Comments on augmentation of local antitumor immunity in liver by interleukin-2 gene transfer via portal vein: a possible explanation for contradictory in vivo and vitro results of interleukin-2 treatment in a rat model of colon carcinoma metastasis.

Abstract

Tanji et al1 have demonstrated in a rat model that interleukin-2 (IL-2) gene transfer to the liver prevents liver metastasis of colon carcinoma cells. IL-2 gene transfer was performed by intraportal injection of an adenovirus containing the human IL-2 gene (AdCMVhIL-2), before the administration of RCN-9 syngeneic colon carcinoma cells. Controls included injection of either adenovirus containing the -galactosidase gene or PBS. The authors suggested that hepatic natural killer (NK) cells, which are located in the liver sinusoids,2,3 are responsible for this effect. Indeed, they demonstrated that hepatic NK cells isolated from AdCMVhIL-2 rats showed an increased cytotoxic activity against the NK-sensitive YAC-1 target cell line, confirming the results of Shiratori et al.4 However, they were unable to show an increased cytotoxic effect of these isolated hepatic NK cells against the RCN-9 colon carcinoma cells.1 In other words, the in vivo effects of preventing liver metastasis of RCN-9 colon carcinoma cells in AdCMVIL-2 treated rats did not coincide with an increased activity of hepatic NK cells of these rats against the same target cell line.