培美曲塞和吉非替尼不同时序应用对人肺腺癌细胞的作用和机制

目的 探讨培美曲塞与吉非替尼不同时序应用对肺腺癌细胞A549和PC-9生长及凋亡的影响, 并阐述其可能机制。方法 MTT法检测各组细胞的增殖抑制情况,流式细胞仪检测各组细胞凋亡及细胞周期分布,Western印迹法检测对EGFR下游信号通路及TS酶蛋白水平表达的影响。结果 培美曲塞序贯吉非替尼、培美曲塞同步联合吉非替尼对PC-9和A549细胞增殖抑制率及凋亡率较单药组均提高（P<0.05）,培美曲塞可以提高EGFR、AKT 、ERK磷酸化水平,而吉非替尼表现为抑制作用, 同时吉非替尼降低TS酶表达。培美曲塞序贯吉非替尼,培美曲塞同步联合吉非替尼抑制EGFR、AKT 、ERK磷酸化水平较单药更强。吉非替尼主要将PC-9、A549细胞阻滞在G0/G1期;培美曲塞主要将细胞阻滞在S期。培美曲塞序贯吉非替尼、培美曲塞同步联合吉非替尼较其他组G2/M期细胞比例提高（P<0.05）。结论 培美曲赛序贯吉非替尼、培美曲赛同步联合吉非替尼在PC-9、A549细胞中均起到协同增效作用,且培美曲赛序贯吉非替尼协同作用更为显著,可能主要与培美曲赛诱导EGFR、AKT 、ERK磷酸化及吉非替尼降低TS酶作用有关。     

多西他赛与吉非替尼不同时序应用对人肺腺癌细胞的作用

目的 探讨多西他赛与吉非替尼不同时序应用对人肺腺癌细胞A549和PC-9的生长影响及其细胞学机制。方法 qPCR-HRM法检测人肺腺癌细胞EGFR和K Ras基因突变,MTT法检测细胞增殖, Western blotting检测细胞信号蛋白及磷酸化表达,FCM法检测细胞周期变化。结果 人肺腺癌A549细胞为EGFR基因野生型,PC-9细胞为EGFR第19外显子突变型。多西他赛和吉非替尼单药或联合用药均能抑制A549和PC-9细胞生长,呈浓度依赖性。多西他赛对A549和PC-9细胞生长的半数抑制浓度（IC₅₀）分别为5.24×10^-7和2.13×10^-8mol／L,吉非替尼分别为1.28×10^-5和4.58×10^-8mol／L。在IC₅₀浓度时,多西他赛序贯吉非替尼对A549和PC-9细胞的生长抑制率分别为60.00%和57.45%,均较单药组明显增高（P＜0.05）;而同时用药只对PC-9细胞有增效作用,抑制率为53.46％,较单药组明显增高（P＜0.05）。多西他赛表现为增强A549、PC-9细胞EGFR和ERK磷酸化,吉非替尼表现为抑制,两药均抑制PC-9细胞IGF-1R磷酸化。多西他赛序贯应用吉非替尼显著抑制EGFR和ERK磷酸化,两药同时应用对抑制PC-9细胞的IGF-1R磷酸化具有增强作用。多西他赛将A549及PC-9细胞阻滞在G₂期,吉非替尼将PC-9细胞明显阻滞在G₁期。结论 多西他赛序贯吉非替尼能够抑制EGFR野生型和突变型的A549及PC-9细胞生长,且呈增效作用,可能与影响细胞EGFR和ERK磷酸化有关;两药同时应用仅对PC-9细胞具有增效作用,可能与IGF-1R磷酸化抑制有关;不同时序应用的效果均可能与细胞周期相关。     

