Preclinical development of tumor-infiltrating lymphocyte (TIL) based adoptive cell transfer (ACT) immunotherapy for patients with sarcoma

Abstract

Background: ACT based on infusion of autologous TILs has the ability to induce complete and durable response in some patients with advanced malignant melanoma. We believe that this approach could also be effective in sarcoma. In this preclinical study we are investigating feasibility of expanding TILs from sarcoma, as well as performing functional in vitro analyses on these TILs. Methods: A portion (> 1 cm3) of the excised sarcoma tumor tissue is cut into fragments and placed in a growth medium containing IL-2 for initial TIL expansion. Afterwards TIL cultures are undergoing a Rapid Expansion Protocol (REP) expansion by adding OKT-3 and feeder cells. Phenotype and functional analyses is performed using flowcytometri and Elispot. Results: To this date we were able to expand TILs from 14 of 15 tumor samples. TILs were harvested and frozen when an estimated number of 100x106 to 200x106 cells were reached. Mean expansion time were 32 days (16 - 61). 87,9 % (36,4 - 99,1) of these cells were CD3 + , and of these 64,7 % (16,3 - 99,1) were CD4 + , and 24,1 % (0,1 - 50,6) were CD8+. REP expansion rates ranged from 630 fold to 2.300 fold, and followed expansion pattern similar to TILs from malignant melanoma. TILs from four tumor samples with three different sarcoma subtypes (undifferentiated pleomorphic sarcoma, myxofibrosarcoma and osteosarcoma) demonstrated reactivity against autologous tumor cells using Elispot. Further assessment is ongoing. Conclusions:We were able to expand TILs from 93% of the included tumor samples to numbers needed for possible future clinical implementation. TILs were a mix of CD4+ and CD8+ with CD4+ being predominant. As of yet we have demonstrated TIL reactivity against autologous tumor cells from four patients with three different sarcoma subtypes. Thus, we conclude that it is feasible to translate TIL ACT into clinical testing in sarcoma patients.