Emerging roles of non-coding RNAs in the metabolic reprogramming of tumor-associated macrophages

LncRNA CRNDE promotes hepatoma cell proliferation by regulating the metabolic reprogramming of M2 macrophages via ERK pathway

BACKGROUND

LncRNA colorectal neoplasia differentially expressed (CRNDE) was found to be an important regulator in many cancers. This project focuses on the function of CRNDE on macrophage metabolic reprogramming and Hepatocellular carcinoma (HCC).

METHOD

qRT-PCR and Immunofluorescence were used to analyze Arg-1, IL-10, CD163, CCL-18, CD206, and CRNDE expression in HCC tissues and macrophages. Western Blotting was used to analyze ERK and p-ERK expression. Edu assay, transwell assay and xenograft experiments were carried out to study cell viability, migrated and invasive capability. Immunohistochemical staining was used to evaluate Ki67 expression. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) was performed for macrophages metabolites analysis.

RESULTS

Arg-1, IL-10, CD163, CD206, and CRNDE were significantly up-regulated in HCC tissues, M2 macrophage and M0 macrophage with CRNDE overexpressed (OV-CRNDE-M0), which downregulated in M0 macrophage with CRNDE knockdown (sh-CRNDE-M0). The conditioned medium (CM) of M2 cells and OV-CRNDE-M0 cells promoted cell viability, invasion, and migration of HCC cells, the effect was reversed by sh-CRNDE-M0 cells CM. OV-CRNDE-M0 cells promoted tumor growth, Ki67 and CD206 expression in xenograft model. 61 metabolites were detected, of which 18 metabolites changed significantly in OV-CRNDE-M0 group compared to M0 group, with 9 upregulated and 9 downregulated. KEGG analysis showed the enrichment pathways were biosynthesis, glyoxylate and dicarboxylate metabolism. SMPDB analysis showed the enrichment pathways were hypoacetylaspartia, canavan disease, and aspartate metabolism.

CONCLUSION

CRNDE regulated the metabolic reprogramming of M2 macrophage via ERK pathway, which thereby contributed to HCC proliferation, migration, and invasion.

Metabolic reprogramming by miRNAs in the tumor microenvironment: Focused on immunometabolism

MicroRNAs (miRNAs) are emerging as a significant modulator of immunity, and their abnormal expression/activity has been linked to numerous human disorders, such as cancer. It is now known that miRNAs potentially modulate the production of several metabolic processes in tumor-associated immune cells and indirectly via different metabolic enzymes that affect tumor-associated signaling cascades. For instance, Let-7 has been identified as a crucial modulator for the long-lasting survival of CD8+ T cells (naive phenotypes) in cancer by altering their metabolism. Furthermore, in T cells, it has been found that enhancer of zeste homolog 2 (EZH2) expression is controlled via glycolytic metabolism through miRNAs in patients with ovarian cancer. On the other hand, immunometabolism has shown us that cellular metabolic reactions and processes not only generate ATP and biosynthetic intermediates but also modulate the immune system and inflammatory processes. Based on recent studies, new and encouraging approaches to cancer involving the modification of miRNAs in immune cell metabolism are currently being investigated, providing insight into promising targets for therapeutic strategies based on the pivotal role of immunometabolism in cancer. Throughout this overview, we explore and describe the significance of miRNAs in cancer and immune cell metabolism.

Long non-coding RNA G23Rik attenuates fasting-induced lipid accumulation in mouse liver

Peroxisome proliferator-activated receptor α (PPARα) is a key mediator of lipid metabolism and metabolic stress in the liver. A recent study revealed that PPARα-dependent long non-coding RNAs (lncRNAs) play an important role in modulating metabolic stress and inflammation in the livers of fasted mice. Here hepatic lncRNA 3930402G23Rik (G23Rik) was found to have active peroxisome proliferator response elements (PPREs) within its promoter and is directly regulated by PPARα. Although G23Rik RNA was expressed to varying degrees in several tissues, the PPARα-dependent regulation of this lncRNA was only observed in the liver. Pharmacological activation of PPARα induced PPARα recruitment at the G23Rik promoter and a pronounced increase in hepatic G23Rik lncRNA expression. A G23Rik-null mouse line was developed to further characterize the function of this lncRNA in the liver. G23Rik-null mice were more susceptible to hepatic lipid accumulation in response to acute fasting. Histological analysis further revealed a pronounced buildup of lipid droplets and a significant increase in neutral triglycerides and lipids as indicated by enhanced oil red O staining of liver sections. Hepatic cholesterol, non-esterified fatty acid, and triglyceride levels were significantly elevated in G23Rik-null mice and associated with induction of the lipid-metabolism related gene Cd36. These findings provide evidence for a lncRNA dependent mechanism by which PPARα attenuates hepatic lipid accumulation in response to metabolic stress through lncRNA G23Rik induction.

