Su Feng, Zhu Shilin, Ruan Jinlan, Muftuoglu Yagmur, Zhang Longbo, Yuan Qianying
Department of Emergency, Xiangya Hospital, Central South University, Changsha, China.
The Second Affiliated Hospital, Hunan University of Chinese Medicine, Changsha, China.
Oncotarget. 2016 Jan 26;7(4):4142-54. doi: 10.18632/oncotarget.6769.
RY10-4, a novel protoapigenone analog, shows potent cytotoxicity against human breast cancer cells. However, breast cancer cell lines overexpressing human epidermal growth factor receptor 2 (HER2), SKBR3 and BT474, showed less sensitivity to RY10-4 when compared to breast cancer cells lines expressing lower levels of HER2, such as MDA-MB-231 and MCF-7 cells. This was associated with aberrant hyperactivity in Notch signaling in cells treated with RY10-4, since treatment with RY10-4 causes an increase in Notch activity by 2-to3.5-fold in SKBR3 and BT474 cell lines. The increase in activity was abrogated with a γ-secretase inhibitor, DAPT, or with Notch1 small-interfering RNA (si-Notch1). Cell proliferation was inhibited more effectively by RY10-4 plus DAPT or si-Notch1 than either agent alone. RY10-4 plus DAPT increases apoptosis in both HER2-overexpressing cell lines by two-fold compared to RY10-4 alone, while DAPT alone has no significant effects on apoptosis. In addition, we previously found RY10-4 could inhibit tumor growth through the PI3K/AKT pathway. Here we report that the combination of RY10-4 and DAPT exhibit additive suppression on AKT phosphorylation, contributing to the anti-cancer effects. In an animal model, this combination therapy inhibits the growth of SKBR3 tumor xenografts in nude mice to a greater extent than treatment with either reagent alone. These results indicate that the aberrant activation of Notch signaling impedes the inhibitory effect of RY10-4 on HER2-amplified cell proliferation. Furthermore, these adverse effects can be prevented by treatment combining RY10-4 with a Notch pathway inhibitor.
新型原芹菜素类似物RY10-4对人乳腺癌细胞显示出强大的细胞毒性。然而，与表达较低水平HER2的乳腺癌细胞系（如MDA-MB-231和MCF-7细胞）相比，过表达人表皮生长因子受体2（HER2）的乳腺癌细胞系SKBR3和BT474对RY10-4的敏感性较低。这与用RY10-4处理的细胞中Notch信号异常亢进有关，因为用RY10-4处理会使SKBR3和BT474细胞系中的Notch活性增加2至3.5倍。用γ-分泌酶抑制剂DAPT或Notch1小干扰RNA（si-Notch1）可消除活性增加。与单独使用任何一种药物相比，RY10-4加DAPT或si-Notch1能更有效地抑制细胞增殖。与单独使用RY10-4相比，RY10-4加DAPT可使两种HER2过表达细胞系中的细胞凋亡增加两倍，而单独使用DAPT对细胞凋亡无显著影响。此外，我们之前发现RY10-4可通过PI3K/AKT途径抑制肿瘤生长。在此我们报告，RY10-4和DAPT的组合对AKT磷酸化具有累加抑制作用，有助于抗癌效果。在动物模型中，这种联合疗法比单独使用任何一种试剂更能抑制裸鼠体内SKBR3肿瘤异种移植物的生长。这些结果表明，Notch信号的异常激活阻碍了RY10-4对HER2扩增细胞增殖的抑制作用。此外，将RY10-4与Notch途径抑制剂联合治疗可预防这些不良反应。
