The correlation between the expression of multidruc resistance related gene and cell apoptosis and clinical significance in non-small cell lung cancer

Objective: To explore the correlation and clinical significance between expression of MDR (multidrug resistance) related gene MRP, MDR₁, C-erbB-2 and cell apoptosis in non-small cell lung cancer (NSCLC). Methods: RT-PCR, Immunohistochemistry were used to examine the expression of mRNA and protein in the MDR and apoptosis related gene. Apoptosis cells were assayed by Terminal deoxynucleotidyl transferase (TdT)- mediated biotin dUTP nick end-labeling (TUNEL). Results: The positive rates of MRP, MDR₁, C-erbB-2, bcl-2, C-myc mRNA in 63 cases NSCLC were 81.0% (51/63), 38.1%(24/63), 47.6%(30/63), 65.1% (41/63), 76.2% (48/63) respectively. Their levels were higher than those of corresponding proteins (74.6%, 34.9%, 46.0%, 61.9%, 71.4%, respectively). The significant association was found between the mRNA level and the protein expression (r=+0.764,P<0.02). The C-myc expression in 2 cases adjacent and benign lung tissue were light positive, and another 3 cases were negative. The positive correlation were demonstrated between C-myc and C-erbB-2 (r=+0.547, p=0.001) as well as bcl-2 and C-erbB-2 (r=+0.486, p=0.023) in NSCLC. There is no any correlation among bcl-2, C-myc and MRP or MDRI. There exists inverse correlation between apoptotic index and bcl-2 (r=−0.587, p=0.017), and no any correlation among apoptotic index and MRP or MDRI or C-erbB-2 or C-myc. The average apoptotic index were higher in the effective chemotherapy group (27.2±2.1, 30.5±1.8) than that in the non-effective chemotherapy group (9.4±1.3, 12.6±2.4) with adenocarcinoma and squamous cell carcinoma (p=0.01, p=0.004). The positive rates of bcl-2, MRP, C-erbB-2 expression in the effective chemotherapy group (31.8%, 40.9%, 22.7%, respectively) were lower than those in the non-effective chemotherapy group (77.4%, 90.3%, 67.7%, respectively) (p=0.036, p=0.012, p=0.01), but MDR₁ and C-myc expression have no any significant difference (p=0.067, p=0.282). The median survival time in the patients with coexpression of more than three MDR and/or apoptosis related genes are shorter (8.6 months) than that in those patients with coexpression of less than three MDR and/or apoptosis related genes (15.5 months)(p=0.01). Conclusion: The multidrug resistance in NSCLC is not only related to many drug resistance genes, but also involved in cell apoptosis and apoptosis related gene expression. The coexpression of MDR and apoptosis related gene is related to the survival time. This work was supported by the Grant from Beijing Natural Science Foundation(No.7992005), and a Grant from Postdoctoral Foundation of National Committee of Education of China.     

多药耐药基因与细胞凋亡基因产物在非小细胞肺癌中的表达及其意义

 目的　检测非小细胞肺癌 (NSCLC)多药耐药相关基因及细胞凋亡基因的表达 ,探讨其表达的相关性及临床病理意义。方法　采用SP免疫组化法检测 113例NSCLC中多药耐药相关蛋白 (MRP)、谷胱甘肽巯基转移酶π(GST π)、肺耐药相关蛋白 (LRP)、突变型 p5 3和bcl 2的表达。 结果　NSCLC中MRP、GST π、LRP、p5 3和bcl 2的检出率分别为79.6 5 %、75 .2 2 %、80 .5 3%、6 1.95 %、5 9.2 9%。MRP、LRP和bcl 2的表达与组织学类型有关 (P <0 .0 5 )。p5 3与肿瘤细胞的分化程度有关 (P <0 .0 5 ) ,随着肿瘤细胞分化的恶性程度增加呈递增趋势。MRP与GST π、LRP表达之间 ,p5 3和bcl 2表达之间相关性有统计学意义 (P <0 .0 5 )。结论　不同组织学类型NSCLC的多药耐药性各不相同 ,且其耐药性之间还存在一定的相关性。检测NSCLC的多药耐药性有助于指导肺癌的化疗。     

