Purpose: This study is designed to test the hypothesis that programmed cell death-1 (PD-1) siRNA will inhibit tumor growth.
Methods: PD-1 siRNA was complexed with a cationic lipid and then incorporated into solid lipid nanoparticles (SLNs) prepared with lecithin, cholesterol and an acid-sensitive stearic acid-PEG2000 conjugate by solvent evaporation (1). The SLNs were characterized to determine their morphology, particle size, zeta potential, entrapment efficiency of siRNA, in vitro release, and in vitro cellular uptake. The function of the PD-1 siRNA-SLNs was confirmed by measuring PD1 expression on macrophage J774A.1 cell surface using a flow cytometry assay (2). Moreover, the antitumor activity of the PD-1 siRNA-SLNs were evaluated in a mouse model.
Results: The PD-1 siRNA-SLNs were spherical, and their particle size, polydispersity index, and zeta potential were141 ± 5 nm, 0.17 ± 0.02, and 20.7 ± 4.7, respectively. The entrapment efficiency of the siRNA in the SLNs was about 98.9%. The burst release of the PD-1 siRNA from the SLNs was minimal. In cell culture, PD-1 siRNA-SLNs reduced PD-1 protein expression on J774A.1 macrophage cell surface (Fig. 1). In mice with subcutaneously implanted B16-F10 melanoma cells, PD-1 siRNA-SLNs significant inhibited the tumor growth, as compared to a control siRNA-SLNs (Fig. 2).
Conclusion: The animal model results showed that it was feasible to control tumor growth using PD-1 siRNA-incorporated solid lipid nanoparticles.
(1) Aldayel AM, O'Mary HL, Valdes SA, Li X, Thakkar SG, Mustafa BE, Cui Z. Lipid nanoparticles with minimum burst release of TNF-α siRNA show strong activity against rheumatoid arthritis unresponsive to methotrexate. J control release 2018, 283, (280-289).
(2) Wu, Y., Gu, W., Li, L., Chen, C., Xu, ZP. Enhancing PD-1 gene silence in T lymphocytes by comparing the delivery performance of two inorganic nanoparticle platform. Nanomaterials 2019, 9, (2).
Mahmoud Hanafy– Graduate student, University of Texas at Austin, College of Pharmacy, Austin, Texas
Zhengrong Cui– Professor, University of Texas at Austin, Austin, Texas
Wedad Sakran– Cairo, Al Qahirah, Egypt
Mahmoud Mahmoud– Visiting Research Scholar, The University of Texas at AustinCollege of Pharmacy-Pharmaceutics, Austin, TX