Regulation of CD38 in proliferating chronic lymphocytic leukemia cells stimulated with CD154 and IL-4

BACKGROUND AND OBJECTIVES: Chronic lymphocytic leukemia (CLL) cells, like normal B-cells, exist in two populations in vivo: quiescent cells in the peripheral circulation and proliferating cells in lymph nodes. The surface marker CD38 has roles in cell adhesion and signaling. Its expression correlates with poor clinical outcome and is associated with expression of the signaling intermediate ZAP-70, which is also a marker of poor prognosis. We investigated the regulation of CD38 and ZAP-70 in proliferating CLL cells. DESIGN AND METHODS: We cultured CLL cells on a stromal cell layer that maintains viability and also with some stromal cells expressing CD40 ligand (CD154) in order to measure changes in expression of CD38 and ZAP-70. RESULTS: We demonstrated up-regulation of CD38 expression by CD154. The degree of up-regulation did not correlate with clinical stage or mutational status. In addition in the majority of cases tested ZAP-70 expression increased in parallel with up-regulation of CD38 although discordant cases were also observed. INTERPRETATION AND CONCLUSIONS: Overall we demonstrated that regulation of CD38 in CLL is dynamic and dependent on signals from CD154 and a stromal cell layer. We speculate that CD38 and ZAP-70 are expressed in lymph node leukemic cells in both good and poor prognosis patients, but, in cases with good clinical outcome, these molecules are down-regulated in the peripheral blood whereas in cases with poor prognosis their expression is maintained.