Modulation of DNA synthesis via adenosine receptors in human epidermoid carcinoma (A431) cells

The activation of A1 and A2 adenosine receptors was shown to modulate DNA synthesis. In A431 cells, low concentrations of adenosine (approximately 10 microM) inhibited while higher concentrations (approximately 100 microM) stimulated [14C]thymidine incorporation. Epidermal growth factor (EGF) (10 ng/ml) could partially alleviate the inhibitory effects and further enhance the stimulatory effects of adenosine. Treatment of the cells with adenosine analogues (R-PIA and NECA) and antagonists (theophylline and DPCPX), which are selective for either the A1 (inhibitory) or A2 (stimulatory) receptors, indicated the involvement of these two receptors in the biphasic response to adenosine.