Cell growth inhibition of human cell lines by human tissue extracts

Abstract

1. 1. A membrane-associated factor affecting cell growth of human established cell lines and diploid cell strains in vitro has been isolated from human tissues including liver, kidney and spleen. Cell growth inhibition by the crude material could be reversed by excess washing. 2. 2. The factor could be solubilized and was found to be of macromolecular nature, thermolabile and active within a narrow pH-range. 3. 3. Incorporation of 14 C-thymidine into DNA was strongly inhibited in treated cells, but kinetic analysis suggested that DNA synthesis is not primarily affected by the inhibitor. 4. 4. RNA synthesis and protein synthesis studied by incorporation of 14 -C-uridine and 14 C-amino acids into RNA and protein respectively are also suppressed by the inhibitor and inhibition of these macromolecules appears to precede inhibition of DNA synthesis. 5. 5. The relationship of the isolated material to mediators involved in cell growth inhibition of confluent diploid cell strains in vitro is discussed.