Enhanced Therapeutic Efficacy of Photodynamic Therapy Using Hybrid Liposomes Containing Indocyanine Green in a Triple-Negative Breast Cancer Mouse Model

Triple-negative breast cancer (TNBC) is characterized by the absence of hormone receptors and human epidermal growth factor receptor 2 (HER2) expression, rendering hormone therapy and HER2-targeted treatments ineffective. Consequently, conventional chemotherapy remains the primary therapeutic option, despite its severe side effects and poor prognosis. Hybrid liposomes (HL) composed of phospholipids and polyethylene glycol (PEG)-based surfactants have been reported to have therapeutic effects on various cancers without containing anticancer drugs. In this study, we investigated whether photodynamic therapy (PDT) with HL containing indocyanine green (HL/ICG) enhanced the therapeutic effect of HL alone in a mouse model of subcutaneous implantation of triple-negative breast cancer (TNBC) cells in vivo. HL/ICG selectively accumulated in tumors in mice implanted with 4T1-Luc cells, a TNBC cell line. Histological analysis of resected tumor tissues following HL/ICG-mediated PDT revealed a significant increase in cells positive for oxidative stress markers, indicating elevated intracellular oxidative damage. Additionally, a marked presence of apoptotic cells was observed, suggesting that PDT effectively induced programmed cell death in tumor tissues. These results indicate that PDT with HL/ICG induces oxidative stress-mediated apoptosis in tumors derived from 4T1-Luc cells and significantly enhances the therapeutic efficacy of HL alone in vivo, highlighting its potential as a promising strategy for the treatment of TNBC.