Codelivery of Shikonin and siTGF-β for enhanced triple negative breast cancer chemo-immunotherapy

Although chemoimmunotherapy has achieved considerable success in cancer treatment in recent years, the cure for triple-negative breast cancer (TNBC) remains elusive. The unsatisfied outcomes are likely attributed to deficient tumor immunogenicity, a strong immunosuppressive tumor microenvironment (ITM) and tumor metastasis. To address this issue, we constructed an effective codelivery system, combined with tumor growth factor β (TGF-β) small interference RNA (siTGF-β) and shikonin (SK), to achieve successful chemoimmunotherapy of TNBC. The SK/siTGF-β NPs (approximately 110 nm) exhibited a uniform structure and good stability. Conjugated FA presented enhanced cellular uptake in 4T1 cells, and siTGF-β escaped from lysosomes because of the "proton sponge" effect of PEI. Furthermore, SK actually induced satisfactory immunogenic cell death (ICD) and the resulting dendritic cell (DC) maturation facilitated a distinctly enhanced cytotoxic T lymphocyte (CTL) response, generating a positive effect on tumor suppression. Simultaneously, the successful silencing of TGF-β alleviated the TGF-β-mediated ITM and inhibited the epithelial-to-mesenchymal transition (EMT), contributing to the infiltration of CTLs, suppression of regulatory T lymphocyte (Treg) proliferation and lung metastasis inhibition. Thus, the SK/siTGF-β NPs demonstrated the strongest therapeutic effect with delayed tumor growth (TIR = 88.5%) and lung metastasis restraint (77.3%). More importantly, tumor rechallenge assay suggested that the codelivery system produced a long-term immunological memory response to prevent tumor recurrence. Based on boosting the immune response and combating the ITM, SK/siTGF-β NPs would be a potential approach for TNBC therapy.