[The relationship between multi-drug resistance and proportion of leukemia stem cells and expression of drug transporters in drug-resistant leukemia K562/ADM cells].
OBJECTIVE
To investigate the drug resistance, proportion of leukemia stem cells (LSC) and expression of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) in drug-sensitive and multidrug-resistant leukemia cell population.


METHODS
The multidrug-resistant leukemia K562/ADM cell and its parental K562 cell were used as the model cells. The drug sensitivity was tested with a MTT assay. Flow cytometry was employed to detect the immunophenotype of stem cells and the expression of P-gp and BCRP. The self-renewal and proliferating potential were examined with methylcellulose colony-forming unit assay.


RESULTS
K562/ADM cells were highly resistant to adriamycin, daunorubicin and etoposide. The amount of CD34+, CD123+ and CD34+ CD38- cells in K562/ADM cells was much higher than that in K562 cells, and the proportion of CD34+ CD38- CD123+ cells (LSC) in K562/ADM cells was (5.23 +/- 0.21)% versus (1.27 + 0.17)% in K562 cells, which was 4.12-fold higher than that in K562 cells. Both P-gp and BCRP were overexpressed in K562/ADM cells relative to K562 cells, and the K562/ADM cells coexpressing P-gp and BCRP were 11.25-fold higher over K562 cells. The proportion of CD34+ CD38- CD123+ BCRP+ and CD34+ CD38- P-gp+ BCRP+ cells in K562/ADM cells were (4.13 +/- 0.40)% and (5.80 +/- 1.19)% respectively, which were 3.66- and 11.37-fold higher than the same cells in K562 cells [(1.13 +/- 0.15)% and (0.51 +/- 0.01)%]. Furthermore, drug-resistant K562/ADM cells displayed 4.17-time greater colony-forming ability over the parent K562 cells, corresponding to the proportion of LSCs in K562/ADM cells.


CONCLUSIONS
The ABC transporters-overexpressing LSC population exists in drug-resistant leukemic K562/ADM cells relative to drug-sensitive K562 cells, and the drug-resistant LSCs may be the source of chemotherapeutic resistance of leukemia.
Laboratory Center for Medical Science, School of Medicine, Lanzhou University, Lanzhou, China.
Juan
J
Yi
Jing
J
Chen
Jing
J
Sun
Hu-Lai
HL
Wei
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D006801:Humans; D020014:K562 Cells; D007938:Leukemia / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism*
C116614:ABCG2 protein, human; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D009363:Neoplasm Proteins