Systematic analysis of integrated bioinformatics to identify upregulated THBS2 expression in colorectal cancer cells inhibiting tumour immunity through the HIF1A/Lactic Acid/GPR132 pathway

BACKGROUND

THBS2, a member of the extracellular matrix glycoprotein family, can effectively inhibit tumour growth and angiogenesis. This study aimed to investigate the biological role of THBS2 in various types of cancers and the mechanisms underlying the malignant progression of colorectal cancer (CRC).

METHODS

THBS2 expression in pan-cancer tissues and cell lines was assessed using the HPA, TISCH and CCLE databases. The CIBERSORT, ESTIMATE, TIMER, xCell and ssGSEA (implemented using the IOBR R package) algorithms were used to calculate the proportion of tumour-infiltrating immune cells based on the expression profile of THBS2 in TCGA-COAD cohort. The clusterprofiler R package was used to implement GO and KEGG pathway enrichm SNVs were compared between the high- and low-THBS2-expression groups using the maftools R package. Additionally, immunotherapy responses were compared between the high- and low-THBS2-expression groups based on immunophenoscores (IPSs). CT26 cells were engineered to overexpress THBS2 (CT26-THBS2) to investigate its regulatory effects on HIF1 and cellular metabolism. The conditioned medium from CT26-THBS2 cells was collected to examine its effect on the M2 polarisation of RAW264.7 macrophages. Subsequently, in vitro experiments were performed to validate the inhibitory effects of M2-polarised macrophages on T-cell proliferation and cytotoxicity. A CT26-THBS2 tumour-bearing mouse model was constructed to validate the impact of high THBS2 expression in tumour cells on the tumour microenvironment in vivo.

RESULTS

THBS2 expression was upregulated in a majority of tumours, including COAD, and was positively associated with ESTIMATEScore, ImmuneScore and StromalScore. Furthermore, THBS2 expression was positively associated with angiogenesis and epithelial-mesenchymal transition and negatively associated with DNA repair, cell cycle and DNA replication in most tumours. THBS2 expression was considerably associated with progression-free interval (PFI) and positively associated with MSI in COAD. THBS2 methylation levels were remarkably lower in COAD tissues than in healthy tissues. The high expression of THBS2 in CT26 cells remarkably promoted the nuclear translocation of HIF1 and consequently enhanced lactate metabolism in cells. In vitro and in vivo experiments revealed that lactate released by tumour cells promoted M2 polarisation of macrophages, leading to inhibition of T-cell proliferation and cytotoxicity.

CONCLUSIONS

THBS2 expression is associated with PFI, immune cell infiltration, immune regulation, cell death, cell migration, epithelial-mesenchymal transition, angiogenesis and genomic variations in COAD. THBS2 may serve as a biomarker for immunotherapy in COAD. Upregulated THBS2 expression in CRC cells inhibits anti-tumour immunity through the HIF1A/lactic acid/GPR132 pathway.

Loss of the mammalian G-protein coupled receptor, G2A, modulates severity of invasive pulmonary aspergillosis

Background

Aspergillus fumigatus is a well-known opportunistic pathogen that causes a range of diseases including the often-fatal disease, invasive pulmonary aspergillosis (IPA), in immunocompromised populations. The severity of IPA is dependent on both host- and pathogen-derived signaling molecules that mediate host immunity and fungal growth. Oxylipins are bioactive oxygenated fatty acids known to influence host immune response and Aspergillus developmental programs. Aspergillus synthesizes 8-HODE and 5,8-diHODE that have structural similarities to 9-HODE and 13-HODE, which are known ligands of the host G-protein-coupled receptor G2A (GPR132).

Materials and methods

Oxylipins were extracted from infected lung tissue to assess fungal oxylipin production and the Pathhunter β-arrestin assay was used to assess agonist and antagonist activity by fungal oxylipins on G2A. An immunocompetent model of A. fumigatus infection was used to assess changes in survival and immune responses for G2A-/- mice.

Results

Here we report that Aspergillus oxylipins are produced in lung tissue of infected mice and in vitro ligand assays suggest 8-HODE is a G2A agonist and 5,8-diHODE is a partial antagonist. To address the hypothesis that G2A could be involved in the progression of IPA, we assessed the response of G2A-/- mice to A. fumigatus infection. G2A-/- mice showed a survival advantage over wild-type mice; this was accompanied by increased recruitment of G2A-/- neutrophils and increased levels of inflammatory markers in A. fumigatus-infected lungs.

Conclusions

We conclude that G2A suppresses host inflammatory responses to Aspergillus fumigatus although it remains unclear if fungal oxylipins are involved in G2A activities.

