Melanoma differentiation-associated gene-7 (mda-7)/
interleukin-24 (IL-24) has shown potent
tumor cell apoptosis inducing capacity in multiple
cancers. However, the apoptosis induction capacity of mda-7/IL-24 was low and directly correlated with the adhesion to
tumor cells.Cell adhesion molecule
integrin α(v)β(3) expressed on the surface of several types of solid
tumor cells, and they bind to
arginine-glycine-aspartic acid (RGD) which enhanced the adhesion to
tumor cells. This rout was exploited to construct a
tumor-targeting gene RGD-IL-24 which can express RGD-MDA-7/IL-24
protein that includes the cell adhesive sequence (164)Arg-(165)Gly-(166)Asp (A
Glycine residue was inserted into the recombinant MDA-7/IL-24 between Arg164 and Asp165 to form a RGD motif). We successfully got the MDA-7/IL-24 mutant by overlapping polymerase chain reaction (PCR) and evaluated its therapeutic efficacy for tumor cell lines MCF-7, HeLa, HepG2, and normal human lung fibroblast (NHLF) line. And we found that the expression of pCDNA3.1/RGD-IL-24 was same to the expression of pCDNA3.1/IL-24. The RGD-IL-24 enhanced the apoptosis-inducing function in
tumor cells, but not in normal cells. In tumor cell lines, the apoptosis-inducing activities of RGD-IL-24 was significantly higher than IL-24 detecting by MTT assay,
Annexin V, and
Hoechst 33258 analysis. Further, pCDNA3.1/RGD-IL-24 showed a significant increase in the ratio of pro-apoptotic (bax) to anti-apoptotic (bcl-2)
proteins in tumor cell lines, but not in NHLF cell line. Together, these results suggest that RGD-IL-24 can enhance the apoptosis of
tumor cells and may provide a promising drug in
tumor therapy.