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Direct Comparison of Chol-siRNA Polyplexes and Chol-DsiRNA Polyplexes Targeting STAT3 in a Syngeneic Murine Model of TNBC.

ABSTRACT: RNA interference (RNAi) molecules have tremendous potential for cancer therapy but are limited by insufficient potency after intravenous (IV) administration. We previously found that polymer complexes (polyplexes) formed between 3'-cholesterol-modified siRNA (Chol-siRNA) or DsiRNA (Chol-DsiRNA) and the cationic diblock copolymer PLL[30]-PEG[5K] greatly increase RNAi potency against stably expressed LUC mRNA in primary syngeneic murine breast tumors after daily IV dosing. Chol-DsiRNA polyplexes, however, maintain LUC mRNA suppression for ~48 h longer after the final dose than Chol-siRNA polyplexes, which suggests that they are the better candidate formulation. Here, we directly compared the activities of Chol-siRNA polyplexes and Chol-DsiRNA polyplexes in primary murine 4T1 breast tumors against STAT3, a therapeutically relevant target gene that is overexpressed in many solid tumors, including breast cancer. We found that Chol-siSTAT3 polyplexes suppressed STAT3 mRNA in 4T1 tumors with similar potency (half-maximal ED₅₀ 0.3 mg/kg) and kinetics (over 96 h) as Chol-DsiSTAT3 polyplexes, but with slightly lower activity against total Stat3 protein (29% vs. 42% suppression) and tumor growth (11.5% vs. 8.6% rate-based T/C ratio) after repeated IV administration of equimolar, tumor-saturating doses every other day. Thus, both Chol-siRNA polyplexes and Chol-DsiRNA polyplexes may be suitable clinical candidates for the RNAi therapy of breast cancer and other solid tumors.

SUBMITTER: Ye Z

PROVIDER: S-EPMC8788547 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background:The prostate cancer microenvironment is highly immunosuppressive; immune cells stimulated in the periphery by systemic immunotherapies will be rendered inactive once entering this environment. Immunotherapies for prostate cancer need to break this immune tolerance. We have previously identified interleukin-15 (IL-15) as the only cytokine tested that activates and expands immune cells in the presence of prostate cancer cells. In the current study, we aimed to identify a method of boosting the efficacy of IL-15 in prostate cancer. Methods:We engineered, by conjugation to a myristoylated peptide, a membrane-localising form of IL-15 (cyto-IL-15) and the checkpoint inhibitor antibodies cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed death ligand 1 (PD-L1) (cyto-abs) to enable them to bind to cell surfaces by non-specific anchoring to the phospholipid bilayer. The efficacy of these agents was investigated by intratumoral administration either alone (cyto-IL-15 or cyto-abs) or in combination (cyto-combo) in subcutaneous TRAMP-C2 prostate tumors in C57BL/6J mice and compared with their non-modified equivalents in vivo. Following the survival endpoint, histological analyses and RNA sequencing were performed on the tumors. Results:Intratumoral injection of cyto-IL-15 or cyto-combo delayed tumor growth by 50% and increased median survival to 28 and 25 days, respectively, compared with vehicle (17 days), whereas non-modified IL-15 or antibodies alone had no significant effects on tumor growth or survival. Histological analysis showed that cyto-IL-15 and cyto-combo increased necrosis and infiltration of natural killer (NK) cells and CD8 T cells in the tumors compared with vehicle and non-modified agents. Overall, the efficacy of cyto-combo was not superior to that of cyto-IL-15 alone. Conclusion:We have demonstrated that intratumoral injection of cyto-IL-15 leads to prostate cancer growth delay, induces tumor necrosis and increases survival. Hence, cytotopic modification in combination with intratumoral injection appears to be a promising novel approach for prostate cancer immunotherapy.

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Direct Comparison of Chol-siRNA Polyplexes and Chol-DsiRNA Polyplexes Targeting STAT3 in a Syngeneic Murine Model of TNBC.

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