Conditional EGFR promotes cell cycle progression and prevention of apoptosis in the absence of autocrine cytokines.
v-ErbB is an oncogene related to the Epidermal Growth Factor Receptor (EGFR). EGFR overexpression has been observed in many pathological situations. There is a truncated form of EGFR, referred to as EGFvIII, which resembles v-ErbB in biological properties and is often expressed in certain human tumors. Aberrant EGFR expression in human cancers is often constitutive and may occur in the presence of mutated oncogenes or tumor suppressor genes. To circumvent these problems, we subcloned v-ErbB into a vector which contains the estrogen receptor hormone binding domain (ER) which renders the v-ErbB:ER protein dependent upon beta-estradiol for activity. v-ErbB:ER conditionally abrogated the cytokine dependence of hematopoietic cells more efficiently than activated v-Ha-Ras, v-Src, Raf or Akt. Abrogation of cytokine-dependence by v-ErbB:ER was not due to the synthesis of autocrine growth factors. Treatment of v-ErbB:ER cells with the EGFR inhibitor AG1478 efficiently induced apoptosis. Induction of apoptosis and prevention of cell cycle progression by the EGFR inhibitor were only observed when the cells were grown in response to v-ErbB:ER activation demonstrating specificity. In contrast, the other inhibitors suppressed cell cycle progression when the cells were grown in response to v-ErbB:ER or the cytokine interleukin-3. When MEK and either EGFR or PI3K/mTOR inhibitors were added, an enhanced apoptotic response was observed. Thus this conditional ErbB construct is useful to elucidate EGFR signaling and anti-apoptotic pathways in the absence of autocrine cytokine expression.
Shelton
John G
JG
Department of Microbiology & Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA.
Steelman
Linda S
LS
Abrams
Steven L
SL
White
Edmund R
ER
Akula
Shaw M
SM
Franklin
Richard A
RA
Bertrand
Fred E
FE
McMahon
Martin
M
McCubrey
James A
JA
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D019898:Autocrine Communication; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D017077:Culture Media, Conditioned; D016207:Cytokines / Q000172:deficiency*; D004247:DNA / Q000096:biosynthesis; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D051379:Mice; D018739:Oncogene Proteins v-erbB / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D011960:Receptors, Estrogen; D014170:Transformation, Genetic
D017077:Culture Media, Conditioned; D016207:Cytokines; D018739:Oncogene Proteins v-erbB; D011960:Receptors, Estrogen; D004247:DNA; D011494:Protein Kinases; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases