A dual-action liposome-peptide formulation synergistically counteracts a gain-of-function p53 mutant

Inactivation of p53 tumor suppressor functions, often through missense mutations, is essential for carcinogenesis. A sub-class of such p53 missense mutations gains new functions, including drug resistance and enhanced proliferation, in addition to its loss of function. Among the most frequent gain-of-function p53 mutants, R273H occurs in tumors of many tissue origins and imparts aggressive character and resistance to drugs to the tumor. Tumors bearing p53R273H are generally resistant to all available therapies, and need for novel interventions are urgently needed. Interaction of p53R273H with Positive Coactivator 4 (PC4), an abundant chromatin-associated protein, is essential for acquiring the gain-of-function properties. Previously, we developed a chemically modified peptide, NLS-p53(380-386), targeting PC4 that abrogated the interaction of p53R273H with PC4 and reversed many of its gain-of-function properties. We earlier demonstrated that cationic phosphatidylcholine-stearylamine (PC-SA) liposomes possess inherent anti-tumor properties. To improve efficacy, pharmacokinetics, and delivery, we entrapped the PC4-targeted peptide into PC-SA liposome. We synthesized the NLS-p53(380-386) peptide and entrapped in PC-SA liposome. We used MTT assay, confocal microscopy, flow cytometry, qRT-PCR, and western blotting to investigate the biological effects of the p53-entrapped PC-SA. Pretreatment with the PC-SA liposome entrapped peptide enhanced the chemosensitivity of widely used anticancer drug doxorubicin in cell lines bearing p53R273H mutation. The doxorubicin-induced cell-killing effect was much more enhanced when pretreated with the liposome-entrapped peptide than when pretreated with either the free peptide or the liposome alone. The liposome-encapsulated peptide is a promising formulation for developing therapies targeting tumors bearing the p53R273H.