ELIMINATION OF ESTABLISHED LIVER METASTASES BY HUMAN INTERLEUKIN 2-ACTIVATED NATURAL-KILLER-CELLS AFTER LOCOREGIONAL OR SYSTEMIC ADOPTIVE

An in vivo model of liver metastasis induced by human gastric carcinom a was established in nude mice and used for locoregional or systemic i mmunotherapy with a subset of human A-natural killer (NK) cells define d previously. A single intrasplenic (i.s.) delivery of A-NK cells (1 x 10(7)) and interleukin 2 (IL-2; 60,000 international units, twice a d ay for 5 days, i.p.) to animals with 3-day established liver metastase s, but not IL-2 alone, resulted in rapid (within 24 h) elimination of the majority of metastases and significantly improved survival. A sing le i.s. or i.v. transfer of these effector cells and IL-2 significantl y prolonged survival of the mice with 3-day established metastases (P < 0.03 and P < 0.02, respectively) compared with untreated mice, Using Cr-51-labeled A-NK cells, it was determined that, at best, 75% of 1 x 10(7) cells delivered i.s., and up to 50% of those delivered i.v. wer e found in the liver 30 min-4 h later. Using image analysis with Di-O dye-labeled A-NK cells, 60-100% of A-NK cells delivered i.s. or i.v. w ere detected in the liver 24 h later. By light microscopy, 3-day liver metastases were mostly intravascular, but some had already begun to s pread into liver tissue, When rhodamine- or Di-O dye-labeled A-NK cell s were injected i.s. or i.v. to study their distribution in the liver, they were detectable by confocal fluorescence microscopy in tumor-fre e tissue and in association with tumor cells 12-24 h after transfer. N o evidence for selective localization of A-NK cells to liver metastase s was obtained; many A-NK cells were randomly distributed in tissue an d not associated with visible metastases. However, confocal fluorescen ce and electron microscopy showed some A-NK cells to be in cell-to-cel l contact with tumor cells, both in the blood vessels and liver tissue . These results indicate that a majority of human A-NK cells transferr ed i.s. or i.v. to mice with liver metastases have the capacity to mig rate to the liver and to enter liver tissue and tumor metastases in vi vo. The presence of these effector cells even in a modest number in th e liver leads to elimination of most, but not all, metastases and to s ignificantly prolonged survival of animals treated with A-NK cells and IL-2.