肝细胞生长因子诱导敏感非小细胞肺癌细胞对吉非替尼耐药及机制的研究

背景与目的肝细胞生长因子(hepatocyte growth factor,HGF)受体(c-Met)可能与非小细胞肺癌(non-small cell lung cancer,NSCLC)对吉非替尼耐药有关。本研究旨在探讨HGF诱导不同基因型NSCLC对吉非替尼耐药及耐药机制。方法选择NSCLC细胞EGFR突变型PC-9和EGFR野生型H292,用HGF诱导这两株细胞,通过MTT法检测细胞增殖,PI法检测细胞周期,Annexin V-PE法检测细胞凋亡,应用免疫印迹(Western blot)技术检测细胞中c-Met、p-Met的表达。结果吉非替尼对PC-9和H292的生长抑制作用呈浓度依赖性,HGF诱导后吉非替尼抑制两种细胞的生长曲线往右移。PC-9和H292的HGF和吉非替尼处理组(HG)比吉非替尼处理组(G)均有更高的存活率(P<0.05),HG组与G组两组间细胞凋亡及细胞周期无统计学差异(P>0.05)。HGF明显增加PC-9和H292中p-Met的表达。吉非替尼能明显抑制HGF诱导PC-9增加表达的p-Met,但不能抑制HGF诱导H292增加表达的p-Met。结论 HGF可诱导敏感肺癌细胞PC-9和H292对吉非替尼耐药,HGF刺激c-Met磷酸化可能是敏感肺癌细胞对吉非替尼耐药的重要机制。     

糖酵解在非小细胞肺癌吉非替尼耐药中的作用研究

目的 探讨糖酵解在非小细胞肺癌（non-small cell lung cancer,NSCLC）吉非替尼（Gefitinib）耐药中的变化及作用。方法 体外培养NSCLC亲本细胞PC-9和A549,并采用浓度递增法构建NSCLC吉非替尼耐药细胞PC-9-GR和A549-GR,通过CCK-8和平板克隆形成实验鉴定细胞耐药性,葡萄糖摄取检测试剂盒和乳酸测试盒分别检测葡萄糖代谢和乳酸产出水平,qRT-PCR和Western blot实验检测细胞糖酵解关键酶的mRNA和蛋白表达水平。采用糖酵解抑制剂2-脱氧-D-葡萄糖（2-deoxy-D-glucose,2-DG）抑制细胞糖酵解后,观察细胞活力及吉非替尼耐药性的变化情况。结果相较于各自亲本细胞,耐药细胞PC-9-GR和A549-GR对吉非替尼抵抗性增强（均P<0.01）,葡萄糖代谢速率和乳酸产出水平提高（均P<0.01）;糖酵解关键酶HK2、LDHA和PFK的mRNA表达水平升高（均P<0.001）,HK2、LDHA、PFKP和PKM2的蛋白表达水平增加（均P<0.001）。2-DG对耐药细胞活力的抑制作用较各自亲本...     

c-Met信号通道参与HGF诱导不同基因型非小细胞肺癌细胞株对吉非替尼耐药

背景与目的肝细胞生长因子(hepatocyte growth factor,HGF)诱导非小细胞肺癌(non-small cell lung cancer,NSCLC)对吉非替尼耐药,可能与其受体c-Met激活有关。本研究旨在探讨c-Met及其下游信号通道是否参与HGF诱导不同基因型NSCLC细胞株对吉非替尼耐药。方法选择人NSCLC细胞株表皮生长因子受体(epidermal growth factor receptor,EGFR)突变型PC-9、PC9/R和EGFR野生型H292、A549,用HGF诱导细胞,通过MTT法检测细胞增殖,Annexin V-FITC法检测细胞凋亡,应用免疫印迹技术检测细胞中c-Met及下游通道的变化。结果吉非替尼对PC9、H292、A549的生长抑制作用呈浓度依赖性,HGF诱导后吉非替尼抑制细胞的生长曲线明显往右移。在PC9、H292、A549细胞中,吉非替尼和HGF处理组的细胞凋亡率比吉非替尼处理组均减少(P<0.05),在PC9/R细胞中无明显减少(P>0.05)。HGF能激活PC9、H292、PC9/R、A549细胞中c-Met及其下游通道蛋白。在PC9、H292、A549细胞中,吉非替尼和HGF处理组的p-Met、p-Akt、p-Stat3、p-Erk1/2蛋白表达比吉非替尼处理组均增高,在PC9/R细胞中无明显增高。结论在体外HGF诱导不同基因型NSCLC细胞株对吉非替尼耐药,c-Met及其下游信号通道参与HGF诱导不同基因型NSCLC细胞株对吉非替尼耐药。     

