Objective To establish a method for detection folylpolyglutamate syntbetase (FPGS),explore the change of FPGS in the drug-resistant A549 cells induced by methotrexate(MTX) enantiomer,and provide new tools to further investigate drug resistant mechanism. Methods A549 cell lines induced by L-( + )-MTX and D-( - )-MTX (25 μmol/L) were chosen to raise three cell lines as compared with MTX-sensitive cell line. Then FPGS were extracted for the CEIA-LIF and western blot was performed. After validation, FPGS antibodies were labeled by fluoreacein isothiocyanate (FITC) and produced a immune response with former-extracted FPGS. CELA-LIF can separate and detect labeled proteins according ruination time of the protein with different size and detect FPGS in drug resistant cell lines induced with L-(+)-MTX and D-(- )-MTX. The accuracy was evaluated as compared with western blot assay. Results The separation time of CEIA-LIF for labeled FPGS antibody and the immune complexes were7. 1 min and 8.9 min, and the resolving power was 4. 5. The process of protein separation and detection can be accomplished in less than 10 minutes. Western blot analysis showed there was no non-specific bands appears in the extract of these three cell lines after the freeze-thaw in liquid nitrogen. The minimum detection level in sensitive cell strains was 0. 68 mg/μl. The consent of FPGS in L-(+)-MTX and D-( - )-MTX induced cells were 46. 59% and 48. 36% compared with drug sensitive cell strains with CELA-LIF. Conclusions CELA-LIF was established in this experiment. It is efficient and sensitive for detecting of FPGS, which is similar to western blot method. The level of FPGS in L-( + )-MTX and D-( - )-MTX induced drug resistant cell lines is significantly lower, indicating the expression of FPGS is damaged.%目的 为观察甲氨蝶呤(MTX)对映体诱导肺癌A549细胞株耐药后叶酰聚谷氨酸合成酶(folylpolyglutamate synthetase,FPGS)含量变化,建立一种用毛细管电泳免疫-激光诱导荧光术(CEIA-LIF)测定FPGS的方法,以便为深入探讨肿瘤耐药机制提供新的实验手段.方法 实验分别选用耐药浓度为25 μmol/L的L-(+)-MTX和D-(-)-MTX肺癌A549耐药细胞株,以MTX敏感的细胞株作对照,培养获取上述3株细胞,并粗提取FIGS做CEIA-LIF和免疫印迹(WB)实验;用异硫氰酸荧光素(FITC)标记FPGS抗体,与提取的FPGS进行免疫反应;然后采用CEIA-LIF,根据不同分子量蛋白具有不同的迁移时间,分离检测标记蛋白,检测L广(+)-MTX和D-(-)-MTX作用耐药前后3株肺癌A549细胞株中FPGS表达含量;同时用WB作对照,以评价CEIA-LIF的特异性和FPGs定量的准确性.结果 CEIA-LIF分离标记FPGS抗体与免疫复合物的分离时间分别为7.1、8.9 min,分离度(R)=4.5,在10 min内即完成蛋白的分离和检测.经WB鉴定3株细胞液氮冻融裂解后离心提取液中组分与FPGS抗体无非特异性条带出现.CEIA-LIF测定敏感细胞株的检测下限为0.68 mg/μl细胞;而其检测25 μmol/L L(+)-MTX和25 μmol/L D-(-)-MTX诱导耐药细胞中FPGS的表达含量分别为对照组敏感细胞的46.59%和48.36%.结论 本研究建立的CEIA-LIF检测FPGS法具有高效快速的特点,且具与WB类似的特异性;同时提高了检测的敏感度.L-(+)-MTX和D-(-)-MTX诱导耐药后细胞株中FPGS表达含量较敏感细胞株明显减少,证明MTX耐药细胞株FPGS表达含量受损.
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