Abstract
BackgroundPhotoimmunotherapy (PIT) employing antibody-photosensitizer conjugates is a promising treatment for cancer. However, the fixed antigen specificity severely limits the efficacy and the applicability. Here we describe a universal strategy for PIT of cancer by using a near-infrared (NIR) photosensitizer IRDye700DX-conjugated NeutrAvidin, designated as AvIR, together with various biotinylated antibodies (BioAbs) for cellular targeting.MethodsCytotoxicity of AvIR-mediated PIT was evaluated by fluorescence imaging and cell viability assay. Phototoxic effect on tumorigenicity was assessed by tumorsphere-formation assay and Matrigel invasion assay. Cancer stem cell-like side-population (SP) cells were identified by flow cytometry.ResultsCHO cells stably expressing carcinoembryonic antigen or EpCAM were pre-labeled with each BioAb for the corresponding antigen, followed by AvIR administration. NIR light irradiation specifically killed the targeted cells, but not off-targets, demonstrating that the AvIR-mediated PIT does work as expected. CSC-like subpopulation of MCF-7 cells (CD24low/CD44high) and SP of HuH-7 cells (CD133+/EpCAM+) were effectively targeted and photokilled by AvIR-PIT with anti-CD44 BioAb or anti-CD133/anti-EpCAM BioAbs, respectively. As results, the neoplastic features of the cell lines were sufficiently suppressed. Cancer-associated fibroblast (CAF)-targeted AvIR-PIT by using anti-fibroblast activation protein BioAb showed an abolishment of CAF-enhanced clonogenicity of MCF-7 cells.ConclusionsCollectively, our results demonstrate that AvIR-mediated PIT can greatly broaden the applicable range of target specificity, with feasibility of efficacious and integrative control of CSC and its microenvironment.
Highlights
Photoimmunotherapy (PIT) employing antibody-photosensitizer conjugates is a promising treatment for cancer
Solid tumors are generally composed of heterogeneous cell populations, which could arise from cancer stem cells (CSCs) [12], and it is well known that the expression pattern of tumor-associated antigen (TAA) and the organization of the tumor microenvironment often change dynamically depending on the malignant progression and the course of radiotherapy and chemotherapy [13]
We found that IRDye700DX-conjugated NeutrAvidin (AvIR) exerted strong antigen-specific cytotoxicity toward the biotinylated antibody (BioAb)-labeled Chinese hamster ovary (CHO) cells upon NIR irradiation (Fig. 2b)
Summary
Photoimmunotherapy (PIT) employing antibody-photosensitizer conjugates is a promising treatment for cancer. In order to effectively apply the IR700-PIT to a broad range of cancer types and of changes in TAA expression, it is considered necessary to prepare a panel of IR700-mAb conjugates with different specificity corresponding to various target TAAs on a case-by-case basis; such approach is extremely complicated, costly in terms of time and money, and unrealistic. To overcome these problems and realize a highly versatile PIT applicable to various cancers and tumor-supporting cells, we aimed to develop a novel PIT utilizing IR700-conjugated NeutrAvidin, designated as AvIR, in combination with biotinylated antibodies (BioAbs) for cell-specific targeting. If AvIR-mediated PIT works effectively, the sequential or simultaneous use of various BioAbs would be achievable a universal PIT capable of responding to altered expression of TAAs, enabling comprehensive cancer therapy that targets heterogeneous tumor cell populations including CSCs that express different
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