RAS transformation causes sustained activation of epidermal growth factor receptor and elevation of mitogen-activated protein kinase in human mammary epithelial cells.
Activation of the ras oncogene is an important step in carcinogenesis. Human MCF-10A mammary epithelial cells were transformed with a point-mutated form of the Ha-ras oncogene. Epidermal growth factor receptor (EGFR) phosphorylation levels were chronically elevated after EGF induction and the EGFR ligand-driven internalization rate was slower in Ha-ras transformed MCF-10A cells. Additionally, basal levels of p42/44 mitogen-activated protein kinase (MAPK) expression and enzyme activity were significantly higher in Ha-ras transformed cells, localized predominantly in the nucleus. The anti-EGFR monoclonal antibody (MAb) 225 and the EGFR tyrosine kinase inhibitor PD153035 blocked anchorage-independent growth of Ha-ras transformed cells in soft agar and were more effective when used in combination. The MEK inhibitor PD98059 and anti-erbB-2 MAb L26 also suppressed colony formation of Ha-ras transformed cells in soft agar. Therefore, Ha-ras transformation leads to an augmentation in signaling through the EGFR as a result of an increase in ligand-dependent phosphorylation, a decrease in its internalization and an up-regulation in basal p44/42 MAPK levels. These effects may contribute to uncontrolled growth of Ha-ras-transformed human mammary epithelial cells.
Martínez-Lacaci
I
I
Tumor Growth Factor Section, Laboratory of Tumor Immunology and Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Kannan
S
S
De Santis
M
M
Bianco
C
C
Kim
N
N
Wallace-Jones
B
B
Ebert
A D
AD
Wechselberger
C
C
Salomon
D S
DS
D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D000918:Antibody Specificity; D001940:Breast / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000493:pharmacokinetics; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005260:Female; D005786:Gene Expression Regulation; D011905:Genes, ras / Q000235:genetics / Q000502:physiology*; D006131:Growth Inhibitors / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000378:metabolism; D010766:Phosphorylation; D017354:Point Mutation; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D014162:Transfection
D000911:Antibodies, Monoclonal; D004791:Enzyme Inhibitors; D006131:Growth Inhibitors; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D019908:Proto-Oncogene Proteins c-raf; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)