Ikaros Function Research Articles

Transcriptional function of E2A, Ebf1, Pax5, Ikaros and Aiolos analyzed by in vivo acute protein degradation in early B cell development.

Early B cell lymphopoiesis depends on E2A, Ebf1, Pax5 and Ikaros family members. In the present study, we used acute protein degradation in mice to identify direct target genes of these transcription factors in pro-B, small pre-B and immature B cells. E2A, Ebf1 and Pax5 predominantly function as transcriptional activators by inducing open chromatin at their target genes, have largely unique functions and are essential for early B cell maintenance. Ikaros and Aiolos act as dedicated repressors to cooperatively control early B cell development. The surrogate light-chain genes Igll1 and Vpreb1 are directly activated by Ebf1 and Pax5 in pro-B cells and directly repressed by Ikaros and Aiolos in small pre-B cells. Pax5 and E2A contribute to V(D)J recombination by activating Rag1, Rag2, Dntt, Irf4 and Irf8. Similar to Pax5, Ebf1 also represses the cohesin-release factor gene Wapl to mediate prolonged loop extrusion across the Igh locus. In summary, in vivo protein degradation has provided unprecedented insight into the control of early B cell lymphopoiesis by five transcription factors.

Ikaros sets the threshold for negative B-cell selection by regulation of the signaling strength of the AKT pathway

Inhibitory phosphatases, such as the inositol-5-phosphatase SHIP1 could potentially contribute to B-cell acute lymphoblastic leukemia (B-ALL) by raising the threshold for activation of the autoimmunity checkpoint, allowing malignant cells with strong oncogenic B-cell receptor signaling to escape negative selection. Here, we show that SHIP1 is differentially expressed across B-ALL subtypes and that high versus low SHIP1 expression is associated with specific B-ALL subgroups. In particular, we found high SHIP1 expression in both, Philadelphia chromosome (Ph)-positive and ETV6-RUNX1-rearranged B-ALL cells. As demonstrated by targeted knockdown of SHIP1 by RNA interference, proliferation of B-ALL cells in vitro and their tumorigenic spread in vivo depended in part on SHIP1 expression. We investigated the regulation of SHIP1, as an important antagonist of the AKT signaling pathway, by the B-cell-specific transcription factor Ikaros. Targeted restoration of Ikaros and pharmacological inhibition of the antagonistic casein kinase 2, led to a strong reduction in SHIP1 expression and at the same time to a significant inhibition of AKT activation and cell growth. Importantly, the tumor suppressive function of Ikaros was enhanced by a SHIP1-dependent additive effect. Furthermore, our study shows that all three AKT isoforms contribute to the pro-mitogenic and anti-apoptotic signaling in B-ALL cells. Conversely, hyperactivation of a single AKT isoform is sufficient to induce negative selection by increased oxidative stress. In summary, our study demonstrates the regulatory function of Ikaros on SHIP1 expression in B-ALL and highlights the relevance of sustained SHIP1 expression to prevent cells with hyperactivated PI3K/AKT/mTOR signaling from undergoing negative selection.

Foxp3 depends on Ikaros for control of regulatory T cell gene expression and function

Ikaros is a transcriptional factor required for conventional T cell development, differentiation, and anergy. While the related factors Helios and Eos have defined roles in regulatory T cells (Treg), a role for Ikaros has not been established. To determine the function of Ikaros in the Treg lineage, we generated mice with Treg-specific deletion of the Ikaros gene (Ikzf1). We find that Ikaros cooperates with Foxp3 to establish a major portion of the Treg epigenome and transcriptome. Ikaros-deficient Treg exhibit Th1-like gene expression with abnormal production of IL-2, IFNg, TNFa, and factors involved in Wnt and Notch signaling. While Ikzf1-Treg-cko mice do not develop spontaneous autoimmunity, Ikaros-deficient Treg are unable to control conventional T cell-mediated immune pathology in response to TCR and inflammatory stimuli in models of IBD and organ transplantation. These studies establish Ikaros as a core factor required in Treg for tolerance and the control of inflammatory immune responses.

Foxp3 depends on Ikaros for control of regulatory T cell gene expression and function.

Ikaros is a transcriptional factor required for conventional T cell development, differentiation, and anergy. While the related factors Helios and Eos have defined roles in regulatory T cells (Treg), a role for Ikaros has not been established. To determine the function of Ikaros in the Treg lineage, we generated mice with Treg-specific deletion of the Ikaros gene (Ikzf1). We find that Ikaros cooperates with Foxp3 to establish a major portion of the Treg epigenome and transcriptome. Ikaros-deficient Treg exhibit Th1-like gene expression with abnormal production of IL-2, IFNg, TNFa, and factors involved in Wnt and Notch signaling. While Ikzf1-Treg-cko mice do not develop spontaneous autoimmunity, Ikaros-deficient Treg are unable to control conventional T cell-mediated immune pathology in response to TCR and inflammatory stimuli in models of IBD and organ transplantation. These studies establish Ikaros as a core factor required in Treg for tolerance and the control of inflammatory immune responses.

Abstract 5117: CK2 inhibiton exhibits synergistic effect in acute lymphoblastic leukemia

