Drugcarts to Combat Drug Resistance

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DESCRIPTION (provided by applicant): The current proposal focuses on the development of an aptamer-based reagent for prostate cancer therapy. The proposed reagent, called a Drugcart (Drug carrying aptamers for receptor targeting), is a unique design composed of aptamers with two binding specificities in a single stranded nucleic acid sequence. The Drugcarts will have the following functions: 1) encase and solubilize hydrophobic drugs, 2) target the drugs to the appropriate cells, 3) release the drugs at the target cell surface, and 4) pick up other drug molecules to be shuttled into the cell membrane. For this proposed work, we will link the PSMA aptamer to an aptamer that recognizes PD173955, a drug with similar actions as imatinib mesylate (Gleevec). PD173955 will be further modified to the form of a prodrug with covalently linked peptides that are susceptible to cleavage by the serine protease, prostate specific antigen (PSA). Thus, further specificity for prostate cancer cells will be achieved by the requirement for PSA to cleave the drug and make it permeable to the cell. To develop this promising new drug delivery molecule, we have assembled a team of experienced scientists with expertise in biochemistry, molecular biology, cell biology, cancer therapy, and organic synthetic chemistry. The team has already synthesized a PD173955 analog, isolated two PD173955-binding RNA aptamers, and is ready for the next stage of reagent development as defined by the following specific aims: 1 Synthesize PD173955 derivatives that can be cleaved by PSA to form a permeable PD173955 product. The synthesized derivatives of PD173955 will be tested for their cell permeability, susceptibility to cleavage by PSA, and increased permeability of the product PD173955 after PSA cleavage. 2 Create Drugcarts that bind PSMA and PD173955 for delivering PD173955 to cells. Stabilized RNA Drugcarts containing the PSMA and PD173955 aptamers will be synthesized. Binding activity and stability will be evaluated. 3 Establish that the Drugcarts specifically promote PD173955 uptake by cells that express PSMA on their surfaces. Optimized Drugcarts will be used to deliver the PD173955 prodrug to prostate cancer cells. The specificity of this delivery mechanism for cells that express PSMA and to promote cell death will be investigated.