The JUN kinase/stress-activated protein kinase pathway is required for epidermal growth factor stimulation of growth of human A549 lung carcinoma cells.
Epidermal growth factor (EGF) plays a major role in non-small cell lung cancer cell autocrine growth and has been reported to activate the JUN kinase/stress-activated protein kinase (JNK/SAPK) pathway in model cells. Activation of JNK/SAPK leads to the phosphorylation of c-JUN protooncogene on serines 63 and 73. This mechanism is required for and cooperates in the transformation of rat embryo fibroblasts by Ha-RAS. However, the function of JNK/SAPK in human tumor growth is unknown. We have tested several lung carcinoma cell lines. All exhibited UV-C-inducible JNK/SAPK activity; two exhibited constitutive activity in low serum, and two (M103 and A549) exhibited EGF-inducible JNK/SAPK activity. In A549 cells, EGF induced a rapid and prolonged (up to 24 h) activation of the JNK/SAPK pathway that correlated with a 150-190% growth stimulation. Stably transfected clones of A549 cells expressing c-JUN(S63A,S73A), a transdominant inhibitor of c-JUN, completely blocked the EGF-stimulated proliferation effect but did not alter the basal proliferation rate. Consistent with these results JNK antisense oligonucleotides targeted to JNK1 and JNK2 entirely eliminated the EGF-stimulated JNK/SAPK activity and blocked EGF-stimulated growth but not basal growth. In contrast, specific inhibition of the RAF/ERK pathway by PD98059 (MEK1 inhibitor) completely blocked ERK activation by EGF and basal cell growth but not EGF-stimulated growth, thereby dissociating the growth-promoting roles of each pathway. Our observations indicate, for the first time, that JNK/SAPK may be a preferential effector pathway for the growth properties of EGF in A549 cells.
Bost
F
F
Sidney Kimmel Cancer Center, San Diego, California 92121, USA.
McKay
R
R
Dean
N
N
Mercola
D
D
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002455:Cell Division; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008175:Lung Neoplasms / Q000473:pathology*; D048056:Mitogen-Activated Protein Kinase 9; D020928:Mitogen-Activated Protein Kinases; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D014407:Tumor Cells, Cultured
D004791:Enzyme Inhibitors; D005419:Flavonoids; D016376:Oligonucleotides, Antisense; D047428:Protein Kinase Inhibitors; D004815:Epidermal Growth Factor; D011494:Protein Kinases; D048056:Mitogen-Activated Protein Kinase 9; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one