Anti-Cancer Peptide PNC-27 Kills Cancer Cells by Unique Interactions with Plasma Membrane-Bound hdm-2 and with
Patryk Krzesaj1,2, Victor Adler3, Richard D Feinman2
1Department of Pathology, Brooklyn, NY, USA.
Objective:
We have previously shown that the anti-cancer peptide PNC-27 kills cancer cells by co-localizing with membrane-expressed HDM-2, resulting in transmembrane pore formation causing extrusion of intracellular contents. We have also observed cancer cell mitochondrial disruption in PNC-27-treated cancer cells. Our objectives are to determine: 1. if PNC-27 binds to the p53 binding site of HDM-2 (residues 1-109) in the cancer cell membrane and 2. if this peptide causes selective disruption of cancer cell mitochondria.
Methods:
For aim 1, we incubated MIA-PaCa-2 human pancreatic carcinoma cells with PNC-27 in the presence of a monoclonal antibody against the amino terminal p53 binding site of HDM-2 to determine if it, but not negative control immune serum, blocks PNC-27-induced tumor cell necrosis. For the second aim, we incubated these cells with PNC-27 in the presence of two specific dyes that highlight normal organelle function: mitotracker for mitochondria and lysotracker for lysosomes. We also performed immuno-electron microscopy (IEM) with gold-labeled anti-PNC-27 antibody on the mitochondria of these cells treated with PNC-27.
Results:
Monoclonal antibody to the p53 binding site of HDM-2 blocks PNC-27-induced cancer cell necrosis, whereas negative control immune serum does not. The mitochondria of PNC-27-treated cancer cells fail to retain mitotracker dye while their lysosomes retain lysotracker dye. IEM of the mitochondria cancer cells reveals gold particles present on the mitochondrial membranes.
Conclusions:
PNC-27 binds to the p53 binding site of HDM-2 (residues 1-109) inducing transmembrane pore formation and cancer cell necrosis. Furthermore, this peptide enters cancer cells and binds to the membranes of mitochondria, resulting in their disruption.
Insights
The anti-cancer peptide PNC-27 targets the p53 binding site of HDM-2, causing cancer cell death. This peptide also selectively disrupts cancer cell mitochondria, offering a potential new therapeutic strategy.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- The anti-cancer peptide PNC-27 has demonstrated efficacy in killing cancer cells by interacting with membrane-expressed HDM-2.
- Previous observations indicated that PNC-27 treatment leads to mitochondrial disruption in cancer cells.
Purpose of the Study:
- To ascertain if PNC-27 binds to the p53 binding site (residues 1-109) of HDM-2 on the cancer cell membrane.
- To investigate whether PNC-27 selectively disrupts cancer cell mitochondria.
Main Methods:
- Utilized MIA-PaCa-2 human pancreatic carcinoma cells treated with PNC-27.
- Employed a monoclonal antibody against the HDM-2 p53 binding site to assess binding specificity.
- Assessed mitochondrial and lysosomal function using mitotracker and lysotracker dyes.
- Performed immuno-electron microscopy (IEM) with anti-PNC-27 antibody to localize the peptide.
Main Results:
- A monoclonal antibody targeting the HDM-2 p53 binding site inhibited PNC-27-induced cancer cell necrosis.
- PNC-27-treated cancer cells showed impaired mitochondrial function (failed to retain mitotracker) but intact lysosomal function (retained lysotracker).
- IEM confirmed the presence of PNC-27 on the mitochondrial membranes of treated cancer cells.
Conclusions:
- PNC-27 binds to the HDM-2 p53 binding site, inducing pore formation and cancer cell necrosis.
- PNC-27 penetrates cancer cells and targets mitochondrial membranes, leading to their selective disruption.
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