Abstract Survival for pre-B cell Acute lymphoblastic leukemia (B ALL) has improved greatly, however. High risk (HR) subgroups continue to result in significant mortality and morbidity of pediatric oncology patients. Pediatric T-cell acute lymphoblastic leukemia (T-ALL) is a lethal disease, often associated with high-risk clinical features. T-ALL therapy has made less improvement than B ALL and continues to represent a significant number of high-risk outcomes. Novel treatment strategies are required to overcome chemotherapy resistance and improve morbidity for HR B ALL. The development of treatments that can overcome chemotherapy resistance is essential for improving survival in T-ALL. Deletions of IKZF1, resulting in decreased IKAROS function, are present in High-risk ALL patients. Casein kinase 2 (CK2), a protein kinase upregulated in ALL, phosphorylates IKAROS preventing DNA binding reducing transcriptional regulation in ALL patients. Past studies have shown that pharmacologic inhibition of CK2 with CX-4945 rescues IKAROS function as a transcriptional regulator. Receptor tyrosine kinase c-KIT is transcriptionally regulated by IKAROS and is often upregulated in cancer. The purpose of this study was to determine whether restoration of IKAROS via CX-4945 would act in a synergistic manner with c-KIT inhibitor imatinib in ALL.Methods/results B-ALL Nalm6 cells were treated with imatinib over 72-hours to establish the half-maximal inhibitory concentration (IC50). The IC50 was used to determine the concentration range of imatinib to be used in combination with CX-4945 in a 72-hour synergy analysis of cytotoxicity.. Cell viability was measured using WST-1 cell proliferation assay. The data were analyzed using Calcusyn and synergy was defined as a combination index below 0.85. The study was repeated to determine a more precise range of synergy. The cytotoxicity of single drug c-KIT inhibitor, Imatinib, in Nalm6 B-ALL yielded an IC50 of 25uM while CK2 inhibitor CX-4945 resulted in 4uM. When a combination was administered with a constant dose of CX-4945 at 4uM and varying concentrations of imatinib, synergy was observed at multiple dose combinations. Conclusion: The data shows that CK2 inhibitor, CX-4945, and c-KIT inhibitor, imatinib, exhibit a synergistic therapeutic effect. Imatinib is indicated for use in Philadelphia positive (Ph+) acute lymphoblastic leukemia so future studies will include testing CX-4945/imatinib synergy in Ph+ BALL where we expect to see more potent synergistic effect. Citation Format: Daniel Gary Bogush, Joseph Schramm, Katarina Dovat, Yali Ding, Chingakham Singh, Sinisa Dovat. CK2 inhibiton exhibits synergistic effect in acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5117.

Abstract 3271: The casein kinase 2/IKZF1 axis attenuates ceramide accumulation through up-regulation of acid ceramidase: Implications for use of CK2 inhibitors in high-risk pediatric B-cell acute lymphoid leukemia

Abstract Casein Kinase II (CK2), a growth-promoting non-oncogene, is frequently over-expressed in pediatric high-risk B-cell acute lymphoblastic leukemia (B-ALL) leading to proliferation and survival. CK2 phosphorylates the tumor suppressor IKZF1 (IKAROS) resulting in a loss-of DNA-binding activity. Loss of IKZF1 function is associated with poor prognosis in high-risk B-ALL. As such, inhibition of CK2 using silmitasertib (CX-4945), to restore IKZF1 function, is being therapeutically investigated in high-risk B-ALL. CK2 also phosphorylates/activates the mammalian ceramide synthases to increase production of the pro-apoptotic sphingolipid, ceramide (Cer). Therefore, we hypothesized that inhibition of CK2 with CX-4945 would exert both pro-death (restoration of IKAROS function) and pro-survival (decreased Cer production) effects on B-ALL cells. Moreover, this suggests that targeting the sphingolipid metabolic pathway in tandem with CX-4945 could be a novel strategy for treatment of high-risk B-ALL. To this end, we examined the effects of CX-4945 on sphingolipid levels and the enzymes of the sphingolipid metabolic pathway. Unexpectedly, we determined that CX-4945 dose-dependently increased expression of ceramide synthase 1 (CERS1) and acid ceramidase (AC) proteins, in an IKZF1 dependent manner. Increased CERS1 expression/production of C18:0 Cer has been linked to enhanced mitophagy (i.e., lysosomal clearance of damaged mitochondria) in head and neck squamous cell carcinoma. Induction of mitophagy by CX-4945 was confirmed by western blot analysis of mitofusin-1 and Drp-1 levels. Up-regulation of AC, a lysosomal protein, metabolizes C18:0 Cer to sphingosine for recycling and prevents Cer-induced lysosomal membrane permeabilization. Thus, induction of mitophagy and metabolic breakdown of Cer could potentially reduce the apoptotic efficacy of CX-4945 in B-ALL cell lines. We, therefore, tested whether inhibition of AC would synergize with CX-4945 to enhance B-ALL cell death. Indeed, synergy was observed with the AC inhibitor, SACLAC, in multiple cell lines. Consistent with the observation of synergy between CX-4945 and SACLAC, the combination also enhanced cleavage of PARP indicating an enhancement of cell death. We are currently testing the efficacy of a combination of CX-4945 and AC inhibitors in cell-line derived xenograft models of human B-ALL. Together, these findings indicate that simultaneous targeting of CK2 and AC represents a rationally selected combinatorial therapeutic strategy that overcomes the ability of cancer cells to adapt to single agent targeted therapies by altering pro- and/or anti-apoptotic pathways. Citation Format: Jeremy A. Hengst, Diwakar Bastihalli Tukaramrao, Todd Fox, Arati Sharma, Dhimant Desai, Sinisa Dovat. The casein kinase 2/IKZF1 axis attenuates ceramide accumulation through up-regulation of acid ceramidase: Implications for use of CK2 inhibitors in high-risk pediatric B-cell acute lymphoid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3271.

IKZF1 Alterations and Therapeutic Targeting in B-Cell Acute Lymphoblastic Leukemia.

IKZF1 encodes the transcription factor IKAROS, a zinc finger DNA-binding protein with a key role in lymphoid lineage development. IKAROS plays a critical role in the development of lineage-restricted mature lymphocytes. Deletions within IKZF1 in B-cell acute lymphoblastic leukemia (B-ALL) lead to a loss of normal IKAROS function, conferring leukemic stem cell properties, including self-renewal and subsequent uncontrolled growth. IKZF1 deletions are associated with treatment resistance and inferior outcomes. Early identification of IKZF1 deletions in B-ALL may inform the intensification of therapy and other potential treatment strategies to improve outcomes in this high-risk leukemia.

