In vitro cytotoxicity of a novel antitumor antibiotic, spicamycin derivative, in human lung cancer cell lines.
Spicamycin (SPM), produced by Streptomyces alanosinicus, induces potent differentiation in a human leukemia cell line, HL60. One of the derivatives of SPM (SPM-D), KRN5500, has a wide range of antitumor activity against human cancer cell lines. We examined the cytotoxicity of SPM-D in small and non-small cell lung cancer cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and colony assays. SPM-D was active against a wide range of lung cancer cell lines. All three cisplatin (CDDP)-resistant cell lines established in our laboratory (PC-9/CDDP, PC-14/CDDP, and H69/CDDP) showed collateral sensitivity to SPM-D with relative resistance values of 0.43, 0.34, and 0.32, respectively. Intracellular SPM-D in PC-14/CDDP was 35% higher than that for PC-14 suggesting that intracellular accumulation can explain the collateral sensitivity to SPM-D at least in PC-14/CDDP. On the other hand, in PC-9/CDDP cells, no increase of intracellular SPM-D accumulation was observed, but the conversion ratio of a metabolite (the amino nucleoside moiety of spicamycin binding with glycine, SAN-G) from SPM-D evaluated by TLC was higher as compared with that of parental PC-9 cells (45.5% versus 37%; PC-9/CDDP versus PC-9). The increased intracellular metabolism of SPM-D could explain the mechanism of collateral sensitivity in PC-9/CDDP cisplatin-resistant cell lines. To elucidate the determinant of the SPM-D-induced cytotoxicity, we established SPM-D-resistant cell lines, PC-9/SPM-D, PC-14/SPM-D, and H69/SPM-D, by exposing cells to stepwise increases in SPM-D concentration. The relative resistances of these sublines were more than 5000, 46.6, and 37.8 times those of the parental cell lines, respectively. The intracellular concentration of the active metabolite, SAN-G, was found to be decreased in the SPM-D-resistant sublines. This result indicates that the intracellular metabolism of SPM-D to SAN-G is one of the determinants of cellular sensitivity to SPM-D in these SPM-D-resistant cell lines. In conclusion, both drug accumulation and metabolism may contribute to the sensitivity/resistance to SPM-D and both may merit investigation.
Lee
Y S
YS
Pharmacology Division National Cancer Center Research Institute, Tokyo, Japan.
Nishio
K
K
Ogasawara
H
H
Funayama
Y
Y
Ohira
T
T
Saijo
N
N
D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism; D000903:Antibiotics, Antineoplastic / Q000378:metabolism / Q000493:pharmacokinetics / Q000633:toxicity*; D018288:Carcinoma, Small Cell / Q000188:drug therapy* / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D004072:Digitonin / Q000494:pharmacology; D004351:Drug Resistance; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D011684:Purine Nucleosides / Q000378:metabolism / Q000493:pharmacokinetics / Q000633:toxicity; D014407:Tumor Cells, Cultured / Q000737:chemistry
D000903:Antibiotics, Antineoplastic; D011684:Purine Nucleosides; C092296:KRN 5500; D004072:Digitonin; D002945:Cisplatin