Evaluation of CD69 expression as a prognosticator in chronic lymphocytic leukemia

Abstract

Introduction Chronic lymphocytic leukemia (CLL) is the most common type of adult leukemia in the western world. It is a malignancy of mature B cells involving the blood, bone marrow (BM), and lymphoid tissues, and its cells arise from polyclonal expansion of CD5+ B lymphocytes transformed into a monoclonal population by mutational agents. CD69 is an integral membrane protein belonging to the lectin family. It is expressed after activation in all BM-derived cells except erythrocytes. CLL exhibits features of activated and antigen-experienced B lymphocytes and CD69 overexpression. CD69 is significantly correlated with poor clinical and biological prognostic factors, and this supports its introduction into routine laboratory assessment and, possibly, in a prognostic scoring system for CLL after an adequate standardization process. Objective The aim of this study was to detect CD69 expression in newly diagnosed patients with CLL by flow cytometry and correlate it with clinical and laboratory parameters to evaluate it as a prognostic factor. Patients and methods This study was conducted on 40 B-CLL patients who attended Ain Shams University Hospitals over 1 year. All patients were subjected to full medical history and clinical examination, RAI staging according to disease burden and the degree of BM involvement, abdominal ultrasonography, complete blood count with examination of peripheral blood smears, BM aspiration with morphological examination, and immunophenotyping of BM or whole peripheral blood applying monoclonal antibodies CD20, CD79b, FMC7, serum IgM, CD5/CD19, CD10, CD103, CD123, CD23, and CD38, and κ and λ light chains and CD69 expression. Results In the current study all of the studied B-CLL patients expressed CD69. Among the 40 studied patients 23 had high CD69 expression (group I) and 17 had low CD69 expression (group II). A highly significant elevation in group I patients compared with group II patients was found (P = 0.000). A highly significant reduction in hemoglobin (Hb) level (P = 0.001), elevation in lactate dehydrogenase concentration (P = 0.006), elevation in RAI staging, and elevation in CD38 expression (P = 0.005) were observed in group I. A highly significant negative correlation was found between CD69% and Hb level (P = 0.008) and platelet count (P = 0.009). A highly significant positive correlation was found between CD69% and hepatomegaly (P = 0.008) and RAI stage (P = 0.008) and significant positive correlation was found between CD69% and CD38% expression (P = 0.012). An association study was conducted between CD69% expression and all the standard prognostic factors in B-CLL patients. There was a highly significant association between CD69% expression and presence of hepatomegaly (P = 0.002) and a significant association between CD69% expression and presence of splenomegaly (P = 0.028) and low Hb levels (P = 0.013). Conclusion Several clinical and biological variables have been reported to predict the outcome of CLL patients, such as advanced patient age, male sex, higher absolute lymphocyte count, greater extent of lymphadenopathy, and raised serum β2-microglobulin levels, all of which are associated with inferior prognosis. In the current study all of the studied B-CLL patients expressed CD69. CLL patients were divided into two subsets with significantly different prognosis: those with high CD69 (group I) (≥30%) and those with low CD69 (group II) (<30%) expression; both were compared with respect to the different studied parameters. There was highly significant elevation of CD69 in group I compared with group II. There was a highly significant reduction in Hb level and elevation in lactate dehydrogenase concentration in group I patients in comparison with group II patients. A highly significant relation was found between the two groups with respect to RAI staging: an advanced RAI stage was found among group I patients in comparison with group II patients. The current study evaluated CD69 as a prognosticator and studied the significant association of its high expression with the standard prognostic factors, notably splenomegaly (P = 0.028) and hepatomegaly (P = 0.002), low Hb level, low platelet count, and advanced RAI stage. CD69 expression is associated with both immunoglobulin variable heavy chain mutation status and survival. It is recommended to perform a larger prospective study on CD69 expression in B-CLL patients, studying its relation to overall survival and progression-free survival and its re-evaluation during the course of treatment as we recommend assessment of this marker by flow cytometry among independent prognostic markers in B-CLL.