ROR-1 Expression in the Diagnosis and Monitoring of Minimal Residual Disease in Chronic Lymphocytic Leukemia

Abstract

Background. In view of similar morphological and phenotypic characteristics of some B-cell lymphoproliferative diseases and despite the known phenotype of tumor cells, a search is currently underway for new diagnostic markers, the expression of which remains stable during chronic lymphocytic leukemia (CLL) treatment and can be used for both diagnosis and assessment of residual tumor population. One of such markers is ROR-1. Aim. To assess the expression and feasibility of the ROR-1 marker using В-lymphocytes in minimal residual disease (MRD) dynamics and monitoring in CLL. Materials & Methods. Hematological and immunophenotypic analyses were performed in 110 CLL patients (50 of them with newly diagnosed disease and 60 on therapy). In addition to that, 20 patients with reactive lymphocytosis and 32 donors were examined. The ROR-1 expression in В-lym-phocytes were measured with FACS Canto II flow cytometer using the following monoclonal antibody panel: CD45, CD19, CD20, and ROR-1. Results. The analysis showed that ROR-1 is essentially not expressed in normal and reactive В-lymphocytes and is detected in 100 % of CLL tumor cells both at disease onset and on therapy. The ROR-1 expression does not change during CLL treatment and can be used not only for CLL diagnosis but also for detection of MRD. Bone marrow aspirates (п = 64) and peripheral blood samples (п = 6) were analysed for MRD assessment by two methods: according to the standardized protocol, recommended by ERIC (European Research Initiative on CLL) in 2007, with FACS Canto II flow cytometer (BD Biosciences) and using DuraClone RE CLB Tube (Beckman Coulter) with Navious flow cytometer (Beckman Coulter).