Targeting Melanoma Growth and Metastasis with Systemic Delivery of Liposome-Incorporated Protease-Activated Receptor-1 Small Interfering RNA
2008

Departments of Cancer Biology, Experimental Therapeutics, and Gynecologic Oncology, The University of Texas M. D. Anderson Cancer Center, Texas
Abstract
The thrombin receptor [protease-activated receptor-1 (PAR-1)] is overexpressed in highly metastatic melanoma cell lines and in patients with metastatic lesions. Activation of PAR-1 leads to cell signaling and up-regulation of genes involved in adhesion, invasion, and angiogenesis. Herein, studies stable and silence PAR-1 spread through the use of lentiviral short hairpin RNA and found significant decreases in both tumor and metastasis of deadly melanoma cells. The use of viruses for therapy is not ideal as it can induce toxic immune responses and possible gene alterations following viral integration. Therefore, we also used systemic delivery of PAR1 small interfering RNA (siRNA) incorporated into neutral liposomes [1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC)] to decrease melanoma growth and metastasis in vivo. Significant decreases in tumor growth, weight, and metastatic lung colonies were found in those treated with PAR-1 siRNA-DOPC. The in vivo effects of PAR-1 on invasion and angiogenesis were analyzed via immunohistochemistry. Concomitant decreases in vascular endothelial growth factor, interleukin-8, and matrix metalloproteinase-2 expression levels, as well as decreased blood vessel density (CD31), were found in tumor samples from PAR-1 siRNA-treated mice, suggesting that PAR-1 is a regulator of melanoma cell growth and metastasis by affecting angiogenic and invasive factors. We propose that siRNA incorporated into DOPC nanoparticles could be delivered systemically and used as a new modality for melanoma treatments.