Purification of a cytotoxic factor from human and rat tissues.

Human and rat normal tissues and tumours have been studied for the presence of toxic substances, possibly of importance in the development of cachexia in patients with cancer and other chronic diseases. The toxic effect of tissue extracts was gauged by measuring the inhibition of growth of mouse L-cells in 1-ml cultures, as revealed by reduced incorporation of [14C]leucine into cell protein. A common cytotoxic substance of mol. wt. approximately 700 daltons was isolated from all rat and human tissues tested, including tumours. The isolation procedure involved tissue homogenization, followed by pressure dialysis, gel filtration of concentrated pressure dialysates, cation exchange chromatography, and thin layer chromatography. Amounts isolated from different tissues varied by a factor of 3. The purified substance reacted with ninhydrin and a few other reagents for amino groups. It was completely resistant to acid and enzymatic hydrolysis. The evidence thus suggests that the substance is an amine. It is toxic to L-cells, HeLa cells and normal rat fibroblasts in concentrations of 10-20 muM, producing cell death and lysis during incubation overnight.