Pedersen Mikkel W, Tkach Vadim, Pedersen Nina, Berezin Vladimir, Poulsen Hans S
Department of Radiation Biology, The Finsen Center, Copenhagen University Hospital, Copenhagen, Denmark.
Int J Cancer. 2004 Feb 20;108(5):643-53. doi: 10.1002/ijc.11566.
Tumor cell motility is one of the rate-limiting steps of invasion, which defines progression toward a more malignant phenotype. Elevated expression of epidermal growth factor receptor (EGFR) in many cancers is associated with progression of superficial to invasive forms of the disease. The naturally occuring type III mutant epidermal growth factor receptor (EGFRvIII) is a tumor-specific, ligand-independent, constitutively active variant of the epidermal growth factor receptor. EGFRvIII is expressed frequently by a number of human solid tumours including those of the lung, breast, prostate, brain and ovary. Our study was designed to investigate the effect of EGFRvIII expression on cell motility and compare it to that of ligand-activated EGFR using transfected fibroblasts. We show here using time-lapse video recording that expression of EGFRvIII greatly enhances the motility of fibroblasts independently of ligand stimulation. In addition, expression of EGFRvIII caused a marked increase in the number of cellular protrusions (lamellipodia) and a reduction in the number of stress fibers and focal adhesions. The EGFR tyrosine kinase inhibitor, AG1478, and the MEK inhibitor, U0126, blocked these cellular effects of EGFRvIII. Two cell lines expressing different levels of EGFR were used for comparison. The low-expressing cell line responded to EGF treatment by increasing motility in a manner very similar to the motility induced by EGFRvIII. In contrast, the high-expressing cell line responded to EGF by detachment from the extracellular matrix and decreased motility. Cellular detachment was correlated to a high phosphorylation of PLC-gamma, whereas increased motility was correlated to a high level of ERK phosphorylation. Overall these results indicate that tumor-associated EGFR mutations might be critical for tumor cell motility, invasion and thus progression of disease.
肿瘤细胞运动是侵袭的限速步骤之一，它决定了向更恶性表型的进展。许多癌症中表皮生长因子受体（EGFR）表达升高与疾病从浅表形式向侵袭形式的进展相关。天然存在的III型突变表皮生长因子受体（EGFRvIII）是表皮生长因子受体的肿瘤特异性、非配体依赖性、组成型活性变体。EGFRvIII在包括肺癌、乳腺癌、前列腺癌、脑癌和卵巢癌在内的多种人类实体瘤中频繁表达。我们的研究旨在研究EGFRvIII表达对细胞运动的影响，并使用转染的成纤维细胞将其与配体激活的EGFR的影响进行比较。我们在此通过延时视频记录表明，EGFRvIII的表达极大地增强了成纤维细胞的运动，而与配体刺激无关。此外，EGFRvIII的表达导致细胞突起（片状伪足）数量显著增加，应力纤维和粘着斑数量减少。EGFR酪氨酸激酶抑制剂AG1478和MEK抑制剂U0126阻断了EGFRvIII的这些细胞效应。使用两个表达不同水平EGFR的细胞系进行比较。低表达细胞系对EGF处理的反应是通过增加运动，其方式与EGFRvIII诱导的运动非常相似。相比之下，高表达细胞系对EGF的反应是脱离细胞外基质并降低运动。细胞脱离与PLC-γ的高磷酸化相关，而运动增加与ERK磷酸化水平高相关。总体而言，这些结果表明肿瘤相关的EGFR突变可能对肿瘤细胞运动、侵袭以及疾病进展至关重要。
