抗肿瘤细胞多药抗性基因MDR1和MRP1双靶位自剪切核酶的合成及其在体外活性研究

多药耐药基因MDR1和 (或 )MRP1过度表达是引起肿瘤细胞对化疗药物产生多重耐药性的重要原因 .在以往研究抗MDR1基因的核酶 (196MDR1 Rz)的基础上 ,合成了针对MRP1基因 2 10和 730编码子的核酶 (2 10MRP1 Rz ,730MRP1 Rz) ,同时利用RNA二级结构分析程序mfold 3 0设计合成了一种双靶位自剪切核酶体系 (Coat) .将 196MDR1 Rz和 2 10MRP1 Rz基因同时载入到该体系中 ,建立了抗MDR1 MRP1双靶位核酶 .在无细胞体系中对上述核酶进行的生物活性实验表明 ,2 10MRP1 Rz与 730MRP1 Rz相比能够更有效地切割底物 ;载入Coat的抗MDR1和MRP1核酶均能得以有效释放 ,同时切割各自的靶RNA序列 ,切割效率与单靶位核酶一致 ;

Quantitative detection of peripheral MDR genes in breast cancer before chemotherapy and their clinical significances

Objective： To explore expressions of multidrug resistance gene （MDR） product P170 and peripheral blood MDR1 mRNA in breast cancer tissue and their clinical significances. Methods： Fluorescent quantitative RT-PCR and immunohistochemistry were used to detect peripheral blood MDR1 mRNA before chemotherapy in breast cancer tissue samples from 32 cases with P170 positive （trial group） and 11 cases with P170 negative （control group）. Results： There were 14 cases （43.75%） peripheral blood MDR1 mRNA positive and 18 cases （56.25%） negative in 32 cases P170 positive breast cancer patients, while there were 6 cases （54.55%） peripheral blood MDR1 mRNA positive and 5 cases （45.45%） negative in 11 cases P170 negative breast cancer patients; there wasn＇t a significance difference with peripheral blood MDR1 mRNA express rate in P170 positive （43.75%） group and P170 negative （54.55%） group （x2 = 0.383, P 〉 0.05）. There were 12 cases （37.50%） Her-2 positive and 20 cases （62.50%） negative in P170 positive group; there were 2 cases （18.18%） Her-2 positive and 9 cases （81.82%） negative in P170 negative group; there wasn＇t a significance difference with Her-2 positive rate in P170 positive group （37.50%） and P170 negative （18.18%） group （χ^2= 1.391, P 〉 0.05）. There were 13 cases （40.63%） ER positive and 19 cases （59.37%） negative in P170 positive group; there were 7 cases （63.64%） ER positive and 4 cases （36.36%） negative in P170 negative group; there wasn＇t a significance difference with ER positive rate in P170 positive group （40.63%） and P170 negative （63.64） group （χ^2 = 1.742, P 〉 0.05）. There were 20 cases （62.50%） PR positive and 12 cases （37.50%） negative in P170 positive group; there were 4 cases （36.36%） PR positive and 7 cases （63.64%） negative in P170 negative group; there wasn＇t a significance difference with PR positive rate in P170 positive group （62.50%） and P170 negative （36.36%） group （χ^2 = 2.267, P 〉 0.05）. There were 9 cases （28.12%） with lymphaden metastasis and 23 cases （71.88%） without lymphaden metastasis in P170 positive group; there were 5 cases （45.45%） with lymphaden metastasis and 6 cases （54.55%） without lymphaden metastasis in P170 negative group; there wasn＇t a significance difference with lymphaden metastasis rate in P170 positive group （28.12%） and P170 negative （45.45%） group （χ^2 = 1.120, P 〉 0.05）. Conclusion： 1） There were possibly MDR expressing infrequently in carcinoma tissue and peripheral blood before chemotherapy. 2） FQ-RT-PCR for detecting of peripheral blood MDR1 mRNA is special, sensitive and reliable. It can be used as new molecular biology diagnostic maker dynamic detecting peripheral blood MDR1 mRNA for regulating chemotherapy proposal and elevating chemotherapy effect.

