Tuftsin (TF) is an
immunomodulator tetrapeptide (
Thr-Lys-Pro-Arg) that binds to the receptor
neuropilin-1 (Nrp1) on the surface of cells. Many reports have described anti-
tumor activity of
tuftsin to relate with nonspecific activation of the host immune system.
Lidamycin (LDM) that displays extremely potent cytotoxicity to
cancer cells is composed of an
apoprotein (LDP) and an enediyne chromophore (AE). In addition, Ec is an EGFR-targeting
oligopeptide. In the present study, LDP was used as
protein scaffold and the specific carrier for the highly potent AE. Genetically engineered fusion
proteins LDP-TF and Ec-LDP-TF were prepared; then, the enediyne-energized fusion
protein Ec-LDM-TF was generated by integration of AE into Ec-LDP-TF. The
tuftsin-based fusion
proteins LDP-TF and Ec-LDP-TF significantly enhanced the phagocytotic activity of macrophages as compared with LDP (P < 0.05). Ec-LDP-TF effectively bound to
tumor cells and macrophages; furthermore, it markedly suppressed the growth of human
epidermoid carcinoma A431 xenograft in athymic mice by 84.2 % (P < 0.05) with up-regulated expression of TNF-α and IFN-γ. Ec-LDM-TF further augmented the therapeutic efficacy, inhibiting the growth of A431 xenograft by 90.9 % (P < 0.05); notably, the Ec-LDM-TF caused marked down-regulation of CD47 in A431 cells. Moreover, the best
therapeutic effect was recorded in the group of animals treated with the combination of Ec-LDP-TF with Ec-LDM-TF. The results suggest that
tuftsin-based, enediyne-energized, and EGFR-targeting fusion
proteins exert highly antitumor efficacy with CD47 modulation.
Tuftsin-based fusion
proteins are potentially useful for treatment of EGFR- and CD47-overexpressing
cancers.