Dual Targeting Novel WDR5/ATAD2 Oncogenic Signaling through CK2/Ikaros Axis Demonstrates Synergistic Efficacy in T-ALL

Background WD repeat-containing protein 5 (WDR5) is highly expressed in human cancers and its high expression is linked with adverse prognoses. However, the oncogenic roles of WDR5 and underlying mechanisms are undefined in T-cell acute lymphoblastic leukemia (T-ALL). Casein Kinase II (CK2) is a pro-oncogene, and CK2-mediated IKAROS dysfunction plays critical roles in high-risk ALL, and CK2 inhibitor CX-4945 has the anti-leukemic effect by restoring IKAROS function. This study aims to explore the synergistic anti-leukemic efficacy of dual targeting novel WDR5/ATAD2 oncogenic signaling via the CK2/IKAROS axis in T-ALL. Methods Clinical samples from 38 T-ALL patients and 32 healthy controls were obtained from Zhongda Hospital Southeast University. The expression of WDR5 and ATAD2 were tested by q-PCR and Western blot. RNA-seq was performed after CEM cells were treated with WDR5 inhibitor (OICR-9429), CX-4945 and vehicle control for 72 hours. The human leukemia xenograft mouse model is established by intravenously injected with WDR5 knockdown CEM (CEM-shWDR5) cells and shRNA control (CEM-shNC) into NSG mice. Mice were treated for 25 days in 4 groups [CEM-shNC + vehicle, CEM-sh WDR5 + vehicle; CEM-shNC + CX-4945 (100 mg/kg via gavage), CEM-sh WDR5 + CX-4945]. Leukemia burden in mice spleen and bone marrow was analyzed by flow cytometry. The survival of mice was compared by the Kaplan-Meier method. The synergistic effect of CX-4945 and OICR-9429 was analyzed by CCK8 assay. This study was approved by the Ethics Committee of Zhongda Hospital Southeast University Results WDR5 ishighly expressed in T-ALL patients compared with normal controls( P<0.001) and is higher in the relapsed samples than paired newly-diagnosed controls ( P<0.05) (Fig. 1A-B). WDR5 knockdown in T-ALL cells significantly suppressed cell proliferation and induced cell cycle arrest in vitro ( P<0.01) (Fig. 1C), and in vivo leukemia development (Fig. 1D). Also, WDR5 inhibitor OICR-9429 induces cell proliferation and cell cycle arrest in the cells. RNA-seq revealed that ATAD2 is downregulated upon OICR-9429 treatment and indicated that ATAD2 is the downstream target of WDR5. WDR5 knockdown suppresses ATAD2 expression ( P<0.01) (Fig. 1E). In addition, ATAD2 ishighly expressed in T-ALL patients versus normal controls ( P<0.05) (Fig. 1F), and ATAD2 silencing significantly suppresses cell proliferation and induces cell cycle arrest of T-ALL cells ( P<0.01) (Fig. 1G). These data indicate WDR5/ATAD2 signaling act as a novel potential oncogenic pathway in T-ALL. Furthermore, we found that IKAROS transcriptionally suppresses WDR5 expression, and CK2-mediated hyperphosphorylation of IKAROS is one of the major mechanisms of IKAROS dysfunction in ALL. CX-4945 strongly suppresses WDR5 expression in an IKAROS-dependent manner (Fig. 1H-J). The synergistic effect of CX-4945 with WDR5 disruption on cell proliferation suppression and cell cycle arrest was observed in T-ALL both in in vitro and in vivo xenograft mouse model. The combination of CX-4945 with WDR5 disruption significantly prolonged the survival of mice compared with single CX-4945 [55(52-58) days vs. 38.5(36-41) days， P<0.001] and single WDR5 disruption control [55(52-58) days vs. 41.5(39-44) days, P<0.001] (Fig. 1K). Consistently, the combination significantly reduces the size and weight of the spleen (Fig. 1L), % human CD45+ T-ALL cells in the spleen (Fig. 1M) and bone marrow (data not shown), and the expression of WDR5 and ATAD2 in the spleen versus single treatment controls ( P<0.01) (Fig. 1N-P). Finally, a synergistic effect of CX-4945 with OICR-9429 on cell proliferation suppression and down-regulation of WDR5 and ATAD2 was observed in the primary leukemic cells from T-ALL patients (Fig. 2A-D). Together, these data indicated the synergistic efficacy of CX-4945 with OICR-9429 on T-ALL and the novel model was summarized in Fig.2E. Conclusion In this study, we identified a novel WDR5/ATAD2 oncogenic signaling regulated by CK2/IKAROS axis in T-ALL. Our study reveals a model that dual targeting WDR5/ATAD2 signaling through direct inhibiting oncoproteins and via CK2/IKAROS axis to transcriptionally repress the oncoprotein to achieve synergistic efficacy. Our results further highlight the combination of CX-4945 with WDR5 inhibition is a potential option for the therapy of T-ALL patients.

Suppressing IKZF1 Deletion-Mediated Activation of Ras Oncogenic Signaling By the Combination of Azacitidine and Flumatinib in High-Risk B-ALL

