The most effective tumor-promoting agent, phorbol-myristate-acetate, lowers cyclic adenosine 3′5′-monophosphate levels in mouse skin. A decrease is seen 1 hr after treatment; at 2 hr, a minimum is reached and maintained for 24 hr. At 48 hr, the cyclic adenosine 3′,5′-monophosphate level rises to control or greater values. Theophylline inhibits phorbol-myristate-acetate-promoted tumorigenesis. It appears that a decrease in cyclic adenosine 3′,5′-monophosphate levels is related to tumor promotion.

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This investigation was supported by project grants from the NIH (USPHS Research Grants ES-00505 and CA-08621) and a grant from the Allied Chemical Corporation and is part of a Center Program by the National Institute of Environmental Health Sciences Grant ES-00260. This work was previously reported (4).

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©1974 American Association for Cancer Research.
1974
Cancer Research, Inc.