Mechanisms of taxotere-related drug resistance in pancreatic carcinoma.
BACKGROUND
Pancreatic adenocarcinoma (PAC) is generally refractory to most chemotherapeutic agents, including docetaxel (Taxotere; TXT). Specific mechanisms for TXT-related drug resistance in PAC have not been defined. The hypothesis of this study was that PAC resistance to TXT is primarily related to P-glycoprotein (P-gp), the expression product of multiple drug resistance (MDR)-1, as opposed to lung resistance protein (LRP) or multidrug resistance protein (MRP).


METHODS
The sensitivity of the PAC cell line SUIT-2 and its sublines to TXT, doxorubicin (DOX) and 5-fluorouracil (5-FU) was evaluated with a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. MDR1 (P-gp), MRP, LRP, and beta-tubulin isotype gene expressions were detected at the messenger RNA level by reverse transcription-polymerase chain reaction (RT-PCR). Verapamil and indomethacin (IMC) were used to test the functionality of P-gp and MRP, respectively.


RESULTS
The SUIT-2 subline S-020 and the TXT-selected SUIT-2 cell line S2/TXT were significantly resistant to TXT. Both showed cross-resistance to DOX but no resistance to 5-FU. RT-PCR demonstrated strong expression of P-gp in S-020 and S2/TXT and weaker or no expression in other cells lines. MRP and LRP expression was found in most of these cell lines but had no relationship to the TXT resistance. TXT resistance in S2-020 and S2/TXT could be reversed by verapamil but not by IMC. Levels of beta-tubulin isotype II and III were increased in S2/TXT compared with S-020 and SUIT-2.


CONCLUSIONS
Intrinsic and acquired TXT resistance is primarily mediated by P-gp, but not by MRP or LRP, and is markedly reversed by the P-gp modulator verapamil. Hence future related studies should focus on the use of agents that block the transporter action of P-gp.
Liu
B
B
Department of Surgery, Medical College of Ohio, 3065 Arlington Avenue, Toledo, OH 43614, USA.
Staren
E D
ED
Iwamura
T
T
Appert
H E
HE
Howard
J M
JM
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000230:Adenocarcinoma; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000077143:Docetaxel; D004305:Dose-Response Relationship, Drug; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D005472:Fluorouracil / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins / Q000235:genetics; D017239:Paclitaxel / Q000031:analogs & derivatives / Q000494:pharmacology*; D010190:Pancreatic Neoplasms; D012333:RNA, Messenger / Q000032:analysis; D020112:Rhodamine 123 / Q000493:pharmacokinetics; D043823:Taxoids; D014404:Tubulin / Q000235:genetics; D014407:Tumor Cells, Cultured; D020394:Vault Ribonucleoprotein Particles / Q000235:genetics; D014700:Verapamil / Q000494:pharmacology; D000099187:Major Vault Protein
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000894:Anti-Inflammatory Agents, Non-Steroidal; D000964:Antimetabolites, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; D002121:Calcium Channel Blockers; D000077143:Docetaxel; D005456:Fluorescent Dyes; D005472:Fluorouracil; D007213:Indomethacin; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D017239:Paclitaxel; D012333:RNA, Messenger; D020112:Rhodamine 123; D043823:Taxoids; D014404:Tubulin; D020394:Vault Ribonucleoprotein Particles; D014700:Verapamil; D000099187:Major Vault Protein