The cyclic adenosine 3′,5′ monophosphate-dependent protein kinase system in breast cancer

Components of the cyclic adenosine 3′,5′ monophosphate (AMP) dependent protein kinase sys- tem have been measured in primary tumours from 55 patients with invasive breast cancer. There were highly significant positive correlations between levels of regulatory subunits as measured by cyclic AMP binding proteins and catalytic kinase activity (both basal and cyclic AMP-activated). This suggests that, in general, increased expression of binding proteins is accompanied by a corresponding elevated level of catalytic activity. Nevertheless, individual tumours could have substantially different proportions of regulatory and catalytic activities. Whether such differences influence tumour behaviour remains to be determined.