We next investigated the clinically approved dual PI3Kαδ inhibitor copanlisib in vitro and saw significant (at least twofold) increases in CD21 expression across four of five T-ALL cell lines tested (MOLT4, P = 0.0197; CUTLL-1, P = <0.0001; SUPT1, P = 0.0069; and RPMI 8402, P = 0.0013; Fig. 7A). This evidence concerns the gene CR2 and acute lymphoblastic leukemia.