The effects of treatment of human lung carcinoma cell line A 549 with recombinant DNA-derived human leukocyte interferons A (rIFN-~A) or D (rIFN-aD), and human lymphoblastoid interferon (Wellferon) on in vitro cell invasion were investigated in a quantitative invasion assay using human amnion. The A 549 cells treated with IFN for one day were incubated on the denuded basement membrane of the amnion in the absence of IFN, and cells which penetrated the full thickness of the connective tissue barrier were measured after 4 days. A dose-dependent inhibition of cell invasion was produced by the recombinant IFNs. The one day treatment of cells with 2-4x103 to l'8x 104units/ml of rlFN-~A resulted in a 60-80 per cent inhibition of invasiveness compared to untreated cells. After a one day exposure of cells to 2"2x 104units/ml of rIFN-c~D, cell invasion was reduced by approximately 70 per cent; a concentration of 4"4xl03units/ml had no apparent effect. Similar treatment with lymphoblastoid | FN (6 x 104 units/ml) had no significant effect on cell invasion. Accompanying the one day exposure to rIFN-ccA (1"8 x 104units/ml) or rIFN-~D (2"2 x 104units/ml), (2', 5') oligo (A) synthetase activity was induced approximately 20-fold; a 4-fold induction of enzyme activity was found in cells exposed to lymphoblastoid IFN (6x 104units/ml). After exposure of A 549 cells to the three IFNs at these concentrations, no significant alteration of the ability of the cells to attach to the basement membrane was found. Moreover, none of the one day IFN treatment regimens were cytocidal, and cell proliferation ability was not affected. This model system may be useful for investigating anti-invasive activity of other IFN types and subtypes.
Materials and methods
General reagents and supplies
Dulbecco's phosphate-buffered saline, medium 199, fetal bovine serum (FBS) and a solution of penicillin and streptomycin (all from M.A. Bioproducts, Walkersville, MD, U.S.A.) and a trypsin-EDmA mixture (0"05 per cent trypsin and 0"02 per cent disodium salt of EDTA) (Flow Laboratories, McLean, VA, U.S.A.).