急性白血病中MDR1 MRP和bc1-2基因表达及其临床意义

目的:研究多药耐药基因(MDR1)、多药耐药相关蛋白基因(MRP)和调控细胞凋亡有重要作用的基因(bcl-2)在急性白血病(AL)中的表达以及它们与临床耐药之间的关系。方法:采用地高辛掺入的半定量逆转录聚合酶链反应(RT-PCR)及常规RT-PCR方法检测了54例急性白血病患者和10例正常人骨髓单核细胞中基因的表达情况。结果:54例AL中MDR1/MRP/bcl-2三基因表达阳性率为16.7%(9/54),MDR1/MRP/bcl-2三基因表达均阴性,发生频率为46.3%(25/54)。46例资料完整的白血病患者中三基因表达均阴性者80.0%缓解(CR),MDR1/MRP或MDR1/MRP/bcl-2共表达者无1人CR(P<0.01)。单基因分析表明MDR1、MRP、bcl-2基因表达阳性率分别为28.3%、41.3%和47.8%,其中MDR1阳性者CR率7.7%,明显低于MDR1阴性者CR率72.7%(P<0.01);MRP阳性CR率21.1%,明显低于阴性CR率77.8%(P<0.01);bcl-2阳性CR率36.4%,亦低于阴性CR率70.8%(P<0.05)。结论:MDR1/MRP或MDR1/MRP/bcl-2共表达的患者不易获得CR,白血病患者的耐药除了与MDR1高表达密切相关外,还与非P-糖蛋白(P-gp)介导的MRP及bcl-2表达等因素相关。     

LRP,MRP,MDR1基因在非小细胞肺癌中的表达及其临床意义

目的 探讨肺耐药蛋白（ｌｕｎｇ ｒｅｓｉｓｔａｎｃｅ ｐｒｏｔｅｉｎ,ＬＲＰ）,多药耐药蛋白（ｍｕｌｔｉｄｒｕｇ ｒｅｓｉｓｔａｎｃｅａｓｓｏｃｉａｔｅｄ ｐｒｏｔｅｉｎ,ＭＲＰ）,和多药耐药基因（ｍｕｌｔｉｄｒｕｇ ｒｅｓｉｓｔａｎｅ,ＭＤＲ１）ｍＲＮＡ在非小细胞肺癌（ｎｏｎ－ｓｍａｌｌ ｃｅｌｌ ｃａｎｃｅｒ,ＮＳＣＬＣ）中的共表达及临床意义。方法 ＲＴ－ＰＣＲ检测ＮＳＣＬＣ冰冻组织中上述耐药     

流式细胞术检测急性白血病P-糖蛋白、多药耐药相关蛋白及bcl-2的临床意义

目的 研究急性白血病(AL)患者的P-糖蛋白(p170)、多药耐药相关蛋白(MRP)及bcl-2三种相关蛋白的表达情况,探讨其在AL患者多药耐药中的作用及相互关系.方法 AL患者44例,其中急性非淋巴细胞白血病(ANLL)29例,急性淋巴细胞白血病(ALL)15例,采用不同的化疗方案分别进行2个疗程的标准剂量化疗,按照治疗效果分为完全缓解(CR)组和诱导缓解失败(NR)组.选用12例同期就诊的健康人及良性血液病患者为对照,采用流式细胞术分别测定其p170、MRP、bcl-2的表达情况.结果 AL患者p170、MRP、bcl-2蛋白的表达均显著高于健康对照组,差异有统计学意义(P＜0.05).p170和MRP表达在各型白血病中CR组均低于NR组;NR组24例中22例至少有一或二种蛋白表达增高,且表达具有一定的一致性(P＜0.01).bcl-2的高表达与治疗反应差有关,CR组患者的bcl-2表达明显低于NR组(P＜0.05).结论 p170、MRP、bcl-2均与AL多药耐药的发生有关,是导致预后不良的重要因素.提示bcl-2导致耐药的机制不同于经典的p170途径.     

