Abstract
We have developed panels of human lung cancer cell lines with acquired and inherent resistance to cisplatin. Three parental cell lines, NCI-H69/P (small cell), COR-L23/P (large cell), and MOR/P (adenocarcinoma), were grown in increasing concentrations of cisplatin over a period of 6-9 months. This resulted in the development of sublines, H69/CPR, L23/CPR, and MOR/CPR which were 3- to 8-fold resistant to cisplatin as determined by a 6-day 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. None of the resistant sublines showed a significant change in cellular glutathione content or sensitivity to cadmium chloride (an indicator of metallothionein content), although changes in glutathione-S-transferase activity were seen. The sublines each showed cross-resistance to melphalan. Cisplatin accumulation was unchanged in H69/CPR, 1.3-fold reduced in L23/CPR, and 2.0-fold reduced in MOR/CPR compared with their respective parent lines. In a panel of 10 small cell lung cancer cell lines, there was a 16-fold range of sensitivities to cisplatin. The panels have been used to examine cross-resistance between cisplatin, carboplatin, iproplatin, tetraplatin, and a series of 10 novel ammine/amine dicarboxylate platinum(IV) compounds. Whereas H69/CPR and MOR/CPR showed little or no cross-resistance to any of the other compounds, L23/CPR was generally cross-resistant to all of them. In the panel of small cell lines, whereas the ranking of sensitivity to carboplatin and cisplatin were similar, each of the other compounds provided individual patterns of sensitivity. There was always a wide range of sensitivities among the panel, ranging from 8- to 28-fold. Among the dicarboxylate compounds, there was a great range of potencies, with two compounds (JM273 and JM274) being approximately 100-fold more potent than cisplatin.
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