EGFR mutations in lung cancer: correlation with clinical response to gefitinib therapy

Receptor tyrosine kinase genes were sequenced in non-small cell lung cancer (NSCLC) and matched normal tissue. Somatic mutations of the epidermal growth factor receptor gene EGFR were found in 15of 58 unselected tumors from Japan and 1 of 61 from the United States. Treatment with the EGFR kinase inhibitor gefitinib (Iressa) causes tumor regression in some patients with NSCLC, more frequently in Japan. EGFR mutations were found in additional lung cancer samples from U.S. patients who responded to gefitinib therapy and in a lung adenocarcinoma cell line that was hypersensitive to growth inhibition by gefitinib, but not in gefitinib-insensitive tumors or cell lines. These results suggest that EGFR mutations may predict sensitivity to gefitinib.     

非小细胞肺癌与p16基因CpG岛异常甲基化的关系

目的 :探讨非小细胞肺癌中抑癌基因 p1 6的失活机制 ;方法 :采用甲基化特异性 PCR( MSP)法检测 30例非小细胞肺癌肿瘤组织、30例癌旁组织及 3例正常肺组织中 p1 6基因外显子 1的 Cp G岛异常甲基化情况。结果 :非小细胞肺癌中有 1 2例 ( 4 0 % )肿瘤组织检测到 p1 6基因 5’端 Cp G岛异常甲基化 ,而癌旁组织及正常肺组织均未检测到 p1 6基因的异常甲基化 ,两者之间差异有显著性 ( P<0 .0 0 1 )。结论 :p1 6基因 5’端 Cp G岛异常甲基化与非小细胞肺癌的发生发展有关 ,可能是该基因在非小细胞肺癌中的主要失活机制。     

Studies of the HER-2/neu proto-oncogene in human breast and ovarian cancer

Carcinoma of the breast and ovary account for one-third of all cancers occurring in women and together are responsible for approximately one-quarter of cancer-related deaths in females. The HER-2/neu proto-oncogene is amplified in 25 to 30 percent of human primary breast cancers and this alteration is associated with disease behavior. In this report, several similarities were found in the biology of HER-2/neu in breast and ovarian cancer, including a similar incidence of amplification, a direct correlation between amplification and over-expression, evidence of tumors in which overexpression occurs without amplification, and the association between gene alteration and clinical outcome. A comprehensive study of the gene and its products (RNA and protein) was simultaneously performed on a large number of both tumor types. This analysis identified several potential shortcomings of the various methods used to evaluate HER-2/neu in these diseases (Southern, Northern, and Western blots, and immunohistochemistry) and provided information regarding considerations that should be addressed when studying a gene or gene product in human tissue. The data presented further support the concept that the HER-2/neu gene may be involved in the pathogenesis of some human cancers.     

Advances in crop phenotyping and multi-environment trials

Efficient evaluation of crop phenotypes is a prerequisite for breeding, cultivar adoption, genomics and phenomics study. Plant genotyping is developing rapidly through the use of high-throughput sequencing techniques,while plant phenotyping has lagged far behind and it has become the rate-limiting factor in genetics, large-scale breeding and development of new cultivars. In this paper,we consider crop phenotyping technology under three categories. The first is high-throughput phenotyping techniques in controlled environments such as greenhouses or specifically designed platforms. The second is a phenotypic strengthening test in semi-controlled environments, especially for traits that are difficult to be tested in multi-environment trials(MET), such as lodging, drought and disease resistance. The third is MET in uncontrolled environments, in which crop plants are managed according to farmer's cultural practices. Research and application of these phenotyping techniques are reviewed and methods for MET improvement proposed.     

Toward the primary prevention of cancer

This is the threshold of an era when many of the most prevalent human cancers can, to a significant extent, be prevented through life-style changes or medical interventions. For lung cancer, the leading cause of cancer deaths in the United States, the major cause, cigarette smoking, is known and strategies for reducing smoking are slowly succeeding. Dietary changes can reduce the risk of developing large bowel cancer, the second most common cancer overall. The etiology of the major cancer in women, cancer of the breast, is sufficiently well understood that large-scale medical intervention trials are imminent. Recent changes in the incidence and mortality of these and the other major human cancers are reviewed with a brief explanation as to why these changes have occurred, followed by a summary of the state of knowledge regarding the major causes of cancer.     

Network analysis of oncogenic Ras activation in cancer

To investigate the unregulated Ras activation associated with cancer, we developed and validated a mathematical model of Ras signaling. The model-based predictions and associated experiments help explain why only one of two classes of activating Ras point mutations with in vitro transformation potential is commonly found in cancers. Model-based analysis of these mutants uncovered a systems-level process that contributes to total Ras activation in cells. This predicted behavior was supported by experimental observations. We also used the model to identify a strategy in which a drug could cause stronger inhibition on the cancerous Ras network than on the wild-type network. This system-level analysis of the oncogenic Ras network provides new insights and potential therapeutic strategies.     

