To use exosomes as a vector to deliver siRNA to silence the polo-like kinase 1 gene (PLK-1) in bladder cancer cells.

Exosomes were isolated from both human embryonic kidney 293 (HEK293) cell and mesenchymal stem cell (MSC) conditioned media. Fluorescently labeled exosomes were co-cultured with bladder cancer and normal epithelial cells and uptake quantified by image cytometry. PLK-1 siRNA and negative control siRNA were loaded into HEK293 and MSC exosomes using electroporation. An invasive bladder cancer cell line (UMUC3) was co-cultured with the electroporated exosomes. Real-time PCR was performed. Protein analysis was performed by western blot. Annexin V staining and MTT assays were used to investigate effects on apoptosis and viability.

Bladder cancer cell lines internalize an increased percentage of HEK293 exosomes when compared to normal bladder epithelial cells. Treatment of UMUC3 cells with exosomes electroporated with PLK-1 siRNA achieved successful knockdown of PLK-1 mRNA and protein when compared to cells treated with negative control exosomes.

HEK293 and MSC exosomes were effectively used as a delivery vector to transport PLK-1 siRNA to bladder cancer cells in vitro resulting in selective gene silencing of PLK-1. The use of exosomes as a delivery vector for potential intravesical therapy is attractive.