PNC-27 peptide selectively kills colon cancer stem cells by targeting membrane H/MDM-2 oncoprotein

Colorectal cancer remains a significant health challenge, with cancer stem cells (CSCs) playing a crucial role in tumor initiation, progression, metastasis, and resistance to conventional therapies. Current treatments often fail to eradicate these resilient CSCs, leading to recurrence. The H/MDM-2 oncoprotein is frequently overexpressed on the membranes of cancer cells, but not normal cells, making it an attractive target for selective anticancer strategies. This study investigates the peptide PNC-27, known for its ability to form pores in cancer cell membranes by binding to H/MDM-2, as a potential agent against CD44+ colon cancer stem cells.

Researchers evaluated the anticancer peptide PNC-27 against six human colon cancer cell lines and one normal colonic epithelial cell line (CCD-18Co). They used flow cytometry to quantify CD44 and H/MDM-2 expression. Cell viability and death mechanisms were assessed via MTT assays, LDH release, annexin V binding, and caspase 3 assays. The peptide's effect on tumor growth in vivo was monitored using bioluminescence imaging in a mouse model. The study aimed to confirm PNC-27's selective toxicity and its mechanism of action against cancer stem-like cells.

All six tested colon cancer cell lines exhibited high percentages of CD44 expression, indicating a significant presence of cancer stem-like cells. Crucially, PNC-27 demonstrated specific co-localization with membrane H/MDM-2 exclusively in cancer cells. This binding led to profound cytotoxic effects, resulting in total cell death characterized by tumor cell necrosis, high LDH release, and a notable absence of annexin V binding and caspase 3 activation, suggesting a non-apoptotic cell death pathway.

In vivo experiments further corroborated these findings, showing that PNC-27 induced necrosis specifically in tumor nodules while sparing normal surrounding tissues.