Construction of Multi-ribozyme Expression System and Its Characterization of Cleavage on the MDR1/MRP1 Double Target Substrate in vitro

To improve catalytic activity of ribozyme on its substrate, the multi-ribozyme expression system was designed and constructed from 20 cis-acting hammerhead ribozymes undergoing self-cleavage with 10 trans-acting hammerhead ribozymes inserted alternatively regularly and the plasmid of pGEM-MDR1/MRP1 used to transcribe the MDR1/MRPl（196/210） substrate containing double target sites was also constructed by DNA recombination. Endonuclease digestion analysis and DNA sequencing indicate all the recombinant plasmids were correct. The clea- vage activities were evaluated for the multi-ribozyme expression system on the MDR1/MRP1 substrate in the cell free system. The results demonstrate that the cis-acting hammerhead ribozymes in the multi-ribozyme expression system were able to cleave themselves and the 72 nt of 196Rz and the 71 nt of 210Rz trans-acting hammerhead ribozymes were liberated effectively, and the trans-acting hammerhead ribozymes released were able to act on the MDR1/MRP1 double target RNA substrate and cleave the target RNA at specific sites effectively. The multi- ribozyme expression system of the [Coat＇A196Rz/Coat＇B210Rz]5 is more significantly superior to that of the [Coat＇A 196Rz/Coat＇B210Rz] 1 in cleavage of RNA substrate. The fractions cleaved by [Coat＇A 196Rz/Coat＇B210Rz]5 on the MDR1/MRP1 substrate for 8 h at observed temperatures showed no marked difference. The studies of Mg^2＋ on cleavage efficiency indicate that cleavage reaction is dependent on Mg^2＋ ions concentration. The plot of lg（kobs） vs. lgc（Mg^2＋） displays a linear relationship between 2.5 mmol/L and 20 mmol/L Mg^2＋. It suggests that Mg^2＋ ions play a crucial role in multi-ribozyme cleavage on the substrate.

Reversal of drug resistance of multidrug-resistant human lung cancer cells by an MDR1 ribozyme

MALIGNANT tumor is very harmful to human health, and the mortality is very high. About 50% of the patients with malignancy can be operated on, and the other 50% patients have to be treated with chemotherapy. Because tumors are mostly chemoresistant, chemotherapy for these patients often has no effect. The overexpression of MDR1 gene is very common in hu man malignant tumors, about 50% in previously untreated patients and more than 50% in previously treated patients for whom the tumor is resistant to the previous sensitive

逆转录病毒载体介导的核酶基因转移有效恢复肿瘤细胞的化疗敏感性

目的：为了研究抗ＭＤＲＩ核酶逆转肿瘤细胞中Ｐ－ｇｐ介导的多重耐药性（ＭＤＲ）的作用。方法：首先，我们建立了单纯由Ｐ－ｇｐ介导的、２０倍耐药的人Ｄａｕｄｉ淋巴瘤细胞的模型－Ｄａｕｄｉ／ＭＤＲ２０。同时我们将表达不同抗ＭＤＲ１核酶的逆转录病毒载体（Ｎ２Ａ＋ｔＲＮＡｉｍｅｔ－１９６ＭＤＲ１－Ｒｚ，Ｎ２Ａ＋ｔＢＮＡｉｍｅｔ－１９６ＭＤＲ１－ｓＲｚ和 Ｎ２Ａ＋ｔＲＮＡｉｍｅｔ－ｉＭＤＲＩ－ｓＲｚ）转染到ＧＰ＋ｅｎｖＡＭ１２细胞中进行包装，获得了高滴度的病毒［（１，１～２．５）×１０ｃｆｕ／ｍｌ］。后者用于感染Ｄａｕｄｉ／ＭＤＲ２０。结果：通过一系列分子生物学检测证实，携带３种核酶的逆转录病毒不但整合到ＤＮＡ中，而且也高水平表达相应的核酶ｔＲＮＡｉｍｅｔ－ｉＭＤＲ１－ｓＲｚ，ｔＲＮＡｉｍｅｔ－１９６ＭＤＲ１－ｓＲｚ和ｔＲＮＡｉｍｅｔ－１９６ＭＤＲ１－Ｒｚ。结果表明，ｔＲＮＡｉｍｅｔ－ｉＭＤＲ１－ｓＲｚ和ｔＲＮＡｉｍｅｔ－１９６ＭＤＲ１－ｓＲｚ转导的Ｄａｕｄｉ／ＭＤＲ２０细胞完全逆转了对长春新碱的敏感性，并伴随着ＭＤＲ１ ｍＲＮＡ和Ｐ－ｇｐ表达的阻断。

