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.