Effects of tumor cell viability and inoculum density on growth parameters in the human tumor, soft-agar clonogenic assay.

Four hundred and forty-seven human tumor specimens were accessioned and processed for clonogenic assay, yielding 374 specimens, representing 23 different histiotypes, adequate for culture. Different levels of viable cell inoculum density produced contrasting effects between 255 solid tumors as compared to 72 malignant effusions and 47 bladder washings. All parameters for solid tumor growth were similar except plating efficiency; as inoculum density increased, plating efficiency decreased. For malignant effusions, no significant differences were noted for colony numbers or plating efficiency, but numbers of evaluable cultures increased significantly with increasing inoculum density. Bladder barbotage specimens followed a pattern similar to that of malignant effusions, but the only parameter significantly affected by increasing cell inoculum was colony number which increased proportionally to an increase in number of cells plated. The storage of 109 solid tumors at 4 degrees C, for culture at a later date, resulted in an overall decrease in cell viability (mean, 23.9%) as compared to 161 tumors processed on receipt (mean, 31.1%). This decrease in viability did not adversely affect growth parameters or culture evaluability rates. Based on a lower viable cell inoculum, the percentage of plating efficiencies of stored tumors was significantly higher (geometric mean, 0.127 compared to 0.079 for direct culture), colony numbers were similar for both groups, and culture evaluability rates did not differ greatly (80 and 76%).