EGFR 突变种类与临床疗效关联

癌组织中表皮生长因子受体(epidermal growth factor receptor,EGFR)基因突变是应用靶向药物EGFR酪氨酸激酶抑制剂(tyrosine kinase inhibitor,TKI)治疗的一个重要相关因素及预测指标。对其突变的检测可以指导TKI类药物(TKIs)的最佳应用。该种突变常出现在非小细胞肺癌(NSCLC)中,尤其是在亚洲女性、肺腺癌、非吸烟者中,与非小细胞肺癌患者对TKIs治疗的敏感性密切相关。本文旨在探讨利用EGFR基因的已知突变热点的相关知识选择适合不同分子遗传学背景的群体或/和个体的"个体化"治疗方案,最终达到延长肺癌患者生存时间和提高生活质量的双重目的。     

EGFR突变种类与临床疗效关联

癌组织中表皮生长因子受体（epidermal growth factor receptor,EGFR）基因突变是应用靶向药物EGFR酪氨酸激酶抑制剂（tyrosine kinase inhibitor,TKI）治疗的一个重要相关因素及预测指标。对其突变的检测可以指导TKI类药物（TKIs）的最佳应用。该种突变常出现在非小细胞肺癌（NSCLC）中,尤其是在亚洲女性、肺腺癌、非吸烟者中,与非小细胞肺癌患者对TKIs治疗的敏感性密切相关。本文旨在探讨利用EGFR基因的已知突变热点的相关知识选择适合不同分子遗传学背景的群体或/和个体的＂个体化＂治疗方案,最终达到延长肺癌患者生存时间和提高生活质量的双重目的。     

Investigating the Function of Three Non-Synonymous SNPs in EGFR Gene: Structural Modelling and Association With Breast Cancer

Non-synonymous single nucleotide polymorphisms (nsSNPs) represent common genomic variations that alter protein sequence and function. Some nsSNPs affecting conserved amino acids have been reported to be associated with cancer susceptibility. Interestingly, Epidermal Growth Factor Receptor (EGFR) is commonly overexpressed and mutated in many cancers. In this study, we investigated the structural effect of three deleterious nsSNPs: rs17337451 (R962G), rs1140476 (R977C) and rs17290699 (H988P) within EGFR using computational tools. The modelled mutant dimers showed less stability than wild type EGFR dimer. Furthermore, we showed the important role of R962 and H988 residues in the EGFR dimer formation. We also report preliminary experimental data for SNP R977C suggesting that the variant C977 might confer greater risk for breast cancer. These results contribute to an improved understanding of the EGFR dimer stability and provide new elements for understanding the relationship between EGFR and cancer.     

Association among Polymorphisms in EGFR Gene Exons,Lifestyle and Risk of Gastric Cancer with Gender Differences in Chinese Han Subjects

Background

The epidermal growth factor receptor (EGFR) gene plays a key role in tumor survival, invasion, angiogenesis, and metastatic spread. Recent studies showed that gastric cancer (GC) was associated with polymorphisms of the EGFR gene and environmental influences, such as lifestyle factors. In this study, seven known SNPs in EGFR exons were investigated in a high-risk Chinese population in Jiangsu province to test whether genetic variants of EGFR exons and lifestyle are associated with an increased risk of GC.

Methodology/Principal Findings

A hospital-based case-control study was performed in Jiangsu province. The results showed that smoking, drinking and preference for salty food were significantly associated with the risk of GC. The differences of lifestyle between males and females might be as the reason of higher incidence rates in males than those in females. Seven exon SNPs were genotyped rs2227983,rs2072454,rs17337023,rs1050171,rs1140475, rs2293347, and rs28384375. It was noted that the variant rs2072454 T allele and TT genotype were significantly associated with an increased risk of GC. Interestingly, our result suggested the ACAGCA haplotype might be associated with decreased risk of GC. However, no significant association was examined between the other six SNPs and the risk of GC both in the total population and the age-matching population even with gender differences.

