Clonogenic patterns of human pulmonary adenocarcinoma cell lines (PC-9, PC-13 and PC-14) and how they influence the results of test for chemosensitivity to cisplatin in the human tumor clonogenic assay.

The clonogenic patterns of three human pulmonary adenocarcinoma cell lines (PC-9, PC-13 and PC-14) were studied by human tumor clonogenic assay (HTCA), and factors which could influence the results of tests for the chemosensitivity of these tumor cells to cisplatin in HTCA were determined. The results showed that each tumor cell line had a characteristic clonogenic pattern. The time intervals for the cells to grow to the plateau phase varied from 9 to 16 days, depending on the cell line and number of cells plated. The number of cells plated could substantially influence the results of chemosensitivity tests. The percentage of surviving colonies increased markedly if too many cells (usually 5 X 10(4) or more/plate) were plated. For continuous exposure, the results of chemosensitivity tests were rather stable after 7 days of incubation in each cell line, especially when fewer than 2 X 10(4) cells/plate were plated. For 1-hour exposure, the incubation periods for the results to become stable varied from 7 to 16 days depending on the cell type, number of cells plated and drug concentration. It was stressed that for the correct evaluation of the chemosensitivity of cultured cell lines in HTCA, the clonogenic pattern of each tumor cell line should be checked in detail before further experiments are conducted. The higher the concentration and the longer the exposure time, the more strongly cis-diamminedichloroplatinum (CDDP) suppressed the colony growth in each of the three cell lines in HTCA, and it was recommended that CDDP should be used clinically in such a way as to maintain a high serum level of the active form of CDDP for a long time.