CD38 regulates chronic lymphocytic leukemia proliferation via CD45 phosphatase activity

Chronic lymphocytic leukemia (CLL) growth is dependent on both B cell receptor (BCR) signaling and signals from microenvironmental T helper (Th) cells. We previously described a mechanism where Th cells enhance BCR signaling and proliferation through CD45 phosphatase activity regulation via galectin-1 and CD43. The CLL negative prognostic indicator CD38 is linked to BCR signaling and proliferation, with its expression induced by Th cells. Here, we explore a link between CD38 and CD45 phosphatase activity regulation using patient-derived material in a Th-CLL cell co-culture model. Results demonstrate CD43 and galectin-1 are co-expressed with CD38, defining proliferative CLL cells with augmented CD45 activity. CD38 enzymatic and receptor inhibition regulated CD43 and galectin-1 expression, CD45 activity^hi populations, and CLL proliferation, while leaving Th cells largely unaffected. Mechanistically, CD38- or LGALS1 (galectin-1)-deficient malignant B cell lines further confirmed CD38-mediated regulation of CD45 activity and BCR signaling through CD43 expression and galectin-1 surface binding, while galectin-1 contributed to CD43/CD45 colocalization. Together, this highlights CD38 as an important regulator of CD45 activity via CD43 and galectin-1, in turn acting as a positive modulator of CLL proliferation. Ultimately, the CD38/CD45 molecular hub could be an important therapeutic target in CLL.