Fig. 2

In vitro photoimmunochemotherapy for human gastric cancer cells. a, b Human epidermal growth factor receptor 2 (HER2)-targeting photoimmunotherapy (PIT) induced near-infrared (NIR) light dose-dependent cell death in NCI-N87 cells but not in MKN-45 cells. The percentage of cell death was significantly increased by PIT treatment in combination with 5-fluorouracil (5-FU) compared to PIT alone. Significant cytotoxic effects of 5-FU were observed in both NCI-N87 and MKN-45 cells. Spotted bar: no treatment, oblique line bar: trastuzumab-IR700 (Tra-IR700) (10 μg/ml) alone, unfilled bar: Tra-IR700 (10 μg/ml) followed by NIR light irradiation (PIT alone), filled bar: addition of 5-FU (3 μM). Data are presented as means ± SEM (n = 3, *P < 0.05, **P < 0.01, Student’s t test). c Significant long-term growth inhibition was observed in cells treated by PIT and 5-FU, as determined by the trypan blue exclusion assay. Data are presented as means ± SEM (n = 3, *P < 0.05, ***P < 0.001 vs. treated with PIT alone, Student’s t test). D While 5-FU and/or Tra-IR700 treatment induced an increase in caspase-3 activity, NIR light irradiation (PIT treatment) did not further increase the caspase-3 activity in NCI-N87 cells. Data are presented as means ± SEM (n = 3, *P < 0.05, ***P < 0.001, Student’s t test). Spotted bar: no treatment, oblique line bar: Tra-IR700 (10 μg/ml) alone, unfilled bar: Tra-IR700 (10 μg/ml) followed by NIR light irradiation (PIT alone), filled bar: addition of 5-FU (3 μM)