Targeting SLUG sensitizes leukemia cells to ADR-induced apoptosis.

BACKGROUND AND AIMS Slug is an E-cadherin repressor and a suppressor of PUMA (p53 upregulated modulator of apoptosis) and it has recently been demonstrated that Slug plays an important role in controlling apoptosis. In this study, we examined whether Slug's ability to silence expression suppresses the growth of leukemia HL-60 cells and/or sensitizes leukemia HL-60 cells to adriamycin (ADR) through induction of apoptosis. METHODS SLUG siRNA was transfected into the HL-60 and HL-60(ADR) cell lines (an adriamycin resistant cell line). The stably SLUG siRNA transfected HL-60 and HL-60(ADR) cells was transiently transfected with PUMA siRNA. The mRNA and protein expression of SLUG and PUMA were determined by Quantitative real-time RT-PCR and Western blot assay. The effects of SLUG siRNA alone or combined with ADR or PUMA siRNA on growth and apoptosis in HL-60 and HL-60(ADR) cells was detected by MTT, ELISA and terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay. RESULTS The results showed that SLUG was less expressed in the HL-60 cells, and high expressed in the HL-60(ADR) cells. Obvious down-regulation of SLUG mRNA and protein levels and up-regulation of PUMA mRNA and protein levels after SLUG siRNA transfection was showed in the HL-60(ADR) cells. Treatment with ADR induced SLUG mRNA and protein in the HL-60 cells. Significant positive correlation was observed between basal SLUG mRNA and protein and ADR sensitivity. SLUG gene silencing by SLUG siRNA transfection inhibited growth and induced apoptosis, and increased ADR killing of the HL-60 and HL-60(ADR) cell lines. After the SLUG siRNA transfected HL-60 and HL-60(ADR) cells was transiently transfected with PUMA siRNA, did not increase ADR killing of the HL-60 and HL-60(ADR) cell lines. CONCLUSION SLUG level positively correlated with sensitivity to ADR. SLUG siRNA could effectively reduce SLUG expression and induce PUMA expression and restore the drug sensitivity of resistant leukemic cells to conventional chemotherapeutic agents.