AC-1001 H3 CDR peptide induces apoptosis and signs of autophagy in vitro and exhibits antimetastatic activity in a syngeneic melanoma model

Antibody-derived peptides modulate functions of the immune system and are a source of anti-infective and antitumor substances. Recent studies have shown that they comprise amino acid sequences of immunoglobulin complementarity-determining regions, but also fragments of constant regions. V-H CDR3 of murine mAb AC-1001 displays antimetastatic activities using B16F10-Nex2 murine melanoma cells in a syngeneic model. The peptide was cytotoxic in vitro in murine and human melanoma cells inducing reactive oxygen species (ROS) and apoptosis by the intrinsic pathway. Signs of autophagy were also suggested by the increased expression of LC3/LC3II and Beclin 1 and by ultrastructural evidence. AC-1001 H3 bound to both G- and F-actin and inhibited tumor cell migration. These results are important evidence of the antitumor activity of Ig CDR-derived peptides

The Ig V-H complementarity-determining region 3-containing Rb9 peptide, inhibits melanoma cells migration and invasion by interactions with Hsp90 and an adhesion G-protein coupled receptor

The present work aims at investigating the mechanism of action of the Rb9 peptide, which contains the VHCDR 3 sequence of anti-sodium-dependent phosphate transport protein 2B (NaPi2B) monoclonal antibody RebMab200 and displayed antitumor properties. Short peptides corresponding to the hyper variable complementarity-determining regions (CDRs) of immunoglobulins have been associated with antimicrobial, antiviral, immunomodulatory and antitumor activities regardless of the specificity of the antibody. We have shown that the CDR derived peptide Rb9 induced substrate hyperadherence, inhibition of cell migration and matrix invasion in melanoma and other tumor cell lines. Rb9 also inhibited metastasis of murine melanoma in a syngeneic mouse model. We found that Rb9 binds to and interferes with Hsp90 chaperone activity causing attenuation of FAK-Src signaling and downregulation of active Rac1 in B16F10-Next melanoma cells. The peptide also bound to an adhesion G-protein coupled receptor, triggering a concentration-dependent synthesis of cAMP and activation of PKA and VASP signaling as well as IP-3 dependent Ca2+ release. Hsp90 is highly expressed on the cell surface of melanoma cells, and synthetic agents that target Hsp90 are promising cancer therapeutic drugs. Based on their remarkable antitumor effects, the CDR-H3-derived peptides from RebMab200, and particularly the highly soluble and stable Rb9, are novel candidates to be further studied as potential antitumor drugs, selectively acting on cancer cell motility and invasion. (C) 2016 Elsevier Inc. All rights reserved.

Benzofuroxan derivatives N-Br and N-I induce intrinsic apoptosis in melanoma cells by regulating AKT/BIM signaling and display anti metastatic activity in vivo.

BACKGROUND: Malignant melanoma is an aggressive type of skin cancer, and despite recent advances in treatment, the survival rate of the metastatic form remains low. Nifuroxazide analogues are drugs based on the substitution of the nitrofuran group by benzofuroxan, in view of the pharmacophore similarity of the nitro group, improving bioavailability, with higher intrinsic activity and less toxicity. Benzofuroxan activity involves the intracellular production of free-radical species. In the present work, we evaluated the antitumor effects of different benzofuroxan derivatives in a murine melanoma model. METHODS: B16F10-Nex2 melanoma cells were used to investigate the antitumor effects of Benzofuroxan derivatives in vitro and in a syngeneic melanoma model in C57Bl/6 mice. Cytotoxicity, morphological changes and reactive oxygen species (ROS) were assessed by a diphenyltetrasolium reagent, optical and fluorescence microscopy, respectively. Annexin-V binding and mitochondrial integrity were analyzed by flow cytometry. Western blotting and colorimetry identified cell signaling proteins. RESULTS: Benzofuroxan N-Br and N-I derivatives were active against murine and human tumor cell lines, exerting significant protection against metastatic melanoma in a syngeneic model. N-Br and N-I induce apoptosis in melanoma cells, evidenced by specific morphological changes, DNA condensation and degradation, and phosphatidylserine translocation in the plasma membrane. The intrinsic mitochondrial pathway in B16F10-Nex2 cells is suggested owing to reduced outer membrane potential in mitochondria, followed by caspase -9, -3 activation and cleavage of PARP. The cytotoxicity of N-Br and N-I in B16F10-Nex2 cells is mediated by the generation of ROS, inhibited by pre-incubation of the cells with N-acetylcysteine (NAC). The induction of ROS by N-Br and N-I resulted in the inhibition of AKT activation, an important molecule related to tumor cell survival, followed by upregulation of BIM. CONCLUSION: We conclude that N-Br and N-I are promising agents aiming at cancer treatment. They may be useful in melanoma therapy as inducers of intrinsic apoptosis and by exerting significant antitumor activity against metastatic melanoma, as presently shown in syngeneic mice.