Influence of Dibutyryl CyclicAMP and Theophylline on Cell Surface Antigens on Oncornavirus Transformed Cells

Abstract

IT is well established that cyclic adenosine 3′ : 5′-monophosphate (cyclicAMP) acts as an intracellular transmitter substance regulating many physiological processes^1,2. It was found that the intracellular level of cyclicAMP in transformed and in rapidly growing normal cells is lower than in slowly dividing or stationary normal cells^3,4. Addition of N⁶O²′-dibutyryl adenosine cyclic 3′ : 5′-monophosphoric acid (dbcyclicAMP) to the medium of cultured cells increases the intracellular levels of cyclicAMP5 and has a normalizing effect on tumour cells^6–11. This effect is potentiated by theophylline (Th). Both substances are inhibitors of intracellular cyclic nucleotide phosphodiesterase¹². As a most striking feature, tumour cell morphology is reverted and cells become less agglutinable by wheat germ agglutinin^6,7. Also, transformed cells are restored to controlled growth as they grow to lower saturation density and apparently become contact inhibited during treatment with dbcyclicAMP plus Th^6–8,13.