The development of multiple-drug-resistant (MDR) cancer all too often signals the need for toxic alternative therapy or palliative care. Our recent in vivo and in vitro studies using canine MDR lymphoma cancer cells demonstrate that the Anaphase Promoting Complex (APC) is impaired in MDR cells compared to normal canine control and drug-sensitive cancer cells. Here, we sought to establish whether this phenomena is a generalizable mechanism independent of species, malignancy type, or chemotherapy regime. To test the association of blunted APC activity with MDR cancer behavior, we used matched parental and MDR MCF7 human breast cancer cells, and a patient-derived xenograft (PDX) model of human triple-negative breast cancer. We show that APC activating mechanisms, such as APC subunit 1 (APC1) phosphorylation and CDC27/CDC20 protein associations, are reduced in MCF7 MDR cells when compared to chemo-sensitive matched cell lines. Consistent with impaired APC function in MDR cells, APC substrate proteins failed to be effectively degraded. Similar to our previous observations in canine MDR lymphoma cells, chemical activation of the APC using Mad2 Inhibitor-1 (M2I-1) in MCF7 MDR cells enhanced APC substrate degradation and resensitized MDR cells in vitro to the cytotoxic effects of the alkylating chemotherapeutic agent, doxorubicin (DOX). Using cell cycle arrest/release experiments, we show that mitosis is delayed in MDR cells with elevated substrate levels. When pretreated with M2I-1, MDR cells progress through mitosis at a faster rate that coincides with reduced levels of APC substrates. In our PDX model, mice growing a clinically MDR human triple-negative breast cancer tumor show significantly reduced tumor growth when treated with M2I-1, with evidence of increased DNA damage and apoptosis. Thus, our results strongly support the hypothesis that APC impairment is a driver of aggressive tumor development and that targeting the APC for activation has the potential for meaningful clinical benefits in treating recurrent cases of MDR malignancy.
多药耐药性（MDR）癌症的发展往往意味着需要采用毒性替代疗法或姑息治疗。我们近期利用犬类MDR淋巴瘤癌细胞进行的体内外研究表明，与正常犬类对照组及药物敏感癌细胞相比，MDR细胞中的后期促进复合体（APC）功能存在缺陷。本研究旨在探究这一现象是否可成为跨物种、跨恶性肿瘤类型及化疗方案的普适性机制。为验证APC活性抑制与MDR癌症行为的相关性，我们采用配对的亲代与MDR型MCF7人乳腺癌细胞系，以及人三阴性乳腺癌患者来源异种移植（PDX）模型。实验显示，与化疗敏感配对细胞系相比，MCF7 MDR细胞中APC激活机制（如APC亚基1磷酸化及CDC27/CDC20蛋白结合）显著减弱。与APC功能受损相一致的是，MDR细胞中APC底物蛋白未能有效降解。与我们先前在犬类MDR淋巴瘤细胞中的观察结果相似，使用Mad2抑制剂-1（M2I-1）对MCF7 MDR细胞进行APC化学激活后，可增强APC底物降解并恢复MDR细胞对烷化化疗药物阿霉素（DOX）细胞毒作用的体外敏感性。通过细胞周期阻滞/释放实验，我们发现底物水平升高的MDR细胞有丝分裂进程延迟。经M2I-1预处理后，MDR细胞有丝分裂进程加速，同时伴随APC底物水平下降。在PDX模型中，M2I-1治疗能显著抑制临床MDR人三阴性乳腺癌肿瘤的生长，并呈现DNA损伤增加和细胞凋亡的证据。因此，本研究结果有力支持以下假设：APC功能损伤是肿瘤侵袭性发展的驱动因素，而靶向激活APC可能为MDR恶性肿瘤复发病例的治疗带来具有临床意义的获益。
肿瘤(癌症)患者之家