Human multidrug-resistant cell lines: increased mdr1 expression can precede gene amplification

The development of simultaneous resistance to multiple structurally unrelated drugs is a major impediment to cancer chemotherapy. Multidrug resistance in human KB carcinoma cells selected in colchicine, vinblastine, or Adriamycin is associated with amplification of specific DNA sequences (the multidrug resistance locus, mdr1). During colchicine selection resistance is initially accompanied by elevated expression of a 4.5-kilobase mdr1 messenger RNA (mRNA) without amplification of the corresponding genomic sequences. During selection for increased levels of resistance, expression of this mRNA is increased simultaneously with amplification of mdr1 DNA. Increased expression and amplification of mdr1 sequences were also found in multidrug-resistant sublines of human leukemia and ovarian carcinoma cells. These results suggest that increased expression of mdr1 mRNA is a common mechanism for multidrug resistance in human cells. Activation of the mdr1 gene by mutations or epigenetic changes may precede its amplification during the development of resistance.     

小细胞肺癌的靶向治疗研究进展

小细胞肺癌代表了肺癌中最恶性的类型,是一类预后差并且治疗方案有限的疾病,其5年生存率不到7%,近年来的标准治疗方案主要为化学疗法加上放射疗法。利用基因组分析技术,研究人员发现了一些重要的癌基因驱动着小细胞肺癌的发生发展。鉴于此,小细胞肺癌的发生、发展、转移以及耐药的分子机制需要更深层次的了解,以便为临床治疗小细胞肺癌提供有效的靶标。探讨了小细胞肺癌的靶向治疗研究进展以及未来亟需解决的问题,从而为临床治疗小细胞肺癌提供可靠线索。     

Direct interaction of a ligand for the erbB2 oncogene product with the EGF receptor and p185erbB2

The erbB2 oncogene encodes a 185-kilodalton transmembrane protein whose sequence is similar to the epidermal growth factor receptor (EGFR). A 30-kilodalton factor (gp30) secreted from MDA-MB-231 human breast cancer cells was shown to be a ligand for p185erbB2. An antibody to EGFR abolished the tyrosine phosphorylation induced by EGF and transforming growth factor-alpha (TGF-alpha) but only partially blocked that produced by gp30 in SK-BR-3 breast cancer cells. In two cell lines that overexpress erbB2 but do not expresss EGFR (MDA-MB-453 breast cancer cells and a Chinese hamster ovary cell line that had been transfected with erbB2), phosphorylation of p185erbB2 was induced only by gp30. The gp30 specifically inhibited the growth of cells that overexpressed p185erbB2. An antibody to EGFR had no effect on the inhibition of SK-BR-3 cell colony formation obtained with gp30. Thus, it appeared that gp30 interacted directly with the EGFR and erbB2. Direct binding of gp30 to p185erbB2 was confirmed by binding competition experiments, where gp30 was found to displace the p185erbB2 binding of a specific antibody to p185erbB2. The evidence described here suggests that gp30 is a ligand for p185erbB2.     

Role of the glutathione redox cycle in acquired and de novo multidrug resistance

Drug resistance represents a major obstacle to successful cancer chemotherapy. However, the specific biochemical mechanisms responsible for clinical drug resistance are unknown. In these studies resistance to the antitumor agent adriamycin was found to involve two mechanisms, one that decreased drug accumulation by the P170 mechanism and another that altered the glutathione redox cycle, an important pathway in the detoxification of reactive oxygen. This dual mechanism of drug resistance was demonstrated in cell lines that had acquired the multidrug-resistant phenotype and in human colorectal cancer cells with de novo resistance. These studies support a model of acquired and de novo multidrug resistance that includes alterations in both drug accumulation and the glutathione redox cycle.     

Gene amplification of c-myc and N-myc in small cell carcinoma of the lung

The relationship of the copy numbers of the c-myc and N-myc oncogenes to tumor formation and progression was studied in small cell carcinoma of the lung. When 96 neoplastic lesions from 45 patients were examined, these lesions could be grouped into three categories: high copy (tumors with greater than 3 copies of the N-myc or c-myc gene per haploid genome), middle copy (1.5 to 3 copies per genome), and normal copy. Fourteen of the patients had middle copy tumors, but this was almost always a result of chromosome duplication rather than the amplification of a small genetic locus. In contrast, five patients had high copy tumors, with the increased copy number in each case due to gene amplification. The amplification did not occur in a heterogeneous fashion within individual patients, since all metastatic lesions from patients with high copy lung tumors were also high copy, while none of 41 metastatic lesions from the other patients were high copy. These data suggest that gene amplification is an important step in neoplastic growth in a subset of patients with small cell carcinoma of the lung and that this genetic event occurs relatively early (before metastasis) in this subset.     

