Reversal of multidrug resistance in drug-resistant human gastric cancer cell line SGC7901/VCR by antiprogestin drug mifepristone.
OBJECTIVE
To explore the reversal effect of mifepristone on multidrug resistance (MDR) in drug-resistant human gastric cancer cell line SGC7901/VCR and its mechanisms.


METHODS
Expression of multidrug resistance-associated protein(MRP) was detected using reverse transcription-polymerase chain reaction(RT-PCR). Flow cytometry was used to assay the expression of P-glycoprotein(P-gp), Bcl-2, Bax, and the mean fluorescent intensity of intracellular rhodamine 123 in the cells. Meanwhile, the protein levels of Bcl-2 and Bax were also detected by Western blotting analysis. The sensitivity of cells to the anticancer agent, vincrimycin(VCR), and the intracellular [(3) H]VCR accumulation were determined by tetrazolium blue (MTT) assay and a liquid scintillation counter, respectively.


RESULTS
Expression of MRP and P-gp in SGC7901/VCR cells was 6.04-and 8.37-fold higher as compared with its parental SGC7901 cells, respectively. After treatment with 1, 5, 10, and 20 micromol/L mifepristone, SGC7901/VCR cells showed a 1.34-, 2.29-, 3.11-, and 3.71-fold increase in the accumulation of intracellular VCR, a known substrate of MRP, and a 1.03-, 2.04-, 3.08-, and 3.68-fold increase in the retention of rhodamine 123, an indicator of P-gp function, respectively. MTT assay revealed that the resistance of SGC7901/VCR cells to VCR was 11.96-fold higher than that of its parental cells. The chemosensitivity of SGC7901/VCR cells to VCR was enhanced by 1.02-, 7.19-, 12.84-, and 21.17-fold after treatment with mifepristone at above-mentioned dose. After 96 h of incubation with mifepristone 10 micromol/L, a concentration close to plasma concentrations achievable in human, the expression of Bcl-2 protein was decreased to (9.21+/-0.65)% from (25.32+/-1.44)%, whereas the expression of Bax protein was increased to (19.69+/-1.13)% from (1.24+/-0.78)% (P<0.01). Additionally, the effects of mifepristone on the expression of Bcl-2 and Bax proteins in SGC7901/VCR cells were further demonstrated by Western blotting analysis.


CONCLUSIONS
Mifepristone has potent reversal effect on MDR in SGC7901/VCR via inhibiting the function of MRP and P-gp, modulating the expression of Bcl-2 and Bax proteins, and enhancing the sensitivity to anticancer agent VCR.
Li
Da-Qiang
DQ
State Key Laboratory of Ultrasound Engineering in Medicine, Chongqing Medical University, PO Box 153, Chongqing 400016, China. lidaqiang1974@ sohu.com
Wang
Zhi-Biao
ZB
Bai
Jin
J
Zhao
Jie
J
Wang
Yuan
Y
Hu
Kai
K
Du
Yong-Hong
YH
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D045744:Cell Line, Tumor / Q000187:drug effects; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005456:Fluorescent Dyes; D006727:Hormone Antagonists / Q000494:pharmacology*; D006801:Humans; D015735:Mifepristone / Q000494:pharmacology*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D011372:Progestins / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D020112:Rhodamine 123; D013274:Stomach Neoplasms; D014316:Tritium; D051028:bcl-2-Associated X Protein
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D005456:Fluorescent Dyes; D006727:Hormone Antagonists; D015735:Mifepristone; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011372:Progestins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D020112:Rhodamine 123; D014316:Tritium; D051028:bcl-2-Associated X Protein; C494826:BAX protein, human; C421109:multidrug resistance-associated protein 1