非小细胞肺癌中survivin、bcl-2和bax蛋白与多药耐药基因的表达及其相关性

目的检测非小细胞肺癌(NSCLC)中凋亡蛋白survivin、bcl2、bax与多药耐药有关基因MDR1mRNA和MRPmRNA的表达,探讨其相互关系及意义。方法选取113例NSCLC病例,采用原位分子杂交检测MDR1和MRP基因mRNA的表达,SP免疫组化法检测survivin、bcl2、bax蛋白的表达。结果113例NSCLC中,MDR1mRNA、MRPmRNA及survivin、bcl2、bax蛋白的检出率分别为51.3%、80.5%、79.6%、59.3%、54.9%。survivin和bax的表达与肿瘤分化程度有关(P<0.05),bcl2的表达与肿瘤组织学类型有关(P<0.01)。MDR1mRNA与MRPmRNA(P<0.01)、survivin与MDR1mRNA(P<0.05)、bcl2与MRPmRNA(P<0.05)表达之间存在明显相关性。结论凋亡抑制蛋白survivin的高表达和bcl2的过表达可能是导致NSCLC原发耐药的重要因素,检测survivin和bcl2对临床逆转NSCLC多药耐药性具有指导意义     

肺癌组织端粒酶表达与耐药,凋亡相关基因关系及其临床意义

目的 探讨肺癌冰冻组织端粒酶催化亚单位（ｃａｔａｌｙｔｉｃｐｒｏｔｅｉｎｓｕｂｕｎｉｔ，ｈＴＲＴ／ｈＥＳＴ２）编码基因ｍＲＮＡ表达与细胞凋亡，增殖，耐药及凋亡相关基因的关系及其预后意义方法 应用ＴＲＡＰ－ＰＣＲ，原位杂交检测端粒酶活性（ｔｅｌｏｍｅｒａｓｅａｃｔｉｖｉｔｙ，ＴＡ）及ｈＴＲＴ／ｈＥＳＴ２表达，ＲＴ－ＰＣＲ，免疫组化检测耐药及凋亡相关基因ｍＲＮＡ及蛋白水平，原位杯端标记（ｉｎｓｉｔｕｅ     

非小细胞肺癌CT与相关基因表达的研究

目的：研究非小细胞（ＮＳＣＬＣ）肺癌ＣＴ征象与肺癌相关基因ｐ５３,Ｃ－ｍｙｃ,Ｋ－ｒａｓ,及Ｃ－ｅｒｂＢ２表达间的关系。方法：运用免疫组化法,检测５４例经手术病理证实的非小细胞肺癌组织中的ｐ５３,Ｃ－ｍｙｃ,Ｋ－ｒａｓ及Ｃ－ｅｒｂＢ２基因的表达,并分析其与术前ＣＴ征象间的关系。结果：ｐ５３表达与非小细胞肺癌期别及ＣＴ征象中瘤体大小,深分叶征,毛刺征,空洞征,及纵隔淋巴结转移有关,但与组织类型胸,胸     

非小细胞肺癌组织p53和c-erbB2及MRP蛋白的表达

目的探讨癌组织p53、c-erbB2、MRP蛋白表达与非小细胞肺癌（NSCLC）临床病理特征的关系及其预后评估意义。方法应用免疫组织化学方法检测NSCLC患者的肺组织切除标本p53、c-erbB2、MRP蛋白表达,并与其临床病理参数进行比较分析。结果NSCLC组织p53、c-erbB2、MRP蛋白表达阳性率分别为53.9%（82/152）、44.1%（67/152）及43.4%（66/152）。p53表达与性别、细胞分化程度、临床分期、淋巴结转移有显著关系（P〈0.05）,而c-erbB2与各因素间无统计学差异,肺腺癌MRP蛋白表达阳性率（67.6%）明显高于肺鳞癌（33.0%）,有统计学差异（P〈0.05）。癌组织p53、c-erbB2、MRP 3种蛋白表达均阳性者的1、2、3年生存率明显低于均阴性者（分别P=0.02、0.01和0.00）,p53、c-erbB2、MRP蛋白表达阳性者单纯手术后生存率也明显低于阴性者（P〈0.05）;p53、c-erbB2、MRP 3种蛋白表达均阴性者预后最好,1-2种阳性者次之,3种均阳性者预后最差（P〈0.05）。术后辅助化疗组MRP、c-erbB2蛋白表达阳性者的生存率低于阴性者（P〈0.01）,但p53蛋白表达阳性与阴性患者的生存率无统计学差异（P=0.82）;MRP与c-erbB2表达双阴性者生存率显著高于双阳性者,MRP或c-erbB2单一阳性的生存率介于前两者之间（P=0.01）。多因素Cox分析显示细胞分化程度、c-erbB2是影响NSCLC患者疗效和预后的独立预测因子。结论肿瘤组织p53、c-erbB2、MRP 3种蛋白同时高表达的NSCLC病例预后较差。术后检测p53、c-erbB2、MRP表达对评估可手术NSCLC患者疗效和预后有一定意义。     

