Evaluation of binding of cytotoxic analogs of luteinizing hormone-releasing hormone to human breast cancer and mouse MXT mammary tumor.
Evaluation of binding of cytotoxic analogs of luteinizing hormone-releasing hormone to human breast cancer and mouse MXT mammary tumor.
复制标题
黄体生成素释放激素细胞毒性类似物与人乳腺癌和小鼠 MXT 乳腺肿瘤结合的评估。
DOI：
10.1007/bf01961247
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发表时间：
1992
影响因子：
3.8
通讯作者：
Schally,AV
中科院分区：
文献类型：
--
作者：
Milovanovic,SR;Radulovic,S;Schally,AV
本实验室研制的几种促黄体生成素释放激素（LH-RH）的细胞毒性类似物在人乳腺癌和雌激素非依赖性MXT乳腺癌细胞膜上的结合特性进行了研究。在人乳腺和MXT乳腺肿瘤细胞的膜制备物中证明了[125 I] D-Trp 6-LH-RH和细胞毒性LH-RH类似物[125 I]T-98（[D-Lys 6]LH-RH偶联至戊二酰-2-（羟甲基）蒽醌）（HMAQG）的特异性结合。T-98的配体结合是特异性的、可饱和的，并且依赖于温度、时间和质膜浓度。结合数据的分析表明，在人乳腺癌中，[125 I]T-98的相互作用与两类LH-RH受体的存在一致，一类显示高亲和力和低容量，另一类显示低亲和力和高容量结合。在MXT乳腺癌细胞膜中，T-98与一类可饱和的、特异性的、非合作性的结合位点结合，具有高亲和力和低容量。在MXT乳腺癌细胞膜中，[125 I]T-98的结合和解离速率分别为4.757× 108 M − 1 min − 1和0.016 min−1（t1/2=38.7）。在人乳腺癌中，结合高亲和力位点的结合速率常数（K1 a和K1 b）为2.3× 106 M − 1 min − 1，结合低亲和力位点的结合速率常数为1.8× 104 M − 1 min − 1。解离速率常数分别为K−1a=0.0801 min−1（t1/2a=63.4 min）和K−1b=0.0467 min−1（t1/2b=23.5 min）。[125 I]T-98不被未标记的生长抑素或表皮生长因子置换，但被未标记的T-98或[D-Trp 6]LH-RH完全置换。本实验室合成的LH-RH的细胞毒性激动剂和拮抗剂对[D-Trp 6]LH-RH的置换曲线的分析表明，T-121、AJ-11、T-120、T-133和T-98在从乳腺癌和MXT癌膜置换[125 I] D-Trp 6-LH-RH方面最有效。[125 I] D-Trp 6-LH-RH和[125 I]T-98在人乳腺癌和雌激素非依赖性MXT小鼠乳腺癌细胞膜中的结合动力学和位移曲线分析表明，细胞毒性类似物T-98与LH-RH受体的结合可逆地进行，就像其同类物没有细胞毒性自由基一样。我们的发现可能会为进一步研究携带细胞毒性自由基的LH-RH类似物提供刺激。这种类似物可以靶向乳腺癌和其他具有LH-RH膜受体的癌症。因为抗肿瘤作用可以在具有细胞膜受体的更有选择性的部位发挥更大的程度，所以可以降低外周毒性。
The binding characteristics of several cytotoxic analogs of luteinizing hormone-releasing hormone (LH-RH) developed in our laboratory were examined in membranes from human breast cancer and estrogen independent MXT mammary cancer. Specific binding of [125I]D-Trp6-LH-RH and the cytotoxic LH-RH analog [125I]T-98 ([D-Lys6]LH-RH coupled to glutaryl-2-(hydroxymethyl)anthraquinone) (HMAQG) was demonstrated in membrane preparations from human breast and MXT mammary tumor cells. Ligand binding of T-98 was specific, saturable, and dependent on temperature, time, and plasma membrane concentration. Analysis of the binding data showed that in human breast cancer, interaction of [125I]T-98 was consistent with the presence of two classes of LH-RH receptors, one class showing high affinity and low capacity, and the other class showing low affinity and high capacity binding. In membranes from MXT mammary cancer, T-98 bound to one class of saturable, specific, noncooperative binding sites with high affinity and low capacity. The rates of association and dissociation for [125I]T-98 were calculated to be 4.757×108M−1min−1and 0.016 min−1(t1/2=38.7) in membranes from MXT mammary cancer. In human breast cancer, association rate constants (K1aand K1b) were 2.3×106M−1min−1for binding to high affinity and 1.8×104M−1min−1for binding to low affinity binding sites. Dissociation rate constants were K−1a=0.0801 min−1(t1/2a=63.4 min) and K−1b=0.0467 min−1(t1/2b=23.5 min), respectively. [125I]T-98 was not displaced by either unlabeled somatostatin or epidermal growth factor, but was displaced completely by unlabeled T-98 or [D-Trp6]LH-RH. The analysis of displacement curves of [D-Trp6]LH-RH by cytotoxic agonists and antagonists of LH-RH synthesized in our laboratory showed that T-121, AJ-11, T-120, T-133, and T-98 were the most potent in displacing [125I]D-Trp6-LH-RH from breast and MXT cancer membranes. Binding kinetics and analyses of displacement curves of [125I]D-Trp6-LH-RH and [125I]T-98 in membranes of human breast cancer and estrogen independent MXT mouse mammary cancer suggest that binding of the cytotoxic analog T-98 to the LH-RH receptor proceeds reversibly like that of its congeners without cytotoxic radicals. Our findings may provide a stimulus for further studies with LH-RH analogs carrying cytotoxic radicals. Such analogs could be targeted to breast cancer and other cancers that have membrane receptors for LH-RH. Because the antitumor action may be exerted to a greater degree at more selective sites that have the cell membrane receptors, the peripheral toxicity could be reduced.