Real-time endoscopic fluorescent imaging with IR700 signal for monitoring the therapeutic effects of near infrared photoimmunotherapy

Authors

• T Nagaya
• Y Nakamura
• K Sato
• S Okuyama
• F Ogata
• P Choyke
• H Kobayashi

Abstract

Aim: Near infrared photoimmunotherapy (NIR-PIT), a newly developed cancer treatment, leads to immediate target-selective cell death. However, tumor shrinkage takes several days to occur, making it difficult to detect earlier changes in the tumor. In this study, IR700 dynamic imaging was evaluated for monitoring cytotoxic effects. Method: NIR-PIT was evaluated in gastric cancer mouse model with a HER2- and GFP-express cell line using GFP and IR700 real-time fluorescence imaging with a Pearl Imager, Maestro Imager and fluorescence endoscopy. Relative decreasing of fluorescence intensity (DFI) was calculated. In flank xenograft model, tumor bearing mice were divided into 3 groups: (1) no treatment; (2) NIR-PIT (100 J/cm2) and IR700 DFI > 25% (NIR-PIT-1); (3) NIR-PIT (100 J/cm2) and IR700 DFI = 25% (NIR-PIT-2). In disseminated peritoneal model, tumor bearing mice were randomized into 4 groups: (1) NIR-PIT (20 J/cm2); (2) NIR-PIT (50 J/cm2); (3) NIR-PIT (100 J/cm2); (4) NIR light was administered until IR700 DFI = 50%. Result: Tumor growth was significantly reduced and survival was significantly improved in the NIR-PIT-2 group compared with the NIR-PIT-1 group (p < 0.05 for tumor growth, p < 0.01 for survival) in the flank xenograft model. The IR700 signals decreased immediately after NIR-PIT. In the disseminated peritoneal model, histological specimens revealed that NIR-PIT therapeutic effects were demonstrated only in IR700 DFI = 50% group regardless of NIR light dose. Conclusion: Real-time optical images with IR700 signal was able to assess the therapeutic effect during surgical or endoscopic procedures before morphological changes were observed.

Scientific Focus Area: Cancer Biology

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