Einbond Linda Saxe, Wu Hsan-Au, Su Tao, Chang Tangel, Panjikaran Maya, Wang Xiaomei, Goldsberry Sarah
Columbia University College of Physicians and Surgeons, New York, NY, USA.
J Carcinog. 2010 Nov 18;9:10. doi: 10.4103/1477-3163.72578.
Numerous studies have suggested that digitalis derivatives promise to be superior to existing adjuvant therapy for breast cancer as to effects and side-effects. In the present study, we have used gene expression analysis to determine the molecular action of digitoxin on breast cancer cells and assessed digitoxin's ability to synergize with the chemotherapy agent paclitaxel with respect to inhibition of cell proliferation
We treated (Her2 overexpressing, ER low) MDA-MB-453 human breast cancer cells with digitoxin at four doses {20 ng/ml (26 nM) to 1 μg/ml} and collected RNA at 6 h and 24 h for gene expression analysis. To examine the effects on ER positive cells, we treated MCF7 cells with digitoxin at 1 μg/ml and collected RNA for RT-PCR analysis. In addition, we assayed the growth inhibitory effect of low doses of digitoxin combined with paclitaxel and determined combination index values.
To reveal primary effects, we examined digitoxin's effect 6 h post-treatment with the highest dose, 1μg/ml, and found upregulation of the stress response genes EGR-1 and NAB2, lipid biosynthetic genes and the tumor suppressor gene p21, and downregulation of the mitotic cell cycle gene CDC16 and the replication gene PolR3B. RT-PCR analysis validated effects on stress response, apoptotic and cell cycle genes on MDA-MB-453 and MCF7 cells. Western blot analysis confirmed induction of EGR1 protein at 1 h and ATF3 at 24 h. Paclitaxel, as well as digitoxin, inhibited the in vitro activity of the purified Na(+)-K(+)-ATPase; digitoxin enhanced the growth inhibitory effects of paclitaxel on Her2 overexpressing breast cancer cells.
Our studies show the potential of digitoxin to prevent and treat breast cancer and indicate that the combination of digitoxin and paclitaxel is a promising treatment for ER negative breast cancer. These findings are the first to alert physicians to the possible dangers to patients who take a combination of digitoxin and paclitaxel. The potential dangers ensuing when paclitaxel and digitoxin are combined are dependent on the dose of digitoxin.
大量研究表明，洋地黄衍生物在疗效和副作用方面有望优于现有的乳腺癌辅助治疗方法。在本研究中，我们使用基因表达分析来确定洋地黄毒苷对乳腺癌细胞的分子作用，并评估洋地黄毒苷与化疗药物紫杉醇协同抑制细胞增殖的能力。
我们用四种剂量（20 ng/ml（26 nM）至1 μg/ml）的洋地黄毒苷处理（HER2过表达、雌激素受体低表达）的MDA-MB-453人乳腺癌细胞，并在6小时和24小时收集RNA用于基因表达分析。为了研究对雌激素受体阳性细胞的影响，我们用1 μg/ml的洋地黄毒苷处理MCF7细胞，并收集RNA用于逆转录聚合酶链反应分析。此外，我们测定了低剂量洋地黄毒苷与紫杉醇联合使用的生长抑制作用，并确定了联合指数值。
为了揭示主要作用，我们在使用最高剂量1μg/ml处理6小时后检查了洋地黄毒苷的作用，发现应激反应基因EGR-1和NAB2、脂质生物合成基因以及肿瘤抑制基因p21上调，有丝分裂细胞周期基因CDC16和复制基因PolR3B下调。逆转录聚合酶链反应分析验证了对MDA-MB-453和MCF7细胞应激反应、凋亡和细胞周期基因的影响。蛋白质免疫印迹分析证实1小时时EGR1蛋白和24小时时ATF3被诱导。紫杉醇以及洋地黄毒苷抑制纯化的钠钾ATP酶的体外活性；洋地黄毒苷增强了紫杉醇对HER2过表达乳腺癌细胞的生长抑制作用。
我们的研究显示了洋地黄毒苷预防和治疗乳腺癌的潜力，并表明洋地黄毒苷与紫杉醇联合使用是雌激素受体阴性乳腺癌的一种有前景的治疗方法。这些发现首次提醒医生注意服用洋地黄毒苷和紫杉醇联合药物的患者可能面临的危险。紫杉醇和洋地黄毒苷联合使用时产生的潜在危险取决于洋地黄毒苷的剂量。