吉非替尼联合鸦胆子油乳对肺腺癌细胞的作用及其机制

目的 探讨吉非替尼（Gefitinib, G）联合鸦胆子油乳（Bruceolic oil emulsion, B）对肺腺癌PC-9、A549细胞增殖与凋亡的作用及其机制。方法 取对数生长期的PC-9、A549细胞进行实验,两细胞株在实验中均分为对照组和实验组。采用MTT比色法、TUNEL法及流式细胞技术检测各实验组对肺腺癌细胞的增殖抑制、诱导细胞凋亡及细胞周期阻滞等作用。结果 吉非替尼、鸦胆子油乳单药均能抑制PC-9、A549细胞的生长、增殖并诱导其凋亡,呈浓度和时间依赖效应。与鸦胆子油乳联合后,吉非替尼对PC-9和A549细胞的IC50较单用时分别下降了50.72%和66.56%。两药联合后对两细胞的增殖抑制及凋亡诱导作用进一步增强。结论 吉非替尼联合鸦胆子油乳能显著抑制肺腺癌PC-9、A549细胞增殖、诱导细胞凋亡,可能与药物对细胞周期的阻滞作用有关。两者合用时鸦胆子油乳可对吉非替尼起到增效增敏的作用。     

活性氧在导致吉非替尼耐药细胞凋亡中的作用

研究针对K-ras突变小分子NSC-741909是否可特异性杀伤吉非替尼原发耐药细胞,并对活性氧（reactive oxygen species,ROS）在其中的作用进行探讨。方法:选取H322（K-ras野生）及A549（K-ras突变）人源非小细胞肺癌细胞系,观察吉非替尼对不同细胞系生长的影响;NSC-741909作用于吉非替尼耐药细胞,观察细胞增殖与凋亡的变化;DCFH-DA荧光探针标记细胞内ROS,FCM检测细胞内ROS水平的变化,Western blot检测细胞内JNK通路蛋白变化。结果:K-ras突变型细胞对吉非替尼原发耐药,但NSC-741909可使这种原发耐药细胞出现凋亡;细胞内产生ROS,p-JNK表达增加而总JNK无改变,MKP1表达受抑制。结论:针对K-ras突变的小分子NSC-741909可使吉非替尼耐药细胞产生凋亡,NSC-741909通过使细胞内产生ROS持续激活JNK通路,是其导致吉非替尼耐药细胞凋亡的可能机制之一。      

miR-200c增强肺癌A549细胞对紫杉醇及吉非替尼的敏感度及相关机制

目的 观察上调肺癌A549细胞中miR-200c的表达对紫杉醇、吉非替尼敏感度及两药联合作用的影响及其作用机制。方法 用miR-200c转染肺癌A549细胞,Real-time PCR检测miR-200c表达,MTT法和流式细胞仪检测转染miR-200c后A549细胞对紫杉醇、吉非替尼单药及两药联合的敏感度和细胞凋亡的影响,Western blot检测TUBB3蛋白、EGFR、Akt、MAPK磷酸化蛋白及总蛋白的表达。结果 上调miR-200c表达可增强A549细胞对紫杉醇及吉非替尼敏感度并促进细胞凋亡,对两药联合无明显作用。Western blot显示转染miR-200c联合紫杉醇可下调A549细胞中TUBB3蛋白表达,联合吉非替尼下调EGFR和Akt磷酸化蛋白表达,与两药联合对EGFR和Akt磷酸化蛋白表达无明显影响。 结论 miR-200c可增强肺癌A549细胞对紫杉醇、吉非替尼的敏感度,可能分别与抑制TUBB3表达、抑制EGFR和Akt磷酸化蛋白表达有关,而对两药联合无协同抗肿瘤作用。     

