Ching L-M, Zwain S, Baguley B C
Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
Br J Cancer. 2004 Feb 23;90(4):906-10. doi: 10.1038/sj.bjc.6601606.
5,6-Dimethylxanthenone-4-acetic acid (DMXAA) is currently undergoing clinical evaluation as an antivascular agent for the treatment of cancer. We have previously demonstrated that DMXAA induces apoptosis of vascular endothelial cells in murine tumour sections and in a breast carcinoma biopsy from one patient in a Phase I trial. We wished to determine the tissue selectivity of this effect and its relationship to induced blood flow changes. Mice with Colon 38 tumours were treated with DMXAA and tissues were examined for apoptosis by TdT-mediated dUTP nick-end labelling (TUNEL). Hoechst 33342 was used to stain functional vessels, with the loss of stained vessels used as a measure of tumour vascular collapse. Treatment with DMXAA at 25 mg kg(-1), its maximum tolerated dose (MTD), showed, after 3 h, a 12-fold increase in TUNEL staining of tumour vascular endothelial cells. In contrast, tissue from the heart, brain, liver and spleen showed no increase. Induction of apoptosis in tumour tissue was both dose-dependent, observable at doses as low as 5 mg kg(-1), and time-dependent. Apoptosis was significantly lower in Colon 38 tumours of mice, with a targeted disruption in the TNF gene (TNF(-/-)), or in the TNF receptor 1 gene (TNFR(-/-)), as compared with that in wild-type mice. Increasing the DMXAA dose to 50 mg kg(-1) in these knockout mice raised tumour apoptosis to a level comparable to that induced in wild-type mice given DMXAA at the MTD. For all the data, a significant correlation (r=0.94; P<0.001) was found between logarithmic percentage apoptosis induction and the logarithmic density of Hoechst-stained vessels. These results suggest that blood flow inhibition caused by DMXAA is tumour tissue-specific and is a consequence of induction of apoptosis in tumour vascular endothelial cells.
5,6-二甲基呫吨酮-4-乙酸（DMXAA）目前正在作为一种抗癌血管生成剂进行临床评估。我们之前已经证明，在一项I期试验中，DMXAA可诱导小鼠肿瘤切片以及一名患者乳腺癌活检组织中的血管内皮细胞凋亡。我们希望确定这种效应的组织选择性及其与诱导血流变化的关系。给患有结肠38肿瘤的小鼠注射DMXAA，通过末端脱氧核苷酸转移酶介导的dUTP缺口末端标记法（TUNEL）检测组织中的凋亡情况。用Hoechst 33342对功能性血管进行染色，以染色血管的减少作为肿瘤血管塌陷的指标。以25 mg·kg⁻¹（其最大耐受剂量，MTD）的DMXAA处理后3小时，肿瘤血管内皮细胞的TUNEL染色增加了12倍。相比之下，心脏、大脑、肝脏和脾脏组织未出现增加。肿瘤组织中凋亡的诱导具有剂量依赖性，在低至5 mg·kg⁻¹的剂量下即可观察到，并且具有时间依赖性。与野生型小鼠相比，肿瘤坏死因子基因（TNF⁻/⁻）或肿瘤坏死因子受体1基因（TNFR⁻/⁻）靶向缺失的小鼠的结肠38肿瘤中的凋亡明显更低。在这些基因敲除小鼠中将DMXAA剂量增加至50 mg·kg⁻¹，可使肿瘤凋亡水平提高到与给予MTD的DMXAA的野生型小鼠相当的水平。对于所有数据，在对数诱导凋亡百分比与Hoechst染色血管的对数密度之间发现了显著相关性（r = 0.94；P < 0.001）。这些结果表明，DMXAA引起的血流抑制具有肿瘤组织特异性，是肿瘤血管内皮细胞凋亡诱导的结果。
