College of Food Science and Engineering, Jilin University, Changchun, 130062, China.
Institute of Agricultural Biotechnology, Jilin Academy of Agricultural Sciences, Changchun, 130033, China.
Food Chem Toxicol. 2019 Oct;132:110654. doi: 10.1016/j.fct.2019.110654. Epub 2019 Jun 29.
Cucurbitacin IIa (CuIIa), a tetracyclic triterpenoid harboring anticancer activity, was investigated in A549 cells to reveal its mechanism of targeting on epidermal growth factor receptor (EGFR) signaling pathway. Results showed that CuIIa was capable of inducing apoptosis and cell cycle arrest at G2/M phase. The transcription of EGFR pathway genes and their proteins accumulation was inconsistently influenced by CuIIa. Notably, transcription of Raf1 was significantly upregulated, nevertheless, MEK1 and ERK1 were significantly downregulated. On the other hand, the accumulation of the total and phosphorylated proteins of the most members in EGFR-mitogen-activated protein kinase (MAPK) pathway, as well as CylclinB1 and survivin were also shifted by CuIIa treatment. Remarkably, total MEK remained constant but survivin completely degraded. Moreover, phosphorylated BRAF continuously increased while Raf1 and MEK decreased continuously. CuIIa was further confirmed to be a tyrosine kinase inhibitor (TKI) of EGFR by kinase inhibition assay. The results of molecular simulation showed that the long side chain of CuIIa occupied the binding pocket of EGFR and the ligand was stabilized at the active site of EGFR. In view of the results above, it is suggested that CuIIa inhibits cell proliferation by interfering the EGFR-MAPK signaling pathway.
葫芦素 IIa（CuIIa）是一种具有抗癌活性的四环三萜类化合物，在 A549 细胞中进行了研究，以揭示其靶向表皮生长因子受体（EGFR）信号通路的机制。结果表明，CuIIa 能够诱导细胞凋亡和细胞周期停滞在 G2/M 期。EGFR 通路基因的转录及其蛋白积累受到 CuIIa 的不一致影响。值得注意的是，Raf1 的转录明显上调，然而，MEK1 和 ERK1 明显下调。另一方面，CuIIa 处理还改变了 EGFR-丝裂原活化蛋白激酶（MAPK）通路中大多数成员的总蛋白和磷酸化蛋白以及 CylclinB1 和 survivin 的积累。值得注意的是，总 MEK 保持不变，但 survivin 完全降解。此外，磷酸化 BRAF 持续增加，而 Raf1 和 MEK 持续减少。通过激酶抑制测定进一步证实 CuIIa 是 EGFR 的酪氨酸激酶抑制剂（TKI）。分子模拟的结果表明，CuIIa 的长侧链占据了 EGFR 的结合口袋，配体在 EGFR 的活性位点稳定。鉴于上述结果，建议 CuIIa 通过干扰 EGFR-MAPK 信号通路来抑制细胞增殖。
