Inhibition of foreign-body sarcoma by mammalian RNA?

Long-implanted foreign bodies can provoke sarcoma in several species, although rarely in man. In neoplasia, RNA metabolism is highly active. Several kinds of RNA from 5 species were tested for prevention of foreign-body sarcoma in 8 experiments. Nitrocellulose filters or dialysis bags were the implants used. RNA, usually 1 g/dl, was applied to saturate the filters. They were implanted in groups of 30--50 mice, while concomitant controls received saline-saturated implants. The filters surfaces were 9.8 or 19.6 sq cm with pore diameters (roughness) of 0.05, 0.1 and 0.22 mu. The dialysis bags had 6.3 sq cm surface area and RNA content. Tumour yield was logged weekly. It was compared to that of the controls in each experiment and in the series of trials. Mammalian RNA decreased tumour yield in 9 of 11 trials (1 only at p<0.05), ribosomal RNA (85% reduction) being best. Yeast RNA was inactive. RNA from E.Coli increased tumour yield. Two of three samples of bovine RNase also increased tumour yield, an effect counteracted by admixed RNA. The results would indicate an antitumour effect of mammalian RNA, or a species or concomitant of it, which was irregularly present in the fractions tested, perhaps of ribosomal origin and dialysable.