Bryan Jeffrey N, Kumar Senthil R, Jia Fang, Balkin Ethan R, Lewis Michael R
Department of Veterinary Medicine and Surgery, University of Missouri-Columbia, Columbia, MO, 65211, USA; Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, 65211, USA; Area of Pathobiology, University of Missouri-Columbia, Columbia, MO, 65211, USA.
Cell Biol Int. 2014 Feb;38(2):187-97. doi: 10.1002/cbin.10215. Epub 2013 Dec 9.
Zebularine is a cytidine analogue incorporated into DNA during replication, inhibiting DNA methyltransferase 1 (DNMT1), resulting in demethylation and changes in gene expression. Such modification may improve radiosensitivity in resistant lymphoma cells. The hypothesis of this study was that zebularine and radiation would synergistically inhibit cell growth and viability. Human MEC1 malignant B cells were incubated with 0-200 µM zebularine for 48 h. Media containing zebularine was removed, and the cells were irradiated with 0-2 Gy of either external beam irradiation or (177) Lu-DOTA-TATE, a radiolabelled somatostatin analogue. Concentration and viability were measured over 48-72 h. The proportion of apoptotic cells was identified using an active Caspase 3/7 assay. Zebularine inhibited growth of cells in a dose-dependent manner during exposure. No residual growth inhibition occurred following removal of the drug. Zebularine and external irradiation inhibited cell proliferation in a dose-dependent, synergistic interaction, but the effect on viability was additive. Treatment with zebularine and (177) Lu-DOTA-TATE resulted in less inhibition of proliferation (P = 0.0135), but a synergistic decrease in viability. Apoptotic fraction was much higher in cells irradiated with (177) Lu-DOTA-TATE than external irradiation. External irradiation induces growth arrest rather than apoptosis. Apoptosis is the primary effect of radiopharmaceutical therapy on tumour cells. Treatment with the methylation inhibitor, zebularine, appears to synergistically augment these natural effects in vitro, which could be exploited clinically.
泽布勒林是一种胞苷类似物，在复制过程中掺入DNA，抑制DNA甲基转移酶1（DNMT1），导致去甲基化和基因表达变化。这种修饰可能会提高耐药淋巴瘤细胞的放射敏感性。本研究的假设是泽布勒林和辐射将协同抑制细胞生长和活力。将人MEC1恶性B细胞与0-200μM泽布勒林孵育48小时。去除含有泽布勒林的培养基，然后用0-2 Gy的外照射或（177）Lu-DOTA-TATE（一种放射性标记的生长抑素类似物）对细胞进行照射。在48-72小时内测量浓度和活力。使用活性半胱天冬酶3/7检测法确定凋亡细胞的比例。在暴露期间，泽布勒林以剂量依赖性方式抑制细胞生长。去除药物后未出现残留的生长抑制。泽布勒林和外照射以剂量依赖性的协同相互作用抑制细胞增殖，但对活力的影响是相加的。用泽布勒林和（177）Lu-DOTA-TATE处理导致增殖抑制较少（P = 0.0135），但活力协同降低。用（177）Lu-DOTA-TATE照射的细胞中的凋亡分数比外照射高得多。外照射诱导生长停滞而非凋亡。凋亡是放射性药物治疗对肿瘤细胞的主要作用。用甲基化抑制剂泽布勒林处理似乎在体外协同增强了这些自然效应，这在临床上可能具有应用价值。
