SENSITIVITY OF ISOENZYME ANALYSIS FOR THE DETECTION OF INTERSPECIES CELL-LINE CROSS-CONTAMINATION

The analysis of tile gel electrophoresis banding patterns and relative migration distances for tile individual isoforms of intracellular enz ymes, such as lactate dehydrogenase, purine nucleoside phosphorylase, glucose-6-phosphate dehydrogenase, and malate dehydrogenase, is used r outinely in the biopharmaceutical industry for confirmation of cell li ne species of origin. In the present study, the sensitivity of the tec hnique (AuthentiKit(TM), Innovative Chemistry, Marshfield, MA) for det ermining interspecies cell line cross-contamination was examined. Extr acts were prepared fr om a CHO-K1 line (AA8, Chinese hamster), MRC-5 ( human) cells, and L929 (mouse) cells and from several proportional mix tures of the various binary combinations of cells. The isoenzymes were analyzed according to standard procedures for the: technique. Contami nation of MRC-5 cells with CHO-K1 or with L929 cells was clearly detec table with each enzyme analyzed. Similarly, the contamination of L929 or CHO-K1 cells with MRC-5 cells was readily apparent with each enzyme . On the other hand: contamination of CHO-K1 cells with L929 cells was only detected with lactate dehydrogenase analysis, and contamination of L929 cells with CHO-K1 cells was not detected with any of the four enzymes examined. For the latter case, the analysis of an additional e nzyme (peptidase B) was required. The results indicate that interspeci es cross-contamination should be detectable with isoenzyme analysis if the contaminating cells represent at least 10% of tile total cell pop ulation.