Department of Oncologia Traslazionale, Lab. Trasferimento Genico, Istituto Nazionale per la Ricerca sul Cancro (IST-Nord, B3, Rm18), Largo Rosanna Benzi, 10-16132 Genova, Italy.
Curr Cancer Drug Targets. 2010 Mar;10(2):176-91. doi: 10.2174/156800910791054130.
Altered EGFR activity is a causal factor for human tumor development, including malignant pleural mesotheliomas. The aim of the present study was the evaluation of the effects of Gefitinib on EGF-induced mesothelioma cell proliferation and the intracellular mechanisms involved. Cell proliferation, DNA synthesis and apoptosis were measured by MTT, thymidine incorporation and FACS analysis; EGFR, ERK1/2 and Akt expression and phosphorylation by Western blot, whereas receptor sites were analyzed by binding studies. Gefitinib inhibited EGF-induced proliferation in two mesothelioma cell lines, derived from pleural effusion (IST-Mes2) or tumor biopsy (ZL55). The treatment with Gefitinib induced cell cycle arrest in both cell lines, while apoptosis was observed only for high concentrations and prolonged drug exposure. EGF-dependent mesothelioma cell proliferation was mediated by EGFR and ERK1/2 phosphorylation, while Akt was not affected. Gefitinib inhibited both EGFR and ERK1/2 activation, being maximal at drug concentrations that induce cytostatic effects, suggesting that the proapoptotic activity of Gefitinib is independent from EGFR inhibition. Gefitinib treatment increased EGFR Bmax, possibly through membrane stabilization of inactive receptor dimers that we show to be induced by the drug also in the absence of EGF. EGFR activation of ERK1/2 represents a key pathway for pleural mesothelioma cell proliferation. Low concentrations of Gefitinib cause mesothelioma cell cycle arrest through the blockade of EGFR activity while high concentrations induce apoptosis. Finally, we propose that the formation of inactive EGFR dimers may contribute to the antitumoral activity of Gefitinib.
表皮生长因子受体（EGFR）活性的改变是人类肿瘤发生的一个因果因素，包括恶性胸膜间皮瘤。本研究的目的是评估吉非替尼对 EGF 诱导的间皮瘤细胞增殖的影响及其相关的细胞内机制。通过 MTT、胸苷掺入和 FACS 分析来测量细胞增殖、DNA 合成和细胞凋亡；通过 Western blot 来分析 EGFR、ERK1/2 和 Akt 的表达和磷酸化，而受体则通过结合研究来分析。吉非替尼抑制了两种来源于胸腔积液（IST-Mes2）或肿瘤活检（ZL55）的间皮瘤细胞系中 EGF 诱导的增殖。吉非替尼治疗诱导两种细胞系的细胞周期停滞，而仅在高浓度和延长药物暴露时观察到细胞凋亡。EGF 依赖性间皮瘤细胞增殖由 EGFR 和 ERK1/2 磷酸化介导，而 Akt 不受影响。吉非替尼抑制 EGFR 和 ERK1/2 的激活，在诱导细胞生长抑制作用的药物浓度下达到最大值，这表明吉非替尼的促凋亡活性与 EGFR 抑制无关。吉非替尼治疗增加了 EGFR Bmax，这可能是通过药物诱导的无 EGF 情况下的失活受体二聚体的膜稳定化实现的。EGFR 激活 ERK1/2 代表了胸膜间皮瘤细胞增殖的关键途径。低浓度的吉非替尼通过阻断 EGFR 活性引起间皮瘤细胞周期停滞，而高浓度则诱导细胞凋亡。最后，我们提出失活的 EGFR 二聚体的形成可能有助于吉非替尼的抗肿瘤活性。
