Dynamics of Microvesicle Generation in B Cell Chronic Lymphocytic Leukemia: Implication in Disease Progression

Previously, we reported that B-cell chronic lymphocytic leukemia (CLL) patients contained elevated levels of microvesicles (MVs). However, given the quiescent nature of CLL B-cells and the relative indolence of the disease, the dynamics of MV generation and their unique phenotypes are not clearly defined. In this study, we find that CLL B-cells generate MVs spontaneously and can be further induced by B-cell receptor-ligation. Most interestingly, CLL B-cells predominantly generate CD52(+) MVs, but not CD19(+) MVs in vitro, suggesting preferential usage of CD52 into leukemic-MVs and that the CLL plasma MV phenotypes corroborate well with the in vitro findings. Importantly, we detected increased accumulation of CD52(+) MVs in previously untreated CLL patients with progressive disease. Finally, sequential studies on MVs in pre- and post-therapy CLL patients demonstrate that while the plasma CD52(+) MV levels drop significantly after therapy in most and remain at low levels in some patients, a trend of increased accumulation of CD52(+) MVs was detected in majority of post-therapy CLL patients (25 of 33). In total this study emphasizes that dynamic accumulation of CD52(+) MVs in plasma can be used to study CLL progression and may be a useful biomarker for patients as they progress and require therapy.