[Establishment of Cytarabine-resistant Acute Lymphoblastic Leukemia Cell Lines and Its Resistance Mechanism]

To establish cytarabine-resistant acute lymphoblastic leukemia (ALL) cell lines and investigate its possible resistant mechanism.

Low-concentration cytarabine (Ara-C) continuously induced and cultured Jurkat and Nalm-6 cells to construct cytarabine-resistant cell lines Jurkat/Ara-C and Nalm-6/Ara-C. The cell viability was detected by CCK-8 assay, and the distribution of cell cycle was detected by flow cytometry. Real-time fluorescence quantitative PCR was used to detect the mRNA expression levels of multidrug resistant gene and Ara-C metabolic enzymes. The expression levels of cyclin were detected by Western blot.

Jurkat/Ara-C and Nalm-6/Ara-C drug-resistant cell lines were successfully established, the resistance index of which was 1 973.908±161.163 and 7 231.643± 1 190.624, respectively. Drug-resistant cell lines had no cross-resistance to commonly used chemotherapeutic drugs, such as doxorubicin. Flow cytometry showed that the ratio of G₀/G₁ phase in Jurkat/Ara-C cells increased but G₂/M phase decreased (P<0.05), while the cell cycle distribution of Nalm-6/Ara-C cells did not change in comparison with Nalm-6 cells. The results of real-time quantitative PCR showed that the expression of deoxycytidine kinase (DCK) and cytidine deaminase (CDA) were significantly down-regulated in drug-resistant cells (P<0.05), MRP was up-regulated in Nalm-6/Ara-C cells (P<0.05), while MDR1, LRP and BCRP did not increase in comparison with parental cells. Western blot analysis revealed that cyclinB1 was significantly under-expressed in drug-resistant cells (P<0.05), while cyclinD1 did not change, when compared with parental cells.

Cytarabine-resistant ALL cell lines are successfully established by using low concentration continuous induction method, and its drug-resistant mechanism may be related to the deficiencies of DCK and cyclinB1.