Proteins Regulating Microvesicle Biogenesis and Multidrug Resistance in Cancer

Microvesicles (MV) are emerging as important mediators of intercellular communication. While MVs are important signaling vectors for many physiological processes, they are also implicated in cancer pathology and progression. Cellular activation is perhaps the most widely reported initiator of MV biogenesis, however, the precise mechanism remains undefined. Uncovering the proteins involved in regulating MV biogenesis is of interest given their role in the dissemination of deleterious cancer traits. MVs shed from drug‐resistant cancer cells transfer multidrug resistance (MDR) proteins to drug‐sensitive cells and confer the MDR phenotype in a matter of hours. MDR is attributed to the overexpression of ABC transporters, primarily P‐glycoprotein and MRP1. Their expression and functionality is dependent on a number of proteins. In particular, FERM domain proteins have been implicated in supporting the functionality of efflux transporters in drug‐resistant cells and in recipient cells during intercellular transfer by vesicles. Herein, the most recent research on the proteins involved in MV biogenesis and in the dissemination of MV‐mediated MDR are discussed. Attention is drawn to unanswered questions in the literature that may prove to be of benefit in ongoing efforts to improve clinical response to chemotherapy and circumventing MDR.     

胚胎干细胞分化为血管内皮细胞的分子调控机制

胚胎干细胞在不同的诱导条件下具有多向分化的潜能,多种胞内外信号途径参与其分化过程的调控。现就胚胎干细胞向血管内皮细胞分化的诱导条件及分子机制做一综述,并阐明不同阶段的内皮前体细胞所表达的不同分子标志,同时提出胚胎干细胞在再生医学中的应用前景。     

GALNT14 Involves the Regulation of Multidrug Resistance in Breast Cancer Cells

GALNT14 is a member of N-acetylgalactosaminyltransferase enzyme family and mediates breast cancer cell development. Here, we find that GALNT14 regulates multidrug resistance (MDR) in breast cancer. The expression of GALNT14 is associated with MDR in breast cancer. Higher level of GALNT14 facilitates MCF-7 cells to resist Adriamycin, whereas knockdown of GALNT14 sensitizes cells to Adriamycin. Moreover, the expression of GALNT14 associates with the expression of P-gp, the efflux pump localized on the cell membrane, which could be the underlying mechanism of how GALNT14 induces MDR. In-depth analysis shows that GALNT14 regulates the stability of P-gp. Finally, GALNT14 associates with higher level of P-gp in chemotherapy-resistant human breast cancer tissues. Taken together, our studies reveal a molecular mechanism in breast cancer MDR.     

Modulation of Multidrug Resistance in Cancer Cells by Liposome Encapsulated Doxorubicin

Abstract

A major problem in the chemotherapy of solid tumors and hematologic malignancies is the intrinsic as well as acquired cross resistance to multiple chemotherapeutic agents. Recently, this type of multidrug resistance has been related to a gene, MDR1, and its gene product, p-glycoprotein, which functions as the efflux pump, prevents accumulation of drugs and alters their cytotoxicity. Many drug-resistant human tumors express the MDR1 gene and MDR1 RNA levels are elevated in many cancers that have not responded to chemotherapy. The same persistent observation has been made in recurrent tumors who have responded initially to chemotherapy.

Doxorubicin is one of the most important anticancer agent having significant single agent activity in a variety of cancer types and is now the cornerstone of some widely used combination regimens. Despite the clinical effectiveness of the drug, doxorubicin resistance that arises in malignant cells following repeated courses of treatment is the major problem in the clinical management of neoplastic diseases. Recently, extensive studies have demonstrated that liposome encapsulated doxorubicin effectively modulates the multidrug resistance phenotype in cancer cells by altering the function of p-glycoprotein. This modulation of MDR phenotype by liposomes has been demonstrated in vitro in human breast cancer cells, ovarian cancer cells, human promyelocytic leukemia cells and in human colon cancer cells and in vivo in transgenic mice transfected with a functional MDR1 gene. It appears liposomes can play an effective role as a new modality of treatment for human cancers which have become refractory to chemotherapy. An exciting area of research which soon will emerge will exploit the different binding sites on p-glycoprotein by using combination of liposomes with other pharmacological modulators of MDR to impart maximal overcoming of multidrug resistance in cancer patients.     