MicroRNAs/LncRNAs Modulate MDSCs in Tumor Microenvironment

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of immature cells derived from bone marrow that play critical immunosuppressive functions in the tumor microenvironment (TME), promoting cancer progression. According to base length, Non-coding RNAs (ncRNAs) are mainly divided into: microRNAs (miRNAs), lncRNAs, snRNAs and CircRNAs. Both miRNA and lncRNA are transcribed by RNA polymerase II, and they play an important role in gene expression under both physiological and pathological conditions. The increasing data have shown that MiRNAs/LncRNAs regulate MDSCs within TME, becoming one of potential breakthrough points at the investigation and treatment of cancer. Therefore, we summarize how miRNAs/lncRNAs mediate the differentiation, expansion and immunosuppressive function of tumor MDSCs in TME. We will then focus on the regulatory mechanisms of exosomal MicroRNAs/LncRNAs on tumor MDSCs. Finally, we will discuss how the interaction of miRNAs/lncRNAs modulates tumor MDSCs.

Non-Coding RNAs in the Crosstalk between Breast Cancer Cells and Tumor-Associated Macrophages

Non-coding RNAs (ncRNAs) play a pivotal role in regulating the tumor microenvironment (TME) by controlling gene expression at multiple levels. In tumors, ncRNAs can mediate the crosstalk between cancer cells and other cells in the TME, such as immune cells, stromal cells, and endothelial cells, influencing tumor development and progression. Tumor-associated macrophages (TAMs) are among the most abundant inflammatory cells infiltrating solid cancers that promote tumorigenesis, and their infiltration correlates with a poor prognosis in many tumors. Cancer cells produce different ncRNAs that orchestrate TAM recruitment and polarization toward a tumor-promoting phenotype. Tumor-reprogrammed macrophages shape the TME by promoting angiogenesis and tissue remodeling, and suppressing the anti-tumor activity of adaptive immune cells. TAMs can also produce ncRNA molecules that boost cancer cell proliferation and direct their phenotype and metabolic changes facilitating cancer progression and metastasis. This review will focus on the crosstalk between cancer cells and TAMs mediated by microRNAs and long non-coding RNAs during breast cancer (BC) initiation and progression.

CircGOT1 promotes cell proliferation, mobility, and glycolysis-mediated cisplatin resistance via inhibiting its host gene GOT1 in esophageal squamous cell cancer

Esophageal squamous cell cancer (ESCC) is a prevalent malignant cancer with high incidence and fatality rate. Surging evidences have revealed that circular RNAs (circRNAs) act key role in ESCC tumorigenesis and progression. Therefore, the purpose of this study is to explore the role and regulatory mechanism of a novel circGOT1 in ESCC. In the present study, the transcriptional expression of circGOT1, miR-606 and GOT1, and the epithelial-mesenchymal transition (EMT) and apoptosis-related markers were examined by quantitative PCR. The protein levels of GOT1 and glycolysis-related proteins were detected by Western blotting. In addition, the glycolytic levels were determined via measuring glucose uptake, lactate production, and ATP levels. Then, the function experiments and rescue experiments were used to investigate the function and mechanism of circGOT1 in ESCC. In addition, RNA immunoprecipitation, pull-down, and luciferase activity reporter gene assays were used to analyze the circGOT1/miR-606/GOT1 axis. The xenograft mouse mode was used to determine the function of circGOT1 in vivo. Here, we identified that circGOT1 and GOT1 upregulate, whereas miR-606 was reduced in ESCC tissues and cell lines. High circGOT1 and GOT1 expression associated with poor survival and worse prognosis of ESCC patients, but miR-606 revealed opposite traits. Mechanically, circGOT1 sponged miR-606 to promote GOT1, which induced cell proliferation, migration, aerobic glycolysis, and cisplatin resistance. The tumor growth was reduced by circGOT1 inhibition in xenograft mouse. Our results indicate the oncogene role of circGOT1 in ESCC via an endogenous competition RNA (ceRNA) mechanism to promote GOT1 expression via sponging miR-606.

Targeting monocytes/macrophages in fibrosis and cancer diseases: Therapeutic approaches

Over almost 140 years since their identification, the knowledge about macrophages has unbelievably evolved. The 'big eaters' from being thought of as simple phagocytic cells have been recognized as master regulators in immunity, homeostasis, healing/repair and organ development. Long considered to originate exclusively from bone marrow-derived circulating monocytes, macrophages have been also demonstrated to be the first immune cells colonizing tissues in the developing embryo and persisting in adult life by self-renewal, as long-lived tissue resident macrophages. Therefore, heterogeneous populations of macrophages with different ontogeny and functions co-exist in tissues. Macrophages act as sentinels of homeostasis and are intrinsically programmed to lead the wound healing and repair processes that occur after injury. However, in certain pathological circumstances macrophages get dysfunctional, and impaired or aberrant macrophage activities become key features of diseases. For instance, in both fibrosis and cancer, that have been defined 'wounds that do not heal', dysfunctional monocyte-derived macrophages overall play a key detrimental role. On the other hand, due to their plasticity these cells can be 're-educated' and exert anti-fibrotic and anti-cancer functions. Therefore macrophages represent an important therapeutic target in both fibrosis and cancer diseases. The current review will illustrate new insights into the role of monocytes/macrophages in these devastating diseases and summarize new therapeutic strategies and applications of macrophage-targeted drug development in their clinical setting.