耐药相关基因表达对Ⅲ期非小细胞肺癌新辅助化疗的临床预测价值探讨

背景与目的P-糖蛋白(P-glycoprotein,P-gp)、多药耐药相关蛋白(multidrugresistance-associatedprotein,MRP)、肺耐药蛋白(lungresistanceprotein,LRP)在多药耐药中发挥重要的作用,联合检测它们在评价非小细胞肺癌新辅助化疗中的价值国内外尚未见报道。本研究旨在探讨联合检测P-gp、MRP、LRP对Ⅲ期非小细胞肺癌新辅助化疗敏感性的预测价值。方法应用免疫组化技术检测31例行新辅助化疗的患者化疗前标本及化疗后手术标本。结果化疗前P-gp、MRP、LRP表达的阳性率分别为29.0%(9/31)、45.2%(14/31)及38.7%(12/31),化疗后分别为61.3%(19/31)、51.6%(16/31)及41.9%(13/31)。化疗前MRP和LRP同时阳性者32.3%(10/31),MRP与LRP具相关性(r=0.61,P<0.001)。化疗前P-gp、MRP、LRP表达阳性者化疗有效率分别为44.4%(4/9)、28.6%(4/14)及16.7%(2/12),MRP与LRP同时阳性者有效率为10.0%(1/10)。化疗有效的患者中位生存期为31个月,无效的为15个月,同期直接手术的患者为18个月。结论肿瘤中MRP与LRP共表达者化疗耐药的可能性很大,化疗有效率较低,新辅助化疗意义不大。     

非小细胞肺癌耐药相关基因表达与细胞凋亡相关性及其临床意义

目的探讨非小细胞肺癌（Non－Small CellLung Cancer,NSCLC）多种耐药相关基因MRP、MDR1、c－erbB－2表达与细胞凋亡及相关基因bc1－2、c－myc的关系与意义。方法RT－PCR、免疫组化分析多种耐药、凋亡相关基因mRNA及蛋白表达,原位末端标记Terminaldeoxynucleotidyltransferase（TdT）－mediatedbiotind UT Pnickend－labeling,TUNEL检测凋亡细胞。结果63例NSCLCMRP、MDR1、c－erbB－2、bc1－2、c－mycmRNA阳性率分别为81．0％（51／63）、38．1％（24／63）、47．6％（30／63）、65．1％（41／63）、76．2％（48／63）,均高于相应的蛋白表达水平（分别为74．6％、34．9％、46．0％、61．9％、71．4％）,二者具高度相关性（相关系数r＝＋0．76以上,P＜0．02）,5例癌旁组织仅2例c－myc弱阳性,余皆阴性。c－myc、bc1－2与c－erbB－2呈正相关（r＝＋0．54,P＝0．001,r＝＋0．48,P＝0．023）,与MRP、MDR1无相关性。凋亡指数与bc1－2负相关（r＝－0．58,P＝0．017）,与MRP、MDR1、c－erbB－2、c－myc无相关性;腺癌及鳞癌化疗有效组凋亡指数均数（27．2±2．1,30．5±1．8）高于化疗无效组（9．4±1．3,12．6±2．4）（P＝0．001,P＝0．004）,bcl－2、MRP、c－erbB－2阳性率（31．8％,40．9％,22．9％）低于化疗无效组（77．4％,90．3％,67．5％）（P＝0．03,P＝0．01,P＝0．01）,但两组间MDR1、c－myc表达无显著差异（P＝0．06,P＝0．28）。三种以上耐药及凋亡相关基因共表达者中位生存期（8．6个月）明显短于3种以下共表达者（15．5个月）（P＝0．01）。结论NSCLC耐药不仅与多种耐药基因有关,亦涉及细胞凋亡及其相关基因表达,多种耐药及凋亡相关基因共表达与生存期有关。     

