Abstract
Melittin, which acts as a membrane-disrupting lytic peptide, is not only cytotoxic to tumors, but also vital to normal cells. Melittin had low toxicity when coupled with target peptides. Despite significant research development with the fused toxin, a new fused toxin is needed which has a cleavable linker such that the fused toxin can release melittin after protease cleavage on the tumor cell surface. We describe a novel fused toxin, composed of disintegrin, uPA (urokinase-type plasminogen activator)-cleavable linker, and melittin. Disintegrin is a single strand peptide (73 aa) isolated from Gloydius Ussuriensis venom. The RGD (Arg-Gly-Asp) site of disintegrin dominates its interaction with integrins on the surface of the tumor cells. uPA is over-expressed and plays an important role in tumor cell invasiveness and metastatic progression. The DLM (disintegrin-linker-melittin) linker is uPA-cleavable, enabling DLM to release melittin. We compared binding activity of our synthesized disintegrin with native disintegrin and report that DLM had less binding activity than the native form. uPA-cleavage was evaluated in vitro and the uPA-cleavable linker released melittin. Treating tumors expressing uPA with DLM enhanced tumor cell killing as well as reduced toxicity to erythrocytes and other non-cancerous normal cells. The mechanism behind DLM tumor cell killing was tested using a DNA ladder assay, fluorescent microscopy, flow cytometry, and transmission electron microscopy. Data revealed tumor cell necrosis as the mechanism of cell death, and the fused DLM toxin with an uPA-cleavable linker enhanced tumor selectivity and killing ability.
Highlights
Traditional chemotherapy drugs and radiotherapy is based on the rapid proliferation of cancer cells [1,2], and these treatments increase patient survival and destroy tumors, these methods harm other dividing cells, such as epithelial and hematopoietic stem cells [3,4]
In order to show that DLM is less cytotoxic than melittin and that the cleaved DLM is toxic to tumor cells, an erythrocyte hemolysis assay was used
Melittin coupled to DLM, on contrast, may be safely delivered intravenously and melittin is released after selectively targeting tumor cells with little off-target toxicity
Summary
Traditional chemotherapy drugs and radiotherapy is based on the rapid proliferation of cancer cells [1,2], and these treatments increase patient survival and destroy tumors, these methods harm other dividing cells, such as epithelial and hematopoietic stem cells [3,4]. Tumor-targeted toxins may be helpful for developing novel anti-cancer therapeutics. The uPA cleavage site can be used as a peptide linker to increase affinity and specificity of targeted toxins. Disintegrins, found in snake venom, can target to integrins with strong affinity and block the RGD motif of the integrin functional domain. Disintegrins can inhibit several aspects of tumor cell behavior in vitro and in vivo, such as adhesion, migration, invasion, metastasis, and angiogenesis, by binding to integrins αvβ, αvβ, and/or α5β1 [19,20,21]. An anti-cancer nanoparticle containing contortrostatin has been constructed and it can inhibit tumor growth in two breast carcinoma cell lines, compared with nanoparticle controls or contortrostatin control alone [25]. A disintegrin from Gloydius Ussurinsi’s venom, is a small disulfide-rich peptide (6800 Daltons) with properties similar to contortrostatin (has 65 amino acids and an RGD motif)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
