表皮生长因子受体与他莫西芬耐药机制

雌激素受体及其信号通路在乳腺癌的发生发展中发挥着关键作用.到目前为止,抑制或阻断雌激素信号通路的内分泌治疗尤其是他莫西芬,仍是对雌激素受体阳性乳腺癌患者最有效的治疗手段之一.然而,他莫西芬的耐药问题直接影响了乳腺癌患者的治疗及预后.最近多项研究表明雌激素受体与表皮生长因子受体家族尤其是HER2介导的信号传导通路在多个点上相互交叉,彼此影响,与他莫西芬的耐药密切相关     

细胞自噬与EGFR抑制剂在肿瘤治疗中的研究进展

表皮生长因子受体(EGFR)抑制剂是近些年来肿瘤治疗的新策略。然而,先天性或者获得性耐药问题成为其疗效的一大障碍。自噬,是一种细胞自我消化的过程,并与耐药具有相关性。EGFR的激活能够通过多种信号通路调节自噬过程。EGFR抑制剂能够诱导自噬,然而EGFR诱导自噬的这种特殊作用是双向的。一方面,自噬能够增强EGFR抑制剂的细胞毒性作用,从而成为一种细胞的保护措施;另一方面,EGFR抑制剂治疗后产生的高自噬水平同样能够导致细胞自吞噬性死亡,从而逃脱凋亡,当EGFR抑制剂与一种自噬诱导剂联合应用时可能会产生更显著的治疗作用。因此,调节自噬水平将成为提高肿瘤患者EGFR抑制剂治疗效果的可行之举。     

EGFR-TKI耐药后的治疗策略研究进展

EGFR-TKI用药一段时间后出现的耐药现象是目前临床治疗的难题。本综述列举了EGFR-TKI耐药机制并介绍了多HER通路抑制、EGFR与VEGFR双通路抑制、作用于T790M突变靶点、抑制C-MET、促进PTEN(抑制PI3K)的表达及下游信号途径以及多种新型药物的抗EGFR-TKI耐药作用。     

乳腺癌MDA-231细胞中IL-8与表皮生长因子受体信号通路的关系

目的 探讨IL-8对乳腺癌细胞增殖和侵袭的影响以及IL-8信号通路与表皮生长因子受体(EGFR)信号通路之间的关系.方法 采用ELISA方法检测乳腺癌MDA-231细胞IL-8的分泌及rhEGF、anti-EGFR对IL-8分泌的影响;免疫细胞化学方法检测其膜受体CXCR1和CXCR2的表达;MTT和matrigel invasion(基质凝胶侵袭)方法分析rhIL-8及anti-IL-8对癌细胞增殖和侵袭的影响;Western blot分析rhlL-8及anti-IL-8对EGFR活化的影响.结果 乳腺癌细胞可分泌大量IL-8,其细胞膜表面表达CXCR1和CXCR2两种受体.rhlL-8及其中和抗体对乳腺癌细胞的增殖无明显影响,但可影响其侵袭能力:rhIL-8可提高癌细胞的侵袭活性(P＜0.05),其中和抗体则对癌细胞的侵袭有抑制作用(P＜0.05).rhEGF及anti-EGFR均明显抑制了MDA-231细胞IL-8的分泌(P＜0.05,P＜0.01);未发现rhIL-8对EGFR的酪氨酸磷酸化有任何影响,相反anti-IL-8却诱导了EGFR活化.结论 IL-8不是乳腺癌自分泌的促细胞生长因子,IL-8主要通过促进癌细胞的侵袭而影响肿瘤的发展.乳腺癌中G蛋白耦联受体(GPCR)介导的IL-8信号通路与EGFR信号通路之间并无cross-talk,而是竞争抑制的关系.     

