Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Oncogene. 2012 Jan 5;31(1):68-79. doi: 10.1038/onc.2011.213. Epub 2011 Jun 6.
Ovarian cancers migrate and metastasize over the surface of the peritoneal cavity. Consequently, dysregulation of mechanisms that limit cell migration may be particularly important in the pathogenesis of the disease. ARHI is an imprinted tumor-suppressor gene that is downregulated in >60% of ovarian cancers, and its loss is associated with decreased progression-free survival. ARHI encodes a 26-kDa GTPase with homology to Ras. In contrast to Ras, ARHI inhibits cell growth, but whether it also regulates cell motility has not been studied previously. Here we report that re-expression of ARHI decreases the motility of IL-6- and epidermal growth factor (EGF)-stimulated SKOv3 and Hey ovarian cancer cells, inhibiting both chemotaxis and haptotaxis. ARHI binds to and sequesters Stat3 in the cytoplasm, preventing its translocation to the nucleus and localization in focal adhesion complexes. Stat3 siRNA or the JAK2 inhibitor AG490 produced similar inhibition of motility. However, the combination of ARHI expression with Stat3 knockdown or inhibition produced greatest inhibition in ovarian cancer cell migration, consistent with Stat3-dependent and Stat3-independent mechanisms. Consistent with two distinct signaling pathways, knockdown of Stat3 selectively inhibited IL-6-stimulated migration, whereas knockdown of focal adhesion kinase (FAK) preferentially inhibited EGF-stimulated migration. In EGF-stimulated ovarian cancer cells, re-expression of ARHI inhibited FAK(Y397) and Src(Y416) phosphorylation, disrupted focal adhesions, and blocked FAK-mediated RhoA signaling, resulting in decreased levels of GTP-RhoA. Re-expression of ARHI also disrupted the formation of actin stress fibers in a FAK- and RhoA-dependent manner. Thus, ARHI has a critical and previously uncharacterized role in the regulation of ovarian cancer cell migration, exerting inhibitory effects on two distinct signaling pathways.
卵巢癌在腹腔表面迁移和转移。因此，限制细胞迁移机制的失调可能在疾病的发病机制中尤为重要。ARHI 是一种印迹肿瘤抑制基因，在超过 60%的卵巢癌中下调，其缺失与无进展生存期缩短有关。ARHI 编码一种与 Ras 同源的 26kDa GTPase。与 Ras 相反，ARHI 抑制细胞生长，但它是否也调节细胞迁移尚未被研究。在这里，我们报告说，ARHI 的重新表达降低了 IL-6 和表皮生长因子（EGF）刺激的 SKOv3 和 Hey 卵巢癌细胞的迁移性，抑制了趋化性和贴壁依赖性迁移。ARHI 与细胞质中的 Stat3 结合并隔离 Stat3，阻止其易位到细胞核并定位在焦点粘附复合物中。Stat3 siRNA 或 JAK2 抑制剂 AG490 产生类似的迁移抑制。然而，ARHI 表达与 Stat3 敲低或抑制的组合在卵巢癌细胞迁移中产生最大的抑制作用，与 Stat3 依赖性和 Stat3 非依赖性机制一致。与两种不同的信号通路一致，Stat3 的敲低选择性抑制 IL-6 刺激的迁移，而焦点粘附激酶（FAK）的敲低则优先抑制 EGF 刺激的迁移。在 EGF 刺激的卵巢癌细胞中，ARHI 的重新表达抑制了 FAK（Y397）和 Src（Y416）的磷酸化，破坏了焦点粘连，并阻断了 FAK 介导的 RhoA 信号转导，导致 GTP-RhoA 水平降低。ARHI 的重新表达也以 FAK 和 RhoA 依赖性方式破坏了肌动蛋白应力纤维的形成。因此，ARHI 在调节卵巢癌细胞迁移方面具有关键且以前未被描述的作用，对两种不同的信号通路发挥抑制作用。
