Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America.
PLoS One. 2013;8(2):e56112. doi: 10.1371/journal.pone.0056112. Epub 2013 Feb 6.
Aberrant epidermal growth factor (EGF) signaling is associated with tumor growth in squamous cell carcinoma of the head and neck in humans (HNSCC), and is a major focus of targeted therapy. Cetuximab, a monoclonal antibody against EGFR, has been successful at prolonging survival but has only a 10% tumor shrinkage response rate in a clinical setting. The goal of this study was to compare dacomitinib (PF-00299804), a next generation small molecule tyrosine kinase inhibitor that irreversibly blocks multiple HER family receptors (HER-1 (EGFR), HER-2 and HER-4 tyrosine kinases), to cetuximab, the current FDA approved anti-EGFR medication for HNSCC and erlotinib, an EGFR specific small molecule tyrosine kinase inhibitor. Dacomitinib, erlotinib and cetuximab were tested in a panel of 27 HNSCC cell lines. Treatment with 100 ug/ml of cetuximab or 1 uM of erlotinib inhibited growth by at least 50% in 7/27 cell lines, while treatment with 1 uM of dacomitinib had similar growth inhibition in 17/27 lines. Cell lines representing three levels of sensitivity to dacomitinib were further examined using Western blots, cell cycle and apoptosis analysis. Treatment with 100 nM of dacomitinib reduced EGFR activity and downstream AKT and ERK pathways more effectively than treatment with 100 ug/ml of cetuximab in all ten tested lines. Although both compounds induced apoptosis at similar levels, dacomitinib caused greater G0/G1 arrest. Sensitivity to EGFR blockade was associated with levels of EGFR and ERK and was not associated with common oncogenic mutations and copy number variations. Phosphorylated and total EGFR and ERK levels correlate with sensitivity to both cetuximab and dacomitinib. Three of the four lines in the exquisitely sensitive group had the highest levels of phosphorylated and total EGFR and ERK among the ten lines selected, while the three resistant lines collectively had the lowest levels. Neither pAKT nor tAKT was associated with sensitivity.
表皮生长因子（EGF）信号通路的异常与头颈部鳞状细胞癌（HNSCC）的肿瘤生长有关，是靶向治疗的主要焦点。西妥昔单抗是一种针对 EGFR 的单克隆抗体，已成功延长了患者的生存期，但在临床环境中仅有 10％的肿瘤缩小反应率。本研究的目的是比较达克替尼（PF-00299804），一种不可逆地阻断多种 HER 家族受体（HER-1（EGFR）、HER-2 和 HER-4 酪氨酸激酶）的下一代小分子酪氨酸激酶抑制剂，与目前 FDA 批准的用于 HNSCC 的抗 EGFR 药物西妥昔单抗和埃罗替尼，一种 EGFR 特异性小分子酪氨酸激酶抑制剂。在 27 种 HNSCC 细胞系的小组中测试了达克替尼、埃罗替尼和西妥昔单抗。用 100ug/ml 的西妥昔单抗或 1uM 的埃罗替尼处理时，至少有 7/27 种细胞系的生长受到 50％以上的抑制，而用 1uM 的达克替尼处理时，17/27 种细胞系的生长受到类似的抑制。进一步使用 Western blot、细胞周期和凋亡分析检查代表对达克替尼三种敏感性水平的细胞系。用 100nM 的达克替尼处理比用 100ug/ml 的西妥昔单抗处理更有效地降低 EGFR 活性及其下游 AKT 和 ERK 途径，在所有十种测试的细胞系中都是如此。虽然这两种化合物以相似的水平诱导凋亡，但达克替尼导致更大的 G0/G1 期阻滞。对 EGFR 阻断的敏感性与 EGFR 和 ERK 的水平有关，与常见的致癌突变和拷贝数变异无关。磷酸化和总 EGFR 和 ERK 水平与对西妥昔单抗和达克替尼的敏感性相关。在十种选择的细胞系中，高度敏感组的四种细胞系中的三种具有最高水平的磷酸化和总 EGFR 和 ERK，而三种耐药细胞系则具有最低水平。磷酸化 AKT（pAKT）和总 AKT（tAKT）均与敏感性无关。