PI3K/Akt信号通路在乳腺癌内分泌治疗耐药中的作用及对策

乳腺癌是女性最常见的肿瘤,大约75％的乳腺癌表达雌激素受体和/或孕激素受体.激素受体阳性的转移性乳腺癌患者通常采用内分泌治疗,然而由于内分泌治疗耐药的产生,其应用受到了限制.近年来发现,PI3K/Akt(丝氨酸/苏氨酸激酶)信号通路在乳腺癌的发展中发挥着重要作用.本文对PI3K/Akt信号通路在乳腺癌内分泌治疗耐药中的作用进行了综述,以期为雌激素受体阳性乳腺癌治疗提供新对策.     

NSCLC患者多途径标本检测EGFR基因突变研究进展

表皮生长因子受体(EGFR)属受体酪氨酸激酶家族,调控细胞的增殖、分化、血管生成及凋亡,其信号通路与恶性肿瘤的增殖、侵袭及转移关系紧密。非小细胞肺癌(NSCLC)中发现EGFR酪氨酸激酶区常发生各种突变,这些突变和酪氨酸激酶抑制剂(TKIs)的疗效密切相关。因此,EGFR基因突变的检测是靶向药物EGFR-TKIs治疗有效的一个重要因素及预测指标。本文就NSCLC患者EGFR基因突变不同标本来源,如原发灶肿瘤组织、转移淋巴结组织、外周血、胸腔积液标本检测,做一介绍。     

肿瘤靶向治疗中的适应性耐药

人们普遍认为有必要对非小细胞肺癌进行分子层面的分析.例如,基于EGFR突变状态的治疗已经得到了很好的研究结果.尽管口服EGFR酪氨酸激酶抑制剂(TKIs)在初始治疗中能够取得较好的疗效,但患者的无进展生存时间仍然是有限的.目前的研究主要集中于获得性耐药的作用机制,例如AXL的过表达,或MED12介质的缺失等.而在本综述中,我们主要讨论靶向治疗的适应性而非获得性耐药.在靶向治疗起始之初,肿瘤就可能立即通过重构其信号通路产生适应性耐药.通过丧失ERK负反馈,影响受体酪氨酸激酶(RTK)表达,肿瘤细胞被暴露于多个配体的刺激,随之而来的多个RTKs的激活,导致了典型信号转导通路的重构.在经过MEK抑制剂处理的乳腺癌细胞系以及BRAF抑制剂处理的BRAFV600E黑色素瘤细胞系中,均发现了若干RTKs的过表达.这种RTKs(包括ERBB3)的过表达同样发生于经MEK、PI3K或PI3K/mTOR双抑制剂处理的以Kras突变或EGFR突变为驱动基因的肺癌细胞中.而同时靶向过表达的RT K s能够增加对于肿瘤细胞的杀伤作用.我们推测,很多具有EGFR突变的患者能够产生对靶向药物的适应性耐药.对于这部分患者,在使用EGFR TKIs数小时后进行重新活检,并检测此时究竟哪些RTKs在治疗后出现了过表达.如果同时靶向检测到的RTKs,则能够对肿瘤产生更好的杀伤作用,并能够克服EGFR TKI单药治疗的局限性.     

垂体生长激素腺瘤对生长抑素类似物的耐药机制研究进展

生长抑素类似物能抑制垂体生长激素细胞对生长激素的分泌及相关肿瘤细胞的增殖,是目前垂体生长激素腺瘤临床治疗的首选药物.但部分患者因耐药而影响疗效,其耐药机制涉及生长抑素受体、受体下游信号传导通路、组织病理和细胞黏附分子等因素.     

肿瘤异质性:EGFR突变型非小细胞肺癌患者的时空演变

大多数含有表皮生长因子受体(EGFR)基因突变的非小细胞肺癌患者对EGFR酪氨酸激酶抑制剂(TKI)的治疗显示出显著疗效.然而,所有患者最终都会因原发性或获得性耐药而出现疾病进展.最近几年,虽然有一些研究已经确认了几种在EGFR TKI药物治疗过程中出现的原发性或获得性耐药的机制,并由此而产生出新的潜在的治疗靶点,但是仍有30%的EGFR TKI获得性耐药的原因不明.因此在这篇综述中,我们将详细阐述现已确认的非小细胞肺癌患者的EGFR TKIs耐药机制和克服EGFR TKI耐药的潜在治疗策略.同时我们还突出强调了再活检的重要性,再活检不仅要在出现获得性EGFR-TKI耐药时,也要在开始EGFR TKI治疗时,以便发现其余未知的获得性耐药机制以及对EGFR-TKI药物疗效异质性的分子基础.     