肿瘤多药耐药分子机制研究进展

化疗是治疗恶性肿瘤主要方法之一。然而不幸的是,先天或获得性耐药尤其是多药耐药的发生,最终导致化疗失败。因此,深入探讨多药耐药发生的分子机制,寻找可以有效预测肿瘤化疗敏感性的分子标志物以及逆转多药耐药的分子靶点,是提高化疗效果的有效途径。肿瘤多药耐药分子机制错综复杂,本文主要从DNA损伤修复、ABC转运蛋白家族表达和功能异常、肿瘤干细胞、拓扑异构酶活性改变、上皮间质转分化、谷胱甘肽-S-转移酶表达改变、表观遗传学修饰以及缺氧等方面对肿瘤多药耐药分子机制进行阐述。     

植物微管骨架参与下胚轴伸长调节机制研究进展

微管作为细胞骨架的重要成员,在植物生长发育过程中起重要作用。下胚轴作为研究细胞伸长的模式系统之一,其伸长受到多种信号的调节。该文综述了微管骨架在响应环境和生长发育信号调节下胚轴伸长过程中的作用及机制,旨在帮助读者深入理解微管骨架响应上游信号在植物下胚轴伸长中的作用机理。     

果实花青素生物合成分子机制研究进展

花青素是一种天然的水溶性植物色素,与果实的品质性状密切相关,有益于人体健康。花青素的积累是编码花青素生物合成途径的结构基因协同表达的结果,而结构基因通常由MYB、bHLH和WD40这3类调节基因控制。现已从果实中分离了多种花青素合成的结构基因和调节基因。文章重点介绍了调节基因调控果实花青素生物合成的分子机制,指出在MYB、bHLH和WD40互作的调控网络方面的研究还有很多空白。最新的研究揭示了果实成熟过程中生物内在因素和外界环境通过调节基因影响果实花青素生物合成。上述研究为在分子水平上更好的探索果实花青素的生物合成具有重要意义。     

植物嫁接愈合分子机制研究进展

嫁接能显著改良单一品种的产量、品质和抗逆等性状, 已广泛应用于农业生产。促进砧木和接穗在嫁接面的快速愈合有利于提高嫁接效率。目前对嫁接愈合调控机制尚了解不足, 因此短时间内难以进行有效的技术改良。嫁接愈合过程包括先后发生的创伤应激响应、愈伤组织形成、砧穗细胞通讯以及砧穗再生重连等生理事件, 均涉及复杂而交联的激素应答及基因调控模式。近年来, 相关领域的研究成果为综合解析嫁接愈合的调控机制奠定了基础。该文综述了在嫁接愈合过程中发挥核心作用的植物激素及其应答方式, 以及激素依赖或非依赖的基因表达调控模式, 以期为深入揭示嫁接愈合分子机制提供参考。     

Clinical Evaluation of Liposome Encapsulated Doxorubicin and the Modulation of Multidrug Resistance in Cancer Cells

Abstract

Doxorubicin is the cornerstone of some widely used combination chemotherapy regimens because of its high anticancer activity in a number of human neoplasms. However, its clinical use is highly compromised because of treatment-limiting acute and chronic toxicities of which cardiotoxicity has the most debilitating effect. Our laboratories have demonstrated that liposome encapsulated doxorubicin (LED) provides important advantages in regards to the attenuation of cardiotoxicity in rodents by altering pharmacokinetics and pharmacodynamics of the drug, provides effective protection from immunotoxicity and maintains full therapeutic activity of the drug in liposomes. A Phase I clinical trial of LED in cancer patients has establish the maximum tolerated dose of 90 mg/m² with granulocytopenia being the major treatment-limiting toxicity. We have performed a Phase II trial of LED in 20 recurrent breast cancer patients at a dose of 75 mg/m² as an intravenous infusion every three weeks. Objective responses were observed in 9/20 patients of which 5 demonstrated a complete response. Hematologic toxicity with LED consisted of only grade 1-2 granulocytopenia in some patients, whereas gastrointestinal toxicity, mucositis and venous sclerosis were markedly reduced. Alopecia was complete in all patients. Twelve patients received cumulative LED doses of more than 400 mg/m² and 8 of them received doses of over 500 mg/m². Five of these patients were followed by endomyocardial biopsies and 4 of them were found to be Billingham Grade 0 whereas one of them had Billingham Grade 1 toxicity (cumulative dose of 750 mg/m²). This Phase II trial demonstrates higher therapeutic efficacy of LED than free doxorubicin in recurrent breast cancer patients with strong indication of cardiotoxicity protection at doses of 500-800 mg/m².

