we have previously demonstrated that , by elevating intracellular adenosine 3':5'-cyclic monophosphate ( camp ) levels by inhibition of camp phosphodiesterase with ro 20-1724 or by forskolin stimulation of adenylcyclase , the growth of neoplastically transformed 10t1/2 fibroblasts could be inhibited when these cells were in contact with growth-inhibited nontransformed 10t1/2 cells ( j .
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fibroblasts
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cells