联合检测MDR1/P-gp、C-erbB-2在乳腺癌中的表达及临床意义

目的 :联合检测乳腺癌患者中MDR1/P gp、及C erbB 2的表达 ,并探讨MDR1/P gp与C erbB 2的相关性。方法 :采用荧光定量RT PCR(FQ RT PCR)法检测 5 7例乳腺癌、2 0例对照组 (包括 10例乳腺良性疾病、10例癌旁正常组织 )中MDR1基因的表达 ,同时采用免疫组化法检测上述标本中P gp及C erbB 2蛋白的表达。 结果 :乳腺癌患者中MDR1基因扩增率及P gp蛋白阳性率分别为 5 0 .88% (2 9/ 5 7)和 4 2 .11% (2 4 / 5 7) ,与正常对照组相比均具有显著性差异 (P <0 .0 1)。MDR1基因扩增率高于P gp蛋白表达 ,二者呈高度相关 ,但并不完全相符 ;乳腺癌中C erbB 2过表达率为 2 8.0 7% (16 / 5 7) ,正常对照组中无C erbB 2蛋白过表达。MDR1/P gp阳性率与C erbB 2过表达呈正相关。结论 :乳腺癌中存在多药耐药基因MDR1及原癌基因C erbB 2的共表达 ,且其表达呈正相关。上述二种基因的表达 ,与乳腺癌的多药耐药有关。     

非小细胞肺癌中多药耐药基因的表达及意义

目的:探讨多药耐药基因(MDR1)和多药耐药相关蛋白基因(MRP)在非小细胞肺癌(NSCLC)中的表达、意义及相关关系.方法:采用原位分子杂交对113例NSCLC组织中MDR1和MRP基因mRNA的表达进行检测.结果:MDR1和MRP基因mRNA在NSCLC组织中的阳性表达率分别为51.3%(58/113)、80.5%(91/113),二者与NSCLC肿瘤组织类型、分化程度、淋巴结转移、TNM分期等无关(P＞0.05).MDR1和MRP的协同阳性(MDR1 /MRP )表达率为48.7%(55/113),二者在NSCLC中的表达之间存在明显相关(P＜0.01).结论:MDR1和MRP是NSCLC原发性多药耐药的重要参与因素,二者联合检测对临床NSCLC的化疗具有指导意义.     

多基因蛋白表达判断早期非小细胞肺癌术后化疗疗效的价值

目的 探讨多基因蛋白表达联合检查判断早期非小细胞肺癌(NSCLC)术后化疗疗效的价值.方法 采用组织芯片与免疫组织化学技术(二步法)相结合的方法,义寸86例NSCLC组织中caspase-3、Fas、bax、bcl-2,survivin,PCNA,Ki67,MGMT,p53,063,p73,p16、p27,VEGF、nm23、P-gP、MRP、LRP、GST-π、TopoⅡ、c-myc、cyclin D1、Her-2、Cox-2、Ku70、Ku80、DNA-PKcs、ERCCI、MSH2和BCRP等30种化疗相关蛋白进行检测,并分析其表达与早期NSCLC术后化疗疗效的关糸.结果 30种化疗相关蛋白在肺癌组织中的表达阳性率在27 9%～91.9%间.经过单因素分析,与早期NSCLC术后化疗效果密切相关的基因有8个,即survivin、P-gp、LRP、Ki67、p53、ERCC1高表达和bax、VEGF低表达的NSCLC患者术后化疗效果差.通过Logistic回归分析显示,ERCC1、survivin、bax和VEGF等4个基因联合检测对早期NSCLC术后化疗疗效的预测特异度达96.5%.结论 ERCC1、survivin、bax和VEGF是一组判断早期NSCLC术后辅助化疗效果、指导早期NSCLC的术后治疗的分子指标.     

In vitro and in vivo downregulation of MRP1 by antisense oligonucleotides: a potential role in neuroblastoma therapy

