Overexpression of TREM1 is Associated with the Immune-Suppressive Microenvironment and Unfavorable Prognosis in Pan-Cancer.

Background: Triggering receptors expressed by myeloid cells-1 (TREM1) is a receptor belonging to the immunoglobulin superfamily and plays an important role in pro-inflammation in acute and chronic inflammatory disorders. However, the understanding of the immunomodulatory roles of TREM1 in the tumor microenvironment remains incomplete. Methods: The expression patterns of TREM1 mRNA in tumors and adjacent normal tissues were compared by analyzing data obtained from the Genotype-Tissue Expression and The Cancer Genome Atlas datasets. Survival analysis was performed to determine the prognostic value of TREM1. Functional enrichment analysis was applied to decipher the discrepancy in biological processes between high- and low-TREM1 groups across various cancers. The correlation between TREM1 and immune cell infiltration determined by using multiple algorithms was evaluated with the Pearson method. Four independent immunotherapy cohorts were adopted to validate the role of TREM1 as a biomarker. Results: TREM1 was elevated in most cancers as verified with clinical samples. Overexpression of TREM1 was linked with undesirable prognosis in patients. Further analysis revealed that TREM1 was positively correlated with immune response, pro-tumor pathways, and myeloid cell infiltration, while being negatively correlated with CD8+ T cell (including infiltration level and biological processes). Concordantly, tumors with high TREM1 levels were more resistant to immunotherapy. Through connective map analysis, therapeutically potential compounds like tozasertib and TPCA-1 were identified, which can be used synergistically with immunotherapy to improve the poor prognosis of patients with high TREM1 levels. Conclusion: Through a systematic and comprehensive pan-cancer analysis, we demonstrated that overexpression of TREM1 in tumors correlated closely with unfavorable outcome, infiltration of immune-suppressive cells, and immune regulation, which highlights its potential use as a tumor prognostic biomarker and a novel target for immunotherapy.

[Expression of triggering receptors expressed by myeloid cells-1 in macrophages stimulated by Porphyromonas gingivalis-lipopolysaccharide].

OBJECTIVE: Soluble triggering receptors expressed by myeloid cells-1 (sTREM-1) and inflammatory cytokine tumor necrosis factor-α (TNF-α) in macrophage cells were stimulated by Porphyromonas gingivalis-lipopolysaccharide (Pg-LPS) to investigate the expression of triggering receptors expressed by myeloid cells-1 (TREM-1) and further explore the correlation between TREM-1 and the pathogenesis of periodontitis. METHODS: THP-1 cells (a human monocytic cell line derived from an acute monocytic leukemia patient) were induced to differentiate THP-1 macrophages by phorbol-12-myristate-13-acetate and were injected with 0 (blank control), 0.5, or 1.0 µg·mL⁻¹ Pg-LPS. The THP-1 cells were then grouped in accordance with incubation time, and each group was incubated for 4, 6, 12, or 24 h. The expression of the TREM-1 mRNA in macrophages was detected by real-time quantitative polymerase chain reaction, while the expression of TREM-1 protein was detected by Western blot; the site where TREM-1 protein expression was observed in macrophages was detected by immunofluorescence staining, and the expression of soluble sTREM-1 and TNF-α in cell culture medium was detected by enzyme-linked immunosorbent assay. RESULTS: Compared with the blank control group, the expression of TREM-1 mRNA, TREM-1 protein, and sTREM-1 in Pg-LPS-stimulated macrophages was significantly upregulated (P<0.05). The expression of TREM-1 mRNA, TREM-1 protein, and sTREM-1 in the supernatant of cell culture was higher in the 1.0 µg·mL⁻¹ Pg-LPS group than in the 0.5 µg·mL⁻¹ group; this expression was statistically significant since the 6, 4, and 4 h time point (P<0.05). Cell immunofluorescence staining showed that TREM-1 protein was positive when the THP-1 macrophages was stimulated by Pg-LPS (1.0 µg·mL⁻¹) for 24 h, and the staining sites of TREM-1 were mainly located in the cell membrane of the macrophages (P<0.05). The expression level of TNF-α increased in groups stimulated by Pg-LPS, and the expression level of TNF-α was significantly higher in 1.0 µg·mL⁻¹ Pg-LPS stimulated groups than in 0.5 µg·mL⁻¹ Pg-LPS-stimulated groups since the 6 h time point (P<0.05). The expressions of TREM-1 mRNA, TREM-1 protein, and sTREM-1 in 0.5 µg·mL⁻¹ Pg-LPS-stimulated macrophages were positively correlated with one another (r=1, P<0.05), but no statistically significant correlation was found in the expression of TNF-α. The positive correlation between sTREM-1 and TNF-α expressions was detected when macrophages were stimulated by 1.0 µg·mL⁻¹ Pg-LPS (r=1, P<0.05). CONCLUSIONS: The expression of TREM-1 mRNA, TREM-1 protein, and sTREM-1 in the culture supernatant in Pg-LPS-stimulated macrophages was significantly upregulated on the basis of the concentration of Pg-LPS; moreover, their upregulation was positively correlated with one another. The expression of TNF-α in the supernatant of cell culture was also upregulated and was positively correlated with the expression of sTREM-1 at the group of high Pg-LPS concentration (1.0 µg·mL⁻¹). Results reveal that TREM-1, which has been realized as a proinflammatory receptor protein, can promote the development of periodontitis by regulating the expression of TNF-α in macrophages.