Conclusions

Smoking, drinking and preference for salty food were significantly associated with the risk of GC in Jiangsu province with gender differences. Although only one SNP (rs2072454) was significantly associated with an increased risk of GC, combined the six EGFR exon SNPs together may be useful for predicting the risk of GC.     

EGF Induces Cell Motility and Multi-Drug Resistance Gene Expression in Breast Cancer Cells

The epidermal growth factor receptor (EGFR) is important for normal development, differentiation, and cell proliferation. Deregulation of EGFR has been observed in breast cancer. EGFR and signal pathways activated by these receptors have been associated with an advanced tumor stage and a poor clinical prognosis in breast cancer, however, the precise mechanisms responsible for this process are still not known. Here we show that treatment of MCF-7 breast cancer cells with EGF activated Akt and ERK, induced morphological changes, and increased cell motility. In addition, the constitutive expression of Raf-1 and the use of a MEK inhibitor demonstrated the participation of the Raf/MEK/ERK pathway in these processes. Importantly we detected that EGF induced MRP-1, 3, 5 and 7 gene expression and an increase in MRP1 promoter activity. In conclusion, treatment of MCF-7 breast cancer cells with EGF, in the absence of other growth factors, resulted in activation of EGFR signal transduction pathways; which were related with cell motility and drug resistance.     

喉癌中p15、p16基因纯合缺失与EGFR基因扩增相关性研究

研究p15、p16基因缺失和EGFR基因扩增的相关性及其与喉癌发生、发展的关系。提取喉癌新鲜组织中基因组DNA,采用聚合酶链反应技术,分别对30例喉癌进行p15基因第2外显子(p15E2)和p16基因第2外显子(p16E2)进行纯合缺失研究;应用FISH方法进行喉癌实体瘤EGFR基因扩增研究。p15E2纯合缺失率为13．3％(4／30),p16E2纯合缺失率为16．7％(5／30),p15E2、p16E2共同缺失率为6．7％(2／30)。在30例喉癌实体瘤EGFR基因扩增频率为30％(9／30),扩增2～8倍。p15E2和p16E2纯合缺失以及二者共同缺失与EGFR基因扩增相关,可能引起细胞周期失控而导致细胞增殖紊乱,在喉癌的发生及恶性进展中发挥一定作用。     

Gene 33 is an endogenous inhibitor of epidermal growth factor (EGF) receptor signaling and mediates dexamethasone-induced suppression of EGF function

We report a mechanism by which the adapter protein Gene 33 (also called RALT and MIG6) regulates epidermal growth factor receptor (EGFR) signaling. We find that Gene 33 inhibits EGFR autophosphorylation and specifically blunts epidermal growth factor (EGF)-induced activation and/or phosphorylation of Ras, ERK, JNK, Akt/PKB, and retinoblastoma protein. The Ack homology domain of Gene 33, which contains the previously identified EGFR binding domain, is both necessary and sufficient for this inhibition of EGFR autophosphorylation. The endogenous Gene 33 polypeptide is induced by EGF, platelet-derived growth factor, serum, and dexamethasone (Dex) in Rat 2 rat fibroblasts. Dex induces Gene 33 expression and inhibits EGFR phosphorylation and EGF signaling. RNA interference-mediated silencing of Gene 33 significantly reverses this effect. Overexpression of Gene 33 completely blocks EGF-induced protein and DNA synthesis in Rat 2 cells, whereas gene 33 RNA interference substantially enhances EGF-induced protein and DNA synthesis in Rat 2 cells. Our results indicate that Gene 33 is a physiological feedback inhibitor of the EGFR, functioning to inhibit EGFR phosphorylation and all events induced by EGFR activation. Our results also indicate a role for Gene 33 in the suppression, by Dex, of EGF signaling pathways. We propose that Gene 33 may function in the cross-talk between EGF signaling and other mitogenic and/or stress signaling pathways.     

