Promising polymers.

We have compared the effects of a and recombinant y interferons (IFNs) on the growth of human lung cancer cell lines in vitro. There was a diversity of response amongst the lines studied, the most sensitive being COR-L23 (a large cell anaplastic carcinoma line) and POC (a small cell line). In these two lines. IFN-y was found to be more potent than IFN-a. During cell growth of line POC in the presence of IFN-y no significant shift in cell cycle distribution occurred. When lines COR-L23 and POC were grown as xenograft tumours in nude mice, daily injection of 4 x 105 units per mouse per day of IFN-y produced no discernible retardation of tumour growth. It is well established that interferons (IFNs) are able to inhibit the growth of mammalian tumour cells in vitro and also of xenografted tumours in nude or immune-deprived mice (Pauker et al. A number of different types of IFN have been used in these experimental studies including human leucocyte or lymphoblastoid (a) IFN, fibroblast (fi) IFN and lymphocyte (immune) (y) IFN. Earlier preparations of IFNs depended upon the purification of very small amounts of material obtained from cells grown in culture (Stewart, 1974), or from human blood (Cantell & Hirvonen, 1977). More recently IFN-a has been produced on a large scale from bulk cell culture and recombinant DNA techniques have allowed large scale production of IFNs from cloned interferon genes in E. coli bacteria. These cloned IFNs show much higher degrees of purity than IFNs purified from mammalian cell cultures. Although IFN-c has been shown in clinical trials to have some activity in lymphomas, breast cancer, melanoma and myeloma, there was no response in either non-small cell (Stoopler et al., 1980) or small cell (Jones et al., 1983) lung cancers. In view of the impending availability for clinical trial of recombinant IFN-y, and our continuing interest in lung cancer therapy, we decided to investigate the comparative effects of IFN-a and IFN-y on lung cancer cells in culture and the effect of IFN-y on the growth of xenograft tumours in nude mice. Materials and methods Interferons Human lymphoblastoid IFN-a was supplied by Dr N. Finter (Wellcome). This highly purified IFN-oa mixture is produced from the Namalwa cell line of Burkitt lymphoma. Its sp. act. was 1.0 x 108 IU mg-I protein (prior to the addition of human serum albumin as stabiliser). Recombinant IFN-y was kindly supplied …