DIVERGENT INVITRO EFFECTS OF RECOMBINANT INTERFERONS ON HUMAN OSTEOSARCOMA CELLS

We investigated the in vitro effects of human recombinant Interferon α (rIFNα) and Interferon γ (rIFNγ) on the proliferation and MCH class II antigen expression of two human osteosarcoma cell Unes SAOS-2 and U2-OS. Addition of low concentrations of either rIFNα (10 U/mL) or rIFNγ (100 U/mL) to the cultures almost completely inhibited the 3H-thymidine incorporation in SAOS-2 cells while even high amounts (10000 U/mL) of rIFNα or rIFNγ did not affect the growth rate of U2-OS cells. This difference was not caused by lack of IFN receptors in U2-OS cells since both cell lines responded to rIFNγ treatment with rapid accumulation of HLA class II mRNA and de novo surface expression of HLA-DR, -DP and -DQ antigens. The induced HLA class II antigens were functionally intact. Osteosarcoma cells treated with rIFNγ stimulated a mixed lymphocyte culture (MLC) response in allogeneic T-lymphocytes while untreated osteosarcoma cells were unable to provoke T-lymphocyte proliferation. These findings indicate that IFNs display divergent effects on two phenotypically closely related tumor cell lines. This should be appreciated also when therapeutic effects of IFNs are evaluated. © 1990.