EGFR Gene Variants Are Associated with Specific Somatic Aberrations in Glioma

A number of gene variants have been associated with an increased risk of developing glioma. We hypothesized that the reported risk variants may be associated with tumor genomic instability. To explore potential correlations between germline risk variants and somatic genetic events, we analyzed matched tumor and blood samples from 95 glioma patients by means of SNP genotyping. The generated genotype data was used to calculate genome-wide allele-specific copy number profiles of the tumor samples. We compared the copy number profiles across samples and found two EGFR gene variants (rs17172430 and rs11979158) that were associated with homozygous deletion at the CDKN2A/B locus. One of the EGFR variants (rs17172430) was also associated with loss of heterozygosity at the EGFR locus. Our findings were confirmed in a separate dataset consisting of matched blood and tumor samples from 300 glioblastoma patients, compiled from publically available TCGA data. These results imply there is a functional effect of germline EGFR variants on tumor progression.     

基于18F-FDG PET/CT参数评价不同EGFR基因状态晚期肺腺癌患者放化疗疗效预测价值

为评价18F-FDG PET/CT参数对不同表皮生长因子受体(epithelial growth factor receptor, EGFR)基因状态晚期肺腺癌患者同步放化疗的疗效预测价值,本研究选择2016年1月至2018年2月我院初诊的100例晚期肺腺癌患者,比较不同EGFR基因状态下晚期肺腺癌患者同步放化疗治疗的临床疗效,并对18F-FDG PET/CT显像中原发病灶的各项代谢参数,代谢肿瘤体积(MTV)、最大标准摄取值(SUVmax)、平均标准摄取值(SUVmean)和总肿瘤糖酵解(TLG)值,以预测不同EGFR基因状态晚期肺腺癌患者同步放化疗效果的受试者工作特征曲线(receiveroperatingcharacteristiccurve,ROC曲线),并进行分析。结果显示,SUVmax预测不考虑EGFR基因状态的晚期肺腺癌患者放化疗疗效的截断值为9.50 (AUC=0.715,敏感度=79.7%,特异性=61%,p=0.031),SUVmax预测EGFR野生型的晚期肺腺癌患者放化疗疗效的截断值为9.50 (敏感度=82.4%,特异性=64.3%, p=0.014)。MTV预测EGFR 19号及21号外显子突变的晚期肺腺癌患者放化疗疗效的截断值分别为93.50(敏感度=63.6%,特异性=92.3%, p=0.021),77.00 (敏感度=83.3%,特异性=69.2%, p=0.041)。综上所述,对于EGFR基因状态不明的肺腺癌患者,SUVmax值可较好的预测放化疗效果,尤其是对于EGFR野生型患者;当EGFR19号及21号外显子突变时,MTV值预测结果优于SUVmax值。     

MET Gene Amplification and MET Receptor Activation Are Not Sufficient to Predict Efficacy of Combined MET and EGFR Inhibitors in EGFR TKI-Resistant NSCLC Cells

Epidermal growth factor receptor (EGFR), member of the human epidermal growth factor receptor (HER) family, plays a critical role in regulating multiple cellular processes including proliferation, differentiation, cell migration and cell survival. Deregulation of the EGFR signaling has been found to be associated with the development of a variety of human malignancies including lung, breast, and ovarian cancers, making inhibition of EGFR the most promising molecular targeted therapy developed in the past decade against cancer. Human non small cell lung cancers (NSCLC) with activating mutations in the EGFR gene frequently experience significant tumor regression when treated with EGFR tyrosine kinase inhibitors (TKIs), although acquired resistance invariably develops. Resistance to TKI treatments has been associated to secondary mutations in the EGFR gene or to activation of additional bypass signaling pathways including the ones mediated by receptor tyrosine kinases, Fas receptor and NF-kB. In more than 30–40% of cases, however, the mechanisms underpinning drug-resistance are still unknown. The establishment of cellular and mouse models can facilitate the unveiling of mechanisms leading to drug-resistance and the development or validation of novel therapeutic strategies aimed at overcoming resistance and enhancing outcomes in NSCLC patients. Here we describe the establishment and characterization of EGFR TKI-resistant NSCLC cell lines and a pilot study on the effects of a combined MET and EGFR inhibitors treatment. The characterization of the erlotinib-resistant cell lines confirmed the association of EGFR TKI resistance with loss of EGFR gene amplification and/or AXL overexpression and/or MET gene amplification and MET receptor activation. These cellular models can be instrumental to further investigate the signaling pathways associated to EGFR TKI-resistance. Finally the drugs combination pilot study shows that MET gene amplification and MET receptor activation are not sufficient to predict a positive response of NSCLC cells to a cocktail of MET and EGFR inhibitors and highlights the importance of identifying more reliable biomarkers to predict the efficacy of treatments in NSCLC patients resistant to EGFR TKI.     

