A Recombinant Human Serum Albumin-Based Drug Delivery System

Here we describe the rationale, design and successful application of genetically engineered human serum albumin protein (rHSA) to co-deliver a fatty acid (FA)-modified molecule and C-terminally fused p53-derived peptide for the treatment of cancer. Our results indicate rHSA fusion proteins are cell permeable and able to promote cytotoxicity in cancer cells via p53 transcription-dependent and ---independent mechanisms. Binding studies demonstrated rHSA fusion proteins effectively bind the p53 inhibitor, MDM2, as well as its homolog, MDMX. MDM2/MDMX inhibition resulted in p53 accumulation and apoptosis following caspase activation. In addition, both rHSA fusion proteins were able to bind the anti-apoptotic mitochondrial proteins, BCI-XI and MCI-1. Cytotoxicity was observed in the p53-mutant cell line, MDA-MB-231, suggesting rHSA fusion proteins are able to trigger apoptosis via direct targeting of mitochondrial proteins. This dual-site mechanism broadens the scope of treatable cancers, in that wild type p53 expression is not a prerequisite for successful rHSA fusion protein-mediated anticancer activity. Our data also confirm this novel HSA-based delivery technology is a feasible approach for the intracellular transport of FA-modified molecules in addition to therapeutic peptides. FA-modified molecules formed highly stable complexes with rHSA fusion proteins and retained internalization and cytotoxic activity in SJSA-1 cells. In addition, co-administration of rHSA fused to a high affinity p53-derived peptide and methotrexate promoted a synergistic cytotoxic effect in SJSA-1 cancer cells. In conclusion, genetically engineered HSA fusion proteins are an effective strategy to co-deliver both FA-modified molecules and highly specific therapeutic peptides, to promote a synergistic cytotoxic effect for the treatment of cancer.