The expression of MRP1 (multidrug resistance protein-1) is associated with chemoresistance and poor prognosis in neuroblastoma. MRP1 antisense oligonucleotides were used in an in vivo mouse-human xenograft model of neuroblastoma to downregulate MRP1. The MRP1 ASO reduced protein levels of MRP1 to an average of 40% of the nil treated controls (p = 0.007). There was significant chemosensitisation to single-agent chemotherapy, VP16 (etoposide), at 1 microg/mL (p = 0.035) and 10 microg/mL (p = 0.02) in comparison to tumours not receiving oligonucleotides. In contrast, MDR1-ASO produced significant chemosensitisation only at 10 microg/mL of VP16 (p = 0.029). No significant chemosensitisation was seen following nonsense oligonucleotides. The downregulation of MRP1 was also associated with an increase in tumour cell death (79% increase in apoptosis index p = 0.0313) and a reduction in cell turnover (42% reduction in mitotic index p = 0.0313), which was not seen with any other oligonucleotide. This new and novel perspective of MRP1 function, which is an apparent involvement in apoptosis and cell cycle progression in neuroblasts, presents a fresh avenue for investigation of the biologic consequences of MRP1 expression that occurs in many tumour cell types. Our work is the first to concurrently explore the effects of downregulation of MRP1 and MDR1 by antisense oligonucleotides in a neuroblastoma xenograft model. It provides rationale for the investigation of therapy adjuvants such as antisense oligonucleotides in the treatment of this malignancy.     

Immunohistochemical expression of multidrug resistance proteins as a predictor of poor response to chemotherapy and prognosis in patients with nodal diffuse large B-cell lymphoma

BACKGROUND/AIMS: The aim of this study was to determine whether expression of P-glycoprotein (P-gp), multidrug-resistance-related protein 1 (MRP1), and lung resistance protein (LRP) was related to the response to induction chemotherapy and prognosis in untreated diffuse large B-cell lymphoma (DLBCL). METHODS: We assessed immunohistochemical expression of P-gp, MRP1 and LRP, using formalin-fixed and paraffin-embedded specimens of lymph node in 41 patients with DLBCL. Association between expression of these three proteins and their impact on clinical outcome and prognosis was statistically evaluated. RESULTS: P-gp was positive in 37% of subjects, MRP1 in 63%, and LRP in 68%. The complete remission rates achieved in the group expressing these multidrug resistance (MDR) proteins was significantly lower than in the group not expressing them (20 versus 58%; p = 0.025 in P-gp, 23 versus 80%; p < 0.001 in MRP1 and 32 versus 69%, p = 0.043 in LRP, respectively). Furthermore, the patients expressing LRP had a shorter overall survival rate than those that did not (median of 26 months versus median not reached; p = 0.013). CONCLUSIONS: These findings suggest that the three MDR proteins are important predictive factors for the clinical outcome and prognosis in patients with DLBCL.     

Survivin、MDR1、MRP在非小细胞肺癌中的表达及意义(英文)

Objective:To investigate the expressions and significance of Survivin,MDR1 and MRP in non-small cell lung cancer(NSCLC).Methods:Immunohistochemical staining was used to detect the expressions of Survivin,MDR1 and MRP.The correlation between the results was assessed and the impact of Survivin on prognoses was also examined.Results:Survivin was expressed in 78% tissues from NSCLC patients but not found in tissues from control patients(P < 0.05).The expression of Survivin was related to the tissue differentiation stage and lymph nodes metastasis of lung cancer.The mean survival time was shorter in patients with Survivin-expression than those who not.There was a significant correlation between MDR1 and Survivin(P < 0.05),whereas no close correlation was found between MRP and Survivin.Conclusion:(1) Survivin is of critical importance in the development of NSCLC,thus may provide an novel therapeutic target for lung cancer;(2) MDR1 and MRP present in tissues from lung cancer synergistically with Survivin,which might be involved in tumour resistance.     

Survivin、MDR1、MRP在非小细胞肺痛中的表达及意义

Objective: To investigate the expressions and significance of Survivin, MDR1 and MRP in non-small cell lung cancer (NSCLC). Methods: Immunohistochemical staining was used to detect the expressions of Survivin, MDR1 and MRP. The correlation between the results was assessed and the impact of Survivin on prognoses was also examined. Results: Survivin was expressed in 78% tissues from NSCLC patients but not found in tissues from control patients (P < 0.05). The expression of Survivin was related to the tissue differentiation stage and lymph nodes metastasis of lung cancer. The mean survival time was shorter in patients with Survivin-expression than those who not. There was a significant correlation between MDR1 and Survivin (P < 0.05), whereas no close correlation was found between MRP and Survivin. Conclusion: (1) Survivin is of critical importance in the development of NSCLC, thus may provide an novel therapeutic target for lung cancer; (2) MDR1 and MRP present in tissues from lung cancer synergistically with Survivin, which might be involved in tumour resistance.