E3 ligase TRIM28 promotes anti-PD-1 resistance in non-small cell lung cancer by enhancing the recruitment of myeloid-derived suppressor cells.

BACKGROUND: Alterations in several tripartite motif-containing (TRIM) family proteins have been implicated in the pathogenesis of lung cancer. TRIM28, a member of the TRIM E3 ligase family, has been associated with tumorigenesis, cell proliferation, and inflammation. However, little is known about TRIM28 expression and its role in the immune microenvironment of non-small cell lung cancer (NSCLC). METHODS: We assessed the clinical significance of TRIM28 in tissue microarrays and TCGA cohorts. We investigated the function of TRIM28 in syngeneic mouse tumor models, the KrasLSL-G12D/+; Tp53fl/fl (KP) mouse model, and humanized mice. Immune cell composition was analyzed using flow cytometry and immunohistochemistry. RESULTS: Our findings revealed a positive correlation between TRIM28 expression and the infiltration of suppressive myeloid-derived suppressor cells (MDSCs) in NSCLC. Moreover, silencing TRIM28 enhanced the efficacy of anti-PD-1 immunotherapy by reshaping the inflamed tumor microenvironment. Mechanistically, we demonstrated that TRIM28 could physically interact with receptor-interacting protein kinase 1 (RIPK1) and promote K63-linked ubiquitination of RIPK1, which is crucial for sustaining activation of the NF-κB pathway. Mutagenesis of the E3 ligase domain corroborated the essential role of E3 ligase activity in TRIM28-mediated NF-κB activation. Further experiments revealed that TRIM28 could upregulate the expression of CXCL1 by activating NF-κB signaling. CXCL1 could bind to CXCR2 on MDSCs and promote their migration to the tumor microenvironment. TRIM28 knockdown increased responsiveness to anti-PD-1 therapy in immunocompetent mice, characterized by increased CD8+T tumor-infiltrating lymphocytes and decreased MDSCs. CONCLUSION: The present study identified TRIM28 as a promoter of chemokine-driven recruitment of MDSCs through RIPK1-mediated NF-κB activation, leading to the suppression of infiltrating activated CD8+T cells and the development of anti-PD-1 resistance. Understanding the regulation of MDSC recruitment and function by TRIM28 provides crucial insights into the association between TRIM28 signaling and the development of an immunosuppressive tumor microenvironment. These insights may inform the development of combination therapies to enhance the effectiveness of immune checkpoint blockade therapy in NSCLC.

E3 ligase TRIM15 facilitates non-small cell lung cancer progression through mediating Keap1-Nrf2 signaling pathway.

BACKGROUND: Recent studies have indicated that some members of the tripartite motif (TRIM) proteins function as important regulators for non-small cell lung cancer (NSCLC), However, the regulatory mechanism underpinning aberrant expression of TRIM in NSCLC remains unclear. Here we report that TRIM15 plays important roles in NSCLC progression through modulating Keap1-Nrf2 signaling pathway. METHODS: TRIM15 expression was evaluated by western blot analysis, tissue microarray-based immunohistochemistry analysis. The interactions between TRIM15 and Keap1 were analyzed by co-immunoprecipitation (Co-IP) and immunofluorescence co-localization assay. The correlation between TRIM15 and Keap1 was measured by Co-IP and ubiquitination analysis in vitro. Gain- and lost-of-function experiments were used to detect TRIM15 promotes proliferation and invasion of NSCLC cells both in vitro and vivo. RESULTS: Here, we revealed that TRIM15 was frequently upregulated in NSCLC samples and associated with poor prognosis. Functionally, TRIM15 knockdown resulted in decreased cancer cell proliferation and metastasis, whereas ectopic TRIM15 expression facilitated tumor cancer cell proliferation and metastasis in vitro and in vivo. Moreover, TRIM15 promoted cell proliferation and metastasis depends on its E3 ubiquitin ligase. Mechanistically, TRIM15 directly targeted Keap1 by ubiquitination and degradation, the principal regulator of Nrf2 degradation, leading to Nrf2 escaping from Keap1-mediated degradation, subsequently promoting antioxidant response and tumor progression. CONCLUSIONS: Therefore, our study characterizes the pivotal roles of TRIM15 promotes NSCLC progression via Nrf2 stability mediated by promoting Keap1 ubiquitination and degradation and could be a valuable prognostic biomarker and a potential therapeutic target in NSCLC. Video Abstract.

