MMSET is dynamically regulated during cell-cycle progression and promotes normal DNA replication

Conditional knockout of the NSD2 gene in mouse intestinal epithelial cells inhibits colorectal cancer progression

BACKGROUND

Nuclear receptor-binding SET domain 2 (NSD2) is a histone methyltransferase, that catalyzes dimethylation of lysine 36 of histone 3 (H3K36me2) and is associated with active transcription of a series of genes. NSD2 is overexpressed in multiple types of solid human tumors and has been proven to be related to unfavorable prognosis in several types of tumors.

METHODS

We established a mouse model in which the NSD2 gene was conditionally knocked out in intestinal epithelial cells. We used azoxymethane and dextran sodium sulfate to chemically induce murine colorectal cancer. The development of colorectal tumors were investigated using post-necropsy quantification, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Compared with wild-type (WT) control mice, NSD2fl/fl -Vil1-Cre mice exhibited significantly decreased tumor numbers, histopathological changes, and cytokine expression in colorectal tumors.

CONCLUSIONS

Conditional knockout of NSD2 in intestinal epithelial cells significantly inhibits colorectal cancer progression.

Drug Discovery Targeting Nuclear Receptor Binding SET Domain Protein 2 (NSD2)

Nuclear receptor binding SET domain proteins (NSDs) catalyze the mono- or dimethylation of histone 3 lysine 36 (H3K36me1 and H3K36me2), using S-adenosyl-l-methionine (SAM) as a methyl donor. As a key member of the NSD family of proteins, NSD2 plays an important role in the pathogenesis and progression of various diseases such as cancers, inflammations, and infectious diseases, serving as a promising drug target. Developing potent and specific NSD2 inhibitors may provide potential novel therapeutics. Several NSD2 inhibitors and degraders have been discovered while remaining in the early stage of drug development. Excitingly, KTX-1001, a selective NSD2 inhibitor, has entered clinical trials. In this Perspective, the structures and functions of NSD2, its roles in various human diseases, and the recent advances in drug discovery strategies targeting NSD2 have been summarized. The challenges, opportunities, and future directions for developing NSD2 inhibitors and degraders are also discussed.

Deciphering cervical cancer-associated biomarkers by integrated multi-omics approach

OBJECTIVES

Cervical Squamous Cell Carcinoma (CESC) is one of the most fatal female malignancies, and the underlying molecular mechanisms governing this disease have not been fully explored. In this research, we planned to conduct the analysis of Gene Expression Omnibus (GEO) cervical squamous cell carcinoma microarray datasets by a detailed in silico approach and to explore some novel biomarkers of CESC.

METHODS

The top commonly differentially expressed genes (DEGs) from the GSE138080 and GSE113942 datasets were analyzed by Limma package-based GEO2R tool. The protein-protein interaction (PPI) network of the DEGs was drawn through Search Tool for the Retrieval of Interacting Genes (STRING), and top 6 hub genes were obtained from Cytoscape. Expression analysis and validation of hub genes expression in CESC samples and cell lines were done using UALCAN, OncoDB, GENT2, and HPA. Additionally, cBioPortal, Gene set enrichment analysis (GSEA) tool, Kaplan-Meier (KM) plotter, ShinyGO, and DGIdb databases were also used to check some important values of hub genes in CESC.

RESULTS

Out of 79 DEGs, the minichromosome maintenance complex component 4 (MCM4), nucleolar and spindle-associated protein 1 (NUSAP1), cell division cycle associated 5 (CDCA5), cell division cycle 45 (CDC45), denticleless E3 ubiquitin protein ligase homolog (DTL), and chromatin licensing and DNA replication factor 1 (CDT1) genes were regarded as hub genes in CESC. Further analysis revealed that the expressions of all these hub genes were significantly elevated in CESC cell lines and samples of diverse clinical attributes. In this study, we also documented some important correlations between hub genes and some other diverse measures, including DNA methylation, genetic alterations, and Overall Survival (OS). Last, we also identify hub genes associated ceRNA network and 31 important chemotherapeutic drugs.

CONCLUSION

Through detailed in silico methodology, we identified 6 hub genes, including MCM4, NUSAP1, CDCA5, CDC45, DTL, and CDT1, which are likely to be associated with CESC development and diagnosis.

Role of DTL in Hepatocellular Carcinoma and Its Impact on the Tumor Microenvironment

Background

The crucial role of DTL has been previously implicated in genomic stability; however, its prognostic value and its relation with tumor immunity in hepatocellular carcinoma (HCC) remain to be further explored.

