Subpopulations of B lymphocytes in patients with breast cancer depending on the PD-L1 status

Abstract

Aim. To study the association between the functional potency and degree of maturity of B lymphocytes and PD-L1 expression in breast cancer patients.Materials and methods. The study included 37 patients with the morphologically verified diagnosis of invasive breast cancer of no special type (IBC NST). The PD-L1 status was determined immunohistochemically using the Ventana SP142 assay (Roche, USA). Using the multiplex flow cytometry-based assay and high-throughput sequencing of the tumor microenvironment, subpopulations of B lymphocytes and their CD27 and PD1 expression profiles were determined, taking into account the PD-L1 status.Results. In the tumor microenvironment, regardless of the PD-L1 status, expression signatures of five lymphocyte subpopulations were determined. However, in PD-L1-positive patients, the levels of B lymphocytes and immunoglobulin class-switched B lymphocytes were higher compared with PD-L1-negative patients. Evaluation of the number of different B lymphocyte subpopulations by flow cytometry showed that PD-1-positive B lymphocytes predominated in the tumor microenvironment in PD-L1-positive patients, regardless of the degree of lymphocyte maturity.Conclusion. The results of the study showed predominance of mature committed B lymphocytes and memory B lymphocytes capable of synthesizing immunoglobulins of different classes and Th2 cytokines involved in type 2 immune response in PD-L-positive tumor microenvironment. It suggests that immunotherapy with PD-L1 inhibitors is highly likely to activate cells with protumor potential and can ultimately contribute to breast cancer progression.