Objective To investigate the antitumor activity of IL-24 delE5 in human leukemia cell line K562. Methods The expression of mda-7/IL-24 and its splice variant induced by TPA in leukemic cell lines, U937 and HL-60, was evaluated. The effects of IL-24 delE5 in K562 on cell proliferation, colony-forming ability, cell cycle, apoptosis, and tumor growth in vivo by using MTr assay, colony forming assay, flow cytometry, Annexin-V/PI and tumor xenograft models in nude mice were assessed. Meantime, the effects of IL-24 delE-5 and mda-7/IL-2A were compared. Results The expression of IL-24 dciE5 was detected in differentiated U937 and HL-60 cells. Transfection with IL-24 delE5 significantly reduced tumor cell viability, inhibited colony formation. Comparing with the control, G_0/G_1 stage add from (24.46±3.99) % to (42.69±3.04) %, caused cell cycle arrest in G_0/G_1 stage and significantly inhibited the growth of K562 transplantation tumor. No significant differences in the aforementioned antileukemia characteristics between IL-24 delE5 and mda-7/IL-24 was found. Conclusion Similar with mda-7/IL-24, IL-24 delE5 can efficiently inhibit the proliferation of K562 in vitro and in vivo, probably through induction of G_0/G_1 cell cycle arrest.

Objective To explore the mechanism of the cell-cycle arrest induced by human melanoma differentiation associated gene-7 (mda-7/IL-24) in chronic myelocytic leukemia cell line K562. Methods Microarray analysis was performed to determine the genes that were differentially regulated by mda-7/IL-24 in K562 cells, and was validated by realtime PCR. The phosphorylated pRb were detected by Western blotting analysis. Results A microarray analysis showed that G_0/G_1 phase-associated genes p21~(WAF-1) and BCCIP were up-egulated, while cdk6 and Smurf2 were down-regulated. The directional change in the expression of the four genes was successfully validated with real-time quantitative RT-PCR. pRb Set~(795) phosphorylation was observed with no modification of the pRb protein level. Conclusion These results suggest that IL-24/mda-7 may inhibit K562 proliferation and induce G_0/G_1 cell cycle angst by up-regulating p21~(WAF-1) and BCCIP, down-regulating cdk6 and Smurf2.