Rekha G K, Sreerama L, Sladek N E
Department of Pharmacology, University of Minnesota Medical School, Minneapolis 55455.
Biochem Pharmacol. 1994 Nov 16;48(10):1943-52. doi: 10.1016/0006-2952(94)90593-2.
A cultured human colon carcinoma cell line, viz. colon C, exhibiting intrinsic cellular resistance to mafosfamide mediated by relatively elevated levels of a cytosolic class-3 aldehyde dehydrogenase was identified. Colon C cells were found to be much less sensitive/more resistant (about 10-fold as judged by LC90 values) to mafosfamide than were two other cultured human colon carcinoma cell lines, viz. RCA and HCT 116b, and, as compared to the barely detectable aldehyde dehydrogenase activity (NADP-dependent enzyme-catalyzed oxidation of benzaldehyde to benzoic acid) in RCA and HCT 116b cells, that in colon C cells was about 200-fold greater. The three cell lines were equisensitive to phosphoramide mustard. Aldehyde dehydrogenase activity was confined to the cytosol in colon C cells (as well as in the other two cell lines) and, on the basis of its physical, immunological and catalytic characteristics, the operative enzyme was judged to be a Type-1 ALDH-3 identical to the Type-1 ALDH-3 expressed in methylcholanthrene-treated human breast adenocarcinoma MCF-7/0 cells and very nearly identical to the Type-1 ALDH-3 expressed in human normal stomach mucosa. Class-1 and class-2 aldehyde dehydrogenases were not found in these cells. The relative insensitivity to mafosfamide on the part of colon C cells was not observed when exposure to mafosfamide was in the presence of benzaldehyde or 4-(diethylamino)benzaldehyde, each a relatively good substrate for ALDH-3, whereas it was retained when exposure to mafosfamide was in the presence of acetaldehyde, a relatively poor substrate for this enzyme. Sensitivity to mafosfamide on the part of HCT 116b and RCA cells, and to phosphoramide mustard on the part of all three cell lines, was unaffected when drug exposure was in the presence of any of the three aldehydes. Together with earlier reports from our laboratory, these observations demonstrate that intrinsic, as well as stable and transient acquired, resistance to oxazaphosphorines, such as mafosfamide and cyclophosphamide, can be mediated by relatively increased levels of cytosolic class-3 aldehyde dehydrogenases.
一种培养的人结肠癌细胞系，即结肠C细胞系，被鉴定出对马磷酰胺具有内在的细胞抗性，这种抗性由相对较高水平的胞质3类醛脱氢酶介导。发现结肠C细胞对马磷酰胺的敏感性远低于/抗性高于（根据LC90值判断约为10倍）另外两种培养的人结肠癌细胞系，即RCA和HCT 116b细胞系。并且，与RCA和HCT 116b细胞中几乎检测不到的醛脱氢酶活性（NADP依赖性酶催化苯甲醛氧化为苯甲酸）相比，结肠C细胞中的醛脱氢酶活性大约高200倍。这三种细胞系对磷酰胺芥的敏感性相同。醛脱氢酶活性局限于结肠C细胞（以及其他两种细胞系）的胞质中，根据其物理、免疫和催化特性，判断起作用的酶是1型ALDH - 3，与经甲基胆蒽处理的人乳腺腺癌MCF - 7/0细胞中表达的1型ALDH - 3相同，并且与人正常胃黏膜中表达的1型ALDH - 3非常接近。在这些细胞中未发现1类和2类醛脱氢酶。当在苯甲醛或4 - （二乙氨基）苯甲醛存在的情况下暴露于马磷酰胺时，未观察到结肠C细胞对马磷酰胺的相对不敏感性，苯甲醛和4 - （二乙氨基）苯甲醛均是ALDH - 3相对较好的底物，而当在乙醛存在的情况下暴露于马磷酰胺时，结肠C细胞仍保持对马磷酰胺的抗性，乙醛是该酶相对较差的底物。当在三种醛中的任何一种存在的情况下进行药物暴露时，HCT 116b和RCA细胞对马磷酰胺的敏感性以及所有三种细胞系对磷酰胺芥的敏感性均未受影响。与我们实验室早期的报告一起，这些观察结果表明，对恶唑磷类药物，如马磷酰胺和环磷酰胺的内在抗性以及稳定和短暂获得的抗性，可由胞质3类醛脱氢酶水平的相对增加介导。
