CD38 and acute promyelocytic leukemia: All-trans retinoic acid (ATRA) is FDA-approved for the treatment of acute promyelocytic leukemia and raises surface CD38 and decreases CD55 and CD59 levels in Dara-refractory MM cell lines as well as patient-derived cells.32,35,36 Therefore, we tested whether ATRA could enhance the cytotoxic activity of Dara against PEL.