T cell reactivity to melanoma Tumor-Associated Antigens before and after surgical removal of metastases

Background: Melanoma the most immunogenic cancer type and metastatic melanoma has poor prognosis. Currently, there are hardly any peripheral blood biomarkers that allow for identification of patient’s prognosis or survival. With most recent advances in melanoma treatment associated with immune based therapy, it is crucial to understand better how the immune system reacts to treatment. Purpose: The main objective of this project was to compare the reactivity of the T cells of patients with stage III or IV metastatic melanoma to tumor associated antigens, before and after surgery where metastatic lesions were removed. This could provide a better insight into the interaction between tumor and T cells. Methods: Peripheral blood mononuclear cells were isolated from blood samples taken before and after surgery. Cells were stimulated over the course of two weeks with overlapping peptide pools of three known melanoma antigens: MelanA, NY-ESO-1 and Cripto-1. After 12 days, the cells were re-stimulated and analyzed using multicolor flow cytometry. CD4 and CD8 positive cells were analyzed for cytokine production, comparing the re-stimulated cells to a negative non re-stimulated control. This gave a set of paired nominal data for each patient, pre and post-surgery. McNemar’s test was used to analyze changes before and after surgery, and Kaplan-Meier analysis were used to investigate correlation between cell reactivity and cytokine production with progression free survival. Results: Surgical removal of metastatic lesions changes reactivity of T cells to MelanA, NY-ESO-1 and Cripto-1. Cripto-1 showed a significant increase in both combined CD4 and CD8 response as well as in exclusive cell type response. We also observed that certain cytokine production patterns correlated with progression from stage III to stage IV melanoma. Conclusions: We show here that surgical removal of metastases amplifies the immune response of melanoma patients. This may provide insight into the complexity of the correlation between cytokine secretion profiles and a favorable immune response to metastatic melanoma