Micha Dimitra, Cummings Jeff, Shoemaker Alex, Elmore Steven, Foster Kelly, Greaves Martin, Ward Tim, Rosenberg Saul, Dive Caroline, Simpson Kathryn
Clinical and Experimental Pharmacology Group, Paterson Institute for Cancer Research, University of Manchester, Manchester, United Kingdom.
Clin Cancer Res. 2008 Nov 15;14(22):7304-10. doi: 10.1158/1078-0432.CCR-08-0111.
This study evaluated epithelial cell death ELISAs that measure circulating cytokeratin 18 in mice bearing small-cell lung cancer xenografts treated with a proapoptotic dose of the BH-3 mimetic ABT-737.
H146 tumor-bearing and non-H146 tumor-bearing severe combined immunodeficient (SCID)/bg mice were treated with ABT-737 or vehicle control. Plasma collected before and 2 to 360 hours after treatment was analyzed by M30 (caspase-cleaved cytokeratin 18) and M65 (intact and cleaved cytokeratin 18) ELISA. In parallel, tumors were interrogated for cleaved caspase-3 and cleaved cytokeratin 18 as biomarkers of apoptosis.
ABT-737-treated tumors regressed by 48 hours (P < 0.01) compared with controls, correlating with increased cleaved cytokeratin 18 (P < 0.01; 6 and 24 hours) and increased intact cytokeratin 18 (P < 0.01; 24 hours). Cleaved cytokeratin 18 levels decreased below baseline between 72 and 360 hours for ABT-737-treated and control mice whereas intact cytokeratin 18 decreased below the level of detection at 8 and 15 days in ABT-737-treated mice only. Apoptosis in tumors reflected changes in circulating cytokeratin 18 (cleaved caspase-3, P < 0.05 at 2 hours and P < 0.001 at 6, 12, and 24 hours; caspase-cleaved cytokeratin 18, P < 0.05 at 15 days, for drug treated versus controls).
ABT-737 caused tumor regression by apoptosis in H146 xenografts that mapped to a drug-specific, early increase in circulating cleaved cytokeratin 18 that subsequently declined. Circulating, intact cytokeratin 18 levels correlated with tumor burden. Cleaved caspase-3 and caspase-cleaved cytokeratin 18 in tumor correlated with treatment (P < 0.05, 2 hours; P < 0.001, 6, 12, and 24 hours; cleaved caspase-3, P < 0.05, 15 days; caspase-cleaved cytokeratin 18), indicating that events in plasma were tumor derived. These circulating biomarker data will be translated to clinical trials wherein serial tumor biopsies are rarely obtained.
本研究评估了上皮细胞死亡酶联免疫吸附测定法（ELISA），该方法用于检测经促凋亡剂量的BH-3模拟物ABT-737治疗的携带小细胞肺癌异种移植瘤小鼠体内循环细胞角蛋白18的水平。
用ABT-737或溶剂对照处理荷H146肿瘤和未荷H146肿瘤的严重联合免疫缺陷（SCID）/bg小鼠。在治疗前以及治疗后2至360小时收集血浆，通过M30（半胱天冬酶切割的细胞角蛋白18）和M65（完整和切割的细胞角蛋白18）ELISA进行分析。同时，检测肿瘤中切割的半胱天冬酶-3和切割的细胞角蛋白18，作为凋亡的生物标志物。
与对照组相比，经ABT-737处理的肿瘤在48小时时出现消退（P<0.01），这与切割的细胞角蛋白18增加（P<0.01；6小时和24小时）以及完整细胞角蛋白18增加（P<0.01；24小时）相关。对于经ABT-737处理的小鼠和对照小鼠，切割的细胞角蛋白18水平在72至360小时之间降至基线以下，而完整细胞角蛋白18仅在经ABT-737处理的小鼠中在8天和15天时降至检测水平以下。肿瘤中的凋亡反映了循环细胞角蛋白18的变化（切割的半胱天冬酶-3，2小时时P<0.05，6、12和24小时时P<0.001；半胱天冬酶切割的细胞角蛋白18，药物处理组与对照组相比，15天时P<0.05）。
ABT-737通过诱导H146异种移植瘤凋亡导致肿瘤消退，这与循环中切割的细胞角蛋白18在药物作用早期特异性增加随后下降有关。循环中完整细胞角蛋白18水平与肿瘤负荷相关。肿瘤中切割的半胱天冬酶-3和半胱天冬酶切割的细胞角蛋白18与治疗相关（P<0.05，2小时；P<0.001，6、12和24小时；切割的半胱天冬酶-3，P<0.05，15天；半胱天冬酶切割的细胞角蛋白18），表明血浆中的这些事件源自肿瘤。这些循环生物标志物数据将转化应用于临床试验，在这类试验中很少能获得系列肿瘤活检样本。
