Monitoring the Systemic Human Memory B Cell Compartment of Melanoma Patients for Anti-Tumor IgG Antibodies

Abstract

Melanoma, a potentially lethal skin cancer, is widely thought to be immunogenic in nature. While there has been much focus on T cell-mediated immune responses, limited knowledge exists on the role of mature B cells. We describe an approach, including a cell-based ELISA, to evaluate mature IgG antibody responses to melanoma from human peripheral blood B cells. We observed a significant increase in antibody responses from melanoma patients (n = 10) to primary and metastatic melanoma cells compared to healthy volunteers (n = 10) (P<0.0001). Interestingly, we detected a significant reduction in antibody responses to melanoma with advancing disease stage in our patient cohort (n = 21) (P<0.0001). Overall, 28% of melanoma patient-derived B cell cultures (n = 1,800) compared to 2% of cultures from healthy controls (n = 600) produced antibodies that recognized melanoma cells. Lastly, a patient-derived melanoma-specific monoclonal antibody was selected for further study. This antibody effectively killed melanoma cells in vitro via antibody-mediated cellular cytotoxicity. These data demonstrate the presence of a mature systemic B cell response in melanoma patients, which is reduced with disease progression, adding to previous reports of tumor-reactive antibodies in patient sera, and suggesting the merit of future work to elucidate the clinical relevance of activating humoral immune responses to cancer.

T follicular regulatory cells in the regulation of B cell responses

“…Anti-tumor antibodies elicited by vaccines can correlate with tumor clearance in melanoma patients [67], and class switched antibodies produced in patients with melanoma can potently kill melanoma cells in vitro, suggesting that humoral immune responses may contribute to anti-tumor immunity [68]. Whether checkpoint blockade elicits antibodies that promote tumor clearance or elicit adverse events is unclear.…”

IgG4 subclass antibodies impair antitumor immunity in melanoma

“…Peripheral blood B cells from patients with melanoma and healthy volunteers were isolated using the B cell enrichment cocktail (Stemcell Technologies) and cultured at a density of 500 cells per well (in 96-well plates) in combination with (3,010 cGy) irradiated autologous PBMCs, Epstein-Barr virus, and the TLR9 agonist CpG 2006, as previously described (28). Single cell suspensions were derived from patient tissues (lymph nodes or melanoma skin lesions) using a Gentle MACs Tissue Dissociator (Miltenyi) and filtered through a 100-μm strainer.…”

Pathways and therapeutic targets in melanoma

“…Interestingly, the B-cell-mediated immune responses were significantly diminished in patients with metastatic melanoma versus primary disease [296]. The impaired B-cell functionality with loss of CD27+ (memory) cells was previously reported in metastatic melanoma [297].…”