Lipid Nanoparticle Delivery of mRNA and siRNA for Concurrent Restoration of Tumor Suppressor and Inhibition of Tumorigenic Driver in Prostate Cancer

Cancer is commonly caused by a gain of function in proto-oncogenes and a simultaneous loss of function in tumor suppressor genes. Advanced prostate cancer (PCa) is often linked with changes in the activity or expression of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), a well-known tumor suppressor, and androgen receptor (AR), a pro-tumorigenic transcription factor. However, no therapies exist for the simultaneous correction of tumorigenic promotion and suppressor depletion. Here, we report that concurrent PTEN restoration and AR silencing by lipid nanoparticle (LNP) delivery of PTEN messenger RNA (mPTEN) and AR small interfering RNA (siAR) elicited synergistic therapeutic effects in PCa cells. We screened various LNP formulations for the optimal delivery of both RNAs. In C4-2 and LNCaP cells, both of which are AR-positive and PTEN-null PCa cell lines, the combinatorial treatment of siAR and mPTEN LNPs resulted in much stronger cytotoxicity in vitro than the treatment of either alone. Western blot analyses revealed concurrent regulation of phosphatidylinositol 3-kinase-protein kinase B (PI3K-AKT) and extracellular signal-regulated kinase (ERK) pathways, leading to increased caspase-3 cleavage-mediated apoptosis. Our findings suggest that the strategy of RNA-mediated concurrent restoration of tumor suppressors and inhibition of tumorigenic drivers could lead to the more effective treatment of PCa and potentially other malignancies.