EGFR/HER2基因敲减对SPC-A-1细胞株细胞生物学特性及相关信号通路的影响

目的： 探讨EGFR/HER2基因沉默对非小细胞肺癌细胞株EGFR酪氨酸激酶信号转导通路的交互影响及其与细胞增殖、凋亡和周期改变的关系。方法： 设计并合成EGFR、HER2及 EGFR/HER2共干扰序列,构建含干扰序列的载体,进行瞬时转染;应用实时荧光定量、蛋白印迹法检测基因沉默效果;用四甲基偶氮唑盐比色法、流式细胞仪检测基因沉默后生物学特性改变;蛋白印迹法检测EGFR下游信号通路蛋白Akt、p-Akt、p-Erk1/2、p-p38表达水平变化;采用SPSS13.0软件分析结果。结果： 在SPC-A-1细胞系中,EGFR干扰组、HER2干扰组、EGFR联合HER2干扰组和EGFR-HER2共干扰组体外细胞增殖率均有下降趋势;除EGFR干扰外,其余各组均可诱发凋亡;各组的细胞周期G1期和S期细胞比例有显著改变;基因沉默效果检测显示EGFR和HER2基因蛋白水平被下调。下游信号通路蛋白检测示EGFR下游信号通路蛋白Akt、p-Akt、p-Erk1/2、p-p38表达水平和细胞增殖、凋亡以及细胞周期改变之间未发现明显相关规律。结论： 单纯EGFR干扰SPC-A-1细胞不能诱发显著凋亡,HER2和EGFR/HER2基因共沉默后诱发的人肺腺癌SPC-A-1细胞凋亡比阴性对照显著增加。EGFR/HER2基因沉默后诱发的细胞增殖、凋亡和细胞周期改变与EGFR家族下游信号通路蛋白之间未发现显著相关关系。     

Dual Inhibition of Met Kinase and Angiogenesis to Overcome HGF-Induced EGFR-TKI Resistance in EGFR Mutant Lung Cancer

Acquired resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) is a serious problem in the management of EGFR mutant lung cancer. We recently reported that hepatocyte growth factor (HGF) induces resistance to EGFR-TKIs by activating the Met/PI3K pathway. HGF is also known to induce angiogenesis in cooperation with vascular endothelial growth factor (VEGF), which is an important therapeutic target in lung cancer. Therefore, we hypothesized that dual inhibition of HGF and VEGF may be therapeutically useful for controlling HGF-induced EGFR-TKI-resistant lung cancer. We found that a dual Met/VEGF receptor 2 kinase inhibitor, E7050, circumvented HGF-induced EGFR-TKI resistance in EGFR mutant lung cancer cell lines by inhibiting the Met/Gab1/PI3K/Akt pathway in vitro. HGF stimulated VEGF production by activation of the Met/Gab1 signaling pathway in EGFR mutant lung cancer cell lines, and E7050 showed an inhibitory effect. In a xenograft model, tumors produced by HGF-transfected Ma-1 (Ma-1/HGF) cells were more angiogenic than vector control tumors and showed resistance to gefitinib. E7050 alone inhibited angiogenesis and retarded growth of Ma-1/HGF tumors. E7050 combined with gefitinib induced marked regression of tumor growth. Moreover, dual inhibition of HGF and VEGF by neutralizing antibodies combined with gefitinib also markedly regressed tumor growth. These results indicate the therapeutic rationale of dual targeting of HGF-Met and VEGF-VEGF receptor 2 for overcoming HGF-induced EGFR-TKI resistance in EGFR mutant lung cancer.     

