Protein phosphatase 2A (PP2A) inactivation is common in cancer, leading to sustained activation of pro-survival
and growth-promoting pathways. PP2A consists of a scaffolding A-subunit, a catalytic C-subunit, and a regulatory B-subunit. The functional complexity of PP2A holoenzymes arises mainly through the vast repertoire of
regulatory B-subunits, which determine both their substrate specificity and their subcellular localization.
Therefore, a major challenge for developing more effective therapeutic strategies for cancer is to identify the
specific PP2A complexes to be targeted. Of note, the development of small molecules specifically directed at
PP2A-B56α has opened new therapeutic avenues in both solid and hematological tumors. Here, we focus on the
B56/PR61 family of PP2A regulatory subunits, which have a central role in directing PP2A tumor suppressor
activity. We provide an overview of the mechanisms controlling the formation and regulation of these complexes,
the pathways they control, and the mechanisms underlying their deregulation in cancer