Translocator protein-targeted photodynamic therapy for direct and abscopal immunogenic cell death in colorectal cancer. (15th October 2021)

• Record Type: Journal Article
• Authors: Xie, Qing; Li, Zhen; Liu, Yang; Zhang, Dawei; Su, Meng; Niitsu, Hiroaki; Lu, Yuanyuan; Coffey, Robert J.; Bai, Mingfeng
• Is Part Of: Acta biomaterialia. Volume 134(2021)
• Page Start: 716
• Page End: 729
• Publication Date: 2021-10-15
• Subjects: TSPO -- Photodynamic therapy -- Immunogenic cell death -- Colorectal cancer -- Anti-tumor immunity; Biomedical materials -- Periodicals; 610.28
• DOI: 10.1016/j.actbio.2021.07.052
• Languages: English
• ISSNs: 1742-7061

Abstract

Abstract: Abscopal effect is an attractive cancer therapeutic effect referring to tumor regression at a location distant from the primary treatment site. Immunogenic cell death (ICD) offers a mechanistic link between the primary and remote therapeutic effects by activating favorable anti-tumor immune responses. In this study, we induced ICD in colorectal cancer (CRC) cell lines in vitro and in vivo by targeting the 18 kDa translocator protein (TSPO), a mitochondrial receptor overexpressed in CRC. Photodynamic therapy (PDT) using a TSPO-targeted photosensitizer, IR700DX-6T, caused effective apoptotic cell death in fourteen CRC cell lines. In a syngeneic immunocompetent CRC mouse model, the growth of tumors subjected to TSPO-PDT was greatly suppressed. Remarkably, untreated tumors in the opposing flank also showed marked growth suppression. Dendritic and CD8 + T cells were activated after TSPO-PDT treatment, accompanied by decreased Treg cells in both treated and non-treated tumors. In addition, a cancer vaccine developed from TSPO-PDT produced a significant tumor inhibition effect. These results indicate that TSPO-PDT could not only directly suppress tumor growth but also dramatically provoke host anti-tumor immunity, highlighting the potential of TSPO-PDT as a successful therapeutic for CRC that exhibits systemic effects. Statement of significance: Abscopal effect is an attractive cancer therapeutic effect referring to tumor regression at a location distant from the primary treatment site. Immunogenic cell death (ICD) offers a mechanistic link between the primary and remote therapeutic effects by activating favorable anti-tumor immune responses. In this study, we report a new therapeutic approach that can reduce the growth of multiple CRC cell lines by inducing ICD. Notably, a direct and abscopal effect was observed in mouse tumor-derived MC38 cells when injected into syngeneic immunocompetent mice. If comparable effects could be achieved in humans, it would establish a novel paradigm for treating micro- and macro-metastasis. Graphical abstract: Image, graphical abstract