Hayes M T, Bartley J, Parsons P G
Queensland Cancer Fund Laboratories, Queensland Institute of Medical Research, Herston, Australia.
Melanoma Res. 1998 Feb;8(1):67-75. doi: 10.1097/00008390-199802000-00012.
The mechanism of action of fotemustine, a relatively new chloroethylnitrosourea, was evaluated in human melanoma cells in order to assess its potential as an agent for hyperthermic limb perfusion. Fotemustine was more toxic to O6-alkylguanine methyl transferase (AGT) deficient (Mer-) cells than Mer+ cells, implicating AGT as a major determinant of resistance. Mer+ cells derived from Mer- cell lines following exposure to the monofunctional alkylating metabolite of dacarbazine (DTIC) were also resistant to fotemustine. Mer status did not influence the replication of fotemustine-damaged adenovirus 5, whereas virus treated with the monofunctional alkylating agent N-methyl-N1-nitro-N-nitrosoguanidine (MNNG) was replicated much more efficiently by Mer+ cells. This suggests that the initial O6-alkylated product, if not immediately repaired, rearranges to form DNA crosslinks which cannot be repaired by AGT. Replication of a control virus was not affected by treating the cells with fotemustine, indicating that the drug acted primarily on DNA rather than at epigenetic levels. Fotemustine generally produced a G2-M block in the cell cycle, most strikingly in Mer- cells at low, minimally toxic concentrations; MNNG and high doses of fotemustine induced S phase arrest. Concurrent hyperthermia (41.5 degrees C for 1 h) increased the toxicity of fotemustine in some cell lines. Fotemustine decomposed in culture medium in two phases; the first was complete within 5 min and was most marked in Mer+ cells. The results suggest that fotemustine may be suitable for isolated limb perfusion in melanoma, with the potential for overcoming resistance by including inhibitors of AGT.
为了评估福莫司汀（一种相对较新的氯乙基亚硝脲）作为热灌注肢体治疗药物的潜力，对其在人黑色素瘤细胞中的作用机制进行了评估。福莫司汀对O6-烷基鸟嘌呤甲基转移酶（AGT）缺陷（Mer-）细胞的毒性比对Mer+细胞更大，这表明AGT是耐药性的主要决定因素。暴露于达卡巴嗪（DTIC）的单功能烷基化代谢产物后从Mer-细胞系衍生而来的Mer+细胞对福莫司汀也具有抗性。Mer状态不影响福莫司汀损伤的腺病毒5的复制，而用单功能烷基化剂N-甲基-N1-硝基-N-亚硝基胍（MNNG）处理的病毒在Mer+细胞中的复制效率更高。这表明最初的O6-烷基化产物如果不立即修复，会重排形成AGT无法修复的DNA交联。用福莫司汀处理细胞对对照病毒的复制没有影响，这表明该药物主要作用于DNA而非表观遗传水平。福莫司汀通常在细胞周期中产生G2-M期阻滞，在Mer-细胞中，在低的、最低毒性浓度下最为明显；MNNG和高剂量的福莫司汀诱导S期阻滞。同时进行的热疗（41.5℃，1小时）在一些细胞系中增加了福莫司汀的毒性。福莫司汀在培养基中分两个阶段分解；第一阶段在5分钟内完成，在Mer+细胞中最为明显。结果表明，福莫司汀可能适用于黑色素瘤的孤立肢体灌注，通过加入AGT抑制剂有可能克服耐药性。
