Roughly one third of all human
cancers are attributable to the functional inhibition of the
tumor suppressor protein p53 by its two negative regulators MDM2 and MDMX, making dual-specificity
peptide antagonists of MDM2 and MDMX highly attractive
drug candidates for anticancer
therapy. Two pharmacological barriers, however, remain a major obstacle to the development of
peptide therapeutics: susceptibility to proteolytic degradation in vivo and inability to traverse the cell membrane. Here we report the design of a fluorescent
lanthanide oxyfluoride nanoparticle (LONp)-based multifunctional
peptide drug delivery system for potential treatment of
acute myeloid leukemia (AML) that commonly harbors wild type p53, high levels of MDM2 and/or MDMX, and an overexpressed
cell surface receptor, CD33. We conjugated to LONp via
metal-thiolate bonds a dodecameric
peptide antagonist of both MDM2 and MDMX, termed PMI, and a CD33-targeted, humanized
monoclonal antibody to allow for AML-specific intracellular delivery of a stabilized PMI. The resultant nanoparticle antiCD33-LONp-PMI, while nontoxic to normal cells, induced apoptosis of AML cell lines and primary leukemic cells isolated from AML patients by antagonizing MDM2 and/or MDMX to activate the p53 pathway. Fluorescent antiCD33-LONp-PMI also enabled real-time visualization of a series of apoptotic events in AML cells, proving a useful tool for possible disease tracking and treatment response monitoring. Our studies shed light on the development of antiCD33-LONp-PMI as a novel class of
antitumor agents, which, if further validated, may help
targeted molecular therapy of AML.