IRF5 is a novel regulator of CXCL13 expression in breast cancer that regulates CXCR5⁺ B‐ and T‐cell trafficking to tumor‐conditioned media

Abstract

Clinical studies using prognostic and predictive signatures have shown that an immune signal emanating from whole tumors reflects the level of immune cell infiltration--a high immune signal linked to improved outcome. Factors regulating immune cell trafficking to the tumor, however, are not known. Previous work has shown that expression of interferon regulatory factor 5 (IRF5), a critical immune regulator, is lost in ~80% of invasive ductal carcinomas examined. We postulated that IRF5-positive and -negative breast tumors would differentially regulate immune cell trafficking to the tumor. Using a focused tumor inflammatory array, differences in cytokine and chemokine expression were examined between IRF5-positive and -negative MDA-MB-231 cells grown in three-dimensional culture. A number of cytokines/chemokines were found to be dysregulated between cultures. CXCL13 was identified as a direct target of IRF5 resulting in the enhanced recruitment of B and T cells to IRF5-positive tumor-conditioned media. The ability of IRF5 to regulate mediators of cell migration was confirmed by enzyme-linked immunosorbent assay, chromatin immunoprecipitation assay, small interfering RNA knockdown and immunofluorescence staining of human breast tumor tissues. Analysis of primary immune cell subsets revealed that IRF5 specifically recruits CXCR5(+) B and T cells to the tumor; CXCR5 is the receptor for CXCL13. Analysis of primary breast tumor tissues revealed a significant correlation between IRF5 and CXCL13 expression providing clinical relevance to the study. Together, these data support that IRF5 directly regulates a network of genes that shapes a tumor immune response and may, in combination with CXCL13, serve as a novel prognostic marker for antitumor immunity.

Role of Tertiary Lymphoid Structures (TLS) in Anti-Tumor Immunity: Potential Tumor-Induced Cytokines/Chemokines that Regulate TLS Formation in Epithelial-Derived Cancers

“…found that the CD4 + T cell infiltrates were most responsible for CXCL13 expression [39]. Data from our lab suggests that the tumor is in fact capable of producing CXCL13 in some cases [57]. This may be in agreement with Gu-Tratien et al .…”

IRF5: a rheostat for tumor‐infiltrating lymphocyte trafficking in breast cancer?

“…In this issue of Immunology and Cell Biology , Pimenta et al 5 show that IRF5 is a novel and direct regulator of CXCL13 expression in mammary epithelial tumor cells. Exogenous expression of IRF5 in breast tumor cell lines lacking endogenous IRF5 induced the production and secretion of numerous cytokines and chemokines, including CXCL13, known to have important roles in the recruitment of specific immune cells to the tumor site.…”

“…Moreover, mice inoculated with human BC cell lines, expressing IRF5 or not, support the ability of this transcription factor to inhibit in vivo tumor formation and in vitro metastasis/ invasion. Together, these data suggest that IRF5 acts as a tumor suppressor gene in BC with its regulation of pro-and antiinflammatory cytokine/chemokine expression helping to modify the tumor immune microenvironment.In this issue of Immunology and Cell Biology, Pimenta et al 5 show that IRF5 is a novel and direct regulator of CXCL13 expression in mammary epithelial tumor cells. Exogenous expression of IRF5 in breast tumor cell lines lacking endogenous IRF5 induced the production and secretion of numerous cytokines and chemokines, including CXCL13, known to have important roles in the recruitment of specific immune cells to the tumor site.…”

IRF5 is increased in labouring myometrium and regulates pro-labour mediators

“…In keeping with this, IRF5-knockout mice are resistant to lethal shock induced by TLR ligands (Takaoka et al 2005), accumulate fewer neutrophils at the site of inflammation due to the reduced levels of chemokines (Xu et al 2012, Weiss et al 2015 and show reductions in serum and or tissue levels of inflammatory cytokines (Paun et al 2008, Feng et al 2012, Duffau et al 2015, Oriss et al 2017. Moreover, myeloid deficiency of IRF5 protects mice from liver fibrosis and alters hepatic macrophage transcriptome response to experimental fibrosis (Alzaid et al 2016) while cells derived from IRF5-knockout mice produce lower levels of proinflammatory cytokines and or chemokines in response to TLR ligands (Tada et al 2011, Duffau et al 2015, Weiss et al 2015. Notably, ChIP seq studies have shown that IRF5 regulates many inflammatory genes in cooperation with the RELA subunit of NF-κB (Saliba et al 2014) while IRF5 knockdown suppresses RELA activation in human monocyte-derived cells (Hedl & Abraham 2012).…”

“…In vitro gene knockout or overexpression studies have demonstrated an essential role of IRF5 in the production of pro-inflammatory cytokines in response to numerous pathogens and TLR ligands (Takaoka et al 2005, Krausgruber et al 2010, Hedl & Abraham 2012, Ren et al 2014. In keeping with this, IRF5-knockout mice are resistant to lethal shock induced by TLR ligands (Takaoka et al 2005), accumulate fewer neutrophils at the site of inflammation due to the reduced levels of chemokines (Xu et al 2012, Weiss et al 2015 and show reductions in serum and or tissue levels of inflammatory cytokines (Paun et al 2008, Feng et al 2012, Duffau et al 2015, Oriss et al 2017. Moreover, myeloid deficiency of IRF5 protects mice from liver fibrosis and alters hepatic macrophage transcriptome response to experimental fibrosis (Alzaid et al 2016) while cells derived from IRF5-knockout mice produce lower levels of proinflammatory cytokines and or chemokines in response to TLR ligands (Tada et al 2011, Duffau et al 2015, Weiss et al 2015.…”