Analyses of ES specific Ras, ERas function in gastric cancer and development for new chemotherapy

背景和目的：ERAS是ras家族中的一个新成员，被发现仅在ES细胞中表达。ERAS在ES细胞向畸胎瘤转化过程中起着至关重要的作用，在ES细胞诱导分化过程中其表达水平逐渐降低。我们研究了ERAS在人胃癌细胞中的表达及其作用。结果：1.ERAS在人胃癌和几乎所有的胃癌细胞系中都有表达。2.ERAS的过表达不能诱导MEK的磷酸化。然而，ERAS的过表达诱导了Akt的磷酸化。3.ERAS转染组对CPT-11的耐药率明显高于亲本系(存活率：对照组为23.0%，ERAS转染组为67.4%，p<0.001)，而对5-氟尿嘧啶、顺铂和紫杉醇无明显耐药。过表达ERAS可显著减少CPT-11诱导的细胞凋亡(p&lt；0.01)。4.雷帕霉素对ERAS转染体有明显的细胞毒作用(存活率：对照组为93.9%，ERAS转染组为68.5%，p&lt；0.01)。5.ERAS在人胃癌组织中的表达约为30%。ERAS的过表达不能诱导MEK的磷酸化，但能诱导Akt的磷酸化。6.基因芯片分析显示，ERAS诱导E-钙粘素表达下调，ABCG2表达上调，ABCG2能够分泌CTPT-11。基因芯片的基因集分析表明，Eas可诱导NF-κB的激活。蛋白质印迹结果也证实了E-钙粘素的抑制作用，并且Eas显著促进了软琼脂中的集落形成，集落数约为对照组的4倍。结论：ERAS在人胃癌和胃细胞系中均有表达，并通过Akt的磷酸化在抗细胞凋亡中发挥重要作用。ERAS可能通过抑制E-钙粘附素和激活NF-κB而与胃癌的增殖和转移有关。

Background and aims: ERas, a novel member of the ras family, was found to be expressed in ES cells only. ERas is constitutively active without any mutations and plays a crucial role when transplanted in the transformation of ES cells to teratomas and the expression level of ERas gradually decreases when ES cells are induced to differentiate. We investigated the expression and the roles of ERas, in human gastric cancer cells.Results: 1. ERas was expressed in human gastric cancer and almost all gastric cancer cell lines. 2. Overexpression of ERas did not induce the phosphorylation of MEK. However, overexpression of ERas induced phosphorylation of Akt. 3. The ERas transfectants were significantly more resistant to CPT-11 than the parent lines (survival rate: control 23.0%, the ERas transfectants 67.4%, p <0.001), but not to 5-Fluorouracil, Cisplatin, and Paclitaxel. Overexpression of ERas significantly reduced CPT-11-induced apoptosis (p <0.01). 4. Administration of Rapamycin significantly induced cytotoxicity to the ERas transfectants (survival rate: control 93.9%, ERas transfectant 68.5%, p <0.01). 5. ERas was expressed in about 30% in human gastric cancer. Overexpression of ERas did not induce the phosphorylation of MEK but induced phosphorylation of Akt. 6. Microarray analysis revealed that ERas induced down-regulation of E-cadherin and up-regulation of ABCG2 which is capable of extruding CTPT-11 from cells. Gene set analyses of microarray indicated that ERas induced activation of NF-κB. E-cadherin inhibition was also confirmed at protein levels by westernblot and ERas significantly promoted colony-formation in soft agar, with about a 4-fold number of colonies as compared with control.Conclusion: ERas was expressed in human gastric cancer and gastric cell lines, and plays crucial roles for anti-apoptosis via phosphorylation of Akt. ERas may be associated with proliferation and metastasis of gastric cancer through inhibition of E-cadherin and activation of NFκB.