Intravesical chemotherapy for bladder cancer has limited efficacy due to the lack of specificity of drugs/drug carriers toward the cancer cells as well as inadequate drug residence time in the bladder due to urine voiding. From analyses of surface receptor expression of UMUC3 bladder cancer cells and the targeting efficacy of different peptides, we selected a peptide (txCD47) that targets the cluster of differentiation 47 (CD47) surface protein overexpressed on these cells as a targeting ligand for docetaxel (DTX) and an albumin nanocarrier of DTX. The IC50 of DTX conjugated to txCD47 (txCD47-DTX) in a 1:1 molar ratio was lowered by a factor of 3 from that of free DTX. By using the albumin molecule (txCD47-BSA) as a delivery vehicle, different amounts of txCD47 can be conjugated to investigate the effects of peptide concentration on targeting efficacy. The IC50 of DTX loaded in txCD47-BSA with 14 txCD47 per albumin molecule was 1 order of magnitude lower than that of free DTX, and a factor of 4 lower than that of txCD47-BSA with 8 txCD47 per albumin molecule. DTX was released from the albumin nanocarrier at a controlled rate, and the endocytosed carrier will release most of its payload inside the cells within 72 h. Thus, txCD47 promotes delivery of the drug/drug carrier, and the resultant enhanced killing efficacy of the drug can potentially alleviate some of the limitations of intravesical chemotherapy against bladder cancer.
Keywords: CD47 targeting; albumin carrier; bladder cancer; docetaxel; intravesical chemotherapy.