A novel mechanism of resistance to epidermal growth factor receptor antagonism in vivo.
Epidermal growth factor receptor (EGFR) is widely expressed in a number of solid tumors including colorectal cancers. Overexpression of this receptor is one means by which a cell can achieve positive signals for survival and proliferation; another effective means is by constitutive activation of EGFR. We have elucidated the role of constitutive EGFR signaling in malignant progression by stably transfecting colon cancer cells with a human transforming growth factor-alpha cDNA (a ligand for EGFR) under repressible control by tetracycline. We show that constitutive expression of transforming growth factor-alpha and its subsequent constitutive activation of EGFR allows for cancer cell survival in response to environmental stress in vitro and in vivo as well. The reversal of constitutive EGFR activation results in the loss of downstream mitogen-activated protein kinase and Akt activation, and a reduction in xenograft size that is associated with decreased proliferation and increased apoptosis. We used CI-1033, a small molecule antagonist of EGFR, to dissect an activation pathway that shows the ability of ERBb2 to activate Akt, but not Erk in the face of EGFR antagonism. This novel escape mechanism is a possible explanation of why anti-EGFR therapies have shown disappointing results in clinical trials.
Rajput
Ashwani
A
Department of Surgical Oncology, Roswell Park Cancer Institute, The State University of New York at Buffalo, Buffalo, New York 14263, USA.
Koterba
Alan P
AP
Kreisberg
Jeffrey I
JI
Foster
Jason M
JM
Willson
James K V
JK
Brattain
Michael G
MG
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D048708:Cell Growth Processes; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation / Q000187:drug effects; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D009025:Morpholines / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases; D016211:Transforming Growth Factor alpha; C420268:Canertinib