Methods

Transcriptional and mutational datasets as well as clinical information were retrieved from the GEO, ICGC, and TCGA databases. Differentially expressed genes (DEGs) were obtained from the comparison of DTL^high and DTL^low expression groups of the TCGA-HCC cohort. Those genes were under KEGG and gene ontology (GO) analyses to decipher the influence of the DTL gene on the biological behavior of HCC tumor cells. The survival status and mutational characteristics of patients according to DTL levels were depicted and analyzed. The DTL overexpression in HCC and its impact on prognosis were further confirmed by a cohort of 114 HCC patients (validation cohort). The TIMER, GEPIA, and TISIDB databases were adopted to investigate the potential relations between DTL levels and the status of immune cells, as well as immune cell infiltrations.

Results

The DTL gene is overexpressed in tumor tissues compared with distant non-malignant liver tissues, and DTL overexpression in HCC would enhance the HCC cells in the activities of cell cycle and division. HCC patients with high DTL expression have unfavorable clinical outcomes and harbor more somatic mutations than those with low DTL expression, and multivariate analysis also revealed that DTL overexpression could act as an independent biomarker for prognosis. Moreover, the DTL gene was positively linked to marker sets of infiltrating activated CD8+ and CD4+ T cells; however, these cells demonstrated to be functionally exhausted.

Conclusions

Patients with a DTL overexpression phenotype in HCC have poorer prognosis than those in the DTL^low group due to the role of the DTL gene in the process of pro-cell proliferation, accompanied by the immunosuppressive microenvironment and T cell exhaustion.

Genome Instability in Multiple Myeloma: Facts and Factors

Multiple myeloma (MM) is a malignant neoplasm of terminally differentiated immunoglobulin-producing B lymphocytes called plasma cells. MM is the second most common hematologic malignancy, and it poses a heavy economic and social burden because it remains incurable and confers a profound disability to patients. Despite current progress in MM treatment, the disease invariably recurs, even after the transplantation of autologous hematopoietic stem cells (ASCT). Biological processes leading to a pathological myeloma clone and the mechanisms of further evolution of the disease are far from complete understanding. Genetically, MM is a complex disease that demonstrates a high level of heterogeneity. Myeloma genomes carry numerous genetic changes, including structural genome variations and chromosomal gains and losses, and these changes occur in combinations with point mutations affecting various cellular pathways, including genome maintenance. MM genome instability in its extreme is manifested in mutation kataegis and complex genomic rearrangements: chromothripsis, templated insertions, and chromoplexy. Chemotherapeutic agents used to treat MM add another level of complexity because many of them exacerbate genome instability. Genome abnormalities are driver events and deciphering their mechanisms will help understand the causes of MM and play a pivotal role in developing new therapies.

Regulation of cell cycle drivers by Cullin-RING ubiquitin ligases

The last decade has revealed new roles for Cullin-RING ubiquitin ligases (CRLs) in a myriad of cellular processes, including cell cycle progression. In addition to CRL1, also named SCF (SKP1-Cullin 1-F box protein), which has been known for decades as an important factor in the regulation of the cell cycle, it is now evident that all eight CRL family members are involved in the intricate cellular pathways driving cell cycle progression. In this review, we summarize the structure of CRLs and their functions in driving the cell cycle. We focus on how CRLs target key proteins for degradation or otherwise alter their functions to control the progression over the various cell cycle phases leading to cell division. We also summarize how CRLs and the anaphase-promoting complex/cyclosome (APC/C) ligase complex closely cooperate to govern efficient cell cycle progression.

The Role of Methyltransferase NSD2 as a Potential Oncogene in Human Solid Tumors

Malignant solid tumors are the leading cause of death in humans, and epigenetic regulation plays a significant role in studying the mechanism of human solid tumors. Recently, histone lysine methylation has been demonstrated to be involved in the development of human solid tumors due to its epigenetic stability and some other advantages. The 90-kb protein methyltransferase nuclear receptor SET domain-containing 2 (NSD2) is a member of nuclear receptor SET domain-containing (NSD) protein lysine methyltransferase (KMT) family, which can cause epigenomic aberrations via altering the methylation states. Studies have shown that NSD2 is frequently over-expressed in multiple types of aggressive solid tumors, including breast cancer, renal cancer, prostate cancer, cervical cancer, and osteosarcoma, and such up-regulation has been linked to poor prognosis and recurrence. Further studies have identified that over-expression of NSD2 promotes cell proliferation, migration, invasion, and epithelial–mesenchymal transformation (EMT), suggesting its potential oncogenic role in solid tumors. Moreover, Gene Expression Profiling Interactive Analysis (GEPIA) was searched for validation of prognostic value of NSD2 in human solid tumors. However, the underlying specific mechanism remains unclear. In our present work, we summarized the latest advances in NSD2 expression and clinical applications in solid tumors, and our findings provided valuable insights into the targeted therapeutic regimens of solid tumors.

