TGFalpha is required for full expression of the transformed growth phenotype of NIH 3T3 cells overexpressing ornithine decarboxylase.
Ornithine decarboxylase (ODC) overexpressed from a heterologous promoter drives the tumorigenic transformation of NIH 3T3 cells and provides a model to investigate the underlying molecular mechanisms. These transformed cells, designated NODC cells, exhibit elevated levels of epidermal growth factor receptor (EGFR) tyrosine kinase (Tyr-k) activity relative to control transfected cells and inhibition of EGFR Tyr-k activation suppresses the transformed growth phenotype of these cells. Thus, ODC-induced transformation of NIH 3T3 cells appears to be mediated, at least in part, by enhanced signaling through the EGFR pathway. Here we extend these studies by evaluating: (i) the effects on growth regulation of overexpressing ODC in EGFR-deficient NIH 3T3 cells; (ii) the potential role of TGFalpha in mediating the EGFR-dependent transformation of NIH 3T3 cells by ODC. Disruption of EGFR-TGFalpha interactions either by deleting EGFR, by treatment with anti-TGFalpha neutralizing antibody or by transfection with a TGFalpha antisense expression vector suppressed acquisition of the full transformed growth phenotype. Specifically, the loss of contact inhibition and the capacity for clonogenic growth appear more dependent on EGFR-TGFalpha interactions than anchorage-independent growth in ODC-overexpressing cells. ODC overexpression does not alter the amount, localization or secretion of TGFalpha. Thus, TGFalpha is not the ODC-responsive component of the EGFR signaling pathway but appears to be critically involved in development of the transformed phenotype of NODC cells.
Geng
H
H
Center for Molecular Medicine and Genetics and Department of Internal Medicine, Wayne State University School of Medicine and John D.Dingell VA Medical Center, Detroit, MI 48201, USA.
Naylor
P H
PH
Dosescu
J
J
Skunca
M
M
Majumdar
A P
AP
Moshier
J A
JA
D016475:3T3 Cells; D000818:Animals; D002471:Cell Transformation, Neoplastic; D066246:ErbB Receptors / Q000502:physiology*; D051379:Mice; D009955:Ornithine Decarboxylase / Q000502:physiology*; D010641:Phenotype; D016211:Transforming Growth Factor alpha / Q000032:analysis / Q000502:physiology*
D016211:Transforming Growth Factor alpha; D066246:ErbB Receptors; D009955:Ornithine Decarboxylase