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Intracellular and extracellular galectin-9 induces STING degradation and promotes suppressive myeloid cell expansion in human tumor-bearing host

ABSTRACT: Galectin-9 (Gal-9) is a versatile immuno-modulatory protein. Its contribution to the expansion of suppressive myeloid cells in human tumors remain to be investigated. For this aim, we used in vitro models bringing together carcinoma cells derived from nasopharyngeal carcinomas (NPC) and CD33+ myeloid precursors. We found that Gal-9 expression in carcinoma cells enhances the generation of HLA-DR-CD33+CD11b+ myeloid-derived suppressor cells (MDSCs) in bystander cells. The underlying mechanisms involve both the intra-cellular and secreted Gal-9. Inside carcinoma cells, Gal-9 up-regulates the expression of a variety of pro-inflammatory cytokines which are critical for MDSC differentiation and recruitment, including IL-1b, IL-6, CCL22, and CX3CL1. This effect is mediated by accelerated degradation of the STING protein resulting from direct interaction of the Gal-9 carbohydrate recognition domain 1 with the STING C-terminus and subsequent enhancement of the TRIMP29-mediated K48-linked ubiquitination of STING. Moreover, we showed that extracellular Gal-9 secreted by carcinoma cells can enter the myeloid cells and trigger the same signaling cascade. Consistently, clinical data from NPC patients show that high concentrations of Gal-9 in tumor cells and plasma samples are associated with shortened disease-free survival. These findings unearth a novel contribution of Gal-9 to the generation of an immunosuppressive microenvironment which favors tumor development.

ORGANISM(S): Homo sapiens

PROVIDER: GSE125942 | GEO | 2020/07/13

REPOSITORIES: GEO

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Project description:Background: In several types of malignancies, especially EBV-associated nasopharyngeal carcinomas, high Galectin-9 (Gal-9) expression is indicative of an aggressive tumor phenotype. The contribution of Gal-9 to the oncogenesis of B-cell lymphomas (BCLs) has not yet been investigated. Methods: The expression of Gal-9, STING, and EBNA1 was measured by immunohistochemical (IHC) staining on tumor sections from 66 BCL patients. Artificial EBV infection of normal primary B cells in vitro was used as an experimental model. The dynamic changes of the transcriptome of EBV-infected B cells undergoing transformation were investigated by bulk RNA-sequencing and bioinformatics analysis. The oncogenic role of Gal-9 was investigated in vitro by addition of recombinant Gal-9 to EBV-infected primary B-cells, and growth assays. The underlying molecular mechanisms were investigated by immunoblotting and immunofluorescent (IF) staining, CHIP and luciferase reporter assays. Results: In clinical specimens of BCLs, Gal-9 expression was significantly associated with tumor stage, latent EBV infection and abundance of the viral latent protein EBNA1. Looking at the transcriptome changes occurring in vitro during EBV-driven B-cell transformation, we could identify a series of genes undergoing long term activation and remaining highly expressed in mature LCLs. The Gal-9 gene is one of them. Its expression is enhanced during the transformation process at the mRNA level and even more at the protein level. This up-regulation results at least in part from its transactivation by EBNA1 which can bind its promoter. Reciprocally, we find that addition of extra-cellular Gal-9 promotes B-cell transformation and establishment of the latent phase of EBV-infection. Concomitantly, extra-cellular Gal-9 blocks STING signaling and enhances STAT3 phosphorylation. Inhibition of Sting signaling or STAT3 phosphorylation blocks B-cell transformation, even in the presence of Gal-9. Conclusion: our data unveil a role of amplification and acceleration for Gal-9 in the process of EBV-driven B-cell transformation. This process might be relevant to the pathogenesis of EBV-associated BCLs.

Project description:Nasopharyngeal carcinoma (NPC) is known for its high metastatic potential. From genomic expression profiles comparing clones derived from the NPC cell line CNE-2, serglycin (SRGN) was identified as one of the most up-regulated genes in the high-metastasis clone. Serglycin protein was secreted by the high-metastasis clone, but not by any of the low-metastasis clones. Suppression of serglycin by shRNA diminished serglycin secretion and subsequently inhibited the migration and invasion of high-metastasis clone, and also reduced its metastasis rate in vivo. Overexpression of serglycin in low-metastasis cells resulted in an increased metastasis rate in vivo. Moreover, secreted serglycin promoted cellular motility in the wild-type low-metastasis cells. Interestingly, suppression of serglycin reduced the protein level of vimentin but did not influence the level of E-cadherin in high-metastasis clone. Proliferation was not influenced by serglycin in both high-and low-metastasis clones. Clinically, serglycin expression was significantly elevated in liver metastases from NPC relative to its expression in primary tumors. The prognostic value of serglycin was evaluated by immunohistochemical staining of tissue microarrays of NPC tissues from 263 patients, followed by multivariate analyses. A high level of serglycin expression in primary NPC was found to be an independent unfavorable indicator for distant-metastasis-free survival and disease-free survival. In summary, serglycin regulates NPC metastasis via autocrine and paracrine means without influencing proliferation, and it serves as a prognostic indicator of metastasis-free survival and disease-free survival for NPC patients. Keywords: Gene Expression experiment High-metastasis clone (S18) and low-metastasis clones (S22 and S26) together with their parental line CNE-2 were subjected for gene expression profiling to identify the genes highly expressed in high-metastasis clone. To explore the molecular mechanism(s) underlying this important biological behavior, we performed genomic expression profiling of these four cell lines from in vitro cultured cells, as well as in vivo xenograft tumors generated in nude mice by subcutaneous injection of the cells into the BALB/c (nu/nu) female mice. Briefly, 1 × 10^5 cells were subcutaneously injected into the left flank of a nude mouse, and the tumors were collected when their volume was 150-250 mm^3.

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Intracellular and extracellular galectin-9 induces STING degradation and promotes suppressive myeloid cell expansion in human tumor-bearing host

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