Byrne P, Tew K, Jemionek J, MacVittie T, Erickson L, Schein P
Blood. 1984 Apr;63(4):759-67.
1,(2-Chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) and other chloroethylnitrosourea anticancer agents in clinical use produce severe and cumulative bone marrow toxicity. Chlorozotocin, a glucose analogue, has demonstrated reduced hematologic toxicity while retaining full antitumor activity. The biochemical-pharmacologic properties of chlorozotocin and CCNU were compared in human bone marrow. After a 2-hr incubation with a 0.1-mM drug concentration, total cellular uptake of chlorozotocin in whole marrow was 2.47 +/- 0.80 pmole/10(4) cells and was not significantly different compared to the uptake of 1.94 +/- 0.53 pmole/10(4) cells with CCNU. The quantitative alkylation of bone marrow DNA by chlorozotocin, 22.8 +/- 1.2 pmole/mg DNA, was equivalent to that produced by CCNU, 22.9 +/- 0.5 pmole/mg DNA. Bone marrow was separated into 14 fractions by centrifugal elutriation. CCNU uptake was found to be greater than that of chlorozotocin in 3 fractions that were primarily composed of lymphocytes, monocytes, and normoblasts. Chlorozotocin uptake was greater than CCNU in 6 fractions that contained primarily mature and immature myeloid cells as well as the highest CFU-GM activity. The two drugs produced a comparable degree of DNA strand breakage and DNA-protein cross-linking as measured by alkaline elution of pooled fractions of elutriated bone marrow. DNA interstrand crosslinking was not found with either drug. The most significant finding of this study is the differences in the site of drug alkylation by chlorozotocin and CCNU in bone marrow chromatin. Endonuclease digestions with MCN, DNase I, and DNase II showed nonrandom alkylation of specific regions of chromatin by the two drugs: CCNU demonstrated a preferential binding to the transcriptionally active regions of chromatin, whereas chlorozotocin predominantly alkylated the transcriptionally inactive regions. These data suggest that the lethal damage of nitrosourea alkylation in human bone marrow is principally expressed in transcriptionally active regions of chromatin.
1,（2-氯乙基）-3-环己基-1-亚硝基脲（CCNU）以及其他临床使用的氯乙基亚硝基脲类抗癌药会产生严重且累积的骨髓毒性。氯脲霉素是一种葡萄糖类似物，已证明其血液学毒性降低，同时保留了完全的抗肿瘤活性。在人骨髓中比较了氯脲霉素和CCNU的生化药理特性。在0.1 mM药物浓度下孵育2小时后，全骨髓中氯脲霉素的总细胞摄取量为2.47±0.80皮摩尔/10⁴个细胞，与CCNU的摄取量1.94±0.53皮摩尔/10⁴个细胞相比无显著差异。氯脲霉素对骨髓DNA的定量烷基化作用为22.8±1.2皮摩尔/毫克DNA，与CCNU产生的22.9±0.5皮摩尔/毫克DNA相当。通过离心淘析将骨髓分离成14个组分。发现在主要由淋巴细胞、单核细胞和成红细胞组成的3个组分中，CCNU的摄取量大于氯脲霉素。在主要包含成熟和未成熟髓细胞以及最高CFU-GM活性的6个组分中，氯脲霉素的摄取量大于CCNU。通过对淘析骨髓的合并组分进行碱性洗脱测定，这两种药物产生的DNA链断裂和DNA-蛋白质交联程度相当。两种药物均未发现DNA链间交联。本研究最显著的发现是氯脲霉素和CCNU在骨髓染色质中药物烷基化位点的差异。用MCN、DNase I和DNase II进行的核酸内切酶消化显示，这两种药物对染色质特定区域的烷基化是非随机的：CCNU表现出优先结合到染色质的转录活性区域，而氯脲霉素主要烷基化转录非活性区域。这些数据表明，亚硝基脲烷基化在人骨髓中的致死损伤主要表现在染色质的转录活性区域。
