Cell-Penetrating Peptide-Mediated siRNA Targeting of LDHC Suppresses Tumor Growth in a Triple-Negative Breast Cancer Zebrafish Xenograft Model

Background: Lactate Dehydrogenase C (LDHC) is a promising therapeutic target due to its highly tumor-specific expression, immunogenicity, and oncogenic functions. We previously showed that LDHC silencing in triple-negative breast cancer (TNBC) cells enhances treatment response to DNA-damage response-related drugs, supporting its therapeutic potential. However, no selective LDHC inhibitors exist, highlighting the need for innovative targeting strategies. Methods: We assessed the physicochemical properties and evaluated the delivery efficiency, anti-tumor activity, and safety of four cell-penetrating peptides (CPPs)—R10, 10R-RGD, cRGD-10R, and iRGD-10R—for siRNA-mediated LDHC silencing in TNBC. Clonogenic assays were used to evaluate effects on olaparib sensitivity, and TNBC zebrafish xenografts were utilized to study in vivo anti-tumor activity. Results: All CPP:siRNA complexes formed uniform nanocomplexes (129–168 nm) with low polydispersity indices (