Ubiquitin-Specific Protease 6 Functions as a Tumor Suppressor in Ewing Sarcoma through Immune Activation

Abstract

Ewing sarcoma is the second most common pediatric bone cancer, with a 5-year survival rate for metastatic disease of only 20%. Recent work indicates that survival is strongly correlated with high levels of tumor-infiltrating lymphocytes (TIL), whose abundance is associated with IFN-inducible chemokines CXCL10 and CCL5. However, the tumor-intrinsic factors that drive chemokine production and TIL recruitment have not been fully elucidated. We previously showed that ubiquitin-specific protease 6 (USP6) directly deubiquitinates and stabilizes Jak1, thereby inducing an IFN signature in Ewing sarcoma cells. Here, we show that this gene set comprises chemokines associated with immunostimulatory, antitumorigenic functions, including CXCL10 and CCL5. USP6 synergistically enhanced chemokine production in response to exogenous IFN by inducing surface upregulation of IFNAR1 and IFNGR1. USP6-expressing Ewing sarcoma cells stimulated migration of primary human monocytes and T lymphocytes and triggered activation of natural killer (NK) cells in vitro. USP6 inhibited Ewing sarcoma xenograft growth in nude but not NSG mice and was accompanied by increased intratumoral chemokine production and infiltration and activation of NK cells, dendritic cells, and macrophages, consistent with a requirement for innate immune cells in mediating the antitumorigenic effects of USP6. High USP6 expression in patients with Ewing sarcoma was associated with chemokine production, immune infiltration, and improved survival. This work reveals a previously unrecognized tumor-suppressive function for USP6, which engenders an immunostimulatory microenvironment through pleiotropic effects on multiple immune lineages. This further raises the possibility that USP6 activity may be harnessed to create a "hot" tumor microenvironment in immunotherapy.Significance: This study reveals a novel tumor-suppressive function for USP6 by inducing an immunostimulatory microenvironment, suggesting that USP6 activity may be exploited to enhance immunotherapy regimens.

Mutant p53 elicits context-dependent pro-tumorigenic phenotypes

“…To confirm these data, expression of several genes engaged in IFNγ response was assessed. Results of qPCR analysis showed significant induction of several IFN-regulated genes with known tumor suppressive functions [ 36 – 38 ], specifically in LN-R273H cells (Fig. 5C ).…”

“…These data further underscore the differential impact of R273C versus R273H in downstream networks of tumor relevance, which could confer a survival advantage of R273C harboring tumors over R273H. R273C induces pro-tumorigenic gene networks in common with R273H but in the absence of interferon response induction, which can involve multiple intermediates with known tumor suppressive functions [ 36 – 38 ]. Future studies are needed to discern transcriptional impact of these observations and to further understand how distinct p53 mutations drive tumor progression.…”

Ubiquitin-specific protease TRE17/USP6 promotes tumor cell invasion through the regulation of glycoprotein CD147 intracellular trafficking

“…Furthermore, the increase in IFN responses by TRE17 suppresses the tumorigenesis of Ewing sarcoma by increasing the secretion of cytokines from tumor cells, which promotes the infiltration of immune cells (42). It is interesting to note that the enhancement of IFN responses is likely due to the increase of surface IFN receptors.…”

CCL8 as a promising prognostic factor in diffuse large B-cell lymphoma via M2 macrophage interactions: A bioinformatic analysis of the tumor microenvironment

“…The research on 1,242 sarcoma specimens indicated that macrophages outnumbered tumor-infiltrating lymphocytes and M2 macrophages were more prominent than M1 macrophages ( 38 ). In Ewing sarcoma, USP6 induced macrophage chemotaxis by enhancing the production of CXCL10 and CCL5 ( 39 ). We verified the positive correlation of CCL8 expression with M2 macrophages by CIBERSORT analysis of the GSE10846 dataset and online analysis of the TIMER dataset.…”