While a role for PKA phosphorylation of the β2AR was evident from these early studies, additional efforts revealed that the β2AR could also be phosphorylated in an agonist-dependent manner in S49 lymphoma cell lines that could not activate PKA either because they lacked the ability to produce cAMP (cyc− cells) or they lacked the PKA catalytic subunit (kin− cells) [20]. This evidence concerns the gene ADRB2 and lymphoma.