Patient-derived melanoma organoid models facilitate the assessment of immunotherapies

Background Only a minority of melanoma patients experience durable responses to immunotherapies due to inter -and intra-tumoral heterogeneity in melanoma. As a result, there is a pressing need for suitable preclinical models to investigate resistance mechanisms and enhance treatment efficacy.Methods Here, we report two different methods for generating melanoma patient-derived organoids (MPDOs), one is embedded in collagen gel, and the other is inlaid in Matrigel. MPDOs in Matrigel are used for assessing the therapeutic effects of anti-PD-1 antibodies (& alpha;PD-1), autochthonous tumor infiltrating lymphocytes (TILs), and small molecule compounds. MPDOs in collagen gel are used for evaluating the chemotaxis and migratory capacity of TILs.Finding The MPDOs in collagen gel and Matrigel have similar morphology and immune cell composition to their parental melanoma tissues. MPDOs show inter-and intra-tumoral heterogeneity and contain diverse immune cells such as CD4+ , CD8+ T, Treg, CD14+ monocytic, CD15+ , and CD11b+ myeloid cells. The tumor microenvironment (TME) in MPDOs is highly immunosuppressive, and the lymphoid and myeloid lineages express similar levels of PD-1, PD-L1, and CTLA-4 as their parental melanoma tissues. Anti-PD-1 antibodies (& alpha;PD-1) reinvigorate CD8+ T cells and induce melanoma cell death in the MPDOs. TILs expanded by IL-2 and & alpha;PD-1 show significantly lower expression of TIM-3, better migratory capacity and infiltration of autochthonous MPDOs, and more effective killing of melanoma cells than TILs expanded by IL-2 alone or IL-2 with & alpha;CD3. A small molecule screen discovers that Navitoclax increases the cytotoxicity of TIL therapy.Interpretation MPDOs may be used to test immune checkpoint inhibitors and cellular and targeted therapies.