2-hydroxyestrone and hydroquinone

The present study was undertaken to examine the effects of iodoacetic acid, a non-phorbol tumor promoter, on metabolic cooperation between mutant human fibroblasts as measured by [14C]citrulline incorporation. Other thiol-reactive polyphenolic compounds such as hydroquinone and 2-hydroxyestrone were also examined. 12-O-Tetradecanoyl phorbol-13-acetate (TPA), a potent skin tumor promoter, inhibited the cell-cell communication by more than 60% at 20 ng/ml. However, iodoacetic acid, hydroquinone, and 2-hydroxyestrone, had no effect on the process even at cytotoxic concentrations. Induction of intercellular contact (agglutination) among lymphocytes during the course of phytohemagglutinin (PHA)-induced blastogenesis was monitored turbidometrically at 620 nm. Hydroquinone and 2-hydroxyestrone suppressed the PHA-induced lymphocyte agglutination at 1-2 microM in vitro concentrations while iodoacetic acid was devoid of any effects at concentrations up to 100 microM. Hydroquinone and 2-hydroxyestrone concomitantly suppressed PHA-induced lymphocyte blastogenesis at 1-2 microM in vitro concentrations while the suppression by iodoacetic acid was significant at 10 microM. All 3 compounds failed to disrupt microtubule assembly, a sulfhydryl-dependent process, in a rat brain crude extract. However, p-benzoquinone, an oxidation product of hydroquinone, did inhibit the process at 1 mM. In summary, these studies suggest that, unlike TPA, thiol-reactive non-phorbol tumor promoters and polyphenolic compounds do not inhibit cell-cell communication between mutant human fibroblasts. Although the compounds demonstrate diverse molecular mechanisms of action, they all inhibit in vitro immune functions suggesting that immunosuppression may play a role in tumor promotion.

Topics: Agglutination; Animals; Cell Communication; Dose-Response Relationship, Drug; Estrone; Female; Hydroquinones; Hydroxyestrones; Indoleacetic Acids; Lymphocyte Activation; Mice; Mice, Inbred Strains; Microtubules; Monophenol Monooxygenase; Phytohemagglutinins