Antitumor effect and underlying mechanism of RGD-modified adenovirus mediated IL-24 expression on myeloid leukemia cells

• We constructed an RGD-engineered recombinant adenoviral vector Ad.RGD-IL-24.
• It could mediate gene transfer into myeloid leukemia cells with high efficiency.
• IL-24 had growth inhibition and differentiation inducement effects on leukemia cells.
• IL-24 could regulate the expression of apoptosis-related proteins of leukemia cells.
• Intracellular IL-24 expression could retard leukemia cell transplanted tumor growth.

Interleukin-24 (IL-24), a member of the IL-10 cytokine gene family, causes growth suppression and apoptosis in various solid tumor cells. However, the effects of IL-24 on hematopoietic malignant cells have not been extensively explored. In this report, we constructed an RGD-engineered recombinant adenoviral vector, Ad.RGD-IL-24, and assessed its effects on human myeloid leukemia cells. Ad vector mediates gene transfer into leukemia cells with high efficiency. Ectopic over-expression of IL-24 has significant growth inhibition and differentiation inducement effects on these cells. Treatment with Ad.RGD-IL-24 could potentially induce leukemia cells' cell-cycle arrest. In addition, IL-24 expression could significantly induce apoptosis of the THP-1 cells. Ad.RGD-IL-24 had a potent effect on the up-regulation of the expression of GRP78/Bip, GADD34 and Bax, down-regulation of the expression of Bcl-2 and Mcl-1, and induced the activation of Caspase-3, which may be responsible for its apoptosis-inducing effect on THP-1 cells. Furthermore, IL-24 expression could retard transplanted leukemia cell tumor growth in vivo in athymic nude mice. These findings showed the marked antitumor activity of IL-24 and provided potential perspectives in designing therapeutic or vaccine strategies in immuno-gene therapy of myeloid leukemia.