Journal Article

Intravital molecular imaging reveals that ROS-caspase-3-GSDME-induced cell punching enhances humoral immunotherapy targeting intracellular tumor antigens

Xu, Yilun, Zhang, Xian, Liu, Fanxuan, Zhang, Zhihong, Zhang, Ren, Qi, Shuhong, Deng, Deqiang, Zhang, Jie, Dai, Bolei, Liu, Lei, Liu, Zheng, Luo, Qingming

2022

Overview

Tumor antigens (TAs)-induced humoral immune responses or TAs-specific antibodies have great application prospects for tumor therapy. However, more than half of TAs are intracellular antigens (intra-Ags) that are hardly recognized by antibodies. It is worthy to develop immunotherapeutic strategies for targeting intra-Ags. We used the far-red fluorescent protein tfRFP as an intracellular antigen to immunize mice and generated a liver metastasis model by injecting tfRFP-expressing B16 melanoma cells (tfRFP-B16) the spleen. Intravital molecular imaging and atomic force microscopy were performed to visualize the formation of tfRFP antigen-antibody complexes (also known as immune complexes) and punched holes in cell membranes. The results showed that the tfRFP-elicited immune responses inhibited the metastasis of tfRFP-expressing melanoma cells in the liver. In the circulating tfRFP-B16 tumor cells, elevated reactive oxygen species (ROS) induced slight caspase-3 activation, a probable key factor in the cleavage of gasdermin E (GSDME) proteins and punching of holes in the tumor cell membrane. Increased tumor cell membrane permeability led to the release of intra-Ag tfRFP and binding with anti-tfRFP antibodies. The formation of tfRFP antigen-antibody complexes on the membranes of tfRFP-B16 cells activated complement components to form membrane attack complexes to further destroy the cell membrane. Neutrophils were rapidly recruited, and F4/80 macrophages phagocytized the dying tumor cells. The process of circulating tumor cell elimination in the tfRFP-immunized mice was triggered through the ROS-caspase-3-GSDME pathway to form intra-Ag-antibody immune complexes, which were involved in the activation of the complement system, as well as the recruitment of neutrophils and F4/80 macrophages. An intra-Ag-elicited humoral immune response is a potent strategy for eliminating liver metastasis, which is unaffected by the liver immune tolerogenic status.

• Publisher: Ivyspring International Publisher Pty Ltd
• Subject: Animals / Antibodies / Antigen-Antibody Complex / Antigens / Antigens, Neoplasm / Cancer / Caspase 3 - metabolism / Cytotoxicity / Immunologic Factors / Immunotherapy / Liver / Liver Neoplasms - metabolism / Melanoma / Membranes / Metastasis / Mice / Mice, Inbred C57BL / Molecular Imaging - methods / Permeability / Proteins / Reactive oxygen species / Reactive Oxygen Species - metabolism / Vaccines