Proteasome Inhibitor Bortezomib Sensitize The Multidrug Resistant K562/DNR Cells To Conventional Chemotherapeutic Drugs

IntroductionMultidrug resistance (MDR) is a major problem in treatment of leukemia with conventional chemotherapeutic drugs,and so how to reverse MDR is made one of top target for study. The proteasome inhibitor bortezomib is a new kind of antitumor drugs .it is observed that bortezomib can induces kinds of tumor cell lines apoptosis , and it is permitted used in refractory and relapsed multiple myeloma clinicaly. In the present study, we combined bortezomib and conventional chemotherapeutic drugs daunorubicin and epirubicin to observe the cytotoxicity to multidrug resistant K562/DNR cells.ObjectTo observe the cytotoxicity to multidrug resistant K562/DNR cells of combination of bortezomib and conventional chemotherapeutic drugs daunorubicin and epirubicin.Methods1.Cell culture: The human leukemia cell line K562/S,K562/DNR grown in RPMI-1640 medium supplemented with 12% fetal bovine serum, penicillin (100 IU/ml), and streptomycin (100 lg/ml) and incubated in 5% CO₂.2.MTT assay the cytotoxicity of bortezomib:Different doses of bortezomib were added in the K562/DNR for 24 hours, the absorbance was measured spectrophotometrically using 550 nm wave length ELISA reader and calculate IC₁₀. The dose less than IC₁₀ was desided for furdur study. 3.MTT assay the reverse fold of multiple resistence:Groupl: K562/DNR+epirubicin;Group2:K562/DNR+epirubicin+bortezomib;Group3:K56 2/DNR+daunorubicin;Group4:K562/DNR+daunorubicin +bortezomib.A value was mesured, reverse fold=IC50 of K562/DNR / IC50 of K562/DNR added bortezomib.4. The apoptosis of cells was analyzed using a FACSCalibur flow cytometer equipped with the Cell Quest and ModFit software.ResultsThe IC₅₀ values of K562/DNR treated with epirubicin and daunorubicin for 24 hr were 417.0ug/ml and 457.7ug/ml,while the IC₅₀ combineded with bortizomib were 210.4ug/ml and 324.9ug/ml. The reverse fold were 1.98- and 1.4-fold.The apoptosis of group 1 is 28.74±4.03%, group 2 is46.72±2.05%. p<0.05.ConclusionsProteasome inhibitors bortizomib sensitize K562/DNR multidmg resistant cells to cytotoxic effects of daunorubicin and epirubicin.