Schultz R M, Andis S L, Shackelford K A, Gates S B, Ratnam M, Mendelsohn L G, Shih C, Grindey G B
Division of Cancer Research, Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285, USA.
Oncol Res. 1995;7(2):97-102.
Based on differential levels of membrane-associated folate binding protein (mFBP) expression, murine L1210 leukemia, human KB epidermoid carcinoma, and human IGROV1 ovarian carcinoma cells maintained under low (physiological) folate conditions (2 nM folinic acid) were used as model systems to investigate the potential role of mFBP in antifolate transport. In addition, L1210 parental cells were compared to a subline, L1210A, expressing high levels of mFBP and defective reduced folate carrier. Antifolates for which KB-derived mFBP has high affinity (5, 10-dideazatetrahydrofolic acid [DDATHF] and homo-DDATHF [0.24 and 0.78 respectively relative to folic acid]) and low affinity (methotrexate [0.002]) were chosen for this study. Protection against DDATHF/homo-DDATHF induced cytotoxicity was achieved preferentially by folic acid compared to folinic acid in IGROV1 and L1210A cells. In IGROV1 cells, cytotoxicity IC50s were increased 18- and 5.5-fold for DDATHF and homo-DDATHF respectively by 20 nM folic acid. Moreover, greater protection was observed in L1210A cells, where IC50s were increased 354- and 80-fold for these same compounds by 20 nM folic acid. Similar protection was not observed in KB cells, suggesting that KB mFBP was not functional in DDATHF transport. Although mFBP expression may be an important determinant in the cytotoxicity of antifolates for certain tumor cells, our data demonstrate a lack of correlation between levels of mFBP and function of mFBP for DDATHF transport in the models studied.
基于膜相关叶酸结合蛋白（mFBP）表达水平的差异，将在低（生理）叶酸条件（2 nM亚叶酸）下培养的小鼠L1210白血病细胞、人KB表皮样癌细胞和人IGROV1卵巢癌细胞用作模型系统，以研究mFBP在抗叶酸转运中的潜在作用。此外，将L1210亲本细胞与表达高水平mFBP且还原型叶酸载体有缺陷的亚系L1210A进行比较。本研究选择了KB来源的mFBP具有高亲和力（5,10-二去氮四氢叶酸[DDATHF]和高同型DDATHF[相对于叶酸分别为0.24和0.78]）和低亲和力（甲氨蝶呤[0.002]）的抗叶酸药物。在IGROV1和L1210A细胞中，与亚叶酸相比，叶酸对DDATHF/高同型DDATHF诱导的细胞毒性具有优先保护作用。在IGROV1细胞中，20 nM叶酸使DDATHF和高同型DDATHF的细胞毒性IC50分别增加了18倍和5.5倍。此外，在L1210A细胞中观察到了更大的保护作用，20 nM叶酸使这些相同化合物的IC50分别增加了354倍和80倍。在KB细胞中未观察到类似的保护作用，这表明KB mFBP在DDATHF转运中不起作用。尽管mFBP表达可能是某些肿瘤细胞抗叶酸细胞毒性的重要决定因素，但我们的数据表明，在所研究的模型中，mFBP水平与mFBP在DDATHF转运中的功能之间缺乏相关性。