GAPex-5 mediates ubiquitination, trafficking, and degradation of epidermal growth factor receptor

Upon ligand stimulation, epidermal growth factor receptor (EGFR) is rapidly ubiquitinated, internalized, and sorted to lysosomes for degradation. Rab5 has been shown to play an important role in the early stages of EGFR trafficking. GAPex-5 is a newly described Rab5 exchange factor. Herein, we investigate the role of GAPex-5 on EGFR trafficking and degradation. Down-regulation of GAPex-5 by RNA interference decreases epidermal growth factor-stimulated EGFR degradation. Moreover, ubiquitination of EGFR is impaired by depletion of GAPex-5. This inhibitory effect is due to a decrease in the interaction between the adapter protein c-Cbl and EGFR, but not the phosphorylation state of EGFR. Consistently, when examined by immunofluorescence microscopy in cells depleted of GAPex-5, ligand-bound EGFR appeared trapped in early endosomes and the trafficking of internalized receptor from early to late endosomes was impaired. In agreement with the depletion studies, EGFR degradation is enhanced by overexpressing GAPex-5 wild type, but not GAPex-5DeltaGAP, a mutant lacking the Ras GTPase-activating protein (GAP) domain. This is consistent with the finding that c-Cbl binds specifically to the Ras GAP domain. Finally, overexpression of dominant negative Rab5a or depletion of all three isoforms of Rab5 does not inhibit ubiquitination of EGFR, which suggests that GAPex-5-mediated EGFR ubiquitination is independent of Rab5 activation. Collectively, the results suggest a novel mechanism by which EGF-stimulated receptor ubiquitination and trafficking are mediated via GAPex-5.     

EML4-ALK 融合基因在非小细胞肺癌中的研究进展

肺癌是发病率和死亡率最高的恶性肿瘤,分子靶向治疗以其特异性高、副反应轻的特点正日益受到关注。近年来临床研究发现EML4-ALK融合基因是除EGFR突变及KRAS突变之外的另-个重要的酪氨酸激酶抑制剂的作用靶点,该融合基因在年轻、不吸烟或少吸烟、腺癌、无EGFR和KRAS突变的非小细胞肺癌患者中发生率较高,且该融合基因阳性者对酪氨酸激酶抑制剂耐药,对于ALK抑制剂(如克唑替尼)则有良好的治疗反应,关于该药的临床试验表明:总有效率达57%(46例确定为部分缓解,1例确定为完全缓解),估计6个月无进展生存概率为72%,常见的副反应是1、2级胃肠道反应。该基因及该药的发现为非小细胞肺癌患者带来了希望。     

Lyso-GM3, its dimer,and multimer: their synthesis,and their effect on epidermal growth factor-induced receptor tyrosine kinase

