Tyrosinase maturation and pigment expression in B16 melanoma: Relation to theophylline treatment and intracellular cyclic AMP

Abstract

We have studied the effects of theophylline treatment on pigmentation characteristics and growth of two B16 melanoma cell lines, HFH-18 and P/140. Cell counts of control and theophylline-treated cultures confirmed that the drug inhibits cell growth. Light and electron microscope cytochemistry with the L-dopa reaction indicated that the two cell lines differ in their ability to transfer Golgi-associated tyrosinase to developing premelanosomes. The results of these experiments, considered with results of electrophoretic analyses and activity measurements by the Pomerantz method, also provide evidence that increased tyrosinase synthesis occurs in response to theophylline treatment. In addition, results indicate that theophylline induces changes in the rate of synthetic or degradative posttranslational modification of tyrosinase. Measurements of intracellular cyclic AMP levels by radioimmunoassay in control cultures and in theophylline- and alpha-MSH-treated cultures were made. Although the hormone induced spectacular increases in cyclic AMP levels, theophylline produced no detectable change. These results indicate that theophylline differs from alpha-MSH because theophylline-induced changes in pigmentation may not require the participation of intracellular cyclic AMP.

Regulation of cell division and of tyrosinase in B16 melanoma cells by imidazole: A possible role for the concept of metabolite Gene regulation in mammalian cells

“…Regulation of CAMP-phosphodiesterase and intracellular cAMP concentration Using purified enzyme from bovine heart tissue, Butcher and Sutherland (1962) showed the CAMP-phosphodiesterase (CAMP-PDE) activity could be inhibited by theophylline and stimulated by imidazole. The effect of theophylline on intracellular CAMP concentrations in melanoma cells has since been studied (Kreider et al, 1975;Steinberg and Whittaker, 1978;White et al, 1979). Therefore, determinations as to whether or not imidazole can regulate intracellular cAMP concentrations were undertaken.…”

“…The effect of theophylline on intracellular CAMP concentrations in melanoma cells has since been studied (Kreider et al, 1975;Steinberg and Whittaker, 1978;White et al, 1979). Therefore, determinations as to whether or not imidazole can regulate intracellular cAMP concentrations were undertaken.…”

“…Studies by Wade and Burkart (1978) suggested that natural mechanisms exist for inhibiting cell division and increasing tyrosinase-specific activity, as B 16 melanoma cells approach confluency, which are not mediated by an increase in endogenous cAMP concentrations. Also, mechanisms for increasing tyrosinase activity by the CAMP-phosphodiesterase inhibitor theophylline may not be entirely CAMP-mediated (White et al, 1979) and have been suggested to result from de nouo synthesis of tyrosinase (Steinberg and Whittaker, 1976;White et al, 1979). In this report we describe the effects of theophylline, CAMP, and the bacterially defined cAMP substitute imidazole on cell replication and on the pretranslational and posttranslational control of tyrosinase activity in B16 mouse melanomacells.…”

“…In melanoma cells, cell replication is inhibited and melanogenesis is stimulated by increased endogenous CAMP concentrations produced by the melanocyte-stimulating hormone (MSH) (Pawelek et al, 1973;White et al, 1979), inhibitors of CAMP-phosphodiesterase (Helson et al, 1974;Kreider et al, 1975;Steinberg and Whittaker, 19761, and by exogenous cAMP or dibutvrvl CAMP additions (Johnson and Pastan, 1972;Kreider et al, 1973). The rate of melanogenesis is controlled by the ac-IKeprint requests should besen1 tn Kllis I.. Khne.…”

A Correlation between Melanogenic Functions and Transformed Phenotypes in Cultured B16 Mouse Melanoma Cells

“…With this method no inhibitory action appeared in any of the DOC-cell lysates of the tyrosinase-negative cell lines (data not shown). The inducibility of tyrosinase activity was examined in the presence of theophylline, which has been reported to be a potent inducer of melanogenesis (16,17 theophylline at 4 mM was most effective for inducing tyrosinase activity in the 0-1 cell line. The effect of theophylline on cell growth also was examined.…”