Sappal Darshan S, McClendon A Kathleen, Fleming James A, Thoroddsen Vala, Connolly Kelly, Reimer Corinne, Blackman Ronald K, Bulawa Christine E, Osheroff Neil, Charlton Peter, Rudolph-Owen Laura A
Department of Molecular and Cellular Oncology, Millennium Pharmaceuticals, Inc., Cambridge, MA 02140, USA.
Mol Cancer Ther. 2004 Jan;3(1):47-58.
MLN944 (XR5944) is a novel bis-phenazine that has demonstrated exceptional efficacy against a number of murine and human tumor models. The drug was reported originally as a dual topoisomerase I/II poison, but a precise mechanism of action for this compound remains to be determined. Several lines of evidence, including the marginal ability of MLN944 to stabilize topoisomerase-dependent cleavage, and the sustained potency of MLN944 in mammalian cells with reduced levels of both topoisomerases, suggest that other activities of the drug exist. In this study, we show that MLN944 intercalates into DNA, but has no effect on the catalytic activity of either topoisomerase I or II. MLN944 displays no significant ability to stimulate DNA scission mediated by either topoisomerase I or II compared with camptothecin or etoposide, respectively. In addition, yeast genetic models also point toward a topoisomerase-independent mechanism of action. To examine cell cycle effects, synchronized human HCT116 cells were treated with MLN944, doxorubicin, camptothecin, or a combination of the latter two to mimic a dual topoisomerase poison. MLN944 treatment was found to induce a G(1) and G(2) arrest in cells that is unlike the typical G(2)-M arrest noted with known topoisomerase poisons. Finally, transcriptional profiling analysis of xenograft tumors treated with MLN944 revealed clusters of regulated genes distinct from those observed in irinotecan hydrochloride (CPT-11)-treated tumors. Taken together, these findings suggest that the primary mechanism of action of MLN944 likely involves DNA binding and intercalation, but does not appear to involve topoisomerase inhibition.
MLN944（XR5944）是一种新型双吩嗪，已在多种小鼠和人类肿瘤模型中显示出卓越疗效。该药物最初被报道为一种双重拓扑异构酶I/II抑制剂，但这种化合物的确切作用机制仍有待确定。包括MLN944稳定拓扑异构酶依赖性切割的能力有限，以及在两种拓扑异构酶水平均降低的哺乳动物细胞中MLN944仍具有持续效力等多项证据表明，该药物存在其他活性。在本研究中，我们发现MLN944可嵌入DNA，但对拓扑异构酶I或II的催化活性均无影响。与喜树碱或依托泊苷相比，MLN944分别对拓扑异构酶I或II介导的DNA断裂均无显著刺激能力。此外，酵母遗传模型也指向一种不依赖拓扑异构酶的作用机制。为研究细胞周期效应，对同步化的人HCT116细胞用MLN944、阿霉素、喜树碱或后两者的组合进行处理，以模拟双重拓扑异构酶抑制剂。结果发现，MLN944处理可诱导细胞出现G(1)期和G(2)期阻滞，这与已知拓扑异构酶抑制剂导致的典型G(2)-M期阻滞不同。最后，对用MLN944处理的异种移植肿瘤进行转录谱分析，发现其调控基因簇与盐酸伊立替康（CPT-11）处理的肿瘤中观察到的不同。综上所述，这些发现表明，MLN944的主要作用机制可能涉及DNA结合和嵌入，但似乎不涉及拓扑异构酶抑制。
