Chromosomes of Tumor Cells. III. Unresponsiveness of Precancerous Hepatic Tissues and Hepatomas to a Mitotic Stimulus2

Abstract

Livers of rats fed the carcinogen 3′-methyl - 4 - dimethylaminoazobenzene [Chemical Abstracts' nomenclature: N,N-dimethyl-p-(m-tolylazo) analine] were exposed to the mitotic stimulus of partial hepatectomy. The hepatic tissue ceases to respond to this mitotic stimulus of partial hepatectomy and injections of serums in the course of carcinogenesis. It appears likely that this behavior of the hepatic tissue is due to an unresponsiveness of the cells. This unresponsiveness of the precancerous liver is reversible and apparently depends on the presence of the carcinogen. A partial hepatectomy does not alter significantly the mitotic rate of hepatomas. This unresponsiveness is independent of the presence of the carcinogen and persists over many cell generations. The noncarcinogenic azo dye, 4-aminoazobenzene (AB), lacks the ability to interfere with the mitotic rate in regenerating hepatic tissue. The possible significance of this unresponsiveness of precancerous tissue and hepatoma cells for the selection of neo-plastic cells is discussed.