A Systematic Comparison of Lipopolymers for siRNA Delivery to Multiple Breast Cancer Cell Lines: <i>In Vitro</i> Studies

Abstract

The small interfering RNA (siRNA) therapy is a promising approach for treatment of a wide range of cancers, including breast cancers that display variable phenotypic features. To explore the general utility of siRNA therapy to control aberrant expression of genes in breast cancer, we conducted a detailed analysis of siRNA delivery and silencing response in vitro in 6 separate breast cancer cell models (MDA-MB-231, MDA-MB-231-KRas-CRM, MCF-7, AU565, MDA-MB-435 and MDA-MB-468 cells). Using lipopolymers for siRNA complexation and delivery, we found a large variation in siRNA delivery efficiency depending on the specific lipopolymer used for siRNA complexation and delivery. Some lipopolymers were effective in all cell types used in this study, indicating the possibility of universal carriers for siRNA therapy. The delivery efficiency for effective lipopolymers was not correlated with dextran uptake in all cells tested, which indicated a receptor-mediated internalization for siRNA complexes with lipopolymers, unlike fluid-phase transfer associated with dextran uptake. Consistent with this, specific inhibitors involved in clathrin- and caveolin-mediated endocytosis significantly (>50%) reduced the internalization of siRNA complexes in all cell types. Using JAK2 and STAT3 silencing in MDA-MB-231 and MDA-MB-468 cells, a general correlation between the uptake and silencing efficiency at the mRNA level was evident, but it appeared that the choice of the target rather than the cell type was more critical for consistent silencing. We conclude that siRNA therapy with well-characterized lipopolymers can be undertaken with multiple breast cancer cell phenotypes with similar efficiency, indicating the general applicability of non-viral RNAi in clinical management of molecularly heterogeneous breast cancers.