef 蛋白水平在晚期浆液性卵巢癌中升高，高 Rgnef mRNA 水平与无进展生存期和总生存期缩短相关，而基因组 ARHGEF28 缺失与患者生存率提高相关。使用转基因和可移植的 Rgnef 敲除小鼠模型，我们发现 Rgnef 对于支持体外三维卵巢球体形成和小鼠肿瘤生长是必需的。通过 RNA 测序和生物信息学分析，我们确定了一个保守的 Rgnef 支持的抗氧化基因特征，包括 Gpx4、Nqo1 和 Gsta4；NF-κB 转录因子的常见靶标。抗氧化治疗增强了 Rgnef 敲除球体的生长，而 Rgnef 的重新表达促进了 NF-κB 依赖性肿瘤球体的存活。这些研究揭示了 Rgnef 在卵巢癌中的新作用，以促进 NF-κB 介导的基因表达，从而保护细胞免受氧化应激。
