[Study of mifepristone on reversing multidrug resistance of leukemic cell line K562/A02].
OBJECTIVE
To study whether progestogen antagonist mifepristone could reverse multidrug resistance of K562/A02 cells and its mechanisms.


METHODS
MTT was used to study the proliferation of K562/A02 cells and sensitivity of K562/A02 cells to ADM after 72 hours treatment with mifepristone. Flow cytometry was used to assay the expression of P-glycoprotein and the mean fluorescent intensity of intracellular daunorubicin. The expressions of apoptosis related proteins (bcl-2, Bax and caspase-3) were assayed by immunohistochemistry and the glucosylceramide synthase mRNA expression by RT-PCR before and after mifepristone treatment.


RESULTS
MTT assay revealed that 2.5, 5.0 and 10 micromol/L mifepristone did not affect the proliferation of K562/A02 cells, but enhanced the sensitivity of K562/A02 cells to ADM, by 1. 68-, 4.17- and 10.71- fold increase, respectively. Expression of P-gp in K562/A02 cells was (49.03 +/- 5.32)%, and was decreased to (28.60 +/- 2.13)% (P < 0.01) after 10 micromol/L mifepristone treatment for 72 hours. and intracellular DNR accumulation in K562/A02 was (61.07 +/- 8.61)%, and was increased to (92.72 +/- 3.48)% (P < 0.01). After 10 micromol/L mifepristone treatment, the expression of bcl-2 protein was decreased from (56 +/- 9)% to (37 +/- 6)% (P < 0.05), Bax and caspase-3 proteins was increased from (40 +/- 5)% to (87 +/- 10)% (P < 0.01), and from (36 +/- 7)% to (89 +/- 6)% (P < 0.01) respectively. RT-PCR analysis revealed that expression of glucosylceramide synthase mRNA was higher in K562/A02 than in K562 cells, whereas 10 micromol/L mifepristone significantly down-regulated its expression in K562/A02 cells.


CONCLUSIONS
Mifepristone at 10 micromol/L could dose-dependently reverse the multidrug resistance of K562/A02 cells. The possible mechanisms are related with decreasing the expression of P-gp, regulating the expression of apoptosis related proteins and decreasing the expression of glucosylceramide synthase.
Kong
De-xiao
DX
Department of Hematology and Oncology, the Second Hospital of Shandong University, Jinan, China.
Chen
Chun-yan
CY
Xu
Fu-yu
FY
Jia
Ji-hui
JH
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D003630:Daunorubicin / Q000493:pharmacokinetics; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D020014:K562 Cells; D015735:Mifepristone / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; D015735:Mifepristone; D004317:Doxorubicin; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase; D003630:Daunorubicin