The NSD2/WHSC1/MMSET methyltransferase prevents cellular senescence-associated epigenomic remodeling

Senescent cells may possess the intrinsic programs of metabolic and epigenomic remodeling, but the molecular mechanism remains to be clarified. Using an RNAi-based screen of chromatin regulators, we found that knockdown of the NSD2/WHSC1/MMSET methyltransferase induced cellular senescence that augmented mitochondrial mass and oxidative phosphorylation in primary human fibroblasts. Transcriptome analysis showed that loss of NSD2 downregulated the expression of cell cycle-related genes in a retinoblastoma protein (RB)-mediated manner. Chromatin immunoprecipitation analyses further revealed that NSD2 was enriched at the gene bodies of actively transcribed genes, including cell cycle-related genes, and that loss of NSD2 decreased the levels of histone H3 lysine 36 trimethylation (H3K36me3) at these gene loci. Consistent with these findings, oncogene-induced or replicative senescent cells showed reduced NSD2 expression together with lower H3K36me3 levels at NSD2-enriched genes. In addition, we found that NSD2 gene was upregulated by serum stimulation and required for the induction of cell cycle-related genes. Indeed, in both mouse and human tissues and human cancer cell lines, the expression levels of NSD2 were positively correlated with those of cell cycle-related genes. These data reveal that NSD2 plays a pivotal role in epigenomic maintenance and cell cycle control to prevent cellular senescence.

The histone methyltransferase WHSC1 is regulated by EZH2 and is important for ovarian clear cell carcinoma cell proliferation

Background

Wolf-Hirschhorn syndrome candidate gene-1 (WHSC1), a histone methyltransferase, has been found to be upregulated and its expression to be correlated with expression of enhancer of zeste homolog 2 (EZH2) in several cancers. In this study, we evaluated the role of WHSC1 and its therapeutic significance in ovarian clear cell carcinoma (OCCC).

Methods

First, we analyzed WHSC1 expression by quantitative PCR and immunohistochemistry using 23 clinical OCCC specimens. Second, the involvement of WHSC1 in OCCC cell proliferation was evaluated by MTT assays after siRNA-mediated WHSC1 knockdown. We also performed flow cytometry (FACS) to address the effect of WHSC1 on cell cycle. To examine the functional relationship between EZH2 and WHSC1, we knocked down EZH2 using siRNAs and checked the expression levels of WHSC1 and its histone mark H3K36m2 in OCCC cell lines. Finally, we checked WHSC1 expression after treatment with the selective inhibitor, GSK126.

Results

Both quantitative PCR and immunohistochemical analysis revealed that WHSC1 was significantly overexpressed in OCCC tissues compared with that in normal ovarian tissues. MTT assay revealed that knockdown of WHSC1 suppressed cell proliferation, and H3K36me2 levels were found to be decreased in immunoblotting. FACS revealed that WHSC1 knockdown affected the cell cycle. We also confirmed that WHSC1 expression was suppressed by EZH2 knockdown or inhibition, indicating that EZH2 is upstream of WHSC1 in OCCC cells.

Conclusions

WHSC1 overexpression induced cell growth and its expression is, at least in part, regulated by EZH2. Further functional analysis will reveal whether WHSC1 is a promising therapeutic target for OCCC.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5638-9) contains supplementary material, which is available to authorized users.

The emerging role for Cullin 4 family of E3 ligases in tumorigenesis

As a member of the Cullin-RING ligase family, Cullin-RING ligase 4 (CRL4) has drawn much attention due to its broad regulatory roles under physiological and pathological conditions, especially in neoplastic events. Based on evidence from knockout and transgenic mouse models, human clinical data, and biochemical interactions, we summarize the distinct roles of the CRL4 E3 ligase complexes in tumorigenesis, which appears to be tissue- and context-dependent. Notably, targeting CRL4 has recently emerged as a noval anti-cancer strategy, including thalidomide and its derivatives that bind to the substrate recognition receptor cereblon (CRBN), and anticancer sulfonamides that target DCAF15 to suppress the neoplastic proliferation of multiple myeloma and colorectal cancers, respectively. To this end, PROTACs have been developed as a group of engineered bi-functional chemical glues that induce the ubiquitination-mediated degradation of substrates via recruiting E3 ligases, such as CRL4 (CRBN) and CRL2 (pVHL). We summarize the recent major advances in the CRL4 research field towards understanding its involvement in tumorigenesis and further discuss its clinical implications. The anti-tumor effects using the PROTAC approach to target the degradation of undruggable targets are also highlighted.

Chromatin-Bound Cullin-Ring Ligases: Regulatory Roles in DNA Replication and Potential Targeting for Cancer Therapy

Cullin-RING (Really Interesting New Gene) E3 ubiquitin ligases (CRLs), the largest family of E3 ubiquitin ligases, are functional multi-subunit complexes including substrate receptors, adaptors, cullin scaffolds, and RING-box proteins. CRLs are responsible for ubiquitination of ~20% of cellular proteins and are involved in diverse biological processes including cell cycle progression, genome stability, and oncogenesis. Not surprisingly, cullins are deregulated in many diseases and instances of cancer. Recent studies have highlighted the importance of CRL-mediated ubiquitination in the regulation of DNA replication/repair, including specific roles in chromatin assembly and disassembly of the replication machinery. The development of novel therapeutics targeting the CRLs that regulate the replication machinery and chromatin in cancer is now an attractive therapeutic strategy. In this review, we summarize the structure and assembly of CRLs and outline their cellular functions and their diverse roles in cancer, emphasizing the regulatory functions of nuclear CRLs in modulating the DNA replication machinery. Finally, we discuss the current strategies for targeting CRLs against cancer in the clinic.

Wolf-Hirschhorn Syndrome Candidate 1 Is Necessary for Correct Hematopoietic and B Cell Development

Immunodeficiency is one of the most important causes of mortality associated with Wolf-Hirschhorn syndrome (WHS), a severe rare disease originated by a deletion in chromosome 4p. The WHS candidate 1 (WHSC1) gene has been proposed as one of the main genes responsible for many of the alterations in WHS, but its mechanism of action is still unknown. Here, we present in vivo genetic evidence showing that Whsc1 plays an important role at several points of hematopoietic development. Particularly, our results demonstrate that both differentiation and function of Whsc1-deficient B cells are impaired at several key developmental stages due to profound molecular defects affecting B cell lineage specification, commitment, fitness, and proliferation, demonstrating a causal role for WHSC1 in the immunodeficiency of WHS patients.

Relationship between NSD2 and tumors

Nuclear receptor binding SET domain-protein 2 (NSD2), also known as MMSET or WHSC1, is a member of the NSD family. Methylation of histone as an important regulatory mechanism in epigenetics plays an important role in transcriptional regulation and chromatin remodeling. The overexpression of NSD2, caused by t(4; 14) (p16; q23) translocation, is closely related to the prognosis of patients with multiple myeloma. In addition, high expression of NSD2 can be detected in many other malignant tumors. NSD2 catalyzes the methylation of the lysine sites of histone, and promotes the initiation and progression of tumors by participating in the interaction among multiple proteins or the regulation of target genes. NSD2 and related signal molecules are expected to be the targets for treatment of various related tumors. Elucidating the mechanism of NSD2 may promote the development of targeted drugs and provide new solutions for the treatment of various NSD2-related tumors.

MB4-2/MB4-3 transcripts of IGH-MMSET fusion gene in t(4;14)pos multiple myeloma indicate poor prognosis

Multiple myeloma (MM) patients with t(4;14) is a heterogeneous group. Prognostic tools capable of predicting the outcome of patients are currently lacking. The MM SET domain (MMSET) protein is universally overexpressed and has been suggested to have an important tumorigenic role. This study analyzed whether the overexpression of full-length (MB4-1) or truncated forms (MB4-2 and MB4-3) of MMSET influence the prognosis of t(4;14)^pos MM patients. A total of 53 symptomatic t(4;14)^pos MM patients were retrospectively analyzed. RT-PCR was performed using cDNA from purified CD138+ bone marrow plasma cells to analyze expression and clinical significance of the IGH-MMSET fusion transcripts corresponding to MB4-1, MB4-2 and