多药耐药基因作用的新发现

目的：观察被照射的小细胞肺癌细胞系在外照射前后其总RNA（核糖核酸）、MDR1 mRNA（多药耐药基因的信使核糖核酸）、药物敏感性和放射敏感性的变化,从而探讨多药耐药基因是否还有其他未被揭示的新作用。方法：采用GWGP80型远距离60Co治疗机对进入指数生长期的NCI-H446小细胞肺癌细胞系进行分次外照射。用Trizol分别提取未照射细胞（S-cell,Sc）和已完成全部外照射剂量的NCI-H446细胞（R-cell,Rc）的总RNA。采用RT-PCR（逆转录聚合酶链反应）法来确定两组细胞MDR1 mRNA表达的高低。通过加入丝裂霉素和逆转剂维拉帕米后的干扰来分别观察外照射前后NCI-H446细胞系存活率的变化。然后对Sc和Rc再给予不同剂量的外照射,1周后计算它们各自的集落形成率（PE）和存活率（S）。结果：在相同细胞数和相同体积的条件下,未照射组和照射组细胞总RNA的浓度分别为25.9 mg/L和16.6 mg/L;未照射组细胞其MDR1 cDNA（多药耐药基因的逆转录脱氧核糖核酸）/β-actin cDNA为1.078,照射组为1.338。在相同浓度的化疗药丝裂霉素的干扰下,照射组细胞的存活率均明显高于未照射组（P〈0.01）;再加入逆转剂维拉帕米后,两组细胞的存活率则变化不大（P〉0.05）。在分别给予2 Gy和4 Gy的外照射后,照射组细胞的存活率（S）分别为（79.67±34.48）%和（23.73±8.62）%,而未照射组的分别为（51.24±11.88）%和（19.40±5.59）%,其差异有统计学意义（P〈0.05）。结论：化疗药以外的损伤因素也可以使多药耐药基因表达增强,而这些损伤因素所引起的多药耐药基因的高表达均可以使细胞对后来的其他损伤因素产生耐受。因此,多药耐药基因应改称耐多种损伤基因似乎更能体现其内涵。

The new findings of multi-drug resistant (MDR) genes's effect

Objective: To observe the change of the total RNA and MDR1 gene,the chemosensitivity and the radio-sensitivity of NCI-H 446 small cell lung cancer cell line,and to explore the other effect of multidrug resistant(MDR) genes.Methods: NCI-H 446 small cell lung cancer cell line which was exponential phase of growth was explored to 60Co treatment machine(GWGP80 type).The total RNA of the cells that were unirradiated(S-cell,Sc) and irradiated(R-cell,Rc) were isolated from homogenate samples by the acid guanidine thiocyanate-phenol chloroform method.The expression of MDR1 mRNA was assessed by qualitative RT-PCR assays.The survival rates of NCI-H446 cell line were respectively observed by the interference of different concentration of Mitomycin C and the reversal agent of verapamil before and after fractioned radiation treatment.The two kinds of cells were administered different doses of radiation treatment again.And then the plating efficiency(PE) and the survival rate(S) respectively one week after that treatment were calculated.Results: For the unirradiated cells,the concentration of the total RNA was 25.9 mg/L and the ratio of the average value of electrophoresis trip from MDR1 cDNA/β-actin cDNA was 1.078;but for the irradiated cells,this two numerical values were 16.6 mg/L and 1.338 respectively.The survival rate of the radiated cells was higher than that of the unradiated cells under the same concentration of Mitomycin C(P<0.01);after adding the reversal agent of Verapamil to the two cell lines,the change of the survival rates of the two cell lines became almost the same level(P>0.05).After 2 Gy and 4 Gy radiation treatment,the survival rates of irradiated cells were(79.67±34.48)% and(23.73±8.62)% respectively and that of unirradiated cells were(51.24±11.88)% and(19.40±5.59)% respectively,there were significant differences(P<0.05).Conclusion: Besides chemotherapy,the other scathing factors can also enhance the expression of its MDR1 gene.The high expression of the MDR1 gene by the scathing factors can bring cells to produce endurance toward other subsequent scathing factors.So,it is more appropriate to calling MDR1 gene the multifold scathing factors-fast gene.