kla-peptide and Breast-Neoplasms

Drug resistance is one of the most important obstacles in effective cancer therapy triggered through various mechanisms. One of these mechanisms is caused by the upregulation of Inhibitor of Apoptosis Proteins (IAPs). IAPs, inhibit apoptosis through direct and/or indirect caspase inhibition, which themselves are antagonized by an endogenous protein called Second Mitochondrial-derived Activator of Caspases, Smac/Diablo, mediated by the presence of a tetrapeptide IAP binding motif at its N-terminus. Accordingly, Smac-based peptides are under intense investigation as anti-cancer drugs and have reached Phase 2 clinical trials, although, Smac based peptides or mimetics alone have not been effective as anti-cancer agents. On the other hand, KLA peptide has shown major toxicity against cancer cells through the induction of apoptosis. Consequently, we designed an anti-cancer chimera by fusing an octa-peptide from the N-terminus of mature Smac protein to a modified proapoptotic KLA peptide (KLAKLCKKLAKLCK) to be called Smac-KLA. This chimera, therefore, possesses both proapoptotic and anti-IAP activities. In addition, we dimerized this chimera via intermolecular disulfide bonds in order to enhance their cellular permeability. Both the Smac-KLA monomeric and dimeric peptides exhibited cytotoxic activity against both MCF-7 and MDA-MB231 breast cancer cell lines at low micromolar concentrations. Importantly, the dimerization of the chimeras enhanced their potency 2-4- fold due to higher cellular uptake.

Topics: Antineoplastic Agents; Apoptosis; Breast Neoplasms; Caspase 3; Caspases; Female; Humans; Inhibitor of Apoptosis Proteins; Intracellular Signaling Peptides and Proteins; MCF-7 Cells; Mitochondrial Proteins; Peptides

Novel molecularly targeted agents that block the development and metastasis of human brain metastatic breast cancer hold great promise for their translational value. In this study, we constructed a novel targeting composite peptide BRBP1-TAT-KLA comprising of three elements: a brain metastatic breast carcinoma cell (231-BR)-binding peptide BRBP1, a cell penetrating peptide TAT, and a proapoptotic peptide KLA. This composite peptide efficiently internalized in 231-BR cells and consequently induced mitochondrial damage and cellular apoptosis. Exposure of 231-BR cells to BRBP1-TAT-KLA significantly decreased cell viability and increased apoptosis compared with the cells treated with the control peptides. In vivo relevance of these findings was further corroborated in the 231-BR tumor-bearing mice that demonstrated significantly delayed tumor development and metastasis following administration of BRBP1-TAT-KLA compared with those treated with TAT-KLA alone. Interestingly, BRBP1-TAT-KLA inhibited the formation of both large and micro-metastases, while TAT-KLA alone failed to significantly reduce micro-metastases in the breast cancer brain metastasis mice. BRBP1-TAT-KLA selectively homed to the tumors in vivo where it induced cellular apoptosis without significant toxicity on non-tumor tissues. Our findings therefore demonstrated the enhanced antitumor effects of the BRBP1 compound peptide BRBP1-TAT-KLA, providing insights toward development of a potential therapeutic strategy for brain metastatic breast cancer.

Topics: Animals; Apoptosis; Brain Neoplasms; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Female; Gene Products, tat; Humans; Intercellular Signaling Peptides and Proteins; Mice; Oligopeptides; Peptide Fragments; Peptides; Xenograft Model Antitumor Assays

Antimicrobial peptides selectively kill bacteria while maintaining low mammalian cell cytotoxicity. However, they become cytotoxic subsequent to internalization. Here we have conjugated the lytic peptide (KLAKLAK)(2) to either a cancer-cell binding peptide (LTVSPWY) selected from peptide libraries or to a gastrin-releasing peptide (GNHWAVGHLM) in order to direct the lytic peptide to cancer cells. Peptide cytotoxicity was tested in breast MCF-7 and MDA-MB-231 cancer cells. The fusion peptides were internalized by cancer cells, disintegrated the cell membrane and induced rapid killing of the cells with IC50 values as low as 4-7 μM. Peptide cytotoxicity was dependent on the targeting receptor. Indeed, addition of free targeting peptide reduced cell killing. Blood lymphocytes and normal human mammary epithelial cells were less sensitive to the fusion peptides. Although most of the cells were killed by necrosis, fusion peptides branched with DNA oligonucleotides induced apoptosis as assayed by annexin V staining and activation of caspase 3. Therefore, the new designed drug peptides might provide a potent and selective anticancer therapy.

Topics: Antimicrobial Cationic Peptides; Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Cell Membrane; Cell Membrane Permeability; Cell Proliferation; Cell Survival; Drug Carriers; Drug Screening Assays, Antitumor; Female; Gastrin-Releasing Peptide; Humans; Intercellular Signaling Peptides and Proteins; Oligonucleotides; Oligopeptides; Peptides; Protein Binding