Research Papers:

Combination photoimmunotherapy with monoclonal antibodies recognizing different epitopes of human epidermal growth factor receptor 2: an assessment of phototherapeutic effect based on fluorescence molecular imaging

Kimihiro Ito _, Makoto Mitsunaga, Takashi Nishimura, Hisataka Kobayashi and Hisao Tajiri

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Oncotarget. 2016; 7:14143-14152. https://doi.org/10.18632/oncotarget.7490

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Kimihiro Ito1, Makoto Mitsunaga1, Takashi Nishimura1, Hisataka Kobayashi2, Hisao Tajiri1

1Division of Gastroenterology and Hepatology, Department of Internal Medicine, The Jikei University School of Medicine, Minato, Tokyo 105-8461, Japan

2Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA

Correspondence to:

Makoto Mitsunaga, e-mail: [email protected]

Keywords: molecular targeted therapy, photoimmunotherapy, HER2, trastuzumab, pertuzumab

Received: November 04, 2015     Accepted: January 31, 2016     Published: February 19, 2016


Photoimmunotherapy is a new class of molecular targeted cancer therapy based on a monoclonal antibody (mAb) conjugated to a photosensitizer and irradiation with near-infrared (NIR) light for both imaging and therapy. Here, we sought to determine the feasibility of combining photoimmunotherapy using conjugates of human epidermal growth factor receptor 2 (HER2)-specific mAb-photosensitizer IR700, trastuzumab-IR700 and pertuzumab-IR700. HER2-expressing and non-expressing cells were treated with mAb-IR700 conjugates and irradiated with NIR light. Fluorescence imaging and cytotoxic effects were examined in cultured HER2-expressng cancer cell lines and in a mouse tumor xenograft model. Trastuzumab-IR700 and pertuzumab-IR700 could specifically bind to HER2 without competing, and the combination treatment of both agents yielded stronger HER2-specific IR700 fluorescence signals than with the treatment with either agent singly. A cytotoxicity assay showed that the combination treatment of both trastuzumab-IR700 and pertuzumab-IR700 followed by NIR light irradiation induced stronger cytotoxic effect than with treatment of either agent plus NIR light irradiation. Furthermore, the phototoxic and cytotoxic effects of mAb depended on HER2-specific IR700 signal intensities. Consistent with in vitro studies, in xenograft tumor models also, IR700 fluorescence imaging-guided NIR light irradiation after the combination treatment of trastuzumab-IR700 and pertuzumab-IR700 led to stronger antitumor effects than by treatment with either agent followed by NIR light irradiation. In conclusion, fluorescence molecular imaging can facilitate the assessment of treatment outcomes of molecular targeted photoimmunotherapy, which holds great potential in facilitating better outcomes in cancer patients.

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