Department of Pathology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, P.R. China.
Department of Pathology, The First Central Hospital of Baoding, Baoding, Hebei 071000, P.R. China.
Int J Mol Med. 2017 Aug;40(2):357-366. doi: 10.3892/ijmm.2017.3039. Epub 2017 Jun 23.
The aim of this study was to investigate the effects of bufalin on the mammalian target of rapamycin (mTOR/p70S6 kinase (p70S6K) signaling pathway and cell apoptosis in orthotopically transplanted tumors in nude mice. The mice were inoculated with human esophageal squamous cell carcinoma (ESCC) ECA109 cells in order to establish a model of orthotopicall transplanted ESCC tumors. The mice are administered low, medium and high doses of bufalin (0.5, 1.0 and 1.5 mg/kg) or rapamycin, or a combination of both. After the tumors were removed, the mRNA expression levels of mTOR, p70S6K, eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), cellular inhibitor of apoptosis protein 1 (cIAP1) and caspase-3 were detected by RT-PCR. In addition, we performed western blot analysis and immunohistochemical analysis to determine the protein expression of mTOR, p70S6K, 4EBP1, cIAP1, active caspase-3, Bcl-2 and Bad in the tumor tissue. The results revealed that bufalin exerted a significant anti-tumor effect in the nude mice with ESCC orthotopically transplanted tumors. This was shown by the decrease in the expression of mTOR, p70S6K and 4EBP1, which suggested that bufalin may possibly be used to inhibit tumor growth via the inhibition of the activation of p70S6K and 4EBP1. We also found that bufalin decreased the expression of cIAP1 and Bcl-2, and increased that of active caspase-3 and Bad, thus indicating that bufalin promoted apoptosis. Thus, our findings suggest that bufalin promotes tumor cell apoptosis, and this may be one of the important anti-tumor mechanisms of action of bufalin.
本研究旨在探讨蟾毒灵对裸鼠原位移植肿瘤中哺乳动物雷帕霉素靶蛋白（mTOR/p70S6 激酶（p70S6K）信号通路和细胞凋亡的影响。将人食管鳞癌细胞（ESCC）ECA109 接种于裸鼠，建立 ESCC 原位移植肿瘤模型。低、中、高剂量蟾毒灵（0.5、1.0、1.5mg/kg）或雷帕霉素或两者联合给药。肿瘤切除后，采用 RT-PCR 检测 mTOR、p70S6K、真核翻译起始因子 4E 结合蛋白 1（4EBP1）、细胞凋亡抑制蛋白 1（cIAP1）和半胱天冬酶-3 的 mRNA 表达水平。此外，还进行了 Western blot 分析和免疫组化分析，以确定肿瘤组织中 mTOR、p70S6K、4EBP1、cIAP1、活性半胱天冬酶-3、Bcl-2 和 Bad 的蛋白表达。结果表明，蟾毒灵对裸鼠 ESCC 原位移植肿瘤具有显著的抗肿瘤作用。这表现为 mTOR、p70S6K 和 4EBP1 的表达降低，表明蟾毒灵可能通过抑制 p70S6K 和 4EBP1 的激活来抑制肿瘤生长。我们还发现蟾毒灵降低了 cIAP1 和 Bcl-2 的表达，增加了活性半胱天冬酶-3 和 Bad 的表达，提示蟾毒灵促进了细胞凋亡。因此，我们的研究结果表明，蟾毒灵促进肿瘤细胞凋亡，这可能是蟾毒灵抗肿瘤作用的重要机制之一。
