Effector T Cell Analysis of Melanoma Tumor-infiltrating Lymphocyte Cultures Using HLA-ABC Semimatched Melanoma Cell Lines

Abstract

The generation of T cells with specific reactivity against tumor-associated antigens is prerequisite for adoptive transfer therapy. Melanoma-specific lymphocyte cultures can be established from tumor-infiltrating lymphocytes (TILs) by in vitro culture with high levels of interleukin-2. In this report, we present TIL data originating from 728 attempted cultures from 33 consecutive melanoma biopsy specimens originating from 30 patients. Cultures were analyzed for the presence of interferon gamma (IFNgamma)-producing cells upon stimulation with a panel of HLA-ABC semimatched melanoma cell lines. We sought to find whether such cell lines could be used to analyze TIL reactivity. Cell lines were used as stimulators to circumvent the need for autologous primary tumor cells. Melanoma-reactive cultures were identified by flow cytometry in 25 of the 30 patients. Four hundred forty-four of 728 (60.9%) cultures contained TILs at the end of experiment. Ninety-one of 318 cultures (28.6%) contained IFNgamma-producing cells after stimulation. In HLA-A*0201 patients IFNgamma analysis was complemented with melanoma-specific tetramer staining. All but one HLA-A*0201 patient had MART-1/Melan-A27-35-directed TILs, with frequencies ranging from 0.1% to 90% of CD8 cells. In addition, tetramer analysis also identified TILs directed against gp100, Tyrosinase, and Her2Neu. Tumor material was collected via needle biopsy in 16 cases and surgery in 18 cases. Overall, surgical material generated more cultures positive for T cells. The described methods are efficient in characterizing clinically relevant melanoma-reactive TILs.