Differential effects of immobilized CCL21 and ICAM1 on TILs with distinct expansion properties

Adoptive T cell therapy (ACT), particularly tumor-infiltrating lymphocyte (TIL), holds great promise for cancer treatment, yet it still faces major challenges such as variability in expansion rates, cytotoxic potency and immune suppression. Recent studies suggest that a "synthetic immune niche" (SIN), composed of immobilized CCL21 and ICAM-1, enhances both the expansion and cytotoxicity of murine and patient-derived T cells. Here, we investigate the mechanism underlying the expansion variability by identifying morphological and molecular markers that distinguish low- and high-expanding TILs and predict their ex vivo expansion potential. We further developed novel SIN-based strategies that differentially reinforce the efficacy of both low- and high-expanding TILs. We demonstrate that a 14-day REP with feeder cells and SIN facilitates the proliferation of the low-expanding cells, while the high-expanding counterparts benefit from a sequential expansion protocol of 7 days with feeder cells only, followed by 7 days with SIN treatment. At the end of the REP both TIL populations display high levels of granzyme B and perforin and reduced levels of exhaustion markers. In conclusion, our findings demonstrate that the refined CCL21+ICAM1 SIN treatment improves expansion rates and activation profiles of both TIL populations, thereby enabling personalized SIN-enhanced protocols for TIL-based immunotherapy.