Background IKZF1 deletion is frequently observed in Ph + acute lymphoblastic leukemia (Ph + ALL), which results in poor prognosis and affects clinical efficacy, and possible resistance to tyrosine kinase inhibitors (TKIs). Ikaros transcriptionally regulates the gene expression of multiple oncogenic pathways including Ras/MAPK signaling. However, it is undefined about the role of IKZF1 genetic defects in the activation of Ras/MAPK signaling and their relations with the efficacy of therapeutic drugs in ALL. This study is to investigate the sensitivity of IKZF1-deletion-mediated activation of RAS signaling to the new combined therapy of TKI Flumatinib (FLU) and the Azacitidine (AZA) in B-ALL cells. Methods The patients' samples were obtained from Zhongda Hospital Southeast University with the approval of the institute's Ethics Committee. The gene expression was tested by qPCR or Western blot. CCK8 Cell proliferation, PI staining cell cycle analysis, and apoptosis assay (Annexin V-FITC/ PI staining) were performed in SUP-B15, the Ph + ALL cells with IKZF1 deletion treated with DMSO control, FLU only, AZA only, and FLU+AZA. The overlapped differential expression genes (DEGs）with the pathways (GO term, KEGG) analysis and gene interaction networks were achieved in the potential oncogenic genes in ALL through databases (OMIM, TTD, and GeneCards), and drug targets over that of SwissTargetPrediction, SuperPred, and SEA. Results AZA or FLU treatment induced the cell proliferation arrest of SUP-B15 cells in a dose-/time-dependent manner (Fig. 1A). The combination of IC50 AZA with various doses of FLU significantly enhanced the effect on cell proliferation arrest versus single-drug controls, and CalcuSyn analysis demonstrated their synergistic effect in the cells (Fig. 1B). Also, the combination significantly increased the G0/G1 phase arrest (Fig. 1C, D), and % of apoptotic cells (Fig. 1E, F) versus the single-drug controls. Consistently, the combination up-regulated the mRNA and protein levels of P53, BAX, and P21, but decreased the MDM2, BCL2, and CyclinE (Fig. 1G, H). A total of 118 overlapped DEGs were identified between the potential oncogenes in ALL and FLU-/AZA-associated genes, and they predominantly enriched in Ras/MAPK oncogenic pathways, in which PTPN11 is at the top of the pathways. Indeed, the combination significantly decreased the mRNA and protein levels of PTPN11 (Fig. 2A, B). PTPN11 is significantly higher expressed in 20 newly-diagnosed Ph +ALL patients versus 20 healthy bone marrow control (Fig. 2C), and it was validated in the GSE13159 dataset (Fig. 2D). PTPN11 high expression is significantly associated with lower overall survival and relapse-free survival compared to that of low expression in our cohorts (Fig. 2E). These data together indicate the combination exerts anti-tumor effect by suppressing RAS/MAPK signaling through down-regulation of PTPN11, and also PTPN11 promotes Ras activation in Ph + B-ALL. Moreover, about 80% of Ph +B-ALL patients have the IKZF1 deletion, our ChIP-seq data showed that IKZF1-encoded Ikaros protein binds to the promoter region of PTPN11 and CK2 inhibitor CX4945 as Ikaros function activator dramatically increase the Ikaros binding to the promoter of PTPN11 in B-ALL cells and Ikaros directly suppresses its promoter activity (Fig. 2F, G). We have reported that CX4945 demonstrated therapeutic efficacy for high-risk B-ALL by restoring Ikaros' function. Here, we observed that pre-treatment of SUP-B15 cells significantly increases the effect of AZA+FLU combination on cell proliferation arrest, and cell cycle arrest (Fig. 2H, I). Taken together, these results reveal a model that IKZF1 deletion-mediated Ras/MAPK activation via PTPN11 has the oncogenic role in Ph + B-ALL and the combination of AZA+FLU exerts the anti-tumor effect by targeting Ikaros/PTPN11/Ras oncogenic signaling. The model is summarized in (Fig. 2J). Conclusions The combination of AZA and FLU has a synergistic anti-leukemia effect on cell proliferation arrest and apoptosis in Ph +ALL cells with IKZF1-deletion by targeting Ikaros/PTPN11/Ras oncogenic signaling. Our data provide experimental evidence for a new potential combination of AZA with FLU in the therapy of Ph +ALL and highlight the likelihood of the novel combination in ALL patients.

Impaired tissue homing by the Ikzf3N159S variant is mediated by interfering with Ikaros function.

AIOLOS, encoded by IKZF3, is a member of the IKZF family of proteins that plays an important role in regulating late B-cell differentiation. Human individuals heterozygous for the AIOLOS p.N160S variant displayed impaired humoral immune responses as well as impaired B and T cell development. We have previously reported that a mouse strain harboring an Ikzf3N159S allele that corresponds to human IKZF3N160S recapitulated immune-deficient phenotypes, such as impaired B cell development and loss of CD23 expression. In this study, we investigated the effect of the Ikzf3N159S variant and found that B1a cell development was impaired in Ikzf3N159S/N159S mice. In addition, CD62L expression was severely decreased in both B and T lymphocytes by the Ikzf3N159S mutation, in a dose-dependent manner. Mixed bone marrow chimera experiments have revealed that most immunodeficient phenotypes, including low CD62L expression, occur in intrinsic cells. Interestingly, while Ikzf3N159S/N159S lymphocytes were still present in the spleen, they were completely outcompeted by control cells in the lymph nodes, suggesting that the capacity for homing or retention in the lymph nodes was lost due to the Ikzf3N159S mutation. The homing assay confirmed severely decreased homing abilities to lymph nodes of Ikzf3N159S/N159S B and T lymphocytes but selective enrichment of CD62L expressing Ikzf3N159S/N159S lymphocytes in lymph nodes. This finding suggests that impaired CD62L expression is the major reason for the impaired homing capacity caused by the Ikzf3N159S mutation. Interestingly, an excess amount of Ikaros, but not Aiolos, restored CD62L expression in Ikzf3N159S/N159S B cells. Together with the loss of CD62L expression due to Ikaros deficiency, the AiolosN159S mutant protein likely interferes with Ikaros function through heterodimerization, at least in activating the Sell gene encoding CD62L expression. Thus, our results revealed that AiolosN159S causes some immunodeficient phenotypes via the pathogenesis referred to as the heterodimeric interference as observed for AiolosG158R variant.

Abstract A088: Targeting endoplasmic reticulum stress-induced apoptosis to reduce health disparity in high-risk B-cell acute lymphoblastic leukemia in Hispanic/Latino children

Abstract B-cell Acute Lymphoblastic Leukemia (ALL) is the most common childhood malignancy. The death rate from B-ALL in Hispanic/Latino (H/L) is 40% higher than in non-Hispanic whites (NHW) after correcting socioeconomic factors. Deletion of one IKZF1 allele is highly increased H/L children, which provides a biological rationale for the worse prognosis of B-ALL in this population. The very high incidence (31% in all children and 65% in children ≥10 yrs) makes the deletion of one IKZF1 allele the most frequent genetic alteration that confers adverse prognosis in B-ALL in H/L children. The IKZF1 gene encodes a DNA-binding protein, IKAROS, which functions as a transcriptional regulator. Identification of IKAROS target genes in B-ALL of H/L children is essential to understand the specificity of B-ALL pathogenesis in those children and develop the targeted treatment to reduce the health disparity in survival for H/L children with B-ALL. Global DNA-binding analysis of primary B-ALL cells from H/L children showed that IKAROS binds to the promoter of eukaryotic elongation factor 2 kinase (eEF2K). eEF2K regulates protein synthesis, cell cycle progression and malignant transformation. The activity of eEF2K is increased in human malignancies, including B-ALL, and eEF2K is a critical regulator of endoplasmic reticulum (ER) stress-induced autophagy and apoptosis in tumor cells. The role of IKAROS in the regulation of eEF2K expression in B-ALL of H/L children was established using gain-of-function and loss-of-function experiments. Overexpression of IKZF1 in H/L B-ALL cells results in reduced expression of eEF2K, while IKZF1 knock-down results in increased transcription of eEF2K in H/L B-ALL. Since IKAROS function in leukemia is regulated by pro-oncogenic Casein Kinase 2 (CK2), we tested whether CK2 can control the ability of IKAROS to regulate the expression of eEF2K in H/L B-ALL. Increased expression of CK2 in H/L B-ALL results in increased expression of the eEF2K gene due to the loss of IKAROS binding to the promoter of the eEF2K genes. Inhibition of CK2 with shRNA and/or a specific CK2 inhibitor, CX-4945, restores IKAROS binding to promoter of eEF2K in high-risk B-ALL with deletion of one IKZF1 allele in H/L children. Restoration of IKAROS binding to promoter of eEF2K in high-risk B-ALL in H/L children results in reduced expression of this gene. This was associated with increased sensitivity to Akt inhibition by MK-2206. Combination treatment with CK2 inhibitor and MK-2206 showed a synergistic effect on B-ALL cells from H/L children. In summary, presented data demonstrate that IKAROS and CK2 regulate ER stress-induced apoptosis via regulation of eEF2K expression in high-risk B-ALL in Hispanic/Latino children. Results suggest that targeting ER stress-induced apoptosis in combination with CK2 inhibitors can be an efficient treatment to reduce the health disparity in survival for Hispanic/Latino children with B-ALL. Citation Format: Sinisa Dovat, Yali Ding, Dhimant Desai, Arati Sharma. Targeting endoplasmic reticulum stress-induced apoptosis to reduce health disparity in high-risk B-cell acute lymphoblastic leukemia in Hispanic/Latino children [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr A088.