Glycosphingolipids, particularly gangliosides, are known to modulate growth factor receptor tyrosine kinase. A well-documented example is the inhibitory effect of GM3 on kinase associated with epidermal growth factor receptor (EGFR) in human epidermoid carcinoma A431 cells. Lyso-GM3 was detected as a minor component in A431 cells, and may function as an auxiliary factor in GM3-dependent inhibition of EGFR. We studied the inhibitory effect of chemically synthesized GM3, lyso-GM3, and its derivatives, on EGFR function, based on their interaction in membrane microdomain, with the following major findings: (1) GM3, EGFR, and caveolin coexist, but tetraspanins CD9 and CD82 are essentially absent, within the same low-density membrane fraction, separated by sucrose density gradient ultracentrifugation. (2) Strong interaction between EGFR and GM3 was indicated by increasing binding of EGFR to GM3-coated polystyrene beads, in a GM3 dose-dependent manner. Confocal microscopy results suggested that three components in the microdomain (GM3, EGFR, and caveolin) are closely associated. (3) Lyso-GM3 or lyso-GM3 dimer strongly inhibited EGFR kinase activity, in a dose-dependent manner, while lyso-GM3 trimer and tetramer did not. >50 μM lyso-GM3 was cytolytic, while >50 μM lyso-GM3 dimer was not cytolytic, yet inhibited EGFR kinase strongly. Thus, lyso-GM3 and its dimer exert an auxiliary effect on GM3-induced inhibition of EGFR kinase and cell growth, and lyso-GM3 dimer may be a good candidate for pharmacological inhibitor of epidermal tumor growth.     

Control of epidermal growth factor receptor endocytosis by receptor dimerization, rather than receptor kinase activation

Given that ligand binding is essential for the rapid internalization of epidermal growth factor receptor (EGFR), the events induced by ligand binding probably contribute to the regulation of EGFR internalization. These events include receptor dimerization, activation of intrinsic tyrosine kinase activity and autophosphorylation. Whereas the initial results are controversial regarding the role of EGFR kinase activity in EGFR internalization, more recent data suggest that EGFR kinase activation is essential for EGFR internalization. However, we have shown here that inhibition of EGFR kinase activation by mutation or by chemical inhibitors did not block EGF-induced EGFR internalization. Instead, proper EGFR dimerization is necessary and sufficient to stimulate EGFR internalization. We conclude that EGFR internalization is controlled by EGFR dimerization, rather than EGFR kinase activation. Our results also define a new role for EGFR dimerization: by itself it can drive EGFR internalization, independent of its role in the activation of EGFR kinase.     

Gefitinib-sensitive EGFR lacking residues 746-750 exhibits hypophosphorylation at tyrosine residue 1045, hypoubiquitination, and impaired endocytosis

Gefitinib-sensitive nonsmall cell lung cancers (NSCLC) are characterized by somatic mutations in the kinase domain of epidermal growth factor receptor (EGFR). The mutant EGFR forms are reported to mediate characteristic signal transduction pathways that are different from those mediated by the wild-type EGFR and are involved in transformation in vivo. We have examined signal transduction pathways initiated from a frequently identified gefitinib-sensitizing mutant EGFR lacking residues 746-750 by employing a mouse fibroblast cell line that is free of endogenous EGFR and transiently transfected COS-7 cells. Upon EGF stimulation, the deletion-mutant EGFR mediated prolonged downstream signals. The analysis of the phosphotyrosine patterns of the receptor revealed that the deletion-mutant EGFR lacked phosphorylation at tyrosine residue 1045, which is the major binding site of Cbl. The EGF-induced endocytosis of the deletion-mutant EGFR was impaired. The ubiquitination and downregulation of the deletion-mutant EGFR were also reduced. On the other hand, another mutant, EGFR, possessing a L858R substitution, exhibited phosphorylation at 1045 and its downstream signalings were not prolonged. These data suggest that the signal transduction pathways initiated from these mutant forms are different, and that impaired endocytosis might be responsible for the prolonged signals mediated by the deletion-mutant EGFR.     

