Loss of lymphocyte cyclic amp dependent protein kinase activity in malignant melanoma

Cyclic AMP dependent protein kinase activity was depressed in whole thymus and spleen as well as in isolated splenic lymphocytes from B16 melanoma bearing C57Bl/6J mice as compared to control animals. A similar loss of enzyme activity was observed in humam peripheral blood lymphocytes from melanoma bearing patients as compared to normal subjects. An unaltered level of activity in the heart of tumor bearing mice suggested some specificity for the lymphoid system. This depressed enzyme activity was the result of a diminished V(max) for cAMP stimulated calf histone phosphorylation. The tumor bearing state in the mouse was also accompanied by a depletion of small lymphocytes from both thymus and spleen and it is hypothesized that the losses of lymphocytes and cAMP dependent protein kinase activity are related.