[Reversal of multidrug resistance in leukemic cell line K562/AO2 by chlordelazine in vitro].
OBJECTIVE
Some recent studies revealed that phenthiazine might be able to reverse tumor cell drug-resistance. Chlorderazin belongs to the phenthiazine compounds. The study aimed to investigate the reversing effect and mechanism of chlorderazin on multidrug resistance of leukemic cell line K562/AO2.


METHODS
(1) The cytotoxicities of chlorderazin were assayed with the tetrazolium dye, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. (2) The reverse effect of chlorderazin on K562/AO2 cells was analyzed with MTT method. The multidrug resistance reversal index (RI) was equal to the ratio of control group IC(50)/test group half inhibition concentration IC(50). (3) The intracellular daunorubicin (DNR) concentrations were measured by the flow cytometry. (4) Mdr1 mRNA expression was detected by reverse transcription-polymerase chain reaction (RT-PCR). The ratio of mdr-1/beta-actin density was calculated.


RESULTS
(1) Chlorderazin 3 micro g/ml showed little toxicity to K562/AO2 cells and the suppression rate was less than 5%, so the concentration of 3 micro g/ml chlorderazin was selected as the experiment concentration. (2) The cytotoxicities of DNR to K562/AO2 were enhanced by 3 micro g/ml of chlorderazin (P < 0.05) and RI was 1.901. (3) Chlorderazin of 3 micro g/ml could increase the intracellular DNR accumulation significantly (P < 0.05), and the fluorescence staining by the flow cytometry was higher (250.95 +/- 18.96) than the control group (112.75 +/- 15.78) and shift right in K562/AO2 cells treated with chlorderazin, and the difference was significant (P < 0.05). (4) Chlorderazin has no significant influence to the expression level of mdr-1 mRNA. Both test group and control group showed a clear mdr-1 mRNA band located at the position of 157 kb. The ratios of mdr-1/beta-actin density were 0.414 +/- 0.012 in the test group and 0.447 +/- 0.027 in the control group, respectively, and the difference was not significant (P > 0.05).


CONCLUSIONS
Chlorderazin could reverse the multidrug resistance by increasing the intracellular DNR accumulation in K562/AO2 cells. The effects had no correlation to the mdr-1 gene. Further study is needed.
Chen
Li-jun
LJ
Department of Pediatrics, Shandong Provincial Hospital, Jinan 250021, China.
Shen
Shao-hua
SH
Wang
Hong-mei
HM
Ye
Xin
X
Jiang
Sha-yi
SY
Gao
Fei
F
Li
Gui-mei
GM
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D000932:Antiemetics / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D002746:Chlorpromazine / Q000494:pharmacology*; D018432:Drug Resistance, Multiple / Q000187:drug effects* / Q000235:genetics; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D020014:K562 Cells; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000932:Antiemetics; D012333:RNA, Messenger; D002746:Chlorpromazine