Clinical relevance of the expression of the CD31 ligand for CD38 in patients with B-cell chronic lymphocytic leukemia

BACKGROUND. CD31 (platelet endothelial cell adhesion molecule-1 [PECAM-1]) is the ligand for CD38, a transmembrane glycoprotein that is expressed on the surface of leukemic cells in many patients with B-cell chronic lymphocytic leukemia (B-CLL). In a previous study, the authors showed that CD38 expression was correlated with a poor prognosis in patients with B-CLL. In the current study, blood samples from patients with B-CLL were examined to identify CD31 surface marker expression, and CD31 expression was correlated with several other known prognostic variables, including CD38. METHODS. Using flow cytometry, peripheral blood samples from 120 patients with B-CLL were analyzed for CD31 and CD38 expression on CD19 positive leukemic B cells. RESULTS. Thirteen of 120 patients (11%) had CD31 expression on < 20% of their B cells, and the remaining patients had various levels of CD31 expression. The median expression of CD31 was 76% of leukemic, CD19 positive cells. Levels of CD31 expression were not correlated with survival outcomes or with any of the known prognostic parameters when all patients were considered. Patients who had high CD38 expression (≥ 20%), as expected, had significantly shorter survival (P = 0.001) compared with patients who had low CD38 expression (< 20%). However, in patients with low CD38 expression, a subgroup with low CD31 expression (< 76%) had significantly longer survival compared with the survival for the entire group (P = 0.0001). Moreover, the survival pattern of patients with low CD38 expression and high CD31 expression was not significantly different from the survival pattern seen in patients with high CD38 expression. CONCLUSIONS. CD31 expression further defined a subgroup of patients with B-CLL who had a different survival outcome. Defining the interaction between CD31 expression and CD38 expression in patients with CLL will require further exploration.