Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520-8040, USA.
Radiat Res. 2012 Sep;178(3):126-37. doi: 10.1667/rr2934.1. Epub 2012 Aug 3.
Agents with selective toxicity to hypoxic cells have shown promise as adjuncts to radiotherapy. Our previous studies showed that the bioreductive alkylating agent KS119 had an extremely large differential toxicity to severely hypoxic and aerobic cells in cell culture, and was effective in killing the hypoxic cells of EMT6 mouse mammary tumors in vivo. However, the limited solubility of that compound precluded its development as an anticancer drug. Here we report our initial studies with KS119W, a water-soluble analog of KS119. The cytotoxicity of KS119W to EMT6 cells in vitro was similar to that of KS119, with both agents producing only minimal cytotoxicity to aerobic cells even after intensive treatments, while producing pronounced cytotoxicity to oxygen-deficient cells. This resulted in large differentials in the toxicities to hypoxic and aerobic cells (>1,000-fold at 10 μM). Low pH had only minimal effects on the cytotoxicity of KS119W. Under hypoxic conditions, EMT6 cells transfected to express high levels of either human or mouse versions of the repair protein O(6)-alkylguanine-DNA alkyltransferase, which is also known as O(6)-methylguanine DNA-methyltransferase, were much more resistant to KS119W than parental EMT6 cells lacking O(6)-alkylguanine-DNA alkyltransferase, confirming the importance of DNA O-6-alkylation to the cytotoxicity of this agent. Studies with EMT6 tumors in BALB/c Rw mice using both tumor cell survival and tumor growth delay assays showed that KS119W was effective as an adjunct to irradiation for the treatment of solid tumors in vivo, producing additive or supra-additive effects in most combination regimens for which the interactions could be evaluated. Our findings encourage additional preclinical studies to examine further the antineoplastic effects of KS119W alone and in combination with radiation, and to examine the pharmacology and toxicology of this new bioreductive alkylating agent so that its potential for clinical use as an adjuvant to radiotherapy can be evaluated.
对乏氧细胞具有选择性毒性的药物已被证明可作为放射治疗的辅助药物。我们以前的研究表明，生物还原烷化剂 KS119 对细胞培养中的严重缺氧细胞和需氧细胞具有极高的差异毒性，并且在体内对 EMT6 小鼠乳腺癌的缺氧细胞有效。然而，由于该化合物的溶解度有限，其作为抗癌药物的开发受到限制。在此，我们报告了 KS119W 的初步研究结果，KS119W 是 KS119 的水溶性类似物。KS119W 对 EMT6 细胞的体外细胞毒性与 KS119 相似，两种药物即使经过密集治疗，对需氧细胞也只有最小的细胞毒性，而对缺氧细胞则产生明显的细胞毒性。这导致缺氧细胞和需氧细胞之间的毒性差异很大（在 10μM 时超过 1000 倍）。低 pH 值对 KS119W 的细胞毒性仅有很小的影响。在缺氧条件下，转染表达高水平人或鼠修复蛋白 O(6)-烷基鸟嘌呤-DNA 烷基转移酶（也称为 O(6)-甲基鸟嘌呤 DNA-甲基转移酶）的 EMT6 细胞比缺乏 O(6)-烷基鸟嘌呤-DNA 烷基转移酶的亲本 EMT6 细胞对 KS119W 更具抵抗力，这证实了 DNA O-6-烷化对该药物的细胞毒性的重要性。使用 EMT6 肿瘤在 BALB/c Rw 小鼠中的肿瘤细胞存活和肿瘤生长延迟测定的研究表明，KS119W 作为放射治疗的辅助药物在体内治疗实体瘤是有效的，对于大多数可以评估相互作用的组合方案，产生相加或超相加的效果。我们的研究结果鼓励进一步进行临床前研究，以单独研究 KS119W 以及与放射治疗联合的抗肿瘤作用，并研究这种新型生物还原烷化剂的药理学和毒理学，以便评估其作为放射治疗辅助剂的临床应用潜力。
