The CT20 peptide causes detachment and death of metastatic breast cancer cells by promoting mitochondrial aggregation and cytoskeletal disruption

• Published in: Cell death & disease 2014-05, Vol.5 (5), p.e1249-e1249
• Main Authors: Lee, M W, Bassiouni, R, Sparrow, N A, Iketani, A, Boohaker, R J, Moskowitz, C, Vishnubhotla, P, Khaled, A S, Oyer, J, Copik, A, Fernandez-Valle, C, Perez, J M, Khaled, A R
• Format: Article
• Language: English
• Subjects: 631/443/319/333; 631/67/1059; 631/67/1347; 631/67/322; Actin Cytoskeleton - drug effects; Actin Cytoskeleton - metabolism; Actin Cytoskeleton - pathology; Animals; Antibodies; Antineoplastic Agents - administration & dosage; Antineoplastic Agents - metabolism; Antineoplastic Agents - pharmacology; bcl-2-Associated X Protein - administration & dosage; bcl-2-Associated X Protein - metabolism; bcl-2-Associated X Protein - pharmacology; Biochemistry; Biomedical and Life Sciences; Breast Neoplasms - drug therapy; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; Cell Adhesion - drug effects; Cell Biology; Cell Culture; Cell Death - drug effects; Cell Line, Tumor; Cell Survival - drug effects; Drug Carriers; Female; Folic Acid - metabolism; Humans; Immunology; Life Sciences; Membrane Potential, Mitochondrial - drug effects; Mice; Mice, Nude; Mitochondria - drug effects; Mitochondria - metabolism; Mitochondria - pathology; Mitochondrial Dynamics - drug effects; Nanoparticles; Original; original-article; Peptide Fragments - administration & dosage; Peptide Fragments - metabolism; Peptide Fragments - pharmacology; Time Factors; Tumor Burden - drug effects; Xenograft Model Antitumor Assays
• ISSN: 2041-4889; 2041-4889
• DOI: 10.1038/cddis.2014.225

Metastasis accounts for most deaths from breast cancer, driving the need for new therapeutics that can impede disease progression. Rationally designed peptides that take advantage of cancer-specific differences in cellular physiology are an emerging technology that offer promise as a treatment for metastatic breast cancer. We developed CT20p, a hydrophobic peptide based on the C terminus of Bax that exhibits similarities with antimicrobial peptides, and previously reported that CT20p has unique cytotoxic actions independent of full-length Bax. In this study, we identified the intracellular actions of CT20p which precede cancer cell-specific detachment and death. Previously, we found that CT20p migrated in the heavy membrane fractions of cancer cell lysates. Here, using MDA-MB-231 breast cancer cells, we demonstrated that CT20p localizes to the mitochondria, leading to fusion-like aggregation and mitochondrial membrane hyperpolarization. As a result, the distribution and movement of mitochondria in CT20p-treated MDA-MB-231 cells was markedly impaired, particularly in cell protrusions. In contrast, CT20p did not associate with the mitochondria of normal breast epithelial MCF-10A cells, causing little change in the mitochondrial membrane potential, morphology or localization. In MDA-MB-231 cells, CT20p triggered cell detachment that was preceded by decreased levels of α 5 β 1 integrins and reduced F-actin polymerization. Using folate-targeted nanoparticles to encapsulate and deliver CT20p to murine tumors, we achieved significant tumor regression within days of peptide treatment. These results suggest that CT20p has application in the treatment of metastatic disease as a cancer-specific therapeutic peptide that perturbs mitochondrial morphology and movement ultimately culminating in disruption of the actin cytoskeleton, cell detachment, and loss of cell viability.