Insertion of functional interleukin-2 (IL-2) gene into a plasmacytoma cell line X63-Ag8.653 substantially reduced tumorigenicity of the resulting cloned cells, designated as X63-m-IL-2. Peritumoral administration of the X63-m-IL-2 cells, producing constitutively large quantities of IL-2, resulted in regressions of established X63-Ag8.653 plasmacytomas growing in the peritoneal cavity of syngeneic mice. In vitro activation of BALB/c spleen cells by co-culture with X63-m-IL-2 cells or their supernatants gave rise to cytotoxic lymphocytes with lymphokine-activated killer (LAK) activity against syngeneic X63-Ag8.653 plasmacytoma and other tumor targets. In contrast, peritumoral administration of X63-Ag8.653 cells carrying an inserted interleukin-4 (IL-4) gene (designated X63-m-IL-4 cells) and producing constitutively large quantities of IL-4 did not result in a therapeutic effect. Moreover, the admixture of the X63-m-IL-4 and X63-m-IL-2 cells substantially diminished the X63-m-IL-2 cell-mediated therapeutic effect. Similarly, IL-4-containing supernatants generated from X63-m-IL-4 cell cultures substantially diminished LAK activation by X63-m-IL-2 cell produced supernatants.

Institute of Molecular Genetics Czechoslovak Academy of Sciences Prague

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