STUDIES ON THE METABOLISM OF MYELOMA AND HYBRIDOMA CELLS

Abstract

The substrate and nutrient utilisation kinetics for batch culture of two parental myelomas, NSl and P3Ul, and their respective hybridomas, 6BB and 2HG11 were studied. Hybridoma 6BB produces an IgM which is for blood group B typing and hybridoma 2HG11 produces an IgG which is against ?-chorionic gonadotrophin. The antibody production for 6BB was observed to be skewed towards non-growth associated kinetics whereas 2HG11, was skewed towards growth associated kinetics. The results from batch cultivation studies of the four cell lines show that glucose and glutamine were not the limiting substrates and by-products such as ammonia and lactate were not at their inhibitory levels. It was observed that the myelomas had higher specific glucose uptake rates compared to their corresponding hybridomas. On the other hand, specific glutamine uptake rates of the hybridomas were higher than their parental myelomas. It was found that the major energy source changed from glucose during growth phase to glutamine during stationary phase. Moreover, the results indicate that the onset of stationary phase for the four cell lines were not due to energy limitation. For the myelomas and hybridomas studied, it was found that majority of the essential amino acids supplied in the basal medium RPMI 1640 were depleted at the end of the batch runs. The results suggest that the amino acids present in this medium is inadequate to support higher cell densities. Consistently, four essential amino acids namely, methionine, phenylalanine, threonine and valine were observed to be completely consumed prior to the onset of stationary phase for the cell lines studied. Increase in the initial concentrations of these amino acids as well as choline chloride and ethanolamine for the hybridomas did not increase the maximum viable cell density significantly. However, changes in the specific growth rate and antibody production rate for the hybridomas were observed. For hybridoma 6BB, an increase of methionine and threonine shortened the doubling time whereas threonine and valine enhanced the antibody production. For hybridoma 2HG11, valine and choline chloride increased the specific growth rate, and methionine and threonine enhanced the antibody production. The effects on cell growth and antibody production induced by these medium components were found to be cell line dependent. For hybridoma 2HG11, adding pairs of medium components, such as valine/choline chloride and methionine/threonine, were observed to have no effect in increasing specific growth rate and antibody production. Hence, for this hybridoma, the formulation of the medium for cell growth and/or antibody production should be based solely on the supplementation of individual medium component.