The Effect of siRNA Down-Regulating XIAP On the Apoptosis and Chemo-Sensitivity of K562 Cells in Vitro.

Failure for chemotherapy in leukemia patients is often due to innate or acquired multi-drug resistance of leukemia cells. The X-linked inhibitor of apoptosis protein (XIAP) is a potent inhibitor of apoptosis and is also involved in drug resistance. The relationship between XIAP and drug resistance is not fully clarified. Here, we manipulated the expression of XIAP in K562 human chronic myelogenous leukemia cells and explore the changes in cell apoptosis and sensitivity to cytarabin.

Small interfering RNA (siRNA) targeting XIAP was created, K562 cells were either transfected with XIAP siRNA or control siRNA by Nucleofector transfection. The siRNAs were labelled with Cy3. Real-time RT-PCR and Western blot were used to determine the expression of XIAP in K562 cells. Flow cytometry was used to detect apoptotic cells and 50% inhibiting concentration (IC50) of cytarabin was also determined.

The transfection rate was 87% in general. The transfection was also confirmed by fluorescence microscopy. After 48h, the expression levels of XIAP mRNA and protein were much lower in XIAP siRNA-transfected cells than in control siRNA-transfected cells (mRNA, 0.37±0.10 vs. 1.41±0.13, P<0.05 ; protein, 0.39±0.03 vs. 0.99±0.08, P<0.05). There was no significant difference in the fractions of apoptotic cells between these two groups at 48h after transfection (37.04%±1.77% vs. 47.43%±1.13%, P>0.05). Cytarabin was added in different concentrations right after Nucleotransfection. After 48h, the IC50 of Cytarabin in the XIAP siRNA-transfected cells was 2.28-fold lower than that in the control siRNA-transfected cells (82.60±21.56μg/ml vs. 188.67±44.48μg/ml, P<0.05). The percentage of apoptotic cells was much higher in the XIAP knockdown cells than in the control cells (47.43%±1.13% vs. 37.04%±1.77% P<0.05).

XIAP siRNA can specifically down-regulate the expressions of XIAP mRNA and protein, promote the drug-sensitivity to cytarabin and increase the cell apoptosis in K562 cells. This might be a novel choice for leukemia treatment.

No relevant conflicts of interest to declare.