PFC体内递增诱导建立S180肿瘤多药耐药模型及其稳定性观察

目的小鼠体内诱导建立获得性S180多药耐药（multi—drug resistance，MDR）模型及其稳定性观察。方法模拟临床顺铂＋氟尿嘧啶＋环磷酰胺（PFC）化疗方案给药，分三个阶段剂量递增法诱导S180腹水瘤小鼠，建立获得性S180MDR实验模型。采用噻唑蓝fMTTl法、流式细胞术动态检测各阶段所诱导细胞对化疗药物的耐药倍数、细胞内药物积累量及细胞膜P-糖蛋白（P-glycoprotein，P—gp）功能活性，并通过检测以上指标观察各阶段所诱导细胞停药后的耐药稳定性：采用实时荧光定量PCR（RT—qPCR）法检测各阶段所诱导细胞MDR-1 mRNA、多药耐药相关蛋白-1（multidrug resistance-associated proteinl，MRP-1）mRNA的表达量。结果与亲本细胞对照组比较，各阶段所诱导S180细胞对化疗药物的耐药倍数随着诱导时间延长和剂量增高而逐渐增大，细胞内阿霉素（adriamycin，ADR）积累量逐渐减少，细胞P—gp功能活性逐渐增强;各阶段所诱导S180细胞MDR-1mRNA、MRP-1 mRNA的表达量也与诱导时间和给药剂量呈正相关：第一、二和三阶段所诱导细胞的稳定耐药时间分别为1周、2周和3周左右。结论模拟临床PFC化疗方案给药，采用分阶段剂量递增小鼠体内诱导法可建立耐药强度高、稳定时间长的获得性S180MDR实验模型。

核酶对肝癌耐药细胞株BEL-7402/DOX耐药性的逆转作用

为逆转多药耐药ｍｄｒ－１基因产物Ｐ－ｇｐ蛋白所介导的肿瘤细胞对多种化疗药物的耐受性，作者设计合成了一种能切割ｍｄｒ－１ｍＲＮＡ第１９６密码子ＧＵＣ序列的锤头状核酶（Ｒｉｂｏｚｙｍｅ），并定向克隆于逆转录病毒载体。经ＰＡ３１７包装后，病毒上清感染ＢＥＬ－７４０２／ＤＯＸ细胞株。经Ｎｏｒｔｈｅｒｎｂｌｏｔ杂交证实，ＰＡ３１７及转化的ＢＥＬ－７４０２／ＤＯＸ细胞中均有病毒的高表达，ＲＴ－ＰＣＲ结果表明，转化细胞中ｍｄｒ－１ｍＲＮＡ与未转化细胞相比明显减少甚至不能扩增出来，流式细胞技术检测发现转化细胞表面Ｐ－ｇｐ的表达与非转化细胞相比明显下降。ＭＴＴ法检测发现转化细胞对多种化疗药物重新产生较高的敏感性。结果提示，此Ｒｉｂｏｚｙｍｅ转化ＢＥＬ－７４０２／ＤＯＸ细胞后能有效抑制ｍｄｒ－１基因的表达，使已产生耐药的肝癌细胞的多药耐药表型发生逆转。

抗肿瘤细胞多药抗性核酶的合成及其活性的研究

目的 研究抗肿瘤细胞多药抗性 (MDR)核酶的生物学活性及其稳定性。方法 构建表达抗MDR1核酶的逆转录病毒载体 (N2A +tRNAmeti 196MDR1 Rz、N2A +tRNAmeti 196MDR1 sRz、N2A +tRNAmeti 1iMDR1 sRz)和合成了裸核酶cDNA。利用体外转录反应合成 5种anti MDR1核酶 (tRNA 196MDR1 Rz、tRNA 196MDR1 sRz、tRNA iMDR1 sRz、196MDR1 sRz和 196MDR1 Rz)及相应的底物A和底物B。在无细胞体系中检测了各种核酶的切割活性和它们对核酸酶降解的稳定性。结果 anti MDR1核酶均能有效发挥切割作用。其中嵌合型核酶的活性高于裸核酶 ,而且经过stem Ⅱ碱基修饰的核酶催化活性较高。核酶的稳定性依次是tRNA 196MDR1 sRz(嵌合型 ) >tRNA 196MDR1 Rz =196MDR1 sRz(裸核酶 )。在对照组 ,突变的tRNA mut iMDR1 sRz没有切割活性。结论 核酶分子经过stem