Near-infrared photothermal/photodynamic therapy with indocyanine green induces apoptosis of hepatocellular carcinoma cells through oxidative stress

Chikara Shirata,Yoshinori Inagaki,Junichi Arita,Takashi Kokudo,Kiyoshi Hasegawa,Nobuhisa Akamatsu,Sho Kiritani,Yoshihiro Sakamoto,Masumitsu Sato,Junichi Kaneko,Norihiro Kokudo

doi:10.1038/s41598-017-14401-0

Abstract

Indocyanine green (ICG) is a photothermal agent, photosensitizer, and fluorescence imaging probe which shows specific accumulation in hepatocellular carcinoma (HCC) cells. We recently developed a photodynamic therapy (PDT) using ICG and near-infrared (NIR) laser as a new anti-cancer treatment for HCC. However, the molecular mechanism underlying this effect needs to be elucidated. HuH-7 cells, a well-differentiated human HCC cell line, were transplanted subcutaneously into BALB/c-nu/nu mice for in vivo experiment. ICG was administered 24 h before NIR irradiation. The irradiation was performed at three tumor locations by 823-nm NIR laser on days 1 and 7. The temperature of HuH-7 xenografts increased to 48.5 °C 3 minutes after ICG-NIR irradiation start. Reactive oxygen species (ROS) production was detected after ICG-NIR irradiation both in vitro and in vivo. There was certain anti-tumor effect and ROS production even under cooling conditions. Repeated NIR irradiation increased the cell toxicity of ICG-NIR therapy; the mean tumor volume on day 9 was significantly smaller after ICG-NIR irradiation compared to tumor without irradiation (87 mm3 vs. 1332 mm3; p = 0.01) in HCC mice xenografts model. ICG-NIR therapy induced apoptosis in HCC cells via a photothermal effect and oxidative stress. Repeated ICG-NIR irradiation enhanced the anti-tumor effect.

Highlights

Indocyanine green (ICG) has been reported as a photothermal agent, photosensitizer, and fluorescence imaging probe
TdT-mediated dUTP nick end labeling (TUNEL) analysis detected apoptosis in tumor tissue after ICG-NIR irradiation, while apoptosis was not detected in only ICG group. (Fig. 1C)
These results suggested that the photothermal effects contribute to the anti-tumor effect of ICG-NIR

Summary

Introduction

Indocyanine green (ICG) has been reported as a photothermal agent, photosensitizer, and fluorescence imaging probe. Near-infrared (NIR) laser-induced photothermal therapy (PTT) uses a photothermal agent to convert optical energy into thermal energy and has the potential as an effective local, minimally invasive anti-tumor treatment[1,2,3]. Photodynamic therapy (PDT) is a noninvasive treatment that combines a photosensitizer and an activating light source. It involves the administration of a photosensitizer, which leads to selective uptake and retention in tumor cells. Combined treatment with the photosensitizer indocyanine green (ICG) and near-infrared (NIR) light irradiation was initially used for treating skin lesions[8]. The expression of organic anion-transporting polypeptide, which is the uptake transporter for ICG, is preserved in HCC tissues, whereas biliary excretion is impaired because of morphological changes associated with cancer progression, leading to accumulation of ICG after preoperative intravenous administration[13,16,17]

Methods

Results

Conclusion