[Temporal expression of triggering receptors expressed by myeloid cells-1 during the development of experimental periodontitis in rat].

Objective: To illuminate the temporal expression of the triggering receptor expressed on myeloid cells-1 (TREM-1) in the experimental periodontitis in rat and to investigate the function of TREM-1 in the pathogenesis of experimental periodontitis in rat. Methods: The experimental periodontitis model was established in the maxillary first molar by means of 'wire ligation + vaccination periodontal pathogen Porphyromanus gingivalis (Pg) + high-sugar diet' in Sprague-Dawley (SD) rats. The experimental animals were divided into six groups: the control group and each of the time points of establishing the models for one week and two to five weeks. There were six rats for each of the six groups. The bone loss of the palatal site was calculated to estimate whether the periodontitis model was successfully established. The expression of TREM-1, proinflammatory cytokines: tumor necrosis factor-α (TNF-α), interleukin (IL)-1ß and IL-6, anti-inflammatory cytokines: IL-4, IL-10 and transforming growth factor-ß (TGF-ß) were examined by using quantitative real-time PCR. The expression level of TREM-1 protein was analyzed by the method of immunohistochemistry. Results: The average bone loss area of the palatal site was (0.17±0.04) mm(2) in the group of three weeks and was statistically significant (P<0.05) compared to the control group [(0.10±0.01) mm(2)]. The experimental periodontitis model was successfully established in the group of three weeks. The expression of TREM-1 increased significantly in the inflamed periodontal tissues and reached to its maximum expression in the three weeks group accounting for 159.50±38.26 in protein expression and 4.35±0.60 in mRNA expression, respectively. TREM-1 expression difference between the three weeks group and control group was statistically significant (P<0.01). The expression of IL-6 by gingival tissues was correlated with the mRNA level of TREM-1 (r=0.813 P=0.049). Conclusions: TREM-1, as a proinflammatory receptor, could facilitate the periodontal inflammatory response. The possible way of TREM-1 to promote inflammation may be through controling the expression of IL-6.

Expression of triggering receptors expressed by myeloid cells-1 in macrophages stimulated by Porphyromonas gingivalis-lipopolysaccharide / 华西口腔医学杂志

