Department of Medical Pharmacology, Faculty of Medicine, University of Ankara, 06100 Ankara, Turkey.
Department of Medical Pharmacology, Faculty of Medicine, University of Ankara, 06100 Ankara, Turkey.
Int J Oncol. 2019 Apr;54(4):1345-1356. doi: 10.3892/ijo.2019.4697. Epub 2019 Jan 28.
Cetuximab is a monoclonal antibody developed to inhibit the binding of growth factors and the subsequent activation of epidermal growth factor receptor (EGFR). Triple‑negative breast cancer (TNBC) is resistant to cetuximab treatment. The aim of the present study was to examine the partial agonistic properties of cetuximab, which not only blocks ligand binding, but also partially triggers EGFR activation, which may lead to cetuximab resistance in TNBC. The phosphorylation of growth factor receptors and their signalling pathways were evaluated by determining the phosphorylation of EGFR, insulin‑like growth factor receptor (IGF‑1R), vascular endothelial growth factor receptor (VEGFR)‑2, Src kinase, phosphoinositide‑3‑kinase (PI3K), extracellular signal‑regulated kinase (ERK1/2) and serine/threonine‑specific protein kinase (Akt) and the degradation of EGFR, and by assessing the morphology and proliferation of MDA‑MB‑231 and MDA‑MB‑468 cells. Cetuximab treatment led to the phosphorylation of EGFR, VEGFR‑2, IGF‑1R and downstream signalling molecules, Src kinase and PI3K in these cells, as well as Akt in the MDA‑MB‑231 cells. The cetuximab‑mediated phosphorylation of IGF‑1R, VEGFR‑2 and Akt was inhibited by the EGFR kinase inhibitor, AG1478, and the Src kinase inhibitor, PP2. Cetuximab treatment led to the degradation of EGFR. The cetuximab‑induced phosphorylation and EGFR degradation were less prominent compared with those induced by EGF. Cetuximab partially inhibited EGF‑mediated responses. Cetuximab, similar with EGF, altered cellular morphology in a serum‑free medium. In both cell lines, the Src kinase inhibitor enhanced the cetuximab‑induced anti‑proliferative response. These results indicate that cetuximab exerts a partial agonistic effect on EGFR, which activates Src kinase and subsequently transactivates IGF‑1R and VEGFR‑2. This partial agonistic property is likely one of the mechanisms underlying the resistance of TNBC to cetuximab.
西妥昔单抗是一种单克隆抗体，旨在抑制生长因子的结合及其随后对表皮生长因子受体 (EGFR) 的激活。三阴性乳腺癌 (TNBC) 对西妥昔单抗治疗具有抗性。本研究旨在研究西妥昔单抗的部分激动特性，其不仅阻断配体结合，而且还部分触发 EGFR 激活，这可能导致 TNBC 对西妥昔单抗产生抗性。通过测定 EGFR、胰岛素样生长因子受体 (IGF-1R)、血管内皮生长因子受体 (VEGFR)-2、Src 激酶、磷酸肌醇 3-激酶 (PI3K)、细胞外信号调节激酶 (ERK1/2) 和丝氨酸/苏氨酸特异性蛋白激酶 (Akt) 的磷酸化以及 EGFR 的降解，评估生长因子受体及其信号通路的磷酸化情况，并评估 MDA-MB-231 和 MDA-MB-468 细胞的形态和增殖情况。西妥昔单抗处理导致这些细胞中 EGFR、VEGFR-2、IGF-1R 和下游信号分子 Src 激酶和 PI3K 的磷酸化，以及 MDA-MB-231 细胞中的 Akt 磷酸化。EGFR 激酶抑制剂 AG1478 和 Src 激酶抑制剂 PP2 抑制了西妥昔单抗介导的 IGF-1R、VEGFR-2 和 Akt 的磷酸化。西妥昔单抗处理导致 EGFR 的降解。与 EGF 诱导的磷酸化相比，西妥昔单抗诱导的磷酸化和 EGFR 降解不太明显。西妥昔单抗部分抑制了 EGF 介导的反应。与 EGF 类似，西妥昔单抗在无血清培养基中改变细胞形态。在两种细胞系中，Src 激酶抑制剂增强了西妥昔单抗诱导的抗增殖反应。这些结果表明，西妥昔单抗对 EGFR 具有部分激动作用，其激活 Src 激酶，随后转激活 IGF-1R 和 VEGFR-2。这种部分激动特性可能是 TNBC 对西妥昔单抗产生抗性的机制之一。
