ILT4 in Colorectal Cancer Cells Induces Suppressive T Cell Contexture and Disease Progression

Abstract

Zijiang Yang,1,* Aiqin Gao,2,* Wenjing Shi,1 Jingnan Wang,1 Xianchao Zhang,3 Zhengyan Xu,3 Tingting Xu,3 Yan Zheng,4 Yuping Sun,5 Fei Yang3 1Department of Oncology, Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250013, People’s Republic of China; 2Department of Thoracic Radiation Oncology, Shandong Cancer Hospital and Institute, Jinan, Shandong, 250117, People’s Republic of China; 3Department of Pathology, Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250013, People’s Republic of China; 4Research Center of Translational Medicine, Jinan Central Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, 250013, People’s Republic of China; 5Proton Center, Shandong Cancer Hospital and Institute, Jinan, Shandong, 250117, People’s Republic of China*These authors contributed equally to this workCorrespondence: Fei YangDepartment of Pathology, Jinan Central Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250013, People’s Republic of ChinaTel [phone]Email [email protected]: Immune checkpoint blockade (ICB) therapy shows little or no clinical benefit in most colorectal cancer (CRC) patients, due to the immunosuppressive T cell contexture in the tumor microenvironment (TME). Immunoglobulin-like transcript (ILT) 4 is an immunosuppressive molecule in myeloid cells. ILT4 is enriched in solid tumor cells, facilitating their proliferation, invasion, and metastasis. However, the regulatory role of ILT4 in T cell immunity of CRC is still undetermined. Here, we aimed to explore how tumor cell-derived ILT4 orchestrates T cell infiltration, subset distribution, and function in CRC.Methods: A total of 145 paraffin-embedded cancer tissues and the corresponding clinicopathological information were collected from CRC patients. Immunohistochemical (IHC) staining and public database analyses determined the correlation of ILT4 expression with different T cell subset densities, IFN-γ levels, and patient outcomes. Paired Ig-like receptor B (PIR-B, ILT4 mouse ortholog)-overexpressing/-downregulated MC38 cells were subcutaneously injected into C57BL/6 mice as a CRC transplantation model. The frequencies, subsets, and IFN-γ levels of T cells in mouse blood and spleens were determined using flow cytometry and immunohistochemistry, respectively.Results: High ILT4 expression in CRC cells was associated with decreased T cell infiltration, disease progression, and poor patient survival. T cell subset analyses indicated that ILT4-high patients showed reduced CD8+ T cell but elevated FOXP3+ regulatory T (Treg) cell frequencies in the TME. High ILT4 levels predicted lower IFN-γ production by tumor-infiltrating lymphocytes (TILs), especially by CD8+T cells in human CRC tissues. Moreover, PIR-B overexpression accelerated MC38 growth in mice, decreased CD3+/CD8+/IFN-γ+ T cell densities, and elevated Treg infiltration in the TME, blood, and spleens. PIR-B knockdown had the opposite effects.Conclusion: ILT4 in CRC cells induced immunosuppressive T cell subset infiltration and impaired IFN-γ production in TILs, suggesting that ILT4 might be a potential immunotherapeutic target and prognostic biomarker.Keywords: immunoglobulin-like transcript 4, colorectal cancer, T cell subsets, IFN-γ, immunosuppression

Keywords

• immunoglobulin-like transcript 4
• colorectal cancer
• t cell subsets
• ifn-γ
• immunosuppression