Bone Marrow Lymphocyte Subpopulation in Chronic Lymphocytic Leukemia Patients with Different Responses to Chemotherapy

Abstract

AIM. To analyze the bone marrow lymphocyte subpopulation based on targeted assessment of PD-1, PD-L1, and LAG-3 marker expression in chronic lymphocytic leukemia (CLL) patients with different responses to chemotherapy.

MATERIALS & METHODS. In 33 CLL patients, PD-1, PD-L1, and LAG-3 antigen expression on В-, Т-, and NK-cells of the bone marrow (BM) was analyzed by flow cytofluorometry prior to treatment and after 6 cycles of chemotherapy with rituximab. Patients were aged 58–68 years (median 64 years); there were 14 women and 19 men. Hematologic response was assessed by measurements of minimal residual disease (MRD). On this basis, patients were divided into two groups: group 1 (n = 20) with satisfactory hematologic response (MRD < 1 %) and group 2 (n = 13) with unsatisfactory hematologic response (MRD ≥ 1 %).

RESULTS. Prior to treatment, the count of PD-1-, LAG-3-, CD38-, and ZAP-70-expressing BM tumor B-cells was lower in patients of group 1 than in those of group 2. After treatment, their decrease was more pronounced in group 1. Prior to treatment, patients in group 1 had a higher count of BM T-lymphocytes with CD3+, CD4+, CD8+, CD8+/CD28+, CD8+/CD28–, and CD8+/CD38+ phenotype including PD-1- but neither PD-L1- nor LAG-3-expressing T-cells.

After treatment, increased T-cells with CD3+, CD4+, CD8+, Treg, CD8+/CD28+, and CD8+/CD28– phenotype including PD-1+ T-lymphocytes were detected in both groups but more pronounced in group 2. In this group, CD3+ и CD4+ T-lymphocytes maintained LAG-3 expression. Prior to treatment, all patients showed decreased NK-cells in BM. After treatment, group 1 showed a higher count of NK-cells with CD3–/CD16+/CD56+ and CD3–/CD16+/CD56+/PD-1+ phenotype and a lower count of NK-cells with CD3–/CD16+/CD56+/LAG-3+ phenotype. PD-L1 expression in NK-cells was not detected, whereas in Т- and В-cells it was moderate prior to treatment and was not identified after hematologic response was achieved.

CONCLUSION. The values determined by the targeted assessment of PD-1 and LAG-3 expression in BM В-, Т-, and NK-cells prior to chemotherapy may well be used in clinical practice as additional prognostic factors in CLL. PD-1 and LAG-3 overexpression in Т-lymphocytes and NK-cells in CLL patients with MRD-positive status after chemotherapy can be regarded as evidence of the functional deficiency of these cells.