Granzyme B production by activated B cells derived from breast cancer-draining lymph nodes.

B lymphocytes with regulatory or effector functions synthesize granzyme B (GZMB). We investigated the frequency and phenotype of GZMB-producing B cells in breast tumor-draining lymph nodes (TDLNs). Mononuclear cells were isolated from 48 axillary lymph nodes and were stimulated with anti-BCR (B cell receptor), recombinant interleukin (IL)-21 and CD40 L alone or in combination. Flow cytometry was used to evaluate the expression of GZMB in B cells, and in 4 samples the phenotype of GZMB+ B cells was determined. B cells produced GZMB only when stimulated with a combination of IL-21 and anti-BCR for at least 16 h. Adding CD40 L to IL-21 and anti-BCR stimuli resulted in lower GZMB production in B cells. A small fraction of B cells was able to produce perforin in all stimulation conditions, and the majority of GZMB+ B cells were perforin-negative. Both naïve (CD24lowCD27-) and active/memory (CD24hiCD27+) B cells expressed GZMB. In patients with invasive ductal carcinoma, the frequency of GZMB+ B cells was significantly lower in metastatic compared to non-metastatic lymph nodes. The frequency of GZMB+ B cells did not significantly correlate with prognostic factors such as stage, tumor size or Her2 expression. In summary, a subpopulation of both naïve and memory B cells expressed GZMB in breast TDLNs. Our findings underscore the need to investigate the function of GZMB+ B cells in breast tumor immunity.

Correlation of 4-1BBL+ B Cells in Tumor Draining Lymph Nodes with Pathological Characteristics of Breast Cancer.

BACKGROUND: B cells can increase the expression of granzyme B in CD8+ T cells through 4-1BBL/4-1BB interaction and promote anti-tumor immunity. OBJECTIVE: To investigate the expression of 4-1BBL on B cells in the breast tumor draining lymph nodes (TDLNs) and its association with disease parameters. METHODS: Using Ficoll-Hypaque gradient centrifugation, mononuclear cells were isolated from axillary lymph nodes of 42 patients. Cells received 4 hours of PMA/Ionomycin stimulation, in vitro. Both unstimulated and stimulated cells were stained with anti‒CD19 and anti‒4-1BBL antibodies and subjected to flow cytometry. RESULTS: 4-1BBL expression was detected on 2.8 ± 1.7% of unstimulated B cells, while 27.4 ± 11.9% of B cells expressed this co-stimulatory molecule following stimulation. In steady state, the percentage of 4-1BBL+ B cells was not associated with cancer characteristics. However, in patients with invasive ductal carcinoma, the percentage of 4-1BBL expressing B cells in stimulated condition had a decreasing trend in grade III, compared to grade II+I. In addition, significantly higher frequency of 4-1BBL+ B cells was seen in the TDLNs of ER+ or PR+ compared with ER‒ or PR‒ patients (p=0.021 and p=0.015, respectively). No significant associations were observed between the frequency of 4-1BBL+ B cells and the number of involved LNs, Her2 expression or disease stage. CONCLUSIONS: The frequency of 4-1BBL+ B cells significantly increased following a short time activation, and showed relative and significant associations with tumor grade and estrogen receptor status, respectively. More investigations are required to evaluate the potential of 4-1BBL+ B cells for use in immunotherapy.