Non-viral inducible caspase 9 mRNA delivery using lipid nanoparticles against breast cancer: An in vitro study

Breast cancer is a complex heterogeneous disease with unique molecular subtypes, which limits the development of optimized treatment strategies for each subtype. Cancer gene therapy and potential therapeutics for advanced/refractory cancers can be promising for breast cancer. Combining tumor-tropic lipid nanoparticles (LNPs) and inducible caspase-9 (iC9) mRNA, we aimed to develop a novel treatment strategy for refractory breast cancer. LNP's anti-tumor effects were tested in vitro in three breast cancer cell lines: MDA-MB231, SKBR3, and MCF-7. Tumor cells were treated with LNPs encapsulated with eGFP or iC9 mRNA and chemical inducers of dimerization (CID). Apoptosis-related genes were evaluated by reverse transcriptase quantitative PCR. LNPs could efficiently deliver encapsulated GFP mRNA to all three cancer cell lines (>80% GFP expression. in target cells). Furthermore, LNPs encapsulated with iC9 mRNA (iC9-LNPs) and CID showed cytotoxic activity against all cancer cell lines in vitro. Interestingly, susceptibility to iC9 gene therapy was heterogeneous among cancer cell lines. iC9-LNPs with CID-induced potent cytotoxic effects against SKBR3 and MDA-MB231 cells, but only a mild cytotoxic effect on MCF7 cells. Quantification of apoptosis-related genes suggested that a high BAX/Bcl-2 ratio might be associated with iC9-LNP + CID susceptibility. Thus, cancer gene therapy using iC9-LNPs and CID could be a promising alternative for the treatment of breast cancers, especially for aggressive breast cancers.