ANTITUMOR-ACTIVITY OF PROTEIN-A IN A MOUSE SKIN MODEL OF 2-STAGE CARCINOGENESIS

Protein A (PA) is an immunostimulating glycoprotein (mel. wt. 43 000 k Da) obtained from Staphylococcus aureus cowan I. The antitumour proper ty of PA is well documented in the literature in various transplantabl e rumours of rats and mice. In the present set of investigations, the antitumour property of PA was tested in Swiss albino mice in a two-sta ge initiation-promotion mouse skin carcinogenesis model. The animals w ere initiated topically with a single subcarcinogenic dose (52 mu g) o f 7,12-dimethylbenzanthracene (DMBA). PA was administered intraperiton eally (1 mu g/animal), twice weekly for 2 weeks. Promotion was perform ed by twice weekly applications of 12-O-tetradecanoyl phorbol-13-aceta te (TPA) at a dose of 5 mu g/animal for 32 weeks. The result showed th at the treatment schedule can effectively check the onset of tumorigen esis, the cumulative number of tumours and the average number of tumou rs per mouse. In the PA administered group, 30% of the animals remaine d tumour free until the termination of the experiments (i.e. 32 weeks of promotion). Thus the present study proves that protein A can effect ively inhibit DMBA initiated and TPA promoted mouse skin carcinogenesi s.