CD38 expression does not change in B-cell chronic lymphocytic leukemia

Since the first description by Damle et al,1several investigators demonstrated the independent prognostic significance of CD38 expression in predicting survival of patients suffering from B-cell chronic lymphocytic leukemia (B-CLL).2-9 But despite confirming its prognostic value, Hamblin et al recently reported that CD38 expression may vary during the course of the disease, enriching the scientific debate about the biological significance of the expression of this molecule on neoplastic B lymphocytes.8 In addition, Chevallier et al have shown that CD38 expression may change during the evolution of the disease, suggesting that such an expression may be a secondary event in B-CLL.9 In particular, they recorded an increased expression during the disease progression in some cases. Other investigators, however, reported that CD38 expression is a constant overtime in some of their patients serially tested.1 7 

In light of this, we reviewed 162 B-CLL patients diagnosed and followed up at our institutions in the last 3 years. We analyzed 29 patients in which CD38 expression on peripheral B cells was evaluated more than one time, to verify whether a change in the immunophenotypic profile occurred.

To detect the percentage of neoplastic B cells displaying the CD38 molecule on their surface, we used a 3-color fluorescence staining: peridinin chlorophyll A protein (PerCP) for CD45s, fluorescein isothiocyanate (FITC) for CD19s, and phycoerythrin (PE) for CD38s. All monoclonal antibodies were purchased from Becton Dickinson Immunocytometry System (BDIS, San Jose, CA). CellQuest software and FACSCalibur flow cytometer (BDIS) were used. All cases were immunologically typical (CD5⁺CD23⁺) B-CLL. Positivity was defined as expression of CD38 on CD19⁺ cells of at least 30%. Globally, CD38 expression was recorded on 34% of B-CLL patients. In the patient group in which the determination of CD38 expression was done more than one time, the mean number of determinations was 2.4 (range, 2-5), and the mean time between the first and the last determinations was 17 months (range, 2-41 months). As shown in Table 1, we did not find a variation in CD38 expression of more than 10% between the first determination and the second determination. Interestingly, variations were not recorded in patients with progressive disease (stage shift and/or increase in peripheral blood lymphocytes or in node size) and in patients with stable disease as well. Moreover, no differences were found among circulating and bone marrow B cells in terms of CD38 expression in those cases in which the determination was performed on both samples (data not shown). In addition, other conditions, such as spontaneous spleen rupture, viral infection (ie, Herpes zoster), broncopneumonia, or hemodialysis for acute renal failure were not able to induce an expression of CD38 in 4 cases with CD38⁻ B-CLL tested before these events occurred.

In our opinion, methodological reasons could explain the discordant data reported so far, including the use of cryopreserved samples,10 different cytometers and operators during the time of the study, and different clones of CD38 monoclonal antibodies and gating strategies to detect it.

In conclusion, though our results need to be further corroborated on a greater number of patients followed up for longer time, our feeling is that CD38 expression does not change during the disease course of B-CLL.