Epigenetic suppression of SLFN11 in germinal center B-cells during B-cell development

Abstract

Background SLFN11 has recently been reported to execute cancer cells harboring replicative stress induced by DNA damaging agents. However, the roles of SLFN11 under physiological conditions remain poorly understood. Germinal center B-cells (GCBs) undergo somatic hypermutations and class-switch recombination, which can cause physiological genotoxic stress. Hence, we tested whether SLFN11 expression needs to be suppressed in GCBs during B-cell development. Objective To clarify the expression profile of SLFN11 in different developmental stages of B-cells and B-cell-derived cancers. Methods We analyzed the expression of SLFN11 by mining cell line databases for different stages of normal B-cells and various types of B-cell-derived cancer cell lines. We performed dual immunohistochemical staining for SLFN11 and B-cell specific markers in normal human lymphatic tissues. We tested the effects of two epigenetic modifiers, an EZH2 inhibitor, tazemetostat (EPZ6438) and a histone deacetylase inhibitor, panobinostat (LBH589) on SLFN11 expression in GCB-derived lymphoma cell lines. We also examined the therapeutic efficacy of these drugs in combination with cytosine arabinoside and the effects of SLFN11 on the efficacy of cytosine arabinoside in SLFN11-overexpressing cells. Results SLFN11 mRNA level was found low in both normal GCBs and GCB-DLBCL (GCB like-diffuse large B-cell lymphoma). Immunohistochemical staining showed low SLFN11 expression in GCBs and high SLFN11 expression in plasmablasts and plasmacytes. The EZH2 and HDAC epigenetic modifiers upregulated SLFN11 expression in GCB-derived lymphoma cells and made them more susceptible to cytosine arabinoside. SLFN11 overexpression further sensitized GCB-derived lymphoma cells to cytosine arabinoside. Conclusions The expression of SLFN11 is epigenetically suppressed in normal GCBs and GCB-derived lymphomas. GCB-derived lymphomas with low SLFN11 expression can be treated by the combination of epigenetic modifiers and cytosine arabinoside.

Precision Oncology with Drugs Targeting the Replication Stress, ATR, and Schlafen 11

“…This observation is related to the transcriptional regulation of SLFN11 by the ETS (erythroblast transformation specificity) transcription factors, and most notably FLI1 [11,122]. Epigenetic modifications, which are frequent in tumorigenesis and chemoresistance, are responsible for the lack of SLFN11 expression in many cancer cells, resulting in chemoresistance to widely used clinical agents that target DNA replication [11,15,121,[124][125][126]. Accordingly, reactivation of SLFN11 expression by epigenetic drugs targeting DNA methy-lation, histone deacetylase (HDAC), and histone methyltransferase EZH2 (Enhancer of zeste homolog 2) can reverse the chemoresistance of cancer cell lines that do not express SLFN11 (Figure 6A) [121,125,127].…”

“…IHC assessment may therefore need to specify whether the SLFN11-positive cells are cancer cells and/or stromal cells. Indeed, SLFN11 is normally expressed in lymphocytes [ 11 , 126 ]. Moreover, SLFN11 activity is not limited to the nucleus [ 133 , 134 , 135 , 137 , 147 ] and it remains to be determined whether cytosolic IHC staining of SLFN11 should be taken into consideration [ 141 , 148 ].…”

Schlafens: Emerging Proteins in Cancer Cell Biology

“…Interestingly, equine Slfn11 inhibits equine infectious anemia virus production by a similar mechanism [ 54 ]. Moreover, SLFN11 is differentially regulated during B cell maturation, and it is epigenetically suppressed in normal germinal center B cells [ 55 ].…”

Schlafen 11 expression in human acute leukemia cells with gain-of-function mutations in the interferon-JAK signaling pathway

“…SLFN11 expression is suppressed in approximately 50% of cancer cells ( Murai et al., 2019 ), primarily by epigenetic mechanisms including promoter hypermethylation at CpG islands ( Moribe et al., 2021 ; Nogales et al., 2016 ; Reinhold et al., 2017 ), histone deacetylation, and histone methylation by the polycomb repressor complex ( Gardner et al., 2017 ; Tang et al., 2018 ). However, little is known on how SLFN11 expression is activated.…”

“…SLFN11 is also induced in human foreskin fibroblasts treated with IFN-β, poly-IC or poly-dAdT ( Li et al., 2012 ), and recent studies showed that SLFN11 expression is regulated by type Ι IFN-dependent and -independent pathways ( Borrego et al., 2020 ). In addition, SLFN11 sensitizes leukemic HAP1 cells to IFN-γ-mediated T cell killing ( Mezzadra et al., 2019 ) and is epigenetically regulated during B-cell differentiation ( Moribe et al., 2021 ). SLFN11 has therefore been described as an IFN-stimulated gene ( Borrego et al., 2020 ; Katsoulidis et al., 2010 ; Li et al., 2012 ; Mavrommatis et al., 2013 ; Mezzadra et al., 2019 ; Puck et al., 2015 ).…”