Genotypic and histological evolution of lung cancers acquiring resistance to EGFR inhibitors

Lung cancers harboring mutations in the epidermal growth factor receptor (EGFR) respond to EGFR tyrosine kinase inhibitors, but drug resistance invariably emerges. To elucidate mechanisms of acquired drug resistance, we performed systematic genetic and histological analyses of tumor biopsies from 37 patients with drug-resistant non-small cell lung cancers (NSCLCs) carrying EGFR mutations. All drug-resistant tumors retained their original activating EGFR mutations, and some acquired known mechanisms of resistance including the EGFR T790M mutation or MET gene amplification. Some resistant cancers showed unexpected genetic changes including EGFR amplification and mutations in the PIK3CA gene, whereas others underwent a pronounced epithelial-to-mesenchymal transition. Surprisingly, five resistant tumors (14%) transformed from NSCLC into small cell lung cancer (SCLC) and were sensitive to standard SCLC treatments. In three patients, serial biopsies revealed that genetic mechanisms of resistance were lost in the absence of the continued selective pressure of EGFR inhibitor treatment, and such cancers were sensitive to a second round of treatment with EGFR inhibitors. Collectively, these results deepen our understanding of resistance to EGFR inhibitors and underscore the importance of repeatedly assessing cancers throughout the course of the disease.     

Epidermal growth factor receptor targeting in cancer: A review of trends and strategies

The epidermal growth factor receptor (EGFR) is a cell-surface receptor belonging to ErbB family of tyrosine kinase and it plays a vital role in the regulation of cell proliferation, survival and differentiation. However; EGFR is aberrantly activated by various mechanisms like receptor overexpression, mutation, ligand-dependent receptor dimerization, ligand-independent activation and is associated with development of variety of tumors. Therefore, specific EGFR inhibition is one of the key targets for cancer therapy. Two major approaches have been developed and demonstrated benefits in clinical trials for targeting EGFR; monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs). EGFR inhibitors like, cetuximab, panitumumab, etc. (mAbs) and gefitinib, erlotinib, lapatinib, etc. (TKIs) are now commercially available for treatment of variety of cancers. Recently, many other agents like peptides, nanobodies, affibodies and antisense oligonucleotide have also shown better efficacy in targeting and inhibiting EGFR. Now a days, efforts are being focused to identify molecular markers that can predict patients more likely to respond to anti-EGFR therapy; to find out combinatorial approaches with EGFR inhibitors and to bring new therapeutic agents with clinical efficacy. In this review we have outlined the role of EGFR in cancer, different types of EGFR inhibitors, preclinical and clinical status of EGFR inhibitors as well as summarized the recent efforts made in the field of molecular EGFR targeting.     

EGFR靶向药物治疗非小细胞肺癌的研究进展

在世界范围内,肺癌是死亡率最高的恶性肿瘤,其中以非小细胞肺癌(non-small cell lung cancer,NSCLC)为主.近年来,随着人表皮生长因子受体(epidermal growth factor receptor,EGFR)突变体的发现,以吉非替尼(gefitinib)和厄洛替尼(erlotinib)为代表的EGFR酪氨酸激酶抑制剂(EGFR-TKIs)对于携带有EGFR敏感突变的NSCLC具有良好的疗效.然而,耐药问题的出现增加了临床治疗的难度,针对非小细胞肺癌的EGFR靶向治疗,目前仍有很多问题亟待解决.本文现就EGFR靶向治疗的现状与发展进行综述.     

The novel SAM domain protein Aveugle is required for Raf activation in the Drosophila EGF receptor signaling pathway

Activation of the Raf kinase by GTP-bound Ras is a poorly understood step in receptor tyrosine kinase signaling pathways. One such pathway, the epidermal growth factor receptor (EGFR) pathway, is critical for cell differentiation, survival, and cell cycle regulation in many systems, including the Drosophila eye. We have identified a mutation in a novel gene, aveugle, based on its requirement for normal photoreceptor differentiation. The phenotypes of aveugle mutant cells in the eye and wing imaginal discs resemble those caused by reduction of EGFR pathway function. We show that aveugle is required between ras and raf for EGFR signaling in the eye and for mitogen-activated protein kinase phosphorylation in cell culture. aveugle encodes a small protein with a sterile alpha motif (SAM) domain that can physically interact with the scaffold protein connector enhancer of Ksr (Cnk). We propose that Aveugle acts together with Cnk to promote Raf activation, perhaps by recruiting an activating kinase.     