Cancer-derived exosomal TRIM59 regulates macrophage NLRP3 inflammasome activation to promote lung cancer progression.

BACKGROUND: Exosomes are emerging as important mediators of the cross-talk between tumor cells and the microenvironment. The communication between tumor-derived exosomes and macrophages has a critical role in facilitating tumor progression. However, the mechanisms by which exosomes modulate tumor development in lung cancer are not fully understood. METHODS: Short hairpin RNA mediated knockdown or exogenous expression of TRIM59 combined with in vitro and in vivo assays were performed to prove the functional significance of TRIM59. Western blotting, real-time PCR, co-immunoprecipitation, immunofluorescence (IF) staining assays, proximity ligation assay (PLA), ubiquitination assays, lactate secretion and lipid droplets content measurement, and rescue experiments were used to evaluate the mechanism. Lewis lung carcinoma (LLC) cells were injected via subcutaneously or tail vein into C57BL/6 wild-type (WT) and transgenic mice to assess the role of TRIM59 in vivo. RESULTS: We demonstrated that tripartite motif-containing 59 (TRIM59) was expressed in lung cancer cells-derived exosomes, and can be transferred to macrophages through the exosomes. Activated macrophages by TRIM59 promote lung cancer progression in vitro and in vivo. Mechanistic investigations revealed that TRIM59 physically interacts with abhydrolase domain containing 5 (ABHD5) and directly induced the ubiquitination of ABHD5 and led to its proteasome-dependent degradation. ABHD5, an lipolytic co-activator, deficiency induced metabolic reprogramming and enabled NLRP3 inflammasome activation in macrophages. Further studies showed that the exacerbation of NLRP3 inflammasome activation by ABHD5 deficiency, provides a positive feedback loop to promote cancer progression by preferentially secrete the proinflammatory cytokine IL-1ß. CONCLUSIONS: Collectively, these data indicate that tumor-derived exosomal TRIM59 converts macrophages to tumor-promoting functions of macrophages via regulating ABHD5 proteasomal degradation, to activate NLRP3 inflammasome signaling pathway to promote lung cancer progression by IL-1ß secretion. Our findings also indicate that tumor-derived exosomal TRIM59 has an important role in intercellular communication for fostering an inflammatory microenvironment and promoting lung metastasis.

[Airway epithelial cells increase macrophage chemotaxis and inflammatory cytokine secretion under hypoxic conditions].

OBJECTIVE: To investigate the effects of airway epithelial cells on macrophages chemotaxis and inflammatory cytokine expression under hypoxic conditions.
 Methods: Human bronchial epithelial cells (HBE) treated with different concentrations (0, 100, 200, 400, 800 µmol/L) of CoCl2 or transfected with HIF-1α siRNA were co-cultured with THP-1-derived M1 macrophages or M2 macrophages. The chemotactic effects on macrophages were analyzed by Transwell assay. The levels of TNF-α, IFN-γ, IL-4, IL-13 and IL-10 in the supernatants of macrophages were detected by ELISA, and HIF-1α or Cav-1 mRNA expression in HBE or macrophages was detected by RT-qPCR.
 Results: HBE cells promoted macrophages chemotaxis in a time- and concentration-dependent manner. Compared to un-transfected group, the chemotactic ability of HBE transfected with HIF-1α siRNA was significantly weakened (P<0.01). Under the same culture conditions, the chemotaxis of M2 macrophages was greater than that in THP1-derived M1 macrophages. The concentrations of TNF-α, IFN-γ, IL-4, IL-13 and IL-10 in the supernatants of macrophages were increased in a time-and concentration-dependent manner. The concentrations of TNF-α and IFN-γ were increased further after co-culturing for 8 and 12 h; while IL-4, IL-13 and IL-10 concentrations were increased further during 24 h of co-culture. The levels of cytokines in the supernatants of macrophages co-cultured with HBE and transfected with HIF-1α siRNA were significantly lower than those in un-transfected cells (P<0.05 or P<0.01). The reduction of TNF-α or IFN-γ was more obvious. The expression of HIF-1α or Cav-1 mRNA in HBE or macrophages was increased in a concentration-dependent manner after 8 or 12 h co-culture, which was significantly reduced when HBE was transfected with HIF-1α siRNA.
 Conclusion: Airway epithelial cells can enhance macrophages chemotaxis and pro-inflammatory cytokines expressions under hypoxic condition. HIF-1α and Cav-1 may be the important mediators in these processes.