Better Prognosis of Dominant-Negative Type of IKZF1 Deletion in BCR-ABL-positive Adult B-Cell Acute Lymphoblastic Leukemia

IntroductionIKZF1 codes Ikaros, which is a member of a family of zinc finger proteins that is required for normal lymphopoiesis. IKZF1 alterations in cases of B-cell acute lymphoblastic leukemia (B-ALL) were mainly analyzed in a pediatric cohort and showed an association with poor prognosis. In adults IKZF1 alterations are found in approximately 50% of B-ALL cases, and 65% of cases with BCR-ABL-positive B-ALL. IKZF1 deletion have several different types of deletions. Deletion of exons 4 to 7 (Δ4-7) leads to nonfunctional isoforms that do not bind DNA. However, they can still dimerize with residual normal isoforms, suppressing the function of the normal Ikaros protein expressed from the nondeleted allele, a so-called "dominant-negative” (DN) effect. Other deletions lead to loss of function (LOF) of Ikaros. The impact of DN and LOF type of IKZF1 deletion on prognosis in adult B-ALL patients has not been elucidated. We evaluated the impacts of IKZF1 deletion types on overall survival (OS) in our cohort. Patients and Methods Hokkaido Leukemia Net (HLN) is prospective cohort study collecting acute leukemia samples from hospitals of North Japan Hematology Study Group (NJHSG) covering Hokkaido, the northernmost island of Japan. In this study, we focused on newly diagnosed adult B-ALL patients. Bone marrow or peripheral blood samples from newly diagnosed B-ALL patients were screened by a fluorescence in situ hybridization (FISH) probe for detecting IKZF1 deletion (Hashiguchi J. J Mol Diagn. 2018). Then DNA specimens from IKZF1 deletion-positive patients were screened for the 4 most common intragenic IKZF1 deletions, Δ4-7, Δ2-7, Δ2-8 and Δ4-8, by polymerase chain reaction (PCR). Samples in which IKZF1 deletion was detected by FISH but in which the types of deletions were not identified were defined as "other". We categorized the patients into a DN group that had Δ4-7, LOF and other group, and wildtype (WT) group based on the types of IKZF1 deletion. This study was conducted in accordance with the Helsinki Declaration and was approved by the institutional review boards. Results Overall, 116 patients with newly diagnosed B-ALL were enrolled in HLN between August 2014 and December 2021 (age range, 17-90 years; median age ,59 years; 55 males and 61 females; 60 BCR-ABL-positive patients and 56 BCR-ABL-negative patients). IKZF1 deletion was detected in 53 cases including 6 cases with bi-allelic deletion. IKZF1 deletions were detected in 68.3% of BCR-ABL-positive B-ALL cases and 21.4% of BCR-ABL-negative B-ALL cases. DN/LOF and other ratio was larger in BCR-ABL-positive B-ALL cases than in BCR-ABL-negative B-ALL cases (20/21 vs 3/9). In patients with BCR-ABL-positive B-ALL, patients with the DN type of IKZF1 deletion had a significantly longer OS than that in the WT group. The 3-year OS rates in the DN, LOF and other, and WT groups were 100%, 60.4%, and 49.9%, respectively (Figure A). Distribution of age, sex, percentage of allogenic hematopoietic stem cell transplantation (allo-HSCT) were not significantly different between the three groups. Survival was analysed by univariate analysis including age, sex, WBC counts, complex karyotype, IKZF1 deletion type and allo-HSCT. Age≥65 was associated with poor OS (P=0.0078) and DN type of IKZF1 deletion was associated with favorable OS (P=0.026). Multivariate analysis showed that older age and DN type of IKZF1 deletion were independently associated with OS (age≥65: HR, 3.510; 95% CI, 1.327 to 9.289, P=0.011; DN type of IKZF1 deletion: HR, 0.200; 95% CI, 0.046 to 0.884, P=0.034; Cox regression). In patients with BCR-ABL-negative B-ALL, there was no statistically significant difference in OS between the three groups, whereas the LOF and other group showed a dismal prognosis. The 3-year OS rates in the DN, LOF and other, and WT groups were 100%, 0%, and 56.5%, respectively (Figure B). Conclusion The prognostic impact of IKZF1 deletion might differ in BCR-ABL-positive and BCR-ABL-negative B-ALL cases and might also depend on the type of deletion. DN type of IKZF1 deletion is independently associated with favorable prognosis in adult BCR-ABL-positive B-ALL patients. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Abstract 846: Transcriptional regulation of Aurora-B kinase expression in B-cell acute lymphoblastic leukemia (B-ALL)