Mutational analysis of the tyrosine phosphatome in colorectal cancers

Tyrosine phosphorylation, regulated by protein tyrosine phosphatases (PTPs) and kinases (PTKs), is important in signaling pathways underlying tumorigenesis. A mutational analysis of the tyrosine phosphatase gene superfamily in human cancers identified 83 somatic mutations in six PTPs (PTPRF, PTPRG, PTPRT, PTPN3, PTPN13, PTPN14), affecting 26% of colorectal cancers and a smaller fraction of lung, breast, and gastric cancers. Fifteen mutations were nonsense, frameshift, or splice-site alterations predicted to result in truncated proteins lacking phosphatase activity. Five missense mutations in the most commonly altered PTP (PTPRT) were biochemically examined and found to reduce phosphatase activity. Expression of wild-type but not a mutant PTPRT in human cancer cells inhibited cell growth. These observations suggest that the mutated tyrosine phosphatases are tumor suppressor genes, regulating cellular pathways that may be amenable to therapeutic intervention.     

Acceleration of emergence of bacterial antibiotic resistance in connected microenvironments

The emergence of bacterial antibiotic resistance is a growing problem, yet the variables that influence the rate of emergence of resistance are not well understood. In a microfluidic device designed to mimic naturally occurring bacterial niches, resistance of Escherichia coli to the antibiotic ciprofloxacin developed within 10 hours. Resistance emerged with as few as 100 bacteria in the initial inoculation. Whole-genome sequencing of the resistant organisms revealed that four functional single-nucleotide polymorphisms attained fixation. Knowledge about the rapid emergence of antibiotic resistance in the heterogeneous conditions within the mammalian body may be helpful in understanding the emergence of drug resistance during cancer chemotherapy.     

吉非替尼靶向治疗非小细胞肺癌的研究

吉非替尼是一种具有抗肿瘤活性的喹唑啉类衍生物,通过竞争抑制ATP与受体区结合,从而抑制酪氨酸激酶活化.吉非替尼主要应用于晚期非小细胞肺癌的二线和三线治疗,其抗肿瘤作用已得到许多研究者的认同.阐述了吉非替尼的药理学、临床研究,吉非替尼疗效的分子预测因素及不良反应的研究成果.     

Amplification and expression of genes associated with multidrug resistance in mammalian cells

In multidrug resistance, which is observed clinically and in tissue culture, cells that are challenged with certain cytotoxic drugs develop resistance not only to the selective agent but also to other, seemingly unrelated, agents. The multidrug-resistant phenotype is associated with DNA sequence amplification and with the overproduction of a number of cytosolic and membrane glycoproteins. The differential amplification and altered expression of at least two related genes, termed multidrug-resistant associated genes has been shown in multidrug-resistant Chinese hamster cells. In multidrug-resistant mouse and human cells, genes homologous to those in Chinese hamster cells are also amplified. The level of expression of these genes varied and did not correlate with their copy number. Furthermore, in Chinese hamster cells, the development of resistance to a single drug and multidrug resistance were closely related, but uncoupled, events. The overexpression of the multidrug-resistant genes was better correlated with the degree of resistance to the selective agent than it was with the extent of multidrug resistance.     

肺炎克雷伯菌药物外排泵mdtl的克隆及分析

[目的]探讨肺炎克雷伯菌ATCC 49790（KP）耐药的分子机制。[方法]以KP基因组DNA为模板来扩增mdtl基因,将mdtl基因扩增产物进行DNA测序及同源性分析;将扩增产物与载体连接后转化到大肠埃希菌KAM32感受态细胞中,对转化子进行药敏分析。[结果]KP的mdtl基因扩增产物与已报道的mdtl基因核苷酸序列同源性达到99%,这个转化子对红霉素、氯霉素和卡那霉素具有很高的耐药性,这种高耐药性能被外排泵抑制剂羰基氰氯苯腙和维拉帕米逆转。[结论]克隆到了KP一多药外排基因。     

鸭源大肠杆菌3种tet基因的多重PCR检测

利用肉汤稀释法测定21株鸭大肠杆菌对四环素等7种抗茵药物的敏感性,并用多重PCR方法同时检测3种四环素耐药基因(tetA、tetB和tetC).结果显示:所有菌株均呈现tetA、tetB和tetC基因阳性,与药敏试验结果阳性符合率76.67%,携带3种tet基因的临床分离鸭大肠杆茵不仅对四环素类药物耐药,还对头孢噻肟、...     

血清microRNA在癌症诊断中的进展

microRNA是长约19到25单位的内生性的微小RNA,它通过与靶信使RNA的3’UTR的特异性结合从而调节靶基因的表达。大量的试验证明了其在肿瘤的发生发展中microRNA发挥了重大的作用。近年来,在血清中发现了稳定存在的microRNA,而对microRNA的研究主要聚焦在血清microRNA与疾病的关系上。通过对患者和正常血清microRNA的检测和对比后,发现了一批可以用于肿瘤临床检测的microRNA。作为新的检测生物标志物,血清microRNA具有方便、快捷以及较高的准确性等优点,甚至可以区分在临床很难诊断的早期肿瘤,诸如非小细胞肺癌、胃癌以及胰腺癌。