The emergence of tumor cells resistant to major classes of cytotoxic agents is a predominant obstacle in cancer treatment. This resistance is frequently related to the expression of a plasma membrane P-glycoprotein (pgp) of 170 Kd that is encoded by a family of MDR genes. Support for the involvement of pgp in MDR has been shown by transaction of sensitive cells with an expression vector containing full length cDNA of the MDR1 gene, which results in the appearance of pgp and the sensitive cells convert to the drug-resistant phenotype. Our studies demonstrate that LED modulates very effectively the MDR phenotype in LZ cells, a Chinese hamster cell line made resistant to doxorubicin and the cellular drug uptake was 2 to 3 fold higher with LED exposure than with free drug. This modulation of drug resistance and enhanced cellular drug uptake is effected by the direct binding of liposomes to pgp on the surfaces of MDR phenotype cells. LED completely inhibited the photoaffinity labeling of pgp by azidopine in membrane vesicles of HL-60/VCR cells and in KB-GSV2 cells transfected with human MDR gene. These studies demonstrate that LED has unique effectiveness in overcoming MDR phenotype in cancer cells and appears to be a potentially attractive modality of treatment of human cancers.     

应用蛋白质组学技术筛选胃癌耐药相关蛋白质

胃癌多药耐药性是临床胃癌化疗失败最主要的原因之一,但其分子机制仍然不太清楚.为了寻找新的胃癌耐药相关的蛋白质,揭示胃癌多药耐药的分子机制,以胃癌细胞SGC7901和长春新碱诱导的耐药胃癌细胞SGC7901/VCR为研究对象,应用二维凝胶电泳(two-dimensionalelectrophoresis,2-DE)技术分离两种细胞的总蛋白质,图像分析识别差异表达的蛋白质点,基质辅助激光解吸电离飞行时间质谱(matrix-assistedlaserdesorption/ionizationtimeofflightmassspectrometry,MALDI-TOF-MS)及电喷雾电离串联质谱(electrosprayionizationtandemmassspectrometry,ESI-Q-TOF)对差异表达的蛋白质点进行鉴定,蛋白质印迹和实时RT-PCR验证部分差异蛋白质在两株细胞中的表达水平,反义核酸转染技术分析HSP27(heatshockprotein27,HSP27)高表达与SGC7901/VCR耐药的相关性.得到了分辨率较高、重复性较好的两株细胞系的二维凝胶电泳图谱,质谱分析共鉴定了24个差异蛋白质点,蛋白质印迹和实时RT-PCR验证了部分差异蛋白的表达水平,反义寡核苷酸抑制HSP27表达能增加SGC7901/VCR对长春新碱的敏感性.研究结果不仅提示这些差异蛋白质如HSP27,Sorcin等可能与胃癌的多药耐药相关,而且为揭示胃癌细胞的多药耐药性产生机制提供了线索.     

分子诊断技术在乳腺癌检测中的最新进展

乳腺癌是一种严重危害女性健康的恶性肿瘤,对其致病基因的检测有助于肿瘤早期诊断、精准治疗及预后评估.本文总结了近年来乳腺癌相关的热点基因,并对相关基因的分子诊断技术、检测方法及应用进行了综述.首次评述了数字PCR方法用于乳腺癌分子检测的进展.全面对比不同分子诊断技术的差别与优缺点,为乳腺癌关键基因的检测提供指导建议与理论支持,并对未来发展趋势做出展望.     

