The molecular evolution of acquired resistance to targeted EGFR blockade in colorectal cancers

Colorectal tumours that are wild type for KRAS are often sensitive to EGFR blockade, but almost always develop resistance within several months of initiating therapy. The mechanisms underlying this acquired resistance to anti-EGFR antibodies are largely unknown. This situation is in marked contrast to that of small-molecule targeted agents, such as inhibitors of ABL, EGFR, BRAF and MEK, in which mutations in the genes encoding the protein targets render the tumours resistant to the effects of the drugs. The simplest hypothesis to account for the development of resistance to EGFR blockade is that rare cells with KRAS mutations pre-exist at low levels in tumours with ostensibly wild-type KRAS genes. Although this hypothesis would seem readily testable, there is no evidence in pre-clinical models to support it, nor is there data from patients. To test this hypothesis, we determined whether mutant KRAS DNA could be detected in the circulation of 28 patients receiving monotherapy with panitumumab, a therapeutic anti-EGFR antibody. We found that 9 out of 24 (38%) patients whose tumours were initially KRAS wild type developed detectable mutations in KRAS in their sera, three of which developed multiple different KRAS mutations. The appearance of these mutations was very consistent, generally occurring between 5 and 6 months following treatment. Mathematical modelling indicated that the mutations were present in expanded subclones before the initiation of panitumumab treatment. These results suggest that the emergence of KRAS mutations is a mediator of acquired resistance to EGFR blockade and that these mutations can be detected in a non-invasive manner. They explain why solid tumours develop resistance to targeted therapies in a highly reproducible fashion.     

Multiplex detection of KRAS and BRAF mutations using cationic conjugated polymers

The mutation detections of KRAS and BRAF genes are of significant importance to predict the responses to anti-cancer therapy and develop new drugs. In this paper, we developed a multi-step fluorescence resonance energy transfer (FRET) assay for multiplex detection of KRAS and BRAF mutations using cationic conjugated polymers (CCP). The newly established detection system could detect as low as 2% mutant DNAs in DNA admixtures. By triggering the emission intensity change of CCP and the dyes labeled in the DNA, four possible statuses (three mutations and one wildtype) can be differentiated in one extension reaction. The detection efficiency of this new method in clinical molecular diagnosis was validated by determining KRAS and BRAF mutations of 51 formalin-fixed paraffin-embedded (FFPE) ovary tissue samples. Furthermore, the result of the CCP-based multi-step FRET assay can be directly visualized under UV light so that no expensive instruments and technical expertise are needed. Thus, the assay provides a sensitive, reliable, cost-effective and simple method for the detection of disease-related gene mutations.     

Prevalence of ras gene mutations in human colorectal cancers

A combination of DNA hybridization analyses and tissue sectioning techniques demonstrate that ras gene mutations occur in over a third of human colorectal cancers, that most of the mutations are at codon 12 of the c-Ki-ras gene and that the mutations usually precede the development of malignancy.     

新基因SNC 66在大肠癌组织中的表达研究

为探讨大肠癌相关新基因SNC66在大肠癌中的表达以及该基因与大肠癌发生的相互关系，分别采用常规RT—PCR和组织原位RT—PCR方法，以β-actin为对照，对SNC66在大肠癌组织和正常大肠粘膜中的表达情况作了配对研究。结果显示，SNC66在大肠癌组织中的表达显著低于其在大肠粘膜中的表达；粘膜组织中，SNC66只在上皮细胞和淋巴细胞中有表达，在其他细胞中未见表达，研究表明SNC66可能是一个新的大肠癌抑癌基因，SNC66基因表达水平的降低可能与大肠癌的发生和发展有关。     

结直肠癌相关的多基因研究

序贯发生的基因突变是结直肠癌多步骤演进的重要推动力。着重介绍参与结直肠癌发生、发展的原癌基因(ras)、抑癌基因(APC、DCC、p53)、转移抑制基因(nm23)等,其中任一基因的改变都可能会引起癌症的发生或转移。研究结直肠癌发生发展的相关基因不仅可以辅助临床诊断,而且以基因及其不同产物作为靶点的生物治疗方式将成为未来有效的干预措施。     

Synergistic response to oncogenic mutations defines gene class critical to cancer phenotype

Understanding the molecular underpinnings of cancer is of critical importance to the development of targeted intervention strategies. Identification of such targets, however, is notoriously difficult and unpredictable. Malignant cell transformation requires the cooperation of a few oncogenic mutations that cause substantial reorganization of many cell features and induce complex changes in gene expression patterns. Genes critical to this multifaceted cellular phenotype have therefore only been identified after signalling pathway analysis or on an ad hoc basis. Our observations that cell transformation by cooperating oncogenic lesions depends on synergistic modulation of downstream signalling circuitry suggest that malignant transformation is a highly cooperative process, involving synergy at multiple levels of regulation, including gene expression. Here we show that a large proportion of genes controlled synergistically by loss-of-function p53 and Ras activation are critical to the malignant state of murine and human colon cells. Notably, 14 out of 24 'cooperation response genes' were found to contribute to tumour formation in gene perturbation experiments. In contrast, only 1 in 14 perturbations of the genes responding in a non-synergistic manner had a similar effect. Synergistic control of gene expression by oncogenic mutations thus emerges as an underlying key to malignancy, and provides an attractive rationale for identifying intervention targets in gene networks downstream of oncogenic gain- and loss-of-function mutations.     

