Abstract
While treating stage III melanoma patients with autologous therapeutic TIL in an adjuvant setting, we previously reported a significant benefit of treatment on both progression-free survival and overall survival in patients with only one invaded lymph node (early stage III) compared to patients with more than one invaded lymph nodes (advanced stage III). In this context, in order to understand the difference of activity of TIL therapy according to the progression of the illness at stage III, the first objective of the present study was to determine potential differences in the characteristics of TIL populations obtained from an early stage III and a more advanced stage III when tumor burden is more important. The second objective was to determine possible differences in tissue expression level of several molecules involved in interactions between tumor cells and T cells between early and advanced stage III considering that the tumor microenvironment of invaded lymph nodes could become more tolerant with the progression of the disease. A total of 47 samples of melanoma invaded LN from stage IIIb (AJCC 2007) melanoma patients treated with TIL plus IL-2 were included in this study. We confirmed that both PFS and OS were significantly associated to the presence of tumor-reactive T-cells among TIL injected to the patients and that these tumor reactive T cells were more frequently observed at the early stage III. Moreover, while analyzing the expression of 17 markers on 34/47 tumor specimens using immunohistochemistry, we identified that 3 tissue markers involved in interactions between melanoma cells and T cells have a significant difference of expression between early and advanced stage III: MHC class I, adhesion molecule ICAM-1 and the co-stimulation molecule LFA-3 had a significantly weaker expression in melanoma tissue specimens from advanced stage III. In addition, the expression of the alpha chain of the IL-2 receptor (CD25) and the nuclear transcription factor Foxp3 was significantly increased in the melanoma tissue specimens from advanced stage III. Our results suggest differences in the immunological status of the tumor microenvironment between early and advanced stage III, which could explain the difference in clinical response to TIL infusion in an adjuvant setting between early and advanced stage III.