Angiotensin II regulation of TGF-beta in murine mesangial cells involves both PI3 kinase and MAP kinase

INTRODUCTION: Chronic activation of the angiotensin II (AngII) type 1 receptor (AT-1) is a central event in the development of chronic kidney disease (CKD), in part through enhanced expression of TGF-beta, and AT-1 receptor blockade inhibits the progression to CKD in a variety of disease states. The AT-1 receptor is a heptahelical Gaq/11-coupled receptor that initiates phospholipase C activity and release of intracellular calcium; recent data suggest that the AT-1 receptor can also activate the epidermal growth factor receptor (EGFR), although the roles of specific EGF-mediated signaling cascades in AT-1 effects on mesangial cell biology are uncertain. We hypothesized that 2 EGFR-activated pathways, PI3 kinase and MAP kinase, are stimulated by the AT-1 receptor and, in part, regulate the effects of AngII on TGF-beta1 levels in mesangial cells. METHODS: We examined the effects of AT-1 receptor activation on EGFR, PI3 kinase, and MAP kinase activation in murine mesangial cells. Upon achieving 60-80% confluence, the medium was changed to low-serum for 48 hr and cells were exposed to either the AT-1 receptor blocker, losartan, the EGFR blocker, AG1478, or control medium, and then stimulated with AngII. Similar experiments were performed using LY294002 and U0126, specific inhibitors of PI3 kinase and MEK, respectively. Total cellular protein lysates and RNA were isolated. Activation of the receptors and pathways was evaluated by immunoblotting and levels of TGF-beta mRNA were measured using real-time quantitative RT-PCR. RESULTS: AngII induced autophosphorylation of EGFR (pY1068) and activated Akt and ERK, downstream targets of PI3 kinase and MAP kinase, respectively. AngII-mediated EGFR autophosphorylation was inhibited by losartan and AG1478. AG1478 also inhibited both basal and AngII-mediated activation of Akt and ERK. Finally, AngII-mediated increase in TGF-beta mRNA was inhibited by losartan, AG1478, LY249002, and U0126. CONCLUSIONS: Stimulation of the AT-1 receptor in murine mesangial cells results in activation of the EGF receptor with subsequent signaling through PI3 kinase and MAP kinase, thereby regulating TGF-beta mRNA levels. These data suggest that AT-1 receptor signaling pathways through EGFR may serve as a therapeutic target to inhibit the development of CKD.     

Functional coupling of the mammalian EGF receptor to the Ras/cAMP pathway in the yeast Saccharomyces cerevisiae

Autophosphorylation of tyrosine residues on the cytoplasmic tail of the epidermal growth factor receptor (EGFR) upon ligand binding leads to recruitment of the Grb2/Sos complex to the activated receptor and to activation of the Ras pathway. The major aim of this study was to ascertain to which extent the EGFR module (receptor, Grb2, hSos1) could work in a lower eukaryote, completely devoid of tyrosine kinase receptors but possessing hortologues to mammalian Ras proteins. We show that the EGFR module can be functionally linked to the Ras/cAMP pathway in a Saccharomyces cerevisiae cdc25 ^ts strain, as monitored by several independent biological readouts, including drop of budding index, decrease of cAMP level and acquisition of thermotolerance. Autophosphorylation of the receptor is a necessary step for RTK-dependent activation of the yeast Ras pathway, since genetic and pharmacological downregulation of the EGFR catalytic activity abolish coupling with the Ras/cAMP pathway. Thus, our results newly indicate that a RTK-based signal transduction module can be functionally coupled to the yeast Ras/cAMP pathway and that our system can be a valuable tool for the screen of drugs inhibiting the kinase activity of the receptor. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.