Hypoxia increases the motility of lung adenocarcinoma cell line A549 via activation of the epidermal growth factor receptor pathway

Abstract

Tumor hypoxia is associated with a malignant phenotype of cancer cells and poor patient prognosis. To investigate the role of hypoxia in tumor progression, we studied the effects of hypoxia in the A549 lung adenocarcinoma cell line. First, we showed that hypoxic treatment decreased cell-cell adhesion and induced a scattering of cancer cells. Concomitant with these morphological changes, the motility of cancer cells was increased, as demonstrated by the Boyden chamber assay. Then, we used oligonucleotide array analyses to identify the genes causally related to the hypoxia-induced motile phenotype. The results showed that the expression of approximately 100 genes was induced more than 5-fold by hypoxia. These included (among others) epidermal growth factor receptor (EGFR), as well as other well-known hypoxia-induced genes, such as vascular endothelial growth factor. Immunohistochemical analyses of primary lung adenocarcinomas confirmed the induction of EGFR in tumor cells in the vicinity of necrotic areas, a histological indicator of tumor hypoxia. Remarkably, the EGFR inhibitor AG1478 (10 µM) completely blocked the increased cell motility induced by hypoxia. Thus, the present study demonstrates the importance of the EGFR pathway in the increased motility of cancer cells that occurs in a hypoxic tumor environment. (Cancer Sci 2007; 98: 506-511) L ung cancer is the leading cause of cancer mortality in the USA, Japan and other developed countries.(1) Among the four major histological subtypes, the increased incidence of lung adenocarcinoma is widely recognized.(2) The prognosis for lung carcinoma patients is generally poor: even if diagnosed and treated successfully, patients with stage I lung carcinoma have a 5-year survival rate of only 70% after surgical resection. Currently, the molecular mechanisms underlying the progression of lung adenocarcinomas are not well understood.(4,5) Clearly, the understanding of these mechanisms is essential in establishing more rational therapeutic approaches for the treatment of lung adenocarcinoma patients.Epidermal growth factor receptor (EGFR) is a receptor-type tyrosine kinase that is frequently overexpressed in lung cancer. (6) Besides this overexpression, gene mutation and amplification of EGFR also occurs in lung cancer, especially in lung adenocarcinomas.(7-11) Although it is generally assumed that EGFR is involved in tumor cell proliferation, migration and antiapoptotic signaling, (6) our knowledge concerning the roles of EGFR signaling in the development and progression of lung cancer is still incomplete.There is now increased recognition that hypoxia plays important roles in tumor biology. (12)(13)(14)(15) It has been shown experimentally that hypoxia induces genetic instability, promotes the selection of hypoxia-resistant clones, and facilitates the metastasis of cancer cells.(12-15) Also, low oxygen tension in tumors is associated with a poor prognosis for patients.(13) With regard to cell motility, studies indicate that hypoxia increases the motility of cancer cells ...

Hypoxia Suppression of Bim and Bmf Blocks Anoikis and Luminal Clearing during Mammary Morphogenesis

“…Although hypoxia has been shown to enhance both EGFR (Wang et al , 2007) and Erk activity (Minet et al , 2000), our results are the first to demonstrate such activation by hypoxia in suspended cells and in the context of 3D culture. It is well established that EGFR-mediated mitogen-activated protein kinase signaling acts as a negative regulator of Bim and Bmf expression in adherent MCF-10A cells (Reginato et al , 2003; Schmelzle et al , 2007).…”

Role of cGMP-dependent protein kinase in regulation of pulmonary vascular smooth muscle cell adhesion and migration: effect of hypoxia

“…There have been reports of specific proteins involved in promoting cell migration in hypoxia in different cell types, such as hypoxia-induced mitogenic factor in endothelial cells (24) and EGF receptor (EGFR) in adenocarcinoma cells (25). There have been reports showing the regulation of migration of VSMC through the mitogen-activated protein kinase ERK1/2 (2,14).…”

Co-Activation of Epidermal Growth Factor Receptor and c-MET Defines a Distinct Subset of Lung Adenocarcinomas

“…25,26,27 Single nucleotide polymorphism array (Affymetrix human mapping 50K XbaI array) analysis was performed using GIM (Genome Imbalance Map) algorithm as described previously. 28 …”