Integrin-Linked Kinase Expression Characterizes the Immunosuppressive Tumor Microenvironment in Colorectal Cancer and Regulates PD-L1 Expression and Immune Cell Cytotoxicity

Abstract

Integrin-linked kinase (ILK) has been implicated as a molecular driver and mediator in both inflammation and tumorigenesis of the colon. However, a role for ILK in the tumor microenvironment (TME) and immune evasion has not been investigated. Here, we show a correlation of ILK expression with the immunosuppressive TME and cancer prognosis. We also uncover a role for ILK in the regulation of programmed death-ligand 1 (PD-L1) expression and immune cell cytotoxicity. Interrogation of web-based data-mining platforms, showed upregulation of ILK expression in tumors and adjacent-non tumor tissue of colorectal cancer (CRC) associated with poor survival and advanced stages. ILK expression was correlated with cancer-associated fibroblast (CAFs) and immunosuppressive cell infiltration including regulatory T cells (Treg) and M2 macrophages (M2) in addition to their gene markers. ILK expression was also significantly correlated with the expression of different cytokines and chemokines. ILK expression showed pronounced association with different important immune checkpoints including PD-L1. Deletion of the ILK gene in PD-L1 positive CRC cell lines using a doxycycline inducible-CRISPR/Cas9, resulted in suppression of both the basal and IFNγ-induced PD-L1 expression via downregulating NF-κB p65. This subsequently sensitized the CRC cells to NK92 immune cell cytotoxicity. These findings suggest that ILK can be used as a biomarker for prognosis and immune cell infiltration in colon cancer. Moreover, ILK could provide a therapeutic target to prevent immune evasion mediated by the expression of PD-L1.

Integrin-linked kinase expression in myeloid cells promotes colon tumorigenesis

“…Reduced expression levels of Arg1 observed in ILK-KO cells also correlated with reduced levels of Arginase-1 protein in ILK-KO BMDMs during M2 polarization ( Supplementary Figure 3 ). Our results also correspond with our earlier report indicating a correlation between ILK expression and markers of M2 macrophages ( 45 ). These observations establish that ILK is required for macrophage M2 polarization.…”

“…Despite its central role in cell-extracellular matrix interactions, the mechanistic details of ILK upregulation is not fully understood yet but is considered to be cell type- and context-dependent ( 60 , 61 ). For examples, our earlier report demonstrates a correlation between ILK overexpression and markers of M2 macrophages ( 45 ), indicating a cancer-promoting cue driving ILK upregulation. Even the mechanistic details could also vary within the same cell type depending on the stimulation.…”

Application of CRISPR-Cas9 gene editing technology in basic research, diagnosis and treatment of colon cancer

“…SIAE is a gene that regulates the acetylation of Neu5AC. SIAE gene knockout can increase the acetylation level of Neu5AC and enhance the killing ability of NK cells Figure 5C ( 142 ).…”