Recovery of cell subpopulations from human tumour xenografts following dissociation with different enzymes.

Human epidermoid tumours (Co112, HEp3, A431, ME180) grown in nude mice were dissociated using four different enzyme cocktails: 0.025% collagenase, 0.05% pronase, 0.04% DNase; 0.1% protease IX; 0.14% trypsin, 0.04% DNase; 0.025% collagenase, 0.02% DNase. Using these different enzymatic procedures, the total cell yields, host to tumour cell ratios, plating efficiencies and cell cycle distribution profiles obtained from each tumour model were compared. For all tumours tested, enzyme cocktail 1 was the most effective in releasing the greatest total number of cells g-1 tumour. However, for each tumour the percentage of neoplastic cells recovered, the plating efficiency and the cell cycle distributions varied according to the enzyme cocktail used to dissociate the tumour. For example, for HEp3 tumours, the highest plating efficiency was achieved using enzyme cocktail 4, whereas for ME180 tumours, this enzyme cocktail produced the lowest plating efficiency. Further, the effect of lethally irradiated (HR) feeder cells on the plating efficiency of the various tumours was found to be influenced by the enzymes chosen to dissociate the tumours. These studies indicate that the choice of an enzyme dissociation technique may profoundly influence the results obtained using human tumour xenografts.