Characterization of Human Tumor-Infiltrating Lymphocytes Expanded in Hollow-Fiber Bioreactors for Immunotherapy of Cancer

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Abstract
We attempted to grow tumor-infiltrating lymphocytes (TIL) from 34 fresh tumors of eight different histologies using flasks for the initiation phase and hollow fiber bioreactors to expand TIL to therapeutic numbers. Overall success rate was 76% (26/34) including melanoma (9/14, 64%) and renal cell carcinoma (11/11, 100%). The mean number of days required to reach successful initiation (1 × 109 TIL) for all tumor types was 29 ± 16 days (mean ± S.D.). Therapeutic doses of TIL required an average of 88 ± 23 days (initiation plus expansion) with an average TIL number of 3.2 × 1010 ± 2.8 × 1010. TIL phenotype was predominantly CD4+ in 53% (16/30) and CD8+ in 47% (14/30), renal cell carcinoma samples accounted for 12/14 of the predominantly CD8+ TIL. Cells bearing the natural killer (NK) phenotype represented only 0–7% of TIL while LAK phenotype represented 0–68% (mean 11 ± 15%); LAK was the predominant phenotype in one patient with kidney cancer. Cytotoxicity tests showed consistent NK and LAK activity in addition to cytolysis of autologous tumor. Autologous tumor cell restricted cytolysis was noted for three TIL cultures. The overall success rate and characteristics of TIL were similar to our results with TIL expanded in semi-permeable plastic bags. This work confirms that hollow-fiber bioreactors are a suitable alternative to semi-permeable bags and roller bottle systems for the expansion of human TIL for therapeutic use in cancer patients.