We investigated the ability of retinoic acid (RA) to alter the binding of epidermal growth factor (EGF) to Rat-1 and Swiss mouse 3T3 cells, the EGF-related induction of ornithine decarboxylase (ODC) activity and DNA synthesis. Pretreatment of 3T3 cells with 10-10-10-5 M RA produced a dose-dependent increase in EGF binding. The increased EGF binding appeared to result from an increased number of EGF receptors and did not occur in Rat-1 cells which, unlike 3T3 cells, possessed measureable amounts of cellular retinoic acid binding protein (CRABP). Both cell lines responded to RA pretreatment with an increase in EGF- and TPA-induced ODC activity, without a concomitant increase in DNA synthesis in either cell line. We suggest that the increase in EGF binding induced by RA in 3T3 cells is apparently unrelated to alterations in EGF-induced biological responses and to the presence of CRABP.
ASJC Scopus subject areas
- Cancer Research