有氧运动对肺腺癌吉非替尼获得性耐药的影响

目的:分析不同强度有氧运动对肺腺癌吉非替尼获得性耐药的影响,并探讨其潜在机制及临床意义.方法:建立由吉非替尼诱导的肺腺癌耐药细胞系PC-9-GR.通过ROS相关指标试剂盒、Western blot及流式细胞术检测亲本细胞系PC-9与耐药细胞系PC-9-GR中ROS相关指标、缺氧诱导因子1(HIF-1)与乙醛脱氢酶1(A...     

中国人结直肠癌患者碱基切割修复基因胚系突变及与腺瘤样息肉基因体细胞突变的关系研究

取42例经过病理确认的结直肠癌患者癌组织及癌旁正常组织,抽提基因组DNA,应用单链构象多态性分析(SSCP)、变性高效液相色谱(DHPLC)分析,结合DNA直接测序,在全基因分析humanmutY homologue(MYH)基因胚系突变的同时,探讨其对结直肠癌细胞adenomatous polyposis coli(APC)基因体细胞突变的影响.结果42例患者中检出6例(14.29%)携带MYH基因的胚系突变,其中3例(7.14%)为MYH基因第2外显子单体型突变c.53C>T/c.74G>A(p.Pro18Leu/p.Gly25 Asp),3例(7.14%)为第12外显子的单碱基替换导致的错义突变c.972G>C(p.Gln324His).初步分析显示,这两种突变在正常对照组的检出较低,仅为3/213(1.41%)和0/59(0%).另一方面4/6例携带MYH基因胚系突变患者的癌组织样本中检出5个APC基因体细胞突变.本文结果提示,散发性结直肠癌患者中频繁检出MYH基因的胚系突变,其存在可能导致细胞DNA氧化损伤修复功能减弱,并使机体细胞APC基因发生突变的风险增高,从而可能参与部分结直肠癌的发生.     

铁死亡调控机理及其在肿瘤治疗中的应用

铁死亡(ferroptosis)为最近鉴定出的一种新的细胞程序性死亡模式,越来越多证据表明铁死亡在肿瘤的发生发展中扮演了重要角色.综述了近年来铁死亡的调控机制研究进展,包括经典和非经典的铁死亡诱导过程、活性氧自由基(reactive oxygen species,ROS)及非编码RNA在铁死亡调控中的作用.论述了铁死亡...     

溶瘤病毒的肿瘤治疗作用研究

通过探讨几种溶瘤病毒包括溶瘤新城疫病毒、溶瘤单纯疱疹病毒、溶瘤腺病毒和溶瘤痘病毒等治疗肿瘤的作用,为溶瘤病毒应用于肿瘤治疗提供新的启示。     

Colorectal cancer: mutations in a signalling pathway

Protein kinases are enzymes that are important for controlling cellular growth and invasion, and their malfunction is implicated in the development of some tumours. We analysed human colorectal cancers for genetic mutations in 340 serine/threonine kinases and found mutations in eight genes, including in three members of the phosphatidylinositol-3-OH kinase (PI(3)K) pathway. The discovery of this mutational activation of a key cell-signalling pathway may provide new targets for therapeutic intervention.     

Nanocarriers for siRNA delivery to overcome cancer multidrug resistance

Multidrug resistance(MDR)is an extremely complexed phenomenon in tumor chemotherapy and is one of the major obstacles for successful treatment.Discovery of RNA interference(RNAi)offers a new strategy with great potential to reverse MDR.Specific genes,which contribute to the emerging of MDR,can be silenced by RNAi.However,many natural barriers have to be overcome for efficient and safe delivery of siRNA.In recent years,the various kinds of nanocarriers,such as liposomes,cationic polymers,and inorganic materials,have been developed to deliver siRNA and show good results in reversing MDR.This review mainly summarizes the barriers in siRNA delivery and recent progress in designing nanotechnology-based siRNA delivery systems to overcome tumor MDR.     

Secondary mutations as a mechanism of cisplatin resistance in BRCA2-mutated cancers

Ovarian carcinomas with mutations in the tumour suppressor BRCA2 are particularly sensitive to platinum compounds. However, such carcinomas ultimately develop cisplatin resistance. The mechanism of that resistance is largely unknown. Here we show that acquired resistance to cisplatin can be mediated by secondary intragenic mutations in BRCA2 that restore the wild-type BRCA2 reading frame. First, in a cisplatin-resistant BRCA2-mutated breast-cancer cell line, HCC1428, a secondary genetic change in BRCA2 rescued BRCA2 function. Second, cisplatin selection of a BRCA2-mutated pancreatic cancer cell line, Capan-1 (refs 3, 4), led to five different secondary mutations that restored the wild-type BRCA2 reading frame. All clones with secondary mutations were resistant both to cisplatin and to a poly(ADP-ribose) polymerase (PARP) inhibitor (AG14361). Finally, we evaluated recurrent cancers from patients whose primary BRCA2-mutated ovarian carcinomas were treated with cisplatin. The recurrent tumour that acquired cisplatin resistance had undergone reversion of its BRCA2 mutation. Our results suggest that secondary mutations that restore the wild-type BRCA2 reading frame may be a major clinical mediator of acquired resistance to platinum-based chemotherapy.