Enhancing chemo-immunotherapy in triple-negative breast cancer: Co-delivery of doxorubicin and berberine using nanoparticles to downregulate PD-L1 and eliminate cancer stem cells.

Doxorubicin (DOX), a prominent chemotherapeutic agent for triple-negative breast cancer, can induce immunogenic cell death (ICD), while simultaneous enriching cancer stem cells (CSCs) and enhancing PD-L1 expression, leading to treatment resistance and tumor recurrence. Herein, we propose an innovative nanoparticle delivery system co-encapsulating DOX and berberine (BER), a natural alkaloid eliminating CSCs and downregulating PD-L1, to enhance chemo-immunotherapy effectiveness. In this study, a modified solvent-dialysis approach was used to encapsulate DOX and BER with hyaluronic acid (HA) and chitosan (CS). The formulation was characterized by size, zeta potential, morphology and FT-IR. In vitro studies evaluated encapsulation efficiency, cellular uptake, cytotoxicity, apoptosis, and disruption of CSC-enriched mammospheres. In vivo experiments assessed tumor-targeting efficacy, antitumor activity, and safety in a triple-negative breast cancer (TNBC) mouse model. Consequently, (DOX + BER) NPs promoted tumor accumulation, reduced systemic toxicity, and advanced treatment in TNBC. Targeted distribution to CD44-positive CSCs and TNBC cells reduced CSC viability and PD-L1 expression. Investigations demonstrated that (DOX + BER) NPs superior to free DOX. These findings suggest that the HA-CS nanoparticle delivery system for DOX and BER co-administration may help to treat TNBC by eliminating CSCs and downregulating PD-L1. This unique combination therapy improves DOX-triggered ICD, improving chemo-immunotherapy responsiveness.