Spectrum of EGFR Gene Copy Number Changes and KRAS Gene Mutation Status in Korean Triple Negative Breast Cancer Patients

Anti-epidermal growth factor receptor (EGFR) therapy has been tried in triple negative breast cancer (TNBC) patients without evaluation of molecular and clinical predictors in several randomized clinical studies. Only fewer than 20% of metastatic TNBCs showed response to anti-EGFR therapy. In order to increase the overall response rate, first step would be to classify TNBC into good or poor responders according to oncogenic mutation profiles. This study provides the molecular characteristics of TNBCs including EGFR gene copy number changes and mutation status of EGFR and KRAS gene in Korean TNBC patients. Mutation analysis for EGFR, KRAS, BRAF and TP53 from a total of 105 TNBC tissue samples was performed by direct sequencing, peptide nucleic acid-mediated PCR clamping method and real-time PCR. Copy number changes of EGFR gene were evaluated using multiplex ligation-dependent probe amplification. Out of all 105 TNBCs, 15.2% (16/105) showed EGFR copy number changes. Among them, increased or decreased EGFR copy number was detected in 13 (5 single copy gain, 2 amplification and 4 high-copy number amplification) and 3 cases (3 hemizygous deletion), respectively. The mutation frequencies of KRAS, EGFR and TP53 gene were 1.9% (G12V and G12D), 1.0% (exon 19 del) and 31.4%, respectively. There was no BRAF V600E mutation found. Future studies are needed to evaluate the clinical outcomes of TNBC patients who undergo anti-EGFR therapy according to the genetic status of EGFR.     

LAPTM4B is a PtdIns(4,5)P2 effector that regulates EGFR signaling,lysosomal sorting,and degradation

Lysosomal degradation is essential for the termination of EGF‐stimulated EGF receptor (EGFR) signaling. This requires EGFR sorting to the intraluminal vesicles (ILVs) of multi‐vesicular endosomes (MVEs). Cytosolic proteins including the ESCRT machineries are key regulators of EGFR intraluminal sorting, but roles for endosomal transmembrane proteins in receptor sorting are poorly defined. Here, we show that LAPTM4B, an endosomal transmembrane oncoprotein, inhibits EGF‐induced EGFR intraluminal sorting and lysosomal degradation, leading to enhanced and prolonged EGFR signaling. LAPTM4B blocks EGFR sorting by promoting ubiquitination of Hrs (an ESCRT‐0 subunit), which inhibits the Hrs association with ubiquitinated EGFR. This is counteracted by the endosomal PIP kinase, PIPKIγi5, which directly binds LAPTM4B and neutralizes the inhibitory function of LAPTM4B in EGFR sorting by generating PtdIns(4,5)P₂ and recruiting SNX5. PtdIns(4,5)P₂ and SNX5 function together to protect Hrs from ubiquitination, thereby promoting EGFR intraluminal sorting. These results reveal an essential layer of EGFR trafficking regulated by LAPTM4B, PtdIns(4,5)P₂ signaling, and the ESCRT complex and define a mechanism by which the oncoprotein LAPTM4B can transform cells and promote tumor progression.     

Endophilin,Lamellipodin, and Mena cooperate to regulate F‐actin‐dependent EGF‐receptor endocytosis

The epidermal growth factor receptor (EGFR) plays an essential role during development and diseases including cancer. Lamellipodin (Lpd) is known to control lamellipodia protrusion by regulating actin filament elongation via Ena/VASP proteins. However, it is unknown whether this mechanism supports endocytosis of the EGFR. Here, we have identified a novel role for Lpd and Mena in clathrin‐mediated endocytosis (CME) of the EGFR. We have discovered that endogenous Lpd is in a complex with the EGFR and Lpd and Mena knockdown impairs EGFR endocytosis. Conversely, overexpressing Lpd substantially increases the EGFR uptake in an F‐actin‐dependent manner, suggesting that F‐actin polymerization is limiting for EGFR uptake. Furthermore, we found that Lpd directly interacts with endophilin, a BAR domain containing protein implicated in vesicle fission. We identified a role for endophilin in EGFR endocytosis, which is mediated by Lpd. Consistently, Lpd localizes to clathrin‐coated pits (CCPs) just before vesicle scission and regulates vesicle scission. Our findings suggest a novel mechanism in which Lpd mediates EGFR endocytosis via Mena downstream of endophilin.