ENZYMATIC AND CHROMOSOMAL CHARACTERIZATION OF HELA VARIANTS

Seven strains of HeLa cells have been characterized by the number of chromosomes and the activity of the enzymes alkaline phosphatase, glucose-6-phosphate dehydrogenase, 6-phosphogluconic dehydrogenase, and lactic dehydrogenase. All seven strains were found to differ as to chromosome numbers and enzyme levels despite the fact that two strains were called HeLa and three were called HeLa S3. Three strains were found to have a stemline in which greater than 60% of the cells demonstrated a single chromosome number, and this characteristic was stable for at least 6 months. A nomenclature for these clones has been suggested by the use of the stemline chromosome number as a subscript following HeLa. These three clones were, therefore, designated HeLa₆₅, HeLa₇₁, and HeLa₇₅. Karyotypes were made of the stemlines of these clones and were compared with enzyme levels. Alkaline phosphatase showed the greatest variation from cell line to cell line with a 200-fold difference in levels, whereas glucose-6-phosphate dehydrogenase showed variation in activity over a 12-fold range, lactic dehydrogenase over an 8-fold range, and 6-phosphogluconic dehydrogenase over a 2-fold range. It is suggested that human cell strains can be used for biochemical studies if they are cloned and if the clones are relatively stable at least with respect to modal chromosome number and karyotype.