吉非替尼对肺癌细胞株A549和H1975放射敏感度的影响及其机制

目的 本研究旨在探讨小分子表皮生长因子受体（epidermal growth factor receptor, EGFR）酪氨酸激酶抑制剂吉非替尼是否能增加肺癌细胞株A549和H1975的放疗敏感度及其机制。方法 选取两种非小细胞肺癌细胞株A549和H1975,分为单纯X线组和X线+吉非替尼组。单纯X线组采用单纯X线照射,X线+吉非替尼组经10 μmol/L吉非替尼作用24 h后行X线照射。两株细胞不同分组细胞,采用克隆形成实验检测放射敏感度,免疫荧光激光共聚焦显微镜观察X线照射后不同时间点细胞核中磷酸化H2AX（γ-H2AX）亮点在细胞中的定位情况,Western blot法检测放疗后胞质胞核蛋白中EGFR的表达。结果 克隆形成实验中,A549细胞X线+吉非替尼组在各放疗剂量点的SF2值（0.3475）低于单纯X线组（0.4833）;H1975细胞X线+吉非替尼组与单纯X线组在各放疗剂量点的SF2值分别为0.3094和0.3207,无明显差异。免疫荧光结果显示,照射4 Gy后各时间点X线+吉非替尼组A549细胞核中γ-H2AX亮点相比单纯X线多;单纯X线组和X线+吉非替尼组H1975细胞γ-H2AX亮点在各时间点无明显差异; Western blot结果显示,A549细胞经4Gy照射后EGFR有入核现象,而预先经吉非替尼处理再接受4Gy照射,EGFR蛋白绝大部分位于细胞质内;H1975细胞,单纯X线组和X线+吉非替尼组EGFR蛋白均在细胞质中表达,胞核中几乎没有,且两组无明显差异。结论 吉非替尼能增加肺癌细胞株A549的放射敏感度,可能与阻止放疗后EGFR入核进行双链断裂（double strand break,DSB）修复有关;对H1975细胞无影响,与其放疗后EGFR不入核相关。     

烟草烟雾通过ROS/Sirt3/SOD2通路诱导NSCLC细胞吉非替尼耐药

背景与目的 表皮生长因子受体(epidermal growth factor receptor, EGFR)基因突变是非小细胞肺癌(non-small cell lung cancer, NSCLC)最常见的驱动基因突变。为延长患者生存时间，NSCLC EGFR酪氨酸激酶抑制剂(tyrosine kinase inhibitors, TKIs)耐药是目前急需解决的重大难题。本研究主要探究烟草烟雾(cigaree smoke, CS)诱导NSCLC发生吉非替尼耐药的机制。方法 体外培养PC-9、A549细胞，分别经1μmol/L吉非替尼处理4 h、10%CS萃取物(CS extract, CSE)处理48 h。Western blot检测沉默蛋白3(Sirtuin 3, Sirt3)、超氧化物歧化酶2(superoxide dismutase 2, SOD2)蛋白表达，使用DCFH-DA探针检测细胞内活性氧(reactive oxygen species, ROS)水平，CCK-8试剂盒检测细胞活性，Ed U检测细胞增殖能力。Sirt3过表达质粒(OV-Sirt3)转染于PC-9和A54...     

BIM induction of apoptosis triggered by EGFR-sensitive and resistance cell lines of non-small-cell lung cancer

We sought to improve the understanding of oncogene-dependent and independent non-small-cell lung cancer (NSCLC), which could provide insight into mechanism of sensitivity and/or resistance to tyrosine kinase inhibitors or chemotherapeutics. NSCLC cell lines with different EGFR genotypes were used in this study; MTT assay and flow cytometry were applied to study the sensitivities of these cell lines to gefitinib and cisplatin. Western blot was performed to determine the expression levels of BIM and other Bcl-2 family proteins pre- and pro-treatment. Gefitinib provoked apoptosis of caspase activation via the intrinsic pathways and significantly up-regulated expression of BIM protein in drug-sensitive PC-9 cell line, but not resistant PC-9/BB4 cell line. The knockdown of BIM expression by RNA interference virtually eliminated gefitinib-induced cell killing in PC-9 cells in vitro. Cisplatin could induce apoptosis of the cell lines, including H1299, A549, PC-9, and PC-9/BB4 cells, but which was not associated with overexpression of BIM. BIM is involved in TKI-induced apoptosis in sensitive EGFR-mutant cell line. Down-regulation of BIM and resistance to gefitinib were both seen in the acquired resistant PC-9/BB4 cell line. The induction of BIM may have a role in the treatment of TKI-resistant tumors.     