肿瘤多药耐药与自噬、DNA修复和肿瘤干细胞相关的分子机制研究进展

肿瘤多药耐药(multi-drug resistance,MDR)所导致的化疗失败,依旧是肿瘤治疗中存在的难点。虽然针对MDR,已经成功开发了三代靶向三磷酸腺苷结合盒转运体(ATP binding cassette transporter,ABC)的抑制剂,也有MDR调节剂和化学增敏剂,多功能纳米载体和RNA干扰等方法可有效逆转MDR,但是由于肿瘤多药耐药机制的复杂性,MDR依然是肿瘤治疗中面临的难题。将从目前研究比较集中的ABC转运体异常表达; DNA损伤修复的改变和细胞凋亡的异常;自噬诱导与耐药及肿瘤干细胞与耐药等四方面入手,针对目前MDR机制的研究进展做一综述,旨在为MDR的研究提供思路和方法。     

尼古丁调控细胞凋亡的分子机制

尼古丁是烟草中生物碱的主要成分,其生物学作用广泛。尼古丁参与影响神经系统、呼吸系统和心血管系统等重要器官的发育,并与癌症的发生有着密切的关系。尼古丁通过对细胞凋亡的调控,发挥其生物学作用。现对尼古丁调控细胞凋亡相关的各种信号通路及其分子机制进行综述。     

耐多药结核分枝杆菌的研究进展

耐多药结核分枝杆菌(Mycobacterium tuberculosis,Mtb)的产生和播散,尤其是泛耐药菌株的出现,已成为新世纪结核病控制的三大难题之一。Mtb耐药机制的研究有助于快速分子诊断工具的发展,且能指导抗结核新药的开发。了解耐多药结核分枝杆菌的耐药机制、分子特征及治疗的研究进展,将为耐多药Mtb的防治提供依据。     

胸苷酸合成酶表达调控的分子机制

胸苷酸合成酶(thymidylate synthase,TS)是生物体内催化胸苷酸合成所必需的酶．多年来一直作为肿瘤化疗的重要靶酶。对TS基因调控机制的研究表明：基因扩增、转录、翻译和翻译后过程都参与了TS表达的调控。先前的研究表明：TS可与自身的mRNA结合形成TS-mRNA复合物,使mRNA翻译受阻,5-氟尿嘧啶(5-fluorouracil,5-FU)等抗代谢药物可与TS蛋白结合,结合后的复合物不能与TS mRNA作用,导致体内TS的表达升高,是肿瘤细胞产生抗药性的重要分子机制之一。现对TS基因表达调控研究进展、翻译调控与抗药性产生的分子机制进行综述。     

植物种子寿命的生理及分子机制研究进展

种子寿命是衡量种子质量高低的关键指标之一,直接关系到种子萌发、萌发后幼苗的生长发育以及作物产量高低。种子寿命的调控是一个复杂的生物学过程,影响种子寿命的因素包括环境因素、种子自身的结构、营养成分组成及含量以及调控种子寿命相关的关键基因。研究储藏过程中种子生理生化指标的变化,以及相应关键基因的生物学功能,掌握调控种子寿命的生理及分子机制,对于减少种子内部能量消耗,进一步延长种子寿命具有重要意义。该文综述了近年来国内外有关调控种子寿命的生理及分子机制,重点阐述了调控种子寿命的相关关键基因的研究进展,并讨论了各种外部因素对种子寿命的调控机理。     

P-糖蛋白对结肠癌多药耐药的影响

结肠癌是常见的消化道恶性肿瘤。对术后患者以及无法采用手术治疗的患者,临床多采用化疗、放疗等综合性治疗方法。随着大量化疗药物在临床的广泛使用,结肠癌多药耐药性成为化疗失败的最主要原因。研究表明,P-糖蛋白(P-glycoprotein, P-gp)作为ATP结合盒(ABC)转运蛋白超家族成员之一,与多种肿瘤的多药耐药相关,其介导的多药耐药已经成为目前研究的热点。本文旨在通过对P-糖蛋白的结构、耐药机制以及逆转P-糖蛋白介导的结肠癌多药耐药新发现进行阐述,引导读者对P-糖蛋白在结肠癌多药耐药中的作用有更深入的了解。