The Lipid Receptor G2A (GPR132) Mediates Macrophage Migration in Nerve Injury-Induced Neuropathic Pain

Nerve injury-induced neuropathic pain is difficult to treat and mechanistically characterized by strong neuroimmune interactions, involving signaling lipids that act via specific G-protein coupled receptors. Here, we investigated the role of the signaling lipid receptor G2A (GPR132) in nerve injury-induced neuropathic pain using the robust spared nerve injury (SNI) mouse model. We found that the concentrations of the G2A agonist 9-HODE (9-Hydroxyoctadecadienoic acid) are strongly increased at the site of nerve injury during neuropathic pain. Moreover, G2A-deficient mice show a strong reduction of mechanical hypersensitivity after nerve injury. This phenotype is accompanied by a massive reduction of invading macrophages and neutrophils in G2A-deficient mice and a strongly reduced release of the proalgesic mediators TNFα, IL-6 and VEGF at the site of injury. Using a global proteome analysis to identify the underlying signaling pathways, we found that G2A activation in macrophages initiates MyD88-PI3K-AKT signaling and transient MMP9 release to trigger cytoskeleton remodeling and migration. We conclude that G2A-deficiency reduces inflammatory responses by decreasing the number of immune cells and the release of proinflammatory cytokines and growth factors at the site of nerve injury. Inhibiting the G2A receptor after nerve injury may reduce immune cell-mediated peripheral sensitization and may thus ameliorate neuropathic pain.

N-Palmitoylglycine and other N-acylamides activate the lipid receptor G2A/GPR132

The G-protein-coupled receptor GPR132, also known as G2A, is activated by 9-hydroxyoctadecadienoic acid (9-HODE) and other oxidized fatty acids. Other suggested GPR132 agonists including lysophosphatidylcholine (LPC) have not been readily reproduced. Here, we identify N-acylamides in particular N-acylglycines, as lipid activators of GPR132 with comparable activity to 9-HODE. The order-of-potency is N-palmitoylglycine > 9-HODE ≈ N-linoleoylglycine > linoleamide > N-oleoylglycine ≈ N-stereoylglycine > N-arachidonoylglycine > N-docosehexanoylglycine. Physiological concentrations of N-acylglycines in tissue are sufficient to activate GPR132. N-linoleoylglycine and 9-HODE also activate rat and mouse GPR132, despite limited sequence conservation to human. We describe pharmacological tools for GPR132, identified through drug screening. SKF-95667 is a novel GPR132 agonist. SB-583831 and SB-583355 are peptidomimetic molecules containing core amino acids (glycine and phenylalanine, respectively), and structurally related to previously described ligands. A telmisartan analog, GSK1820795A, antagonizes the actions of N-acylamides at GPR132. The synthetic cannabinoid CP-55 940 also activates GPR132. Molecular docking to a homology model suggested a site for lipid binding, predicting the acyl side-chain to extend into the membrane bilayer between TM4 and TM5 of GPR132. Small-molecule ligands are envisaged to occupy a "classical" site encapsulated in the 7TM bundle. Structure-directed mutagenesis indicates a critical role for arginine at position 203 in transmembrane domain 5 to mediate GPR132 activation by N-acylamides. Our data suggest distinct modes of binding for small-molecule and lipid agonists to the GPR132 receptor. Antagonists, such as those described here, will be vital to understand the physiological role of this long-studied target.

Direct interaction of Ikaros and Foxp1 modulates expression of the G protein-coupled receptor G2A in B-lymphocytes and acute lymphoblastic leukemia

Ikaros and Foxp1 are transcription factors that play key roles in normal lymphopoiesis and lymphoid malignancies. We describe a novel physical and functional interaction between the proteins, which requires the central zinc finger domain of Ikaros. The Ikaros-Foxp1 interaction is abolished by deletion of this region, which corresponds to the IK6 isoform that is commonly associated with high-risk acute lymphoblastic leukemia (ALL). We also identify the Gpr132 gene, which encodes the orphan G protein-coupled receptor G2A, as a novel target for Foxp1. Increased expression of Foxp1 enhanced Gpr132 transcription and caused cell cycle changes, including G2 arrest. Co-expression of wild-type Ikaros, but not IK6, displaced Foxp1 binding from the Gpr132 gene, reversed the increase in Gpr132 expression and inhibited G2 arrest. Analysis of primary ALL samples revealed a significant increase in GPR132 expression in IKZF1-deleted BCR-ABL negative patients, suggesting that levels of wild-type Ikaros may influence the regulation of G2A in B-ALL. Our results reveal a novel effect of Ikaros haploinsufficiency on Foxp1 functioning, and identify G2A as a potential modulator of the cell cycle in Ikaros-deleted B-ALL.