HUMAN GASTRIC-CARCINOMA TRANSDUCED WITH THE IL-2 GENE - INCREASED SENSITIVITY TO IMMUNE EFFECTOR-CELLS IN-VITRO AND IN-VIVO

We transduced a human gastric carcinoma cell line, HR, with the interl eukin 2 (IL-2) gene, Stable HR transfectants secreted nanogram quantit ies of biologically active IL-2 and had significantly increased expres sion of IL-2 mRNA relative to that in parental cells. Expression of in tracellular IL-2 protein was not quantitatively different in the paren tal and IL-2 gene-transduced cells, although the former did not. secre te IL-2, Surface expression of lL-2 receptors was comparable in the pa rental and transduced cells at the mRNA or protein levels. Nevertheles s, in vitro proliferation of IL-2 gene-transduced HR cells was signifi cantly more rapid than that of parental cells, Both parental and IL-2 gene-transduced HR cells were equally sensitive to lysis by IL-2-activ ated natural killer (A-NK) cells, as measured in 4 hr Cr-51-release as sasys or to apoptosis induced by NK or A-NK cells, assessed in 1 hr H- 3-TdR-release assays. In 24 hr MTT assays, however, the IL-2 gene tran sduced cells were significantly more sensitive to these effector cells than were parental cells, Upon intrasplenic injection of 5 x 10(6) pa rental or transduced HR cells into nude mice, liver metastases develop ed, Metastases of parental HR cells killed the animals in 24 days, in contrast, metastases of the IL-2 gene-transduced HR cells became necro tic by day 14 and were found to be surrounded by murine NK cells and m acrophages. Survival of nude mice injected with IL-2 gene-transduced H R cells was significantly prolonged (>50 days) relative to that of mic e injected with parental HR. Thus, IL-2 gene-transduced HR cells produ ced sufficient amounts of functional IL-2 in vivo to be able to recrui t to the tumor site and support functions of endogenous cytotoxic immu ne effector cells, which were responsible for regression of hepatic me tastases and significant improvement of survival in these mice. (C) 19 97 Wiley-Liss, Inc.