Laboratory of Molecular Biophysics , National Institute of Environmental Health Sciences , Research Triangle Park , North Carolina 27709 .
J Biol Chem 265 : 3669-73 ( 1990)
Abstract
Previously , we have shown that prostaglandins are necessary , but not sufficient , for the stimulation of mitogenesis in BALB/c 3T3 fibroblasts by epidermal growth factor ( EGF ) ( Nolan , R. D. , Danilowicz , R. M. , and Eling , T. E. ( 1988 ) Mol .
Pharmacol .
33 , 650-656 ) .
The purpose of this work was to extend these findings to another potent mitogen , platelet-derived growth factor ( PDGF ) , and to determine if metabolism of arachidonic acid to prostaglandins is necessary for stimulation of expression of the protooncogene c-myc by EGF , which is an early event in the mitogenic cascade .
In BALB/c 3T3 cells grown to about 70% confluence and deprived of serum for 16-24 h , PDGF stimulated [ 3H]thymidine uptake into DNA significantly in a concentration-dependent manner , but did not increase production of prostaglandin E2 ( PGE2 ) .
The addition of indomethacin , a prostaglandin H synthase inhibitor , or nordihydroguaiaretic acid , a lipoxygenase inhibitor , did not affect PDGF-stimulated thymidine uptake into DNA .
In addition , PGE2 enhanced EGF-dependent , but not PDGF-dependent , mitogenesis .
Taken together , the data support the hypothesis that prostaglandins are not involved in PDGF-dependent mitogenesis .
In contrast , indomethacin ( 10(-6 ) M ) and nordihydroguaiaretic acid ( 10(-6 ) M ) inhibited EGF-stimulated thymidine uptake and c-myc expression by approximately 50% .
Addition of PGG2 ( 10(-7 ) to 10(-5 ) M ) in the presence of indomethacin and EGF restored the ability of EGF to elevate c-myc RNA levels and DNA synthesis .
When PGF2 alpha ( 10(-8 ) to 10(-5 ) M ) was added in the presence of EGF , c-myc RNA levels and thymidine incorporation were elevated up to 5-6-fold above levels observed with EGF alone .
These data support the hypothesis that metabolism of arachidonic acid to prostaglandins is necessary for stimulation of c-myc expression by EGF in BALB/c 3T3 cells .