Measurement of antagonistic effects of growth factors and interferons

Effects of interferons on cultured human melanocytes in vitro: interferon-beta but not-alpha or -gamma inhibit proliferation and all interferons significantly modulate the cell phenotype

The effects of human recombinant interferon-alpha-2a (rIFN-alpha), natural interferon-beta (nIFN-beta) and recombinant interferon-gamma (rIFN-gamma) on the proliferation, morphology and antigen expression of cultured human melanocytes were studied in vitro. The investigations were performed in 12-O-tetradecanoylphorbol-13-acetate (TPA)- and serum-containing melanocyte growth medium (MGM), in TPA- and serum-free complete melanocyte medium (CMM) and its mitogen reduced variant (RMM). In MGM, none of these interferons inhibited the growth of normal melanocytes at concentrations 1-10,000 international units (IU)/ml over a period of 5 d. Only nIFN-beta, dose dependently, inhibited melanocyte proliferation in CMM and RMM in a 6- and 12-d assay (growth inhibition at 10,000 IU/ml; 77-80% of the controls, p less than 0.001). In contrast, rIFN-alpha and rIFN-gamma exerted no (RMM), or minor effects (CMM) on melanocyte proliferation (only in 12-d assays at 10,000 IU/ml: 24% and 21% of the controls respectively, p less than 0.01). In parallel experiments performed on melanoma cells, all three interferons were potent inhibitors of proliferation in a 5-d serum-free assay (growth inhibition at 10,000 IU/ml; rIFN-alpha 59%, nIFN-beta 78%, rIFN-gamma 56%, all p less than 0.001). In addition, nIFN-beta and also rIFN-gamma caused striking morphologic changes of normal melanocytes in vitro. Especially under greater than or equal to 10 IU/ml rIFN-gamma cytoplasmic spreading and flattening of the cultured melanocytes and their nuclei were seen, thus resembling melanoma cells in vitro. Untreated human melanocytes grown in MGM showed high expression of the melanoma-associated antigens HMB-45 (95-100%) and K.1.2 (40-100%), whereas the progression marker A.1.43 was present only on less than 5% of the cells. Cultured melanocytes were 95-100% positive for histocompatibility antigen class I (HLA-I), 30-75% were positive for ICAM-1, whereas they were negative for HLA-DR. After treatment with rIFN-alpha, increased expression of HLA-I antigens was found; nIFN-beta and rIFN-gamma decreased the labeling with HMB-45 (75-100%) and with K.1.2 (25-80%), whereby the expression of A.1.43 was found slightly increased (5-15%). The HLA class I antigens were upregulated by both nIFN-beta and rIFN-gamma, nIFN-beta being the most potent agent. Also, both nIFN-beta and rIFN-gamma increased the expression of ICAM-1 (nIFN-beta, 75-90%; rIFN-gamma, 90-95%) and induced de novo expression of HLA-DR antigen (nIFN-beta, 15-20%; rIFN-gamma, 65-95%).(ABSTRACT TRUNCATED AT 400 WORDS)

Interactions of interferons and transforming growth factors during clonal growth of mouse or human cells in soft agar and in mice

The mouse fibroblast-like transformed cell line C-243 adapted to growth in suspension was used as a source of virus-induced interferons (MulFN-alpha, beta), and spontaneously produced active growth factors. These factors were purified from C-243 cells grown as tumors in BALB/c mice, and had properties identical to those of TGF-alpha or TGF-beta isolated by others from different tissues. Exogenous TGF-alpha, beta stimulated colony formation by C-243 cells in soft agar, whereas MulFN-alpha, beta inhibited it. Clonal growth of human lung adenocarcinoma A549 cells in soft agar was inhibited as well by human interferons (types alpha, beta, or gamma) as by TGF-beta. Inhibition was dose-related. Pure EGF, which is an analogue of TGF-alpha, diminished the antiproliferative activity of interferons alpha, beta, and gamma in A549 cells. On the other hand, the anti-mitogenic action of IFN-beta and TGF-beta was clearly synergistic. In mice bearing C-243 cell tumors, TGF-alpha, beta stimulated growth, whereas MulFN-alpha, beta inhibited it. Stimulation of tumor growth was also observed after administration of anti-IFN serum that could neutralize endogenous IFN-alpha, beta. The simultaneous administration of MulFN-alpha, beta and TGF-alpha, beta diminished anti-tumor effects of IFN in mice. Our results suggest that both TGFs and IFNs are autocrine, positive or negative growth factors modulating the rate of proliferation and the neoplastic behavior of the cells. The final effects depend on the target-cell sensitivity and on the relative concentration of the various hormone-like factors. Cancer cells overstimulated by TGF-alpha, beta or by EGF may not respond to IFNs.