SU11274逆转肝细胞生长因子诱导不同EGFR基因型非小细胞肺癌细胞株对吉非替尼耐药

背景与目的：肝细胞生长因子(hepatocyte growth factor,HGF)诱导敏感非小细胞肺癌(nonsmall cell lung cancer,NSCLC)细胞对表皮生长因子受体酪氨酸激酶抑制剂(epidermal growth factor receptor-tyrosine kinase inhibitor,EGFR-TKI)耐药,其机制与c-Met激活有关。本研究探讨c-Met抑制剂SU11274逆转HGF诱导的不同EGFR基因型NSCLC细胞株对吉非替尼耐药及逆转耐药机制。方法：选择人NSCLC细胞株PC9(EGFR突变型)、H292(EGFR野生型)和A549(EGFR野生型),应用吉非替尼和SU11274单独或联合作用于HGF诱导的细胞株。实验分为6组：C组(不加药对照组)、H组(HGF处理组)、G组(吉非替尼处理组)、S(SU11274处理组)、HG组(HGF+吉非替尼处理组)和HGS组(HGF+吉非替尼+SU11274处理组)。MTT法检测对细胞增殖的影响,流式细胞术检测细胞凋亡的影响;应用蛋白质印迹法(Western blot)检测细胞中c-Met及其下游通道Stat3、Akt和Erk1/2蛋白表达水平。结果：吉非替尼对3种细胞的生长抑制作用均呈浓度依赖性,HGF处理能够缓解吉非替尼的增殖抑制作用(P<0.05);不同浓度吉非替尼联合SU11274作用于HGF诱导细胞时,3种细胞株存活率比吉非替尼单独作用于HGF诱导细胞时明显降低(P<0.05);HGS组的细胞凋亡比HG组明显增加(P<0.05);HGS组的c-Met、Stat3、Akt和Erk1/2活化蛋白量比HG组明显减少。结论：c-Met抑制剂SU11274可逆转HGF诱导的不同EGFR基因型NSCLC细胞株对吉非替尼耐药,其机制可能与抑制HGF活化的c-Met及其下游通道蛋白表达有关。     

Combined inhibition of IGFR enhances the effects of gefitinib in H1650: a lung cancer cell line with EGFR mutation and primary resistance to EGFR-TK inhibitors

Purpose

H1650 non-small cell lung cancer (NSCLC) cells display primary resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) although they have a deletion mutation on exon 19 of the EGFR gene. We investigated the effect of inhibition of both insulin-like growth factor receptor (IGFR) and EGFR signaling considering that IGFR signaling pathway has been implicated in the development and progression with therapeutic resistance of various cancers including lung cancer.

Methods

Three human NSCLC cell lines with an EGFR mutation of PC-9, HCC827 and H1650 were used for experiment. Cell viability and proliferative activity were assessed by MTT and three-dimensional culture assay. Combination index was obtained by CalcuSyn software. The change of EGFR- and IGFR-related signals was evaluated by western blots.

Results

H1650 cells were 1,000 times more resistant to gefitinib and erlotinib than HCC827 and PC-9 cells possessing the same EGFR mutation. Phosphatase and tensin homolog loss and sustained phosphorylation of Akt in spite of treatment with gefitinib were evident only in H1650 cells. Interestingly, IGFR phosphorylation was decreased by gefitinib in HCC827 and PC-9 cells while being maintained in H1650 cells. Combined treatment with the IGFR inhibitors α-IR3 and AG1024 enhanced gefitinib-induced growth inhibition and apoptosis, and down-regulated phosphorylation of Akt, EGFR and IGFR.

Conclusion

Combined inhibition of IGFR signaling enhances the growth inhibitory and apoptosis-inducing effects of gefitinib, suggesting that this approach could be useful to overcome the primary resistance to EGFR-TKIs in lung cancer.     

