Co-delivery of siPD-L1 and Tat-HSPB1 by G5PBA Enhances the Efficacy of Antitumor Therapy in Clear Cell Renal Cell Carcinoma

Abstract

Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cell carcinoma and remains challenging to treat at advanced stages due to immune evasion and inefficient intracellular delivery of therapeutic agents. In this study, we synthesized a modified generation 5 (G5) poly(amidoamine) dendrimer (G5PBA) to co-deliver small-interfering RNA targeting programmed death-ligand 1 (siPD-L1) and the antitumor peptide Tat-HSPB1, forming the G5PBA/siPD-L1/Tat-HSPB1 nanocomplex. The agarose gel retardation assay demonstrated that G5PBA efficiently condensed siPD-L1. Furthermore, the peptide encapsulation efficiency and loading capacity were measured, confirming the loading of Tat-HSPB1 into G5PBA/siPD-L1. Flow cytometry showed that G5PBA enhanced the cellular uptake of siPD-L1, while confocal microscopy demonstrated that G5PBA promoted lysosomal escape in Caki-1 cells. Western blot analysis further confirmed that G5PBA effectively reduced the PD-L1 protein expression. In cellular experiments, CCK-8, EdU, and wound-healing assays demonstrated that G5PBA/siPD-L1/Tat-HSPB1 inhibited the viability and migration of ccRCC cells. G5PBA/siPD-L1/Tat-HSPB1 suppressed tumor growth, downregulated PD-L1 expression, enhanced CD4+ and CD8+ T-cell infiltration, and elevated serum levels of IL-2, IL-6, TNF-α, and IFN-γ in mice. Major organs exhibited no obvious histopathological abnormalities upon H&E staining. Serum ALT, AST, and BUN levels showed no significant changes compared with the PBS group, suggesting the preliminary safety profile of G5PBA/siPD-L1/Tat-HSPB1. Collectively, the nanocomplex achieved efficient peptide/siPD-L1 co-delivery and demonstrated significant antitumor activity. This system thus provides a promising strategy and experimental basis for local administration of ccRCC.