title: Asparagine-requiring tumor cell lines and their non-requiring variants: cytogenetics, biochemistry and population dynamics.
abstract: Asparagine-requiring Jensen and Walker rat tumor cells and their asparagine-independent variants have been analyzed. The following results were obtained: (1) Both cell lines have very low levels of asparagine synthetase, and non-requiring revertants isolated from these lines have elevated levels of the enzyme. (2) No differences in chromosome number were detected between the parent Jensen line and five Jensen non-requiring revertants isolated from it. (3) Both Jensen and Walker cells undergo asparagineless death when deprived of this amino acid, although the Jensen cells do so at a more rapid rate. (4) Jensen requiring lines are at a selective advantage when grown in competition with non-requiring variants in complete medium, and their growth rate is more rapid when grown separately. The selective coefficients for the variant with respect to the asparagine-requiring parent ASN(-) line were 0.94 for the competition experiments and 0.83 for growth rate estimates. (5) A somatic cell hybrid between Chinese hamster cells (which require asparagine at low densities, and posses measurable synthetase activity) and the Walker line was found to be asparagine-independent, and it possessed enzyme levels equivalent to the hamster parent. The results of these investigations suggest a parallel with microbial auxotrophic mutants and can be understood in terms of alterations within nuclear structural genes.
mesh_terms: D000641:Ammonia; D000818:Animals; D001216:Asparagine / Q000378:metabolism*; D001224:Aspartic Acid; D001375:Azaguanine; D002279:Carcinoma 256, Walker / Q000378:metabolism*; D002455:Cell Division; D002460:Cell Line; D002470:Cell Survival; D002875:Chromosomes / Q000378:metabolism; D002999:Clone Cells; D006224:Cricetinae; D004351:Drug Resistance; D005260:Female; D005796:Genes; D014644:Genetic Variation; D005828:Genetics, Population; D006822:Hybrid Cells; D008025:Ligases / Q000378:metabolism; D010053:Ovary / Q000378:metabolism; D051381:Rats; D012513:Sarcoma, Experimental / Q000378:metabolism*; D013997:Time Factors
chemical_list: D001224:Aspartic Acid; D001216:Asparagine; D000641:Ammonia; D008025:Ligases; D001375:Azaguanine