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Metformin blocks myeloid-derived suppressor cell accumulation through AMPK-DACH1-CXCL1 axis.

ABSTRACT: Purpose: Tumor development has been closely linked to tumor microenvironment, particularly in terms of myeloid-derived suppressive cells (MDSCs), a heterogeneous population of immature myeloid cells that protect tumors from elimination by immune cells. Approaches aimed at blocking MDSC accumulation could improve cancer clinical outcome. Experimental Design: We investigated that metformin suppressed MDSC migration to inhibit cancer progression. Primary tumor tissues were incubated with metformin, and proinflammatory chemokine production was measured. To study MDSC chemotaxis in vivo, BALB/C nude mice were injected subcutaneously with TE7 cells and treated with metformin. Migration of adoptively transferred MDSCs was analyzed using flow cytometry and immunohistochemistry. Results: The frequency of tumor-infiltrated polymorphonuclear (PMN)-MDSCs was increased compared to their circulating counterparts. There was a significant correlation between PMN-MDSCs accumulation in tumors and ESCC prognosis. Moreover, PMN-MDSCs displayed immunosuppressive activity in vitro. Treatment with metformin reduced MDSC migration in patients. Metformin inhibited CXCL1 secretion in ESCC cells and tumor xenografts by enhancing AMPK phosphorylation and inducing DACH1 expression, leading to NF-κB inhibition and reducing MDSC migration. Knockdown of AMPK and DACH1 expression blocked the effect of metformin on MDSC chemotaxis. Conclusions: A novel anti-tumor effect of metformin, which is mediated by reducing PMN-MDSC accumulation in the tumor microenvironment via AMPK/DACH1/CXCL1 axis.

SUBMITTER: Qin G

PROVIDER: S-EPMC5993496 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Metformin blocks myeloid-derived suppressor cell accumulation through AMPK-DACH1-CXCL1 axis.

Qin Guohui G Lian Jingyao J Huang Lan L Zhao Qitai Q Liu Shasha S Zhang Zhen Z Chen Xinfeng X Yue Dongli D Li Lifeng L Li Feng F Wang Lidong L Umansky Viktor V Zhang Bin B Yang Shengli S Zhang Yi Y

Oncoimmunology 20180313 7

<b>Purpose</b>: Tumor development has been closely linked to tumor microenvironment, particularly in terms of myeloid-derived suppressive cells (MDSCs), a heterogeneous population of immature myeloid cells that protect tumors from elimination by immune cells. Approaches aimed at blocking MDSC accumulation could improve cancer clinical outcome. <b>Experimental Design</b>: We investigated that metformin suppressed MDSC migration to inhibit cancer progression. Primary tumor tissues were incubated w ...[more]

PMID: 29900050

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Project description:BackgroundMyeloid-derived suppressor cells (MDSCs) are potent suppressors of immune function and may play a key role in the development and progression of metastatic cancers. Aerobic exercise has been shown to have anticancer effects, yet the mechanisms behind this protection are largely unknown. Therefore, we examined the effects of physical activity on MDSC accumulation and function.MethodsFemale BALB/c mice were assigned to one of two primary groups: sedentary tumor (SED+TUM) or wheel run tumor (WR+TUM). After 6 weeks of voluntary wheel running, all animals were randomly subdivided into 4 different timepoint groups; 16, 20, 24, and 28 days post-tumor injection. All mice were inoculated with 4T1 mammary carcinoma cells in the mammary fat pad and WR groups continued to run for the specified time post-injection. Spleen, blood, and tumor samples were analyzed using flow cytometry to assess proportions of MDSCs.ResultsCells expressing MDSC biomarkers were detected in the spleen, blood, and tumor beginning at d16. However, since there was no evidence of immunosuppressive function until d28, we refer to them as immature myeloid cells (IMCs). Compared to SED+TUM, levels of IMCs in the spleen were significantly lower (p < 0.05) in WR+TUM at day 16 (33.0 ± 5.2%; 23.1 ± 10.2% of total cells, respectively) and day 20 (33.9 ± 8.1%; 24.3 ± 5.1% of total cells, respectively). Additionally, there were fewer circulating IMCs in WR+TUM at day 16 and MDSC levels were significantly lower (p < 0.05) in the tumor at day 28 in WR+TUM. Additionally, a non-significant 62% and 26% reduction in metastatic lung nodules was observed at days 24 and 28, respectively. At day 28, MDSCs harvested from SED+TUM significantly suppressed CD3+CD4+ T cell proliferation (3.2 ± 1.3 proliferation index) while proliferation in WR+TUM MDSC co-cultures (5.1 ± 1.7 proliferation index) was not different from controls.ConclusionsThese findings suggest that physical activity may delay the accumulation of immunosuppressive MDSCs providing a broader window of opportunity for interventions with immunotherapies.

Project description:BackgroundRadiotherapy is commonly used for locoregionally advanced NSCLC, but radioresistance is a clinical challenge. The long non-coding RNA CBR3-AS1 mediates radioresistance in NSCLC, yet the underlying molecular mechanism is unclear. This study aims to explore whether and how N6-methyladenosine (m6A) modification regulates CBR3-AS1 expression and promotes NSCLC radioresistance.MethodsIntegrative bioinformatics analyses were used to investigate the m6A methyltransferases that were associated with CBR3-AS1 expression and radioresistance of patients using data from The Cancer Genome Atlas of lung adenocarcinoma and squamous cell carcinoma. Clinical samples of 133 patients with NSCLC was collected to validate the correlation of the methyltransferase with radioresistance. The functional role and molecular mechanism of the methyltransferase in radioresistance was investigated through a series of in vitro experiments including m6A MeRIP-PCR, lentivirus transfection, RNA immunoprecipitation, Luciferase reporter, Colony formation, Transwell invasion, Flow cytometry, ELISA and TUNEL assay and in vivo experiments.ResultsThe methyltransferase RNA binding motif protein 15 (RBM15) was identified as it was significantly positively correlated with CBR3-AS1 expression and overall survival of NSCLC patients receiving radiotherapy. The clinical samples demonstrated that the high protein expression of RBM15 was significantly enriched in patients with radioresistance as well as associated with poor prognosis of patients receiving radiotherapy. In vitro, RBM15 silencing enhanced the effects of radiation on the growth and invasion inhibition, and apoptosis induction of NSCLC cells; RBM15 overexpression had the opposite effects. Mechanistically, RBM15 induced CBR3-AS1 upregulation via an m6A-IGF2BP3-dependent mechanism, inducing CXCL1 expression by sponging miR-409-3p to recruit myeloid-derived suppressor cells (MDSCs) and inhibit T cell activity. In vivo, RBM15 silencing suppressed MDSC invasiveness and enhanced CD8 + and CD4 + T cell infiltration, causing NSCLC cells to overcome radioresistance.ConclusionOur study identifies methyltransferase RBM15 as a potential therapeutic target for NSCLC radioresistance whose inhibition reverses resistance through limiting MDSC recruitment via the m6A-IGF2BP3-CBR3-AS1/miR-409-3p/CXCL1 axis.

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Metformin blocks myeloid-derived suppressor cell accumulation through AMPK-DACH1-CXCL1 axis.

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Metformin blocks myeloid-derived suppressor cell accumulation through AMPK-DACH1-CXCL1 axis.

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