The impact of the conjugation manner of targeting agent and tandem cell-penetrating peptide on the efficacy of mitomycin C liposomes in treating triple-negative breast tumors

Triple-negative breast cancer (TNBC) remains one of the most aggressive subtypes with limited therapeutic options. To address this unmet need, this study aimed to enhance the cellular uptake and cytotoxicity of mitomycin C (MMC) using surface-modified nanoliposomes functionalized with poly-L-arginine (PLA), a cell-penetrating peptide, and chondroitin sulfate (CS), a CD44-targeting ligand. Another object was to investigate how the conjugation manner of the targeting agent-chondroitin sulfate (CS), a CD44-targeting ligand, and a tandem cell-penetrating peptide (CPP) made of poly-L-arginine (PLA)-affects the enhancement of cellular uptake and anti-tumor effects of Mitomycin C (MMC) nanoliposomes in triple-negative breast cancer (TNBC). We synthesized and characterized four liposomal formulations; CS-liposomes, PLA-liposomes, PLA-CS-liposomes, and CS-PLA-liposomes and their particle size, polydispersity index, zeta potential, encapsulation efficiency, and drug release were evaluated. In vitro studies on 4 T1 TNBC cells included cytotoxicity (MTT), cellular uptake, apoptosis, cell cycle arrest, and caspase-3/8 expression (qRT-PCR). In vivo efficacy was tested in BALB/c mice bearing orthotopic 4 T1 tumors by monitoring tumor growth, body weight, and histopathology (H&E and Ki-67). Optimized PLA-CS liposomes had a mean particle size of 144.0 ± 2.4 nm, a PDI of 0.31 ± 0.02, and 73 % encapsulation efficiency, with sustained MMC release over 24 h. PLA-functionalized liposomes showed significantly greater cytotoxicity and uptake than free MMC and non-targeted controls. They induced G1 cell cycle arrest and strongly upregulated caspase-3 (+64-fold in CS-PLA, +13-fold in PLA-CS), consistent with activation of the intrinsic apoptosis pathway. Animal studies revealed PLA-CS liposomes produced the strongest tumor suppression (Ki-67 index 6 %), reduced tumor grade to 1, and showed no liver or kidney metastasis. All liposomal formulations performed better than free MMC in tumor control and safety. PLA-CS-liposomes provide a potent and well-tolerated delivery platform for MMC in TNBC, combining improved tumor targeting, enhanced apoptotic response, and favorable organ safety.