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Poptosis or Peptide-Induced Transmembrane Pore Formation: A Novel Way to Kill Cancer Cells without Affecting Normal Cells
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
This review describes a peptide-induced mechanism termed poptosis, in which peptides PNC-27 and its shorter analogue PNC-28, containing the p53 transactivating 12-26 domain, bind HDM-2 in the 1-109 domain within cancer cell membranes, reported to cause transmembrane pore formation and rapid extrusion of cell contents (tumor cell necrosis). The authors state these peptides caused necrosis across solid tissue and hematopoietic tumors without affecting normal cells, which express little or no membrane-bound HDM-2, and describe treatment of a metastatic pancreatic tumor and human leukemias in nude mice, without observed off-target effects. Immuno-electron microscopy visualized pores formed by PNC-27, which the authors describe as forming 1:1 complexes with HDM-2 that dimerize into transmembrane channels, paralleling other membranolytic agents such as streptolysin.
Abstract
Recent advances in cancer treatment like personalized chemotherapy and immunotherapy are aimed at tumors that meet certain specifications. In this review, we describe a new approach to general cancer treatment, termed peptide-induced poptosis, in which specific peptides, e.g., PNC-27 and its shorter analogue, PNC-28, that contain the segment of the p53 transactivating 12-26 domain that bind to HDM-2 in its 1-109 domain, bind to HDM-2 in the membranes of cancer cells, resulting in transmembrane pore formation and the rapid extrusion of cancer cell contents, i.e., tumor cell necrosis. These peptides cause tumor cell necrosis of a wide variety of solid tissue and hematopoietic tumors but have no effect on the viability and growth of normal cells since they express at most low levels of membrane-bound HDM-2. They have been found to successfully treat a highly metastatic pancreatic tumor as well as stem-cell-enriched human acute myelogenous leukemias in nude mice, with no evidence of off-target effects. These peptides also are cytotoxic to chemotherapy-resistant cancers and to primary tumors. We performed high-resolution scanning immuno-electron microscopy and visualized the pores in cancer cells induced by PNC-27. This peptide forms 1:1 complexes with HDM-2 in a temperature-independent step, followed by dimerization of these complexes to form transmembrane channels in a highly temperature-dependent step parallel to the mode of action of other membranolytic but less specific agents like streptolysin. These peptides therefore may be effective as general anti-cancer agents.
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