OBJECTIVE@#Soluble triggering receptors expressed by myeloid cells-1 (sTREM-1) and inflammatory cytokine tumor necrosis factor-α (TNF-α) in macrophage cells were stimulated by Porphyromonas gingivalis-lipopolysaccharide (Pg-LPS) to investigate the expression of triggering receptors expressed by myeloid cells-1 (TREM-1) and further explore the correlation between TREM-1 and the pathogenesis of periodontitis.@*METHODS@#THP-1 cells (a human monocytic cell line derived from an acute monocytic leukemia patient) were induced to differentiate THP-1 macrophages by phorbol-12-myristate-13-acetate and were injected with 0 (blank control), 0.5, or 1.0 μg·mL⁻¹ Pg-LPS. The THP-1 cells were then grouped in accordance with incubation time, and each group was incubated for 4, 6, 12, or 24 h. The expression of the TREM-1 mRNA in macrophages was detected by real-time quantitative polymerase chain reaction, while the expression of TREM-1 protein was detected by Western blot; the site where TREM-1 protein expression was observed in macrophages was detected by immunofluorescence staining, and the expression of soluble sTREM-1 and TNF-α in cell culture medium was detected by enzyme-linked immunosorbent assay.@*RESULTS@#Compared with the blank control group, the expression of TREM-1 mRNA, TREM-1 protein, and sTREM-1 in Pg-LPS-stimulated macrophages was significantly upregulated (P<0.05). The expression of TREM-1 mRNA, TREM-1 protein, and sTREM-1 in the supernatant of cell culture was higher in the 1.0 μg·mL⁻¹ Pg-LPS group than in the 0.5 μg·mL⁻¹ group; this expression was statistically significant since the 6, 4, and 4 h time point (P<0.05). Cell immunofluorescence staining showed that TREM-1 protein was positive when the THP-1 macrophages was stimulated by Pg-LPS (1.0 μg·mL⁻¹) for 24 h, and the staining sites of TREM-1 were mainly located in the cell membrane of the macrophages (P<0.05). The expression level of TNF-α increased in groups stimulated by Pg-LPS, and the expression level of TNF-α was significantly higher in 1.0 μg·mL⁻¹ Pg-LPS stimulated groups than in 0.5 μg·mL⁻¹ Pg-LPS-stimulated groups since the 6 h time point (P<0.05). The expressions of TREM-1 mRNA, TREM-1 protein, and sTREM-1 in 0.5 μg·mL⁻¹ Pg-LPS-stimulated macrophages were positively correlated with one another (r=1, P<0.05), but no statistically significant correlation was found in the expression of TNF-α. The positive correlation between sTREM-1 and TNF-α expressions was detected when macrophages were stimulated by 1.0 μg·mL⁻¹ Pg-LPS (r=1, P<0.05).@*CONCLUSIONS@#The expression of TREM-1 mRNA, TREM-1 protein, and sTREM-1 in the culture supernatant in Pg-LPS-stimulated macrophages was significantly upregulated on the basis of the concentration of Pg-LPS; moreover, their upregulation was positively correlated with one another. The expression of TNF-α in the supernatant of cell culture was also upregulated and was positively correlated with the expression of sTREM-1 at the group of high Pg-LPS concentration (1.0 μg·mL⁻¹). Results reveal that TREM-1, which has been realized as a proinflammatory receptor protein, can promote the development of periodontitis by regulating the expression of TNF-α in macrophages.

Temporal expression of triggering receptors expressed by myeloid cells-1 during the development of experimental periodontitis in rat / 中华口腔医学杂志

Objective@#To illuminate the temporal expression of the triggering receptor expressed on myeloid cells-1 (TREM-1) in the experimental periodontitis in rat and to investigate the function of TREM-1 in the pathogenesis of experimental periodontitis in rat.@*Methods@#The experimental periodontitis model was established in the maxillary first molar by means of 'wire ligation + vaccination periodontal pathogen Porphyromanus gingivalis (Pg) + high-sugar diet' in Sprague-Dawley (SD) rats. The experimental animals were divided into six groups: the control group and each of the time points of establishing the models for one week and two to five weeks. There were six rats for each of the six groups. The bone loss of the palatal site was calculated to estimate whether the periodontitis model was successfully established. The expression of TREM-1, proinflammatory cytokines: tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6, anti-inflammatory cytokines: IL-4, IL-10 and transforming growth factor-β (TGF-β) were examined by using quantitative real-time PCR. The expression level of TREM-1 protein was analyzed by the method of immunohistochemistry.@*Results@#The average bone loss area of the palatal site was (0.17±0.04) mm2 in the group of three weeks and was statistically significant (P<0.05) compared to the control group [(0.10±0.01) mm2]. The experimental periodontitis model was successfully established in the group of three weeks. The expression of TREM-1 increased significantly in the inflamed periodontal tissues and reached to its maximum expression in the three weeks group accounting for 159.50±38.26 in protein expression and 4.35±0.60 in mRNA expression, respectively. TREM-1 expression difference between the three weeks group and control group was statistically significant (P<0.01). The expression of IL-6 by gingival tissues was correlated with the mRNA level of TREM-1 (r=0.813 P=0.049).@*Conclusions@#TREM-1, as a proinflammatory receptor, could facilitate the periodontal inflammatory response. The possible way of TREM-1 to promote inflammation may be through controling the expression of IL-6.