MicroRNA-145增强非小细胞肺癌细胞对吉非替尼敏感性及其机制探讨

目的:探讨微小RNA-145（microRNA-145,miR-145）对非小细胞肺癌细胞系吉非替尼耐药的作用及其可能的潜在机制。方法:实时荧光定量PCR（Q-PCR）方法检测正常细胞及非小细胞肺癌细胞中miR-145的表达差异;不同时间5 μmol/L吉非替尼干预肺癌细胞SPC-A-1和A549后,Q-PCR检测miR-145表达变化;miR-145 mimics和miR-145 inhibitors分别转染SPC-A-1和A549肺癌细胞后,CCK8检测细胞活力变化;双荧光素酶报告系统检测miR-145与ADAM19的靶向结合;miR-145 mimics转染SPC-A-1和A549肺癌细胞,Western blot检测ADAM19蛋白表达;Western blot检测5 μmol/L吉非替尼干预后,SPC-A-1和A549肺癌细胞中ADAM19蛋白的表达;miR-145 mimics转染SPC-A-1和A549肺癌细胞,再用5 μmol/L吉非替尼干预,Western blot检测ADAM19蛋白的表达;采用siRNA抑制ADAM19表达,再用5 μmol/L吉非替尼干预,CCK8检测细胞活力;采用BALB/C雌性裸鼠皮下接种肿瘤细胞的方法,观察上述效应。结果:Q-PCR结果显示,与正常肺上皮细胞系BEAS-2B相比较,肺癌细胞SPC-A-1和A549中miR-145表达明显降低;5 μmol/L吉非替尼干预SPC-A-1和A549细胞后,miR-145表达显著上调;转染miR-145 mimics后,CCK8结果显示两种细胞细胞活力下降;双荧光素酶报告系统结果显示,miR-145靶向结合ADAM19基因的3'-UTR区;Western blot结果显示,5 μmol/L吉非替尼诱导SPC-A-1和 A549细胞后,两种细胞中ADAM19蛋白表达均降低;miR-145 mimics转染SPC-A-1和A549细胞,之后给予5 μmol/L吉非替尼治疗,ADAM19蛋白表达下调;siRNA抑制SPC-A-1和A549细胞中ADAM19表达,再给予5 μmol/L吉非替尼治疗,CCK8结果显示,两种细胞的细胞活力显著降低;过表达BALB/C雌性裸鼠的miR-145后,显著抑制皮下肿瘤生长,并且增强吉非替尼的抗肿瘤效果。结论:miR-145显著增强肺癌细胞SPC-A-1和A549对吉非替尼的敏感性,其机制可能是通过靶向结合AMDM19基因的3'-UTR区域,从而抑制其表达。miR-145有可能成为治疗非小细胞肺癌吉非替尼耐药的有效靶点。     

miR-148a 靶向HMGB3抑制非小细胞肺癌细胞迁移、侵袭和增强顺铂抗肿瘤效应的机制研究

目的:探讨miR-148a靶向HMGB3抑制非小细胞肺癌细胞迁移和侵袭的作用机制。方法:采用RT-qPCR和Western blot检测非小细胞肺癌组织和癌旁组织标本中miR-148a和HMGB3相对表达水平;以A549、H1299细胞为研究对象,Transwell和MTT法分别检测过表达miR-148a、敲低HMGB3和DDP干预对细胞迁移、侵袭及细胞活力的影响;TargetScan在线预测、双荧光素酶报告基因实验和Western blot验证miR-148a与HMGB3的靶向关系;miR-148a过表达或敲减HMGB3并联合DDP,Transwell和MTT法检测细胞迁移、侵袭和细胞活力。结果:非小细胞癌组织中miRNA-148a表达明显下调（P<0.05）,HMGB3在mRNA和蛋白水平表达均明显上调（P<0.05）,miR-148a与HMGB3表达呈负相关（r=-0.856 8,P<0.000 1）;过表达miR-148a或敲低HMGB3能明显抑制细胞迁移和侵袭（P<0.05）,过表达miR-148a或敲低HMGB3联合DDP干预,细胞活力明显下降（P<0.05）;TargetScan在线预测、双荧光素酶报告基因实验和Western blot检测表明miR-148a能调控HMGB3表达。结论:miR-148a在非小细胞肺癌组织中表达下调,HMGB3是miR-148a的靶基因,过表达miR-148a能抑制HMGB3表达从而抑制非小细胞肺癌细胞A549、H1299迁移和侵袭并增强顺铂抗肿瘤效应。     

Establishment of a human non-small cell lung cancer cell line resistant to gefitinib