Abstract The Aurora kinases are serine/threonine kinases that are essential for mitosis. Aurora-B kinase is a component of the chromosomal passenger complex (CPC), chromosome condensation, the spindle-assembly checkpoint, and for cytokinesis. The activity of Aurora-B is essential for cellular division and proliferation. Inhibition of Aurora-B is cytotoxic, and inhibitor of Aurora-B - Barasertib (AZD1152) has been tested in clinical trials against different types of malignancies, including leukemia. However, regulation of Aurora-B expression is still largely unknown. Here, we present evidence that expression of Aurora-B in B-cell acute lymphoblastic leukemia (B-ALL) is regulated at the transcriptional level by Ikaros, a transcription factor and tumor suppressor protein. Analysis of global chromatin immunoprecipitation coupled with next-generation sequencing (ChIP-seq) in several B-ALL primary human B-ALL cells and cell lines, showed a strong enrichment of Ikaros at the promoter of the Aurora-B gene. Ikaros functions as a tumor suppressor protein and deletion of Ikaros is associated with development of high-risk B-ALL. Ikaros binding to Aurora-B promoter was confirmed by quantitative chromatin immunoprecipitation (qChIP) in primary B-ALL cells. The role of Ikaros in regulating Aurora-B transcription in B-ALL was tested using gain-of-function and loss-of-function experiments. Overexpression of Ikaros in human B-ALL was associated with strongly reduced transcription and overall expression of Aurora-B. Ikaros knock-down with shRNA results in increased expression of Aurora-B in B-ALL. Since Ikaros function in B-ALL is negatively regulated by pro-oncogenic Casein Kinase II (CK2), we tested whether CK2 can regulate expression of Aurora-B in B-ALL. Overexpression of CK2 via retroviral transduction resulted in increased expression of the Aurora-B gene. Increased expression of CK2 was associated with a loss of Ikaros binding to the Aurora-B gene promoter. Molecular inhibition of CK2 using shRNA resulted in reduced expression of Aurora-B in human B-ALL. Inhibition of CK2 was associated with increased Ikaros binding at the Aurora-B promoter. Ikaros knock-down abolished downregulation of Aurora-B expression in B-ALL cells following treatment with CK2 inhibitors. These data demonstrate that CK2 and Ikaros are critical regulators of Aurora-B expression in B-ALL. In conclusion, these results indicate that expression of the Aurora-B gene in B-ALL is regulated by the CK2-Ikaros signaling axis and provide a novel insight into mechanisms that regulate mitosis in leukemia. Citation Format: Yali Ding, Chunhua Song, Joseph Schramm, Soumya Maru, Daniel Bogus, Dhimant H. Desai, Arati K. Sharma, Chandrika Gowda, Sinisa Dovat. Transcriptional regulation of Aurora-B kinase expression in B-cell acute lymphoblastic leukemia (B-ALL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 846.

Targeting signaling pathways vulnerabilities for the treatment of IKZF1-deleted ph-negative B lymphoblastic leukemia.

7033 Background: Approximately 20% of children diagnosed with B lymphoblastic leukemia (B-ALL) will suffer a relapse, and most adults with B-ALL have a poor prognosis. Genome-wide association studies of B-ALL patients have identified frequent deletions of the gene IKZF1, encoding the master regulator of lymphoid development, IKAROS. These deletions are associated with therapy resistance, increased risk of relapse, and inferior survival. Currently, how loss of IKAROS function contributes to therapy resistance and increased risk of relapse is not fully understood. We used CRISPR-Cas9 genome editing to develop human B-ALL cell lines with various IKZF1 deletions that genetically and phenotypically recapitulate those occurring in patients. Using these isogenic cell lines, we have previously shown IKZF1 deletion results in cell-intrinsic chemoresistance and increased activation of the JAK/STAT signaling pathway (Rogers, Gupta et al. 2021). Methods: Given JAK/STAT is often dysregulated in poor-prognosis leukemia, we investigated the potential mechanisms of aberrant JAK/STAT activation and the therapeutic potential of targeting JAK/STAT in our engineered cell lines. We treated our cells with SH-4-54 (STAT3/5 inhibitor) or tofacitinib (JAK1 inhibitor) alone and in combination with dexamethasone. To elucidate how loss of IKAROS mediates an increase in JAK-STAT activity, we also performed RNAseq of known pathway regulators, comparing IKZF1 wild-type with IKZF1 knockout. Results: The JAK/STAT negative regulator Suppressor of Cytokine Signaling 2 (SOCS2) was significantly downregulated with IKZF1 deletion, validated by RTqPCR and immunoblotting. We further analyzed publicly-available RNAseq data from > 650 pediatric B-ALL samples, finding that SOCS2 expression is significantly lower in patients with low IKZF1expression (likely corresponding to IKZF1 deletion) compared to those with high IKZF1 expression. When we treated our engineered cell lines with tofacitinib or SH-4-54, IKZF1 wild-type cells were sensitive to each compound, suggesting JAK/STAT signaling plays a vital role in cell survival. In contrast, the IKZF1-deleted cells were relatively resistant to JAK/STAT inhibitors alone. However, in combination with dexamethasone, treatment of cells with sub-IC50 levels of SH-4-54 or tofacitinib resulted in re-sensitization to glucocorticoid-induced apoptosis. Conclusions: Our findings support that IKZF1 deletion leads to a targetable upregulation of the JAK/STAT pathway that, when inhibited, results in relative re-sensitization to dexamethasone. JAK/STAT pathway upregulation in IKZF1 deleted cells may be mediated by decreased expression of SOCS2. These results provide initial promise for targeting these vulnerabilities for the treatment of this poor-prognosis disease.

Abstract PR-12: Novel targeted combination therapy to reduce health disparity in high-risk B-cell acute lymphoblastic leukemia in Hispanic/Latino children

