8-Cl-Adenosine Inhibits Proliferation and Causes Apoptosis in B-Lymphocytes via Protein Kinase A-Dependent and Independent Effects: Implications for Treatment of Carney Complex-Associated Tumors

Abstract

Context: Carney complex, a multiple neoplasia syndrome, characterized primarily by spotty skin pigmentation and a variety of endocrine and other tumors, is caused by mutations in PRKAR1A, the gene that codes for the RIα subunit of protein kinase A (PKA). PKA controls cell proliferation in many cell types. The cAMP analogue 8-Cl-adenosine (8-Cl-ADO) is thought to inhibit cancer cell proliferation. Objective: The objective of the study was to study the antiproliferative effects of 8-Cl-ADO on growth and proliferation in B-lymphocytes of Carney complex patients that have PKA defects and to determine whether 8-CL-ADO could be used as a therapeutic agent in the treatment of Carney complex-associated tumors. Design: We used a multiparametric approach (i.e. growth and proliferation assays, PKA, and PKA subunit assays, cAMP and 3H-cAMP binding assays, and apoptosis assays) to understand the growth and proliferative effects of 8-Cl-ADO on human B-lymphocytes. Results: 8-Cl-ADO inhibited proliferation, mainly through its intracellular transport and metabolism, which induced apoptosis. PKA activity, cAMP levels, and 3H-cAMP binding were increased or decreased, respectively, by 8-Cl-ADO, whereas PKA subunit levels were differentially affected. 8-Cl-ADO also inhibited proliferation induced by G protein-coupled receptors for isoproterenol and adenosine, as well as proliferation induced by tyrosine kinase receptors. Conclusions: 8-Cl-ADO in addition to unambiguously inhibiting proliferation and inducing apoptosis in a PKA-independent manner also has PKA-dependent effects that are unmasked by a mutant PRKAR1A. Thus, 8-Cl-ADO could serve as a therapeutic agent in patients with Carney complex-related tumors. 8-Cl-adenosine inhibits cancer cell proliferation, and induces apoptosis in B lymphocytes of Carney complex patients by PKA-independent and dependent effects that are unmasked by a mutant PRKAR1A.