Tumor necrosis factor-related apoptosis-inducing
ligand (TRAIL) mainly induces apoptosis through the extrinsic
death receptor-induced pathway by
ligation with
death receptor 4 (DR4) and
death receptor 5 (DR5). On the basis of the antitumor activity to
cancer cells and no cytotoxity to normal cells of TRAIL and the target of the
epidermal growth factor receptor (EGFR)
ligand peptide, the study constructed a new bispecific fusion
protein and a new bifunctional enediyne-energized fusion
protein and investigated their antitumor efficacy. Bispecific fusion
protein Ec-LDP-TRAIL showed potent binding activity to
cancer cell lines with a high expression of EGFR or DR4/DR5 such as A431 and H460 cells, whereas poor binding activity to NIH/3T3 cells with low expressing EGFR and DR4/DR5. Ec-LDP-TRAIL also showed more potent cytotoxicity to A431 and H460 cells than Ec-LDP, which could result from the TRAIL-inducing apoptosis. Results of an in-vivo efficacy study showed that Ec-LDP-TRAIL at a dose of 10 mg/kg decreased the growth of
epidermoid carcinoma A431 xenografts by 80.19% (P < 0.01) on day 26. Immunohistochemical detection of
nuclear antigen factor Ki-67 suggested that Ec-LDP-TRAIL effectively induced cell
necrosis and inhibited cell proliferation of
tumor. From IC50 values, bispecific and bifunctional energized fusion
protein Ec-LDP-TRAIL-AE was more potent and selective in its cytotoxicity against different
carcinoma cell lines than corresponding
lidamycin in vitro and induction of the cleavage of
poly(ADP-ribose)polymerase was observed in A431 cells treated with Ec-LDP-TRAIL-AE and
lidamycin, respectively. Ec-LDP-TRAIL-AE also significantly inhibited the growth of A431 xenografts in a nude mouse model. These properties suggested that Ec-LDP-TRAIL and Ec-LDP-TRAIL-AE may be promising candidates for targeted
cancer therapy.