Enhanced metastases of a mouse carcinoma after in vitro treatment with murine interferon gamma.

Abstract

We have studied the influence of interferons (IFNs) on the metastatic potential of mouse colon adenocarcinoma, COLON 26, cells. Pre-treatment of the cells in vitro for 24 hr with recombinant murine IFN-gamma (rMuIFN-gamma) significantly increased the number of lung tumour nodules when cells were injected i.v. into immunocompetent BALB/c mice and BALB/c nude mice. However, when MuIFN-gamma-pre-treated cells were injected into beige (NK-deficient) nude mice or anti-asialoGM 1 (asGM 1)-serum-treated BALB/c mice (NK-depleted) no enhancement of metastatic potential was seen. Pre-treatment of COLON 26 cells with recombinant human IFN-alpha A/D (Bg1 I), an IFN with equal activity on human and mouse cells, did not significantly enhance their subsequent metastases in immunocompetent or immunodeficient mice. In fact, there was a small but significant decrease in the number of tumour nodules in the lungs of beige nude and asGM 1-treated mice. The effects of rMuIFN-gamma on COLON 26 cells did not appear to be related to an alteration in MHC expression. COLON 26 cells constitutively express H-2D and H-2K antigens and both IFNs had equal enhancing (approx. 2-fold) activity on the expression of these antigens at the doses used in this experiment (10(3)U/ml). We conclude that pre-treatment with rMuIFN-gamma renders COLON 26 cells resistant to in vivo NK-cell lysis via a mechanism that does not involve changes in MHC expression.