Humoral immune response to melanoma: discovery and evaluation of anti-melanoma antibodies

Student thesis: Doctoral ThesisDoctor of Philosophy


Melanoma, a potentially lethal form of skin cancer, is widely thought to be immunogenic in nature. While numerous studies have examined T cell-mediated immune responses to melanoma and their therapeutic potential, there has been less focus on B cell-mediated immune responses and the tumor-reactive antibodies they produce. The aim of this work was three-fold: (1) to develop a methodology to detect antibodies secreted by human B cells that recognize melanoma cell surface proteins; (2) to evaluate the mature B cell repertoire of individuals with melanoma for antibody subclass composition and the presence and prevalence of anti-tumor antibodies; and (3) to study patient-derived antibodies and two engineered antibodies recognizing melanoma cells for their propensity to activate immune effector cells and their capacity to kill or restrict the growth of tumor cells.
As part of this thesis, a novel tumor cell-based ELISA was developed for the detection of tumor-reactive antibodies. Utilizing this new assay, the presence and prevalence of melanoma-reactive IgG antibodies derived from ex vivo cultured peripheral blood B cells from a cohort of 21 patients with melanoma (Stage I, n=1; Stage II, n=8; Stage III, n=6; Stage IV, n=6) were compared to those from healthy volunteers (n=10). While B cells from melanoma patients secreted IgG antibody concentrations comparable to those from healthy volunteer B cell cultures, a significantly increased reactivity of antibodies derived from patients to primary and metastatic melanoma cells was measured compared to healthy volunteers (P<0.001). Interestingly, there was a significant reduction in antibody responses to melanoma with advancing disease stage that was not found to be solely due to a -ii-reduction in the B cell memory compartment size. Comparing IgG antibody subclass distribution among cutaneous tumors, patient lymph nodes and peripheral blood B cells all isolated from individuals with metastatic disease, elevated proportions of IgG4 subclass antibodies were observed in cutaneous tumors which present a novel finding of this thesis. These findings point to differentially polarized humoral immune responses in cutaneous tumor microenvironments.
Lastly, an antibody derived from a patient was then selected and preliminary evaluations of reactivity and specificity to a range of melanoma cell lines and primary human melanocytes were conducted. Using a live cell imaging cytotoxicity assay, this patient-derived melanoma-specific antibody was observed to kill melanoma cells via antibody-mediated cellular cytotoxicity. Additionally, two engineered monoclonal antibodies recognizing a melanoma associated antigen were found to partially restrict tumor cell migration and adhesion and to kill melanoma cells via antibody-dependent cellular cytotoxicity or phagocytosis.
In summary, examining the humoral immune response to melanoma and the effector function of antibodies targeting melanoma cells provides insight into the discovery of new therapeutic strategies for the treatment of melanoma.
Date of Award3 Jul 2013
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorSophia Karagiannis (Supervisor), Frank Nestle (Supervisor) & James Spicer (Supervisor)

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