Activated natural killer cell tumor retention and cytokine production in colon tumor using a tissue-isolated model

Background, Adoptively transferred activated natural killer (A-NK) cells ar e capable of selectively infiltrating solid tumors, but only at low efficie ncy when administered systemically. It is unclear if human A-NEC cells can be retained in tumor tissue and, if so, what is their action. We investigat ed intratumor A-NK cell retention and in situ cytokine production, using an xenogeneic ex vivo tissue-isolated tumor model, which permits direct intra arterial infusion. Materials and Methods. Human colon adenocarcinoma (HT-29) was implanted in the ovarian fat pad of nude rats. The tumors were perfused ex vice 25 to 30 days postimplant with a known number of cells, and the effluent was collec ted over time. The number of human A-NK cells and cell surface antigen expr ession of cells infused and exiting the tumor were calculated, using cell c ounts and flow cytometry, respectively. Frozen sections were stained with G iemsa and also immunostained for the presence of interleukin-2, -4, and -10 , tumor necrosis factor alpha (TNF-alpha), and interferon. Results. Six perfusions with 8 x 10(6) A-NH cells were performed. The mean number of infused A-NK cells that remained in the tumor at the completion o f perfusion was 4.74 x 10(6) (59.2%). No differences were noted in cellular phenotype between the infused cells and the cells exiting the tumor: expre ssion of the markers CD45 (97.5% vs 94.5%), CD14 (0 vs 0), CD3 (3.83% vs 2. 83%), and CD56 (86% vs 83%) was unchanged, P > 0.05. Microscopic examinatio n of tumor sections showed tumor surrounded by A-NK cells, with some tumor nests infiltrated by A-NK cells. In situ immunopositivity for interleukin-2 (2/6), interleukin-4 (3/6), interleukin-10 (2/6), and TNF-alpha (2/6) spec imens was observed. Immunostaining for interferon-gamma was negative. Conclusions. The retention of A-NK cells in the transplanted human colon tu mor tissue was found to be efficient (59.2 %) in this model. Although perfu sion time was limited, A-NR cells were able to infiltrate the tumor and ini tiate cytokine production. (C) 1999 Academic Press.