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Published on: August 21, 2013
PNC-27, a Chimeric p53-Penetratin Peptide Binds to HDM-2 in a p53 Peptide-like Structure, Induces Selective
Ehsan Sarafraz-Yazdi1, Stephen Mumin1, Diana Cheung2
1NomoCan Pharmaceuticals LLC, New York Blood Center, 310 East 67th Street, New York, NY 10065, USA.
Abstract:
PNC-27, a 32-residue peptide that contains an HDM-2 binding domain and a cell-penetrating peptide (CPP) leader sequence kills cancer, but not normal, cells by binding to HDM-2 associated with the plasma membrane and induces the formation of pores causing tumor cell lysis and necrosis. Conformational energy calculations on the structure of PNC-27 bound to HDM-2 suggest that 1:1 complexes form between PNC-27 and HDM-2 with the leader sequence pointing away from the complex. Immuno-scanning electron microscopy was carried out with cancer cells treated with PNC-27 and decorated with an anti-PNC-27 antibody coupled to 6 nm gold particles and an anti-HDM-2 antibody linked to 15 nm gold particles. We found multiple 6 nm- and 15 nm-labeled gold particles in approximately 1:1 ratios in layered ring-shaped structures in the pores near the cell surface suggesting that these complexes are important to the pore structure. No pores formed in the control, PNC-27-treated untransformed fibroblasts. Based on the theoretical and immuno-EM studies, we propose that the pores are lined by PNC-27 bound to HDM-2 at the membrane surface with the PNC-27 leader sequence lining the pores or by PNC-27 bound to HDM-2.
Insights
The peptide PNC-27 selectively kills cancer cells by targeting HDM-2 on the cell membrane, forming pores that cause cell death. This mechanism involves specific binding and pore formation, sparing normal cells.
Area of Science:
- Biochemistry
- Cell Biology
- Oncology
Background:
- Cancer cells exhibit unique surface protein expressions, such as HDM-2, which can be targeted for therapeutic interventions.
- Peptide-based therapeutics offer targeted delivery and novel mechanisms of action against cancer.
Purpose of the Study:
- To investigate the mechanism by which the peptide PNC-27 selectively induces cancer cell death.
- To elucidate the role of HDM-2 in PNC-27-mediated tumor cell lysis.
Main Methods:
- Conformational energy calculations to model PNC-27 and HDM-2 interactions.
- Immuno-scanning electron microscopy (immuno-EM) to visualize PNC-27 and HDM-2 complexes on cancer cell membranes.
- Treatment of cancer cells and normal fibroblasts with PNC-27.
Main Results:
- PNC-27 binds to HDM-2 on cancer cell membranes, forming 1:1 complexes.
- PNC-27 and HDM-2 complexes induce the formation of ring-shaped pores on the cancer cell surface.
- Pore formation and subsequent tumor cell lysis and necrosis were observed specifically in cancer cells, not in normal fibroblasts.
Conclusions:
- PNC-27 selectively targets and kills cancer cells by forming pores via interaction with HDM-2.
- The proposed mechanism involves PNC-27 binding to HDM-2, leading to membrane disruption and cancer cell death.
- The findings support PNC-27 as a potential therapeutic agent for cancer treatment.
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