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Multiple myeloma is an incurable malignancy with marked clinical and genetic heterogeneity. The cytogenetic abnormality t(4;14) (p16.3;q32.3) confers aggressive behavior in multiple myeloma. Recently, essential oncogenic drivers in a wide range of cancers have been shown to be controlled by super-enhancers (SE). We used chromatin immunoprecipitation sequencing of the active enhancer marker histone H3 lysine 27 acetylation (H3K27ac) to profile unique SEs in t(4;14)-translocated multiple myeloma. The histone chaperone HJURP was aberrantly overexpressed in t(4;14)-positive multiple myeloma due to transcriptional activation by a distal SE induced by the histone lysine methyltransferase NSD2. Silencing of HJURP with short hairpin RNA or CRISPR interference of SE function impaired cell viability and led to apoptosis. Conversely, HJURP overexpression promoted cell proliferation and abrogated apoptosis. Mechanistically, the NSD2/BRD4 complex positively coregulated HJURP transcription by binding the promoter and active elements of its SE. In summary, this study introduces SE profiling as an efficient approach to identify new targets and understand molecular pathogenesis in specific subtypes of cancer. Moreover, HJURP could be a valuable therapeutic target in patients with t(4;14)-positive myeloma. SIGNIFICANCE: A super-enhancer screen in t(4;14) multiple myeloma serves to identify genes that promote growth and survival of myeloma cells, which may be evaluated in future studies as therapeutic targets. Published version The work was supported by the National Research Foundation Singapore and the Singapore Ministry of Education under its Research Centres of Excellence initiative (to W.J. Chng), the NMRC Clinician Scientist Investigator award (to W.J. Chng), the RNA Biology Center at CSI Singapore, NUS, from funding by the Singapore Ministry of Education’s Tier 3 grants, grant number MOE2014-T3–1-006 (to W.J. Chng), the National Natural Science Foundation of China (grant no. 82000212 to Y. Jia), Natural Science Foundation of Zhejiang Province (grant no. LQ21H160022 to Y. Jia), Medical Health Science and Technology Project of Zhejiang Provincial Health Commission (grant no. 2021RC003 to Y. Jia). Y. Jia also thanks the China Scholarship Council (grant no. 201706320167) for financial support to visit National University of Singapore.

Multiple myeloma is an incurable malignancy with marked clinical and genetic heterogeneity. The cytogenetic abnormality t(4;14) (p16.3;q32.3) confers aggressive behavior in multiple myeloma. Recently, essential oncogenic drivers in a wide range of cancers have been shown to be controlled by super-enhancers (SE). We used chromatin immunoprecipitation sequencing of the active enhancer marker histone H3 lysine 27 acetylation (H3K27ac) to profile unique SEs in t(4;14)-translocated multiple myeloma. The histone chaperone

Background Multiple myeloma (MM) is an incurable malignancy characterized by complex heterogeneous cytogenetic abnormalities. Defined as large clusters of cis-acting enhancers, super-enhancers (SEs) could promote oncogenic transcription to which cancer cells highly addicted. Structural maintenance of chromosome 4 (SMC4) is a core subunit of condensin complexes, which contributes to chromosome condensation and segregation. Here, we identified SMC4 as a novel SE-associated oncogene of myeloma cells, whose functional roles in MM remain largely elusive. Methods We performed H3K27ac ChIP-seq and RNA-seq on primary MM patient samples, MM cell lines, normal CD138+ plasma cell and lymphoma cell lines as the controls, then the ROSE analysis was used to annotate SEs and their associated genes. THZ1 as a transcriptional CDK7 inhibitor was used to further filter THZ1-responsive genes. Combined analysis of THZ1-sensitive and SE-associated gene uncovered a number of promising MM oncogenes as SMC4. The public data mining, RNA interference, CRISPR/Cas9 gene editing system, overexpression and a variety of cellular functional assays were performed to determine the oncogenic effects of SMC4 on MM malignant. Transcriptome analysis with SMC4 silencing and overexpression, and the underlying molecular mechanism of SMC4 oncogenic role in MM are ongoing. Results We have demonstrated SMC4 as one of the SE-associated genes specific to MM patient samples and cell lines. SMC4 was related to myelomagenesis with increased expression from MGUS, SMM to MM cases, and overexpression of SMC4 predicted poor overall survival of MM patients, suggesting its clinical relevance. SMC4 silencing in MM cells suppressed cell proliferation and lead to cell apoptosis. Repression of the SMC4-SE region also led to impairment of cell viability and cell growth, consistent with an oncogenic function. Conclusion In summary, our integrative approached by combing H3H27ac ChIP-seq, RNA-seq and THZ1-sensitive transcripts identified the landscape of SEs and novel oncogenic transcripts as SMC4 in MM. Mapping these acquired SEs and their associated genes may provide novel insight into understanding MM biology, and SMC4 may serve as novel therapeutic targets in MM. Citation Format: Yunlu Jia, Jianbiao Zhou, Tze-King Tan, Tae-Hoon Chung, Yongxia Chen, Enfan Zhang, Zhen Cai, Takaomi Sanda, Wee-Joo Chng. Superenhancer-drvien SMC4 promote cell growth and proliferation in multiple myeloma [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 2956.

Overexpression of PRL-3, an oncogenic phosphatase, was identified as a novel cluster in patients with newly diagnosed multiple myeloma. However, the regulation and oncogenic activities of PRL-3 in multiple myeloma warrant further investigation. Here, we report that IL6 activates STAT3, which acts as a direct transcriptional regulator of PRL-3. Upregulation of PRL-3 increased myeloma cell viability and rephosphorylated STAT3 in a biphasic manner through direct interaction and deactivation of SHP2, thus blocking the gp130 (Y759)-mediated repression of STAT3 activity. Abrogation of PRL-3 reduced myeloma cell survival, clonogenicity, and tumorigenesis, and detailed mechanistic studies revealed “deactivation” of effector proteins such as Akt, Erk1/2, Src, STAT1, and STAT3. Furthermore, loss of PRL-3 efficiently abolished nuclear localization of STAT3 and reduced its occupancy on the promoter of target genes c-Myc and Mcl-1, and antiapoptotic genes Bcl2 and Bcl-xL. PRL-3 also played a role in the acquired resistance of myeloma cells to bortezomib, which could be overcome by PRL-3 silencing. Of clinical relevance, STAT3 and PRL-3 expression was positively correlated in five independent cohorts, and the STAT3 activation signature was significantly enriched in patients with high PRL-3 expression. Furthermore, PRL-3 could be used as a biomarker to identify high-risk patients with multiple myeloma that exhibited poor prognosis and inferior outcome even when treated with novel combinational therapeutics (proteasome inhibitors and immunomodulatory imide drugs). Conclusively, our results support a feedforward mechanism between STAT3 and PRL-3 that prolongs prosurvival signaling in multiple myeloma, and suggest targeting PRL-3 as a valid therapeutic opportunity in multiple myeloma. Significance: IL6 promotes STAT3-dependent transcriptional upregulation of PRL-3, which in turn re-phosphorylates STAT3 and aberrantly activates STAT3 target genes, leading to bortezomib resistance in multiple myeloma.

Multiple myeloma (MM), the second most common hematological cancer, is characterized by the accumulation of malignant plasma cells in the bone marrow (BM). Survival of MM cells is highly dependent on the bone marrow microenvironment, which is enriched with an array of growth factors secreted by the BM stromal cells. Amongst these growth factors, interleukin-6 (IL6) has been reported to be a major driver for MM disease progression. In line with the mechanism of action of IL6, MM cells are associated with constitutive activation of the oncogenic STAT3 signaling. ADAR1, an RNA editing enzyme, exists in two distinct isoforms, namely the P110 and P150. Aberrant ADAR1 expression and activity have been reported in various cancer types, however, this remains elusive in MM. Herein, we analyzed the publicly available myeloma patient datasets and identified that ADAR1 is overexpressed in MM and its expression level is closely associated with patients' overall survival. In vitro and in vivo assays revealed that ADAR1 can drive the growth and proliferation of MM cells, underlining its potential oncogenic effects in MM. Till date, much studies have reported the association of aberrant ADAR1 expression and its canonical functions of RNA editing, however, the knowledge on the upstream regulators of ADAR1 is still largely limited. To elucidate the cause of ADAR1 overexpression in MM, human myeloma cell lines were stimulated with IL6 at different time points. Besides potently activating the STAT3 signaling, IL6 stimulation also renders an increased expression of ADAR1 P150 isoform, at both the protein and mRNA level, with minimal effects seen on the P110 isoform, suggesting a transcriptional regulation of P150 by STAT3. Downstream validations with ChiP-qPCR and Luciferase Reporter Assay revealed that ADAR1 P150 is a direct target of STAT3 transcription factor. Specific STAT3 inhibition caused a downregulation of P150 and its oncogenic properties. Likewise, ectopic introduction of P150 rendered a more proliferative profile in the cells. Interestingly, we also observed that IL6-induced-ADAR1 expression could in turn mediate the activity of STAT3 signaling to enhance the oncogenic signaling within MM. Cells with high ADAR1 demonstrated a more rapid IL6-induced-STAT3 activation. In summary, we identified that ADAR1 overexpression is clinically relevant in MM and is driven by the hyperactivity of IL6-STAT3 signaling. Our data suggests that the P150 isoform, instead of the P110, is the more critical driver of MM disease aggressiveness in the patients with constitutively activated STAT3 pathway. The potential interplay between ADAR1 and STAT3 may represent a novel mechanism by which IL6 confers oncogenicity in MM. Citation Format: Phaik Ju Teoh, Tae Hoon Chung, Henry Yang, Polly Chen, Wee Joo Chng. The relationship between ADAR1 and STAT3 and its relevance in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5457.

Hyperdiploid multiple myeloma (H-MM) is the most common form of myeloma. In this gene expression profiling study, we show that H-MM is defined by a protein biosynthesis signature that is primarily driven by a gene dosage mechanism as a result of trisomic chromosomes. Within H-MM, four independently validated patient clusters overexpressing nonoverlapping sets of genes that form cognate pathways/networks that have potential biological importance in multiple myeloma were identified. One prominent cluster, cluster 1, is characterized by high expression of cancer testis antigen and proliferation-associated genes. Tumors from these patients were more proliferative than tumors in other clusters (median plasma cell labeling index, 3.8; P < 0.05). Another cluster, cluster 3, is characterized by genes involved in tumor necrosis factor/nuclear factor-κB signaling and antiapoptosis. These patients have better response to bortezomib as compared with patients within other clusters (70% versus 29%; P = 0.02). Furthermore, for a group of patients generally thought to have better prognosis, a cluster of patients with short survival (cluster 1; median survival, 27 months) could be identified. This analysis illustrates the heterogeneity within H-MM and the importance of defining specific cytogenetic prognostic factors. Furthermore, the signatures that defined these clusters may provide a basis for tailoring treatment to individual patients. [Cancer Res 2007;67(7):2982–9]