Potent and specific antitumor effect of CEA‐targeted photoimmunotherapy

Abstract

Conventional photodynamic therapy (PDT) for cancer is limited by the insufficient efficacy and specificity of photosensitizers. We herein describe a highly effective and selective tumor-targeted PDT using a near-infrared (NIR) photosensitizer, IRDye700DX, conjugated to a human monoclonal antibody (Ab) specific for carcinoembryonic antigen (CEA). The antitumor effects of this Ab-assisted PDT, called photoimmunotherapy (PIT), were investigated in vitro and in vivo. The Ab-IRDye conjugate induced potent cytotoxicity against CEA-positive tumor cells after NIR-irradiation, whereas CEA-negative cells were not affected at all, even in the presence of excess photoimmunoconjugate. We found an equivalent phototoxicity and a predominant plasma membrane localization of Ab-IRDye after both one and six hours of incubation. Either no or little caspase activation and membrane peroxidation were observed in PIT-treated cells and a panel of scavengers for reactive oxygen species showed only partial inhibition of the phototoxic effect. Strikingly, Ab-IRDye retained significant phototoxicity even under hypoxia. We established a xenograft model, which allowed us to sensitively investigate the therapeutic efficacy of PIT by noninvasive bioluminescence imaging. Luciferase-expressing MKN-45-luc human gastric carcinoma cells were subcutaneously implanted into both flanks of nude mice. NIR-irradiation was performed for only the tumor on one side. In vivo imaging and measurement of the tumor size revealed that a single PIT treatment, with intraperitoneal administration of Ab-IRDye and subsequent NIR-irradiation, caused rapid cell death and significant inhibition of tumor growth, but only on the irradiated side. Together, these data suggest that Ab-IRDye-mediated PIT has great potential as an anticancer therapeutics targeting CEApositive tumors.

Spatially selective depletion of tumor-associated regulatory T cells with near-infrared photoimmunotherapy

“…NIR-PIT appears to specifically kill target cells while leaving adjacent normal cells unharmed (15)(16)(17). Although NIR-PIT has been primarily tested with antibodies directed at cancer antigens, it can also be used to kill cells of any type for which there is an appropriate antibody (18)(19)(20). Therefore, NIR-PIT could also be used to deplete a selected subpopulation of immune cells within the tumor tissue.…”

Selective Cell Elimination from Mixed 3D Culture Using a Near Infrared Photoimmunotherapy Technique

“…The target cell type can be adapted with various APC. Various antibodies or antibody fragments, including anti-EGFR, anti-PSMA, anti-mesothelin, and anti-CEA were already used as APCs [15][16][17][18][19][20][21] . Additionally, changing the region of NIR-irradiation can minimize the region treated.…”

“…During the exposure to NIR-light, the cellular membrane ruptures leading to cell death [9][10][11][12][13][14] . NIR-PIT has proven to be effective with multiple antibodies or antibody fragments, including anti-EGFR, anti-HER2, anti-PSMA, anti-CD25, anti-mesothelin, anti-GPC3, and anti-CEA [15][16][17][18][19][20][21] . Therefore, NIR-PIT can be used against a wide variety of target molecules.…”

Alterations of filopodia by near infrared photoimmunotherapy: evaluation with 3D low-coherent quantitative phase microscopy

“…In the NIR-PIT group the volume of 3T3/HER2 cells increased gradually after NIR light exposure although it did not reach significance. Within minutes, cells treated with NIR-PIT rapidly increase in volume leading to rupture of the cell membrane, and extrusion of cell contents into the extracellular space [2][3][4][5] indicating a necrotic rather than apoptotic cell death [6][7][8]. Therefore, the rapid increase in 3T3/HER2 cell volume indicated that NIR-PIT induces necrotic cell death.…”

“…NIR light exposure at 690 nm induces nearly immediate cell necrosis characterized by severe damage to the cell membrane. This mechanism of cell death stands in contrast to traditional photodynamic therapy in which a lipid soluble porphyrin derivative enters the cell and causes damage to the mitochondria resulting in an apoptotic cell death [2][3][4][5]. Cells treated with NIR-PIT undergo rapid volume expansion leading to rupture of the cell membrane and extrusion of cell contents into the extracellular space.…”