Design of human lactoferricin derived antitumor peptides-activity and specificity against malignant melanoma in 2D and 3D model studies

The aim of this study was to develop effective and specific anti-cancer drugs based on membrane active peptides. In previous studies we showed that human lactoferricin (hLFcin) derived peptides facilitate specific killing of cancer cells. These antitumor peptides were found by conventional melanoma two-dimensional (2D) cell cultures to induce apoptosis of cancer cells and to specifically target lipid phosphatidylserine located on the outside of cancer cell membranes. In order to have a more relevant in vitro model able to mimic the natural microenvironments of tumor tissues we established three-dimensional (3D) multicellular tumor spheroids (MCTS). We used a set of (retro) di-peptides derived from LF11, an 11 amino acid long fragment of hLFcin, which differed in peptide length, positive net charge and hydrophobicity and determined antitumor activity and non-specific toxicity on non-neoplastic cells using 2D and 3D model systems. 2D studies unveiled a correlation between length, positive net charge and hydrophobicity of peptides and their specific antitumor activity. (Retro) di-peptides as R-DIM-P-LF11-215 and DIM-LF11-322 with a net charge of +9 and moderate hydrophobicity exhibited the highest specific antitumor activity. Further evaluation of the peptides anticancer activity by 3D in vitro studies confirmed their higher activity and cancer specificity compared to their parent R-DIM-P-LF11, with the exception of DIM-LF11-339. This highly hydrophobic peptide caused cell death mainly at the border of tumor spheroids indicating that too high hydrophobicity may prevent peptides from reaching the center of the spheroids.

The Ig VH 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 V_HCDR 3 sequence of anti-sodium-dependent phosphate transport protein 2B (NaPi2B) monoclonal antibody RebMab200 and displayed antitumor properties. Short peptides corresponding to the hypervariable 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-Nex2 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.