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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.

Background The tumor draining lymph node concept was first described in penile cancer for staging. Immunohistochemistry and histopathology evaluations are routinely used in clinical practice to examine lymph nodes for metastasis. However, these methods are time-consuming with low diagnostic accuracy and micro-metastases might be missed. In this study, we aim to evaluate detection of metastatic cells in draining lymph nodes by flow cytometry. Methods To assess the sensitivity of micro-metastasis detection by FACS (Fluorescence-activated cell sorting), HeLa cells were titrated into Peripheral blood mononuclear cells (PBMCs) and expression of pan-cytokeratin AE1/AE3 was analyzed. Single cell suspensions were separately prepared from 10 regional lymph nodes obtained from 5 patients with invasive penile cancer undergoing radical surgery and lymph node dissection. Lymph node dereived cells were examined for cell surface expression of EpCAM, E-cadherin and intracellular expression of pan-cytokeratin AE1/AE3 by FACS. Results Ten lymph nodes from 5 penile cancer patients were investigated in a head-to-head comparison between FACS and pathology examination of sections. All metastatic lymph nodes verified by pathology examination were also identified by FACS. Two additional lymph nodes with micro-metastases were diagnosed by FACS only. Conclusions FACS analyses of pan-cytokeratin AE1/AE3 stained single cells from tumor draining lymph nodes can be used to detect micro-metastases in patients with penile cancer patients.