Abstract Hispanic/Latino (H/L) children and adolescents have a 40% higher death rate than non-Hispanic whites (NHW) after correcting socioeconomic factors. Recently, we identified an increased incidence of deletion of one IKZF1 allele in H/L children, which provided a biological rationale for the worse prognosis of B-cell acute lymphoblastic leukemia (B-ALL) in this population. The very high incidence (29%) makes the deletion of one IKZF1 allele the most frequent genetic alteration that confers adverse prognosis in B-ALL in H/L children. The IKZF1 gene encodes a DNA-binding protein, Ikaros, which functions as a transcriptional regulator. Our goal is to determine the mechanism through which Ikaros regulates leukemia progression and to develop the novel therapy to treat B-ALL with deletion of one IKZF1 allele to reduce the health disparity in survival for H/L children with B-ALL. Global DNA-binding analysis of primary B-ALL cells from H/L children showed that Ikaros binds to the promoters of CDC20 and ANAPC7 genes. CDC20 and ANAPC7 genes have a critical role in mitosis progression and are essential for cellular proliferation. The role of Ikaros in the regulation of CDC20 and ANAPC7 expression in B-ALL of H/L children was established using gain-of-function and loss-of-function experiments. Overexpression of Ikaros in B-ALL cells results in reduced expression of CDC20 and ANAPC7, while Ikaros knock-down results in increased transcription of CDC20 and ANAPC7 in B-ALL. Since Ikaros function in hematopoietic malignancies is regulated by pro-oncogenic Casein Kinase 2 (CK2), we tested whether CK2 can control the ability of Ikaros to regulate the expression of CDC20 and ANAPC7 in B-ALL. Increased expression of CK2 in B-ALL results in increased expression of CDC20 and ANAPC7 genes due to the loss of Ikaros binding to the promoters of CDC20 and ANAPC7 genes. Inhibition of CK2 with shRNA and/or a specific CK2 inhibitor, CX-4945, restores Ikaros binding to promoters of CDC20 and ANAPC7 in high-risk B-ALL with deletion of one IKZF1 allele in H/L children. Restoration of Ikaros binding to promoters of CDC20 and ANAPC7 in high-risk B-ALL in H/L children results in reduced expression of these genes and cell cycle arrest. CK2 inhibition sensitizes B-ALL cells to treatment with an inhibitor of mitosis – vincristine. Combination treatment with CK2 inhibitor and vincristine showed a synergistic effect on B-ALL cells from H/L children. In summary, presented data demonstrate that IKAROS and CK2 regulate the progression of mitosis in high-risk B-ALL in Hispanic/Latino children. Results suggest that the combination treatment with CK2 inhibitors and vincristine can be an efficient novel treatment to reduce the health disparity in survival for Hispanic/Latino children with B-ALL. Citation Format: Sinisa Dovat, Dimant Desai, Arati Sharma, Chandrika Gowda. Novel targeted combination therapy to reduce health disparity in high-risk B-cell acute lymphoblastic leukemia in Hispanic/Latino children [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PR-12.

Regulation of Heterochromatin Landscape in T-Cell Acute Lymphoblastic Leukemia

Ikzf1 encodes a zinc finger, DNA-binding protein that functions as a tumor suppressor in acute lymphoblastic leukemia (ALL). Deletion and/or loss of Ikaros function results in the development of high-risk leukemia. In the nucleus, Ikaros forms complexes with histone deacetylase complex, NuRD, and it participates in the formation of heterochromatin. The role of Ikaros-mediated formation of heterochromatin in tumor suppression in leukemia is unknown. We determined global genomic occupancy of Ikaros, global heterochromatin distribution, chromatin accessibility, DNA methylation landscape, and gene expression in primary human T-cell ALL (T-ALL), as well as in mouse T-ALL to analyze how Ikaros regulates heterochromatin landscape and gene expression in T-ALL. Results showed that Ikaros DNA occupancy is essential for the recruitment of histone deacetylase 1 (HDAC1), Polycomb repressive complex 2 (PRC2) and formation of facultative heterochromatin, as well as the formation of constitutive heterochromatin (characterized by H3K9me3 occupancy). T-ALL cells with deletion of both Ikzf1 alleles have severely impaired HDAC1 DNA occupancy and reduced H3K27me3. Re-introduction of Ikzf1 via retroviral transduction resulted in the restoration of H3K27me3 facultative heterochromatin, along with HDAC1 DNA occupancy. The H3K27me3 genomic distribution following Ikzf1 re-introduction showed high homology to the H3K27me3 genomic distribution in normal thymocytes. Analysis of H3K9me3 genomic distribution showed that Ikzf1 deletion results in dramatic redistribution of H3K9me3 global occupancy, with reduced H3K9me3 occupancy at pericentromeric loci. Reintroduction of Ikzf1 enhances H3K9me3 enrichment in pericentromeric loci, as well as at the promoters of genes that are involves in cellular proliferation. Analysis of DNA methylation distribution showed that Ikzf1 expression regulates global DNA methylation landscape. The presence of facultative heterochromatin, with enrichment of H3K27me3, inversely correlated with DNA methylation. Global analysis of chromatin accessibility revealed that Ikaros binding resulted in the loss of chromatin accessibility at over 3400 previously-accessible chromatin sites. Dynamic analyses demonstrate the long-lasting effects of Ikaros's DNA binding on heterochromatin distribution and chromatin accessibility. Analysis of gene expression in T-ALL with both Ikzf1 alleles and in Ikzf1-defficient cells (from Ikzf1-defficient T-ALL, and from Ikzf1-wild-type T-ALL following Ikzf1 deletion by CRISPR) showed that Ikaros-induced redistribution of facultative and constitutive heterochromatin results in the repression of several genes that are critical for cell cycle progression, PI3K-AKT-mTOR, and WNT signaling pathway. In conclusion, results suggest that Ikaros' tumor suppressor function in T-ALL occurs via global regulation of the heterochromatin, DNA methylation landscape, and chromatin accessibility, as well as via epigenetic regulation of transcription of the genes that play essential roles in signaling pathways that promote cellular proliferation. DisclosuresNo relevant conflicts of interest to declare.

Abstract 1047: Dual targeting of CK2 and MTOR as a novel therapeutic approach for high-risk B-cell acute lymphoblastic leukemia

Abstract Genomic defect and Casein Kinase II-mediated hyper-phosphorylation of Ikaros tumor suppressor cause the loss of function of Ikaros, and Ikaros dysfunction is characteristics of high-risk B-cell acute lymphoblastic leukemia (HR B-ALL) with poor prognosis. The increased activation of the PI3K/AKT/mTOR pathway is also observed in HR B-ALL and identifies mTOR as an attractive therapeutic target in HR B-ALL. Here, we report that Ikaros represses MTOR transcription and Ikaros' ability to repress MTOR in leukemia is impaired by oncogenic CK2 kinase. Treatment with the CK2 inhibitor, CX-4945, enhances Ikaros activity as a repressor of MTOR, resulting in reduced expression of MTOR in HR B-ALL. Thus, we designed a novel therapeutic approach that implements dual targeting of mTOR: direct inhibition of the mTOR protein (with rapamycin), in combination with Ikaros-mediated transcriptional repression of the MTOR gene (using the CK2 inhibitor, CX-4945). Combination treatment with rapamycin and CX-4945 shows synergistic therapeutic effects in vitro and in patient-derived xenografts from HR B-ALL. These data suggest that such therapy has the potential to reduce the death rate in HR B-ALL. The dual targeting of oncogene transcription, combined with inhibition of the corresponding oncoprotein provides a paradigm for a novel precision medicine approach for treating hematological malignancies. Citation Format: Chunhua Song, Zheng Ge, Yali Ding, Bihua Tan, Elanora Dovat, Yiping Yang, Chandrika Gowda, Sinisa Dovat. Dual targeting of CK2 and MTOR as a novel therapeutic approach for high-risk B-cell acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1047.

Cross Talk between Ikaros and RUNX1 in Myeloid Leukemia

Background: RUNX1 is critically important for normal hematopoiesis within both the lymphoid and myeloid lineages. Mutations or translocations involving RUNX1 have been identified in a variety of myeloid and lymphoid lineage hematopoietic malignancies. RUNX1 interacts with chromatin remodeling complexes and modulates transcriptional regulation of target genes via epigenetic mechanisms.IKAROS is a transcription factor that plays an essential role in normal lymphopoiesis, and mutations of IKZF1, the gene encoding IKAROS, are frequently seen in acute lymphoblastic leukemia (ALL). Despite reports of the presence of IKZF1 mutations in acute myeloid leukemia (AML), there remains a paucity of information regarding a possible role for disrupted IKAROS function in AML.Emerging evidence indicates that the transcriptional programs of these two transcription factors converge on critical pathways in hematopoiesis, such as the Notch1 signaling pathway. We are testing the hypothesis that IKAROS not only contributes to a gene regulatory program in AML, but specifically that the IKAROS and RUNX1 regulatory networks intersect in the pathogenesis of myeloid malignancies.Methods: Chromatin immunoprecipitation followed by next generation sequencing (ChIP-Seq) was utilized to identify the genome-wide binding sites of IKAROS and RUNX1 in the human myeloid sarcoma U937 cell-line. Independent ChIP-seq replicates were generated for these transcription factors, as well as replicates for a panel of activating and repressive histone modifications. The genes bound by IKAROS and RUNX1 as well as the chromatin patterns of these binding sites were analyzed with respect to their pathways were analyzed to understand the mutual and shared roles of these transcription factors.Results: We identified that greater than 30% of RUNX1 binding sites in this myeloid sarcoma cell line are also bound by IKAROS. These sites of co-occupancy are enriched at distal sites marked by the enhancer histone mark H3K27ac. Of the high-confidence IKAROS-RUNX1 shared binding sites, RUNX1 binding motifs predominate; while ETS, IRF4 and CEBPA motifs are also present. A Genome Regions Enrichment of Annotations (GREAT) analysis of the high confidence IKAROS-RUNX1 shared binding sites reveals enrichment for several biological associations, including leukocyte activation, migration, and chemotaxis. Importantly, genes associated with the regulation of chromatin organization and Notch and NFKB signaling cascades are bound by these factors.We have additionally found that IKAROS and RUNX1 are bound to the RUNX1 gene promoter. IKAROS is also independently bound to the RUNX1 gene at an upstream enhancer, also marked by H3K27ac.Conclusions: The role of IKAROS as a tumor suppressor in lymphoid leukemias is well established. Here, we begin to examine a role for IKAROS in myeloid leukemogenesis by defining the IKAROS cistrome in a myeloid sarcoma cell line. We have additionally identified cross talk between IKAROS and the important pan-hematopoietic transcription factor RUNX1 in myeloid malignancy by showing bidirectional transcriptional regulation between these two tumor suppressors, and defining an overlapping set of transcriptionally regulated genes. Future studies, including RNA-Seq experiments in the presence and absence of IKAROS and RUNX1 knockdown, will define the transcriptome, explore the functional consequences of co-occupancy at these identified binding sites, and functionally characterize the relationship between IKAROS and RUNX1 in the context of acute myeloid leukemia. DisclosuresNo relevant conflicts of interest to declare.

A variant in human AIOLOS impairs adaptive immunity by interfering with IKAROS.

In the present study, we report a human-inherited, impaired, adaptive immunity disorder, which predominantly manifested as a B cell differentiation defect, caused by a heterozygous IKZF3 missense variant, resulting in a glycine-to-arginine replacement within the DNA-binding domain of the encoded AIOLOS protein. Using mice that bear the corresponding variant and recapitulate the B and T cell phenotypes, we show that the mutant AIOLOS homodimers and AIOLOS-IKAROS heterodimers did not bind the canonical AIOLOS-IKAROS DNA sequence. In addition, homodimers and heterodimers containing one mutant AIOLOS bound to genomic regions lacking both canonical motifs. However, the removal of the dimerization capacity from mutant AIOLOS restored B cell development. Hence, the adaptive immunity defect is caused by the AIOLOS variant hijacking IKAROS function. Heterodimeric interference is a new mechanism of autosomal dominance that causes inborn errors of immunity by impairing protein function via the mutation of its heterodimeric partner.

IKAROS-Associated Diseases in 2020: Genotypes, Phenotypes, and Outcomes in Primary Immune Deficiency/Inborn Errors of Immunity

IKAROS, encoded by IKZF1, is a zinc finger transcription factor and a critical regulator of hematopoiesis. Mutations in IKZF1 have been implicated in immune deficiency, autoimmunity, and malignancy in humans. Somatic IKZF1 loss-of-function mutations and deletions have been shown to increase predisposition to the development of B cell acute lymphoblastic leukemia (B-ALL) and associated with poor prognosis. In the last 4years, germline heterozygous IKZF1 mutations have been reported in primary immune deficiency/inborn errors of immunity. These allelic variants, acting by either haploinsufficiency or dominant negative mechanisms affecting particular functions of IKAROS, are associated with common variable immunodeficiency, combined immunodeficiency, or primarily hematologic phenotypes in affected patients. In this review, we provide an overview of genetic, clinical, and immunological manifestations in patients with IKZF1 mutations, and the molecular and cellular mechanisms that contribute to their disease as a consequence of IKAROS dysfunction.