[P008] Poster

1:00 PM - 1:50 PM JST(4:00 AM - 4:50 AM UTC)

[P04-900] Photodynamic therapy with hybrid liposomes including indocyanine green suppresses triple–negative breast cancer in vitro and in vivo

○Junna Takai1, Masaki Okumura1, Koichi Goto1, Yoko Matsumoto1, Hideaki Ichihara1 (1. Sojo university (Japan))

Keywords:

breast cancer,photodynamic therapy,apoptosis,hybrid liposome,triple negative breast cancer

Purpose

Breast cancer is classified by the expression status of hormone receptors and HER2. Triple-negative breast cancer (TNBC), lacking all three receptors, has limited targeted options and poorer prognosis, creating a need for novel strategies that preserve quality of life. Hybrid liposomes (HL) selectively accumulate in diverse cancer cells and induce apoptosis. After the Bioethics Committee approval, clinical trials in solid lymphoma demonstrated significant therapeutic effects. In this study, HL containing indocyanine green (ICG), a photosensitive agent, was newly formulated as HL/ICG, and we investigated the therapeutic effects of photodynamic therapy using HL/ICG (HL/ICG-PDT) against 4T1-Luc mouse TNBC cells in vitro and in vivo.

Methods

HL/ICG was prepared by mixing 89 mol% L-alpha-dimyristylphosphatidylcholine (DMPC), 10 mol% polyoxyethylene (25) dodecyl ether (C₁₂(EO)₂₅), and 1 mol% ICG in a 5% glucose solution, followed by ultrasonic irradiation.

The inhibitory effects on the growth of HL/ICG-PDT on 4T1-Luc cells were evaluated using a cell counting kit-8 (CCK-8) assay.

Reactive oxygen species (ROS) generated in 4T1-Luc cells after HL/ICG-PDT were quantified by confocal laser microscopy and flow cytometry using ROS-sensitive fluorogenic probes.

Mice bearing subcutaneous 4T1-Luc tumors received HL/ICG administration followed by near-infrared irradiation to perform HL/ICG-PDT. Tumor volume and weight were recorded, and histology was performed to assess oxidative stress (8-OHdG) and apoptosis (TUNEL).

Results and discussion

HL/ICG-PDT produced a marked reduction in cell viability after near-infrared irradiation, whereas HL/ICG alone and light alone showed minimal effects, indicating a specific photodynamic response. Confocal imaging revealed enhanced intracellular fluorescence consistent with ROS generation, and flow cytometry demonstrated a pronounced rightward shift in ROS-probe fluorescence uniquely in the HL/ICG-PDT group. These findings support that HL/ICG-PDT induces ROS-mediated cell death in 4T1-Luc cells.

In the subcutaneous 4T1-Luc model, all treatment arms reduced tumor progression relative to controls, with HL/ICG-PDT achieving the greatest suppression of tumor volume and the largest decrease in tumor weight. Histological analyses of resected tissues revealed significantly increased oxidative stress markers (8-OHdG)-positive cells and elevated TUNEL-positive apoptotic cells after HL/ICG-PDT, corroborating ROS-driven apoptotic cell death in vivo. These findings support the conclusion that HL/ICG-PDT induces ROS-mediated apoptosis in the 4T1-Luc subcutaneous mouse model.

Conclusion

This study provides the first demonstration that HL/ICG-PDT exerts therapeutic effects against TNBC in vitro and in vivo. HL/ICG-PDT induces ROS-mediated apoptosis, decreases 4T1-Luc cell viability, and inhibits tumor growth while elevating oxidative stress markers, highlighting a promising, less invasive modality to broaden TNBC treatment options.