Mechanisms of resistance of human small cell lung cancer lines selected in VP-16 and cisplatin.
BACKGROUND
The combination of VP-16 and cisplatin is one of the most active regimens available for the treatment of small cell lung cancer (SCLC), however, most tumors eventually become resistant to these drugs.


METHODS
To investigate the problem of resistance to VP-16 and cisplatin in patients with SCLC, we established two resistant sublines from the drug sensitive human SCLC line, NCI-H209, by in vitro selection in VP-16 and cisplatin.


RESULTS
The VP-16-selected cell line, H209/VP, was more than 100-fold resistant to VP-16, and displayed cross-resistance to VM-26 and other topoisomerase II interactive drugs, but not to vinca alkaloids. There was no difference in accumulation of VP-16 in H209/VP compared with its parent cell line. The level of topoisomerase II-alpha was reduced to 8% of that in the parent cell line, and there was an altered form of this enzyme with a molecular weight of 160 kilodaltons (kDa), in addition to the normal 170 kDa protein. The cisplatin-selected cell line, H209/CP, was 11.5-fold resistant to cisplatin, with only a low level of cross-resistance to other platinum compounds including carboplatin, tetraplatin, iproplatin, and lobaplatin. This line was highly cross-resistant to vinca alkaloids, but not to anthracyclines or epipodophyllotoxins. The H209/CP cell line was not resistant to cadium chloride, suggesting that alterations in metallothionein are unlikely to be a cause of resistance. Although glutathione (GSH) levels were increased nearly 2-fold in H209/CP, there was no difference in levels of the GSH-related enzymes glutathione-S-transferase, glutathione peroxidase, and glutathione reductase, compared with the parent line. The H209/CP line had a 1.4-fold elevation of topoisomerase II-alpha. The accumulation of cisplatin was reduced in this cell line, and there were fewer DNA-interstrand cross links formed in the presence of cisplatin in H209/CP, compared with the parent line. Neither H209/VP nor H209/CP expressed MDR1, the gene for P-glycoprotein. The MRP gene was expressed at a slightly higher level in the H209/VP cell line, but there was no significant increase in expression of this gene in the H209/CP cell line.


CONCLUSIONS
The resistance of the H209/VP cell line is associated with an alteration of topoisomerase II-alpha, whereas the resistance in the H209/CP line is associated with reduced drug accumulation.
Jain
N
N
Cancer Research Laboratories, Queen's University, Kingston, Canada.
Lam
Y M
YM
Pym
J
J
Campling
B G
BG
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology / Q000627:therapeutic use*; D002104:Cadmium / Q000494:pharmacology / Q000627:therapeutic use; D019256:Cadmium Chloride; D018288:Carcinoma, Small Cell / Q000188:drug therapy* / Q000201:enzymology / Q000503:physiopathology; D002460:Cell Line; D002712:Chlorides / Q000494:pharmacology / Q000627:therapeutic use; D002945:Cisplatin / Q000494:pharmacology / Q000627:therapeutic use*; D003429:Cross Reactions; D004247:DNA / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000032:analysis / Q000494:pharmacology / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm / Q000235:genetics / Q000502:physiology; D005047:Etoposide / Q000494:pharmacology / Q000627:therapeutic use*; D015972:Gene Expression Regulation, Neoplastic; D005978:Glutathione / Q000032:analysis; D005979:Glutathione Peroxidase / Q000032:analysis; D005980:Glutathione Reductase / Q000032:analysis; D005982:Glutathione Transferase / Q000032:analysis; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000503:physiopathology; D008668:Metallothionein / Q000378:metabolism; D017671:Platinum Compounds / Q000494:pharmacology / Q000627:therapeutic use; D011034:Podophyllotoxin / Q000494:pharmacology / Q000627:therapeutic use; D013713:Teniposide / Q000494:pharmacology / Q000627:therapeutic use; D014407:Tumor Cells, Cultured; D014748:Vinca Alkaloids / Q000494:pharmacology / Q000627:therapeutic use
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D002712:Chlorides; D017671:Platinum Compounds; D014748:Vinca Alkaloids; D002104:Cadmium; D005047:Etoposide; D004247:DNA; D008668:Metallothionein; D013713:Teniposide; D005979:Glutathione Peroxidase; D005980:Glutathione Reductase; D005982:Glutathione Transferase; D004250:DNA Topoisomerases, Type II; D005978:Glutathione; D019256:Cadmium Chloride; D011034:Podophyllotoxin; D002945:Cisplatin