Folkes Lisa K, Greco Olga, Dachs Gabi U, Stratford Michael R L, Wardman Peter
Gray Cancer Institute, Mount Vernon Hospital, P.O. Box 100, Northwood, HA6 2JR, Middlesex, UK.
Biochem Pharmacol. 2002 Jan 15;63(2):265-72. doi: 10.1016/s0006-2952(01)00868-1.
Indole-3-acetic acid and some derivatives are oxidized by horseradish peroxidase, forming a radical-cation that rapidly fragments (eliminating CO(2)) to form cytotoxic products. No toxicity is seen when either indole-3-acetic acid or horseradish peroxidase is incubated alone at concentrations that together form potent cytotoxins. Unexpectedly, 5-fluoroindole-3-acetic acid, which is oxidized by horseradish peroxidase compound I 10-fold more slowly than indole-3-acetic acid, is much more cytotoxic towards V79 hamster fibroblasts in the presence of peroxidase than the unsubstituted indole. The fluorinated prodrug/peroxidase combination also shows potent cytotoxic activity in human and rodent tumor cell lines. Cytotoxicity is thought to arise in part from the formation of 3-methylene-2-oxindole (or analogues) that can conjugate with thiols and probably DNA or other biological nucleophiles. Levels of the fluorinated prodrug in the murine carcinoma NT after intraperitoneal administration of 50 mg/kg were about 200 microM. Although these were 4-5-fold lower than plasma levels (which reached 1mM), the integrated area under the concentration/time curve in tumors over 2 hr was approximately 20 mM min, almost double the exposure needed to achieve approximately 90-99% cell kill in human MCF7 breast or HT29 colon tumor cell lines and CaNT murine cells in vitro, although the human bladder T24 carcinoma cell line was more resistant. The high cytotoxicity of 5-fluoroindole-3-acetic acid after oxidative activation suggests its further evaluation as a prodrug for targeted cancer therapy involving antibody-, polymer-, or gene-directed delivery of horseradish peroxidase or similar activating enzymes.
吲哚 - 3 - 乙酸及其一些衍生物可被辣根过氧化物酶氧化，形成一种自由基阳离子，该阳离子会迅速裂解（消除CO₂）以形成细胞毒性产物。当吲哚 - 3 - 乙酸或辣根过氧化物酶单独以共同形成强效细胞毒素的浓度孵育时，未观察到毒性。出乎意料的是，5 - 氟吲哚 - 3 - 乙酸被辣根过氧化物酶化合物I氧化的速度比吲哚 - 3 - 乙酸慢10倍，但在过氧化物酶存在的情况下，对V79仓鼠成纤维细胞的细胞毒性比未取代的吲哚大得多。这种氟化前药/过氧化物酶组合在人和啮齿动物肿瘤细胞系中也显示出强效的细胞毒性活性。细胞毒性被认为部分源于3 - 亚甲基 - 2 - 氧吲哚（或类似物）的形成，其可与硫醇以及可能与DNA或其他生物亲核试剂结合。腹腔注射50 mg/kg后，小鼠癌NT中的氟化前药水平约为200 microM。尽管这些水平比血浆水平（达到1 mM）低4 - 5倍，但肿瘤中浓度/时间曲线下的积分面积在2小时内约为20 mM·min，几乎是在体外使人MCF7乳腺癌或HT29结肠肿瘤细胞系以及CaNT小鼠细胞达到约90 - 99%细胞杀伤所需暴露量的两倍，尽管人膀胱T24癌细胞系更具抗性。5 - 氟吲哚 - 3 - 乙酸经氧化活化后的高细胞毒性表明，它可作为一种前药进行进一步评估，用于涉及抗体、聚合物或基因导向递送辣根过氧化物酶或类似活化酶的靶向癌症治疗。