The epidermal growth factor receptor (EGFR) tyrosine-kinase inhibitor gefitinib (Iressa, ZD1839) has shown promising activity preclinically and clinically. Because comparative investigations of drug-resistant sublines with their parental cells are useful approaches to identifying the mechanism of gefitinib resistance and select factors that determine sensitivity to gefitinib, we established a human non-small cell lung carcinoma subline (PC-9/ZD) that is resistant to gefitinib. PC-9/ZD cells are approximately 180-fold more resistant to gefitinib than their parental PC-9 cells and PC-9/ZD cells do not exhibit cross-resistance to conventional anticancer agents or other tyrosine kinase inhibitors, except AG-1478, a specific inhibitor of EGFR. PC-9/ZD cells also display significant resistance to gefitinib in a tumor-bearing animal model. To elucidate the mechanism of resistance, we characterized PC-9/ZD cells. The basal level of EGFR in PC-9 and PC-9/ZD cells was comparable. A deletion mutation was identified within the kinase domain of EGFR in both PC-9 and PC-9/ZD, but no difference in the sequence of EGFR cDNA was detected in either cell line. Increased EGFR/HER2 (and EGFR/HER3) heterodimer formations were demonstrated in PC-9/ZD cells by chemical cross-linking and immunoprecipitation analysis in cells unexposed to gefitinib. Exposure to gefitinib increased heterodimer formation in PC-9 cells, but not in PC-9/ZD cells. Gefitinib inhibits EGFR autophosphorylation in a dose-dependent manner in PC-9 cells but not in PC-9/ZD cells. A marked difference in inhibition of site-specific phosphorylation of EGFR was observed at Tyr1068 compared to other tyrosine residues (Tyr845, 992 and 1045). To elucidate the downstream signaling in the PC9/ZD cellular machinery, complex formation between EGFR and its adaptor proteins GRB2, SOS, and Shc was examined. A marked reduction in the GRB2-EGFR complex and absence of SOS-EGFR were observed in PC-9/ZD cells, even though the protein levels of GRB2 and SOS in PC-9 and PC-9/ZD cells were comparable. Expression of phosphorylated AKT was increased in PC-9 cells and inhibited by 0.02 microM gefitinib. But the inhibition was not significant in PC-9/ZD cells. These results suggest that alterations of adaptor-protein-mediated signal transduction from EGFR to AKT is a possible mechanism of the resistance to gefitinib in PC-9/ZD cells. These phenotypes including EGFR-SOS complex and heterodimer formation of HER family members are potential biomarkers for predicting resistance to gefitinib.     

沉默CXCR4的表达逆转肺癌细胞顺铂耐药

目的:探讨沉默CXCR4对肺癌细胞顺铂耐药的影响,并研究其分子作用机制。方法:利用RT-qPCR测定肺癌耐药（A549/DDP）及药物敏感细胞株（A549）中CXCR4 mRNA的表达水平;利用LipofectamineTM 2000将siRNA-CXCR4转染至肺癌耐药细胞株中,RT-qPCR及蛋白质印迹法（Western blot）验证siRNA对CXCR4基因的靶向沉默效率;利用CCK-8法检测沉默CXCR4后肺癌耐药细胞的增殖活性;利用流式细胞仪测定沉默CXCR4后肺癌耐药细胞的凋亡率;利用MTT法测定沉默CXCR4后肺癌耐药细胞对顺铂的敏感性;利用Western blot实验测定沉默CXCR4后CYP1B1蛋白的表达水平。结果:RT-qPCR实验结果显示,肺癌耐药细胞株A549/DDP中CXCR4 mRNA的表达量显著高于药物敏感细胞株（P＜0.01）;体外转染siRNA-CXCR4可明显下调A549/DDP细胞株中CXCR4的表达（P＜0.001）;CCK-8实验结果显示,沉默CXCR4的表达抑制了A549/DDP细胞的增殖活性（P＜0.01）;流式细胞仪实验结果显示,沉默CXCR4的表达促进了A549/DDP细胞凋亡（P＜0.01）;MTT实验结果显示,沉默CXCR4的表达增加了A549/DDP细胞对顺铂的敏感性（P＜0.01）;Western blot实验结果显示,沉默CXCR4后CYP1B1蛋白的表达水平显著降低（P＜0.05）。结论:沉默CXCR4的表达抑制肺癌耐药细胞增殖、促进凋亡,逆转肺癌细胞顺铂耐药,CXCR4正向调控CYP1B1的表达,可能是CXCR4逆转肺癌细胞顺铂耐药的作用机制。