Subjects with chronic lymphocytic leukaemia-like B-cell clones with stereotyped B-cell receptors frequently show MDS-associated phenotypes on myeloid cells

The Hydropathy Index of the HCDR3 Region of the B-Cell Receptor Identifies Two Subgroups of IGHV-Mutated Chronic Lymphocytic Leukemia Patients With Distinct Outcome

The HCDR3 sequences of the B-cell receptor (BCR) undergo constraints in length, amino acid use, and charge during maturation of B-cell precursors and after antigen encounter, leading to BCR and antibodies with high affinity to specific antigens. Chronic lymphocytic leukemia consists of an expansion of B-cells with a mixed immature and "antigen-experienced" phenotype, with either a mutated (M-CLL) or unmutated (U-CLL) tumor BCR, associated with distinct patient outcomes. Here, we investigated the hydropathy index of the BCR of 138 CLL patients and its association with the IGHV mutational status and patient outcome. Overall, two clearly distinct subgroups of M-CLL patients emerged, based on a neutral (mean hydropathy index of -0.1) vs. negatively charged BCR (mean hydropathy index of -1.1) with molecular features closer to those of B-cell precursors and peripheral/mature B-cells, respectively. Despite that M-CLL with neutral HCDR3 did not show traits associated with a mature B-cell repertoire, important differences in IGHV gene usage of tumor cells and patient outcome were observed in this subgroup of patients once compared to both U-CLL and M-CLL with negatively charged HCDR3 sequences. Compared to M-CLL with negatively charged HCDR3 sequences, M-CLL with neutral HCDR3 sequences showed predominance of men, more advanced stages of the disease, and a greater frequency of genetic alterations-e.g., del(17p)-together with a higher rate of disease progression and shorter time to therapy (TTT), independently of other prognostic factors. Our data suggest that the hydropathy index of the HCDR3 sequences of CLL cells allows the identification of a subgroup of M-CLL with intermediate prognostic features between U-CLL and the more favorable subgroup of M-CLL with a negatively charged BCR.

Immunophenotypic analysis of erythroid dysplasia in myelodysplastic syndromes. A report from the IMDSFlow working group

Current recommendations for diagnosing myelodysplastic syndromes endorse flow cytometry as an informative tool. Most flow cytometry protocols focus on the analysis of progenitor cells and the evaluation of the maturing myelomonocytic lineage. However, one of the most frequently observed features of myelodysplastic syndromes is anemia, which may be associated with dyserythropoiesis. Therefore, analysis of changes in flow cytometry features of nucleated erythroid cells may complement current flow cytometry tools. The multicenter study within the IMDSFlow Working Group, reported herein, focused on defining flow cytometry parameters that enable discrimination of dyserythropoiesis associated with myelodysplastic syndromes from non-clonal cytopenias. Data from a learning cohort were compared between myelodysplasia and controls, and results were validated in a separate cohort. The learning cohort comprised 245 myelodysplasia cases, 290 pathological, and 142 normal controls; the validation cohort comprised 129 myelodysplasia cases, 153 pathological, and 49 normal controls. Multivariate logistic regression analysis performed in the learning cohort revealed that analysis of expression of CD36 and CD71 (expressed as coefficient of variation), in combination with CD71 fluorescence intensity and the percentage of CD117⁺ erythroid progenitors provided the best discrimination between myelodysplastic syndromes and non-clonal cytopenias (specificity 90%; 95% confidence interval: 84-94%). The high specificity of this marker set was confirmed in the validation cohort (92%; 95% confidence interval: 86-97%). This erythroid flow cytometry marker combination may improve the evaluation of cytopenic cases with suspected myelodysplasia, particularly when combined with flow cytometry assessment of the myelomonocytic lineage.

Three-fold higher frequency of circulating chronic lymphocytic leukemia-like B-cell clones in patients with Ph-Myeloproliferative neoplasms

Philadelphia chromosome-negative Myeloproliferative neoplasms (Ph-MPN) are accompanied by a markedly increased risk for development of chronic lymphocytic leukemia (CLL) compared to the general population. However, the pattern of onset and the biological characteristics of CLL in patients with coexistent Ph-MPN are highly heterogeneous rendering questionable if the above association reflects a causal relationship between the two disorders or merely represents a random event. By analyzing 82 patients with Ph-MPN and 100 age-matched healthy individuals we demonstrate that MPN patients have an almost threefold higher prevalence of, typically low-count, CLL-like monoclonal B lymphocytosis (MBL) compared to normal adults. The clone size remained unaltered during the disease course and unaffected by the administration of hydroxycarbamide, whereas no patient with Ph-MPN/MBL progressed to CLL during a median follow up of 4 years. Monoclonal B cells in Ph-MPN/MBL patients and normal individuals and in four more patients with coexistence of overt CLL and MPN displayed heterogeneous biological characteristics, while the JAK2V617F mutation was absent in isolated lymphocytes from Ph-MPN patients with coexistence of CLL. Despite its clinical and biological variability, the increased incidence of MBL in Ph-MPN patients along with the one reported for CLL further enforces the notion of a shared pathophysiology among the two malignancies via a common genetic link and/or microenviromental interactions.

Monoclonal B-cell lymphocytosis and early-stage chronic lymphocytic leukemia: diagnosis, natural history, and risk stratification

Monoclonal B lymphocytosis (MBL) is defined as the presence of a clonal B-cell population in the peripheral blood with fewer than 5 × 10(9)/L B-cells and no other signs of a lymphoproliferative disorder. The majority of cases of MBL have the immunophenotype of chronic lymphocytic leukemia (CLL). MBL can be categorized as either low count or high count based on whether the B-cell count is above or below 0.5 × 10(9)/L. Low-count MBL can be detected in ∼5% of adults over the age of 40 years when assessed using standard-sensitivity flow cytometry assays. A number of biological and genetic characteristics distinguish low-count from high-count MBL. Whereas low-count MBL rarely progresses to CLL, high-count MBL progresses to CLL requiring therapy at a rate of 1% to 2% per year. High-count MBL is distinguished from Rai 0 CLL based on whether the B-cell count is above or below 5 × 10(9)/L. Although individuals with both high-count MBL and CLL Rai stage 0 are at increased risk of infections and second cancers, the risk of progression requiring treatment and the potential to shorten life expectancy are greater for CLL. This review highlights challenging questions regarding the classification, risk stratification, management, and supportive care of patients with MBL and CLL.