Studies on the asparagine requirement of the Jensen sarcoma and the derivation of its nutritional variant.

Abstract

When Jensen sarcoma cells were cultured in medium devoid of free l-asparagine, the cell population decreased exponentially for 10 days. The surviving cells then began an exponential proliferation phase. The resulting population did not require asparagine to maintain proliferation. Population growth curves and cloning studies showed that, per 106 original cells, approximately 102 variant cells were present that did not have a nutritional requirement for the amino acid. Cells derived from single cell isolates of the original cell population were tested for variant production. Some failed to give rise to variants initially but did so after several subcultures in medium containing asparagine. Others gave rise to variants after 10–40 days in the absence of the amino acid. These data suggested that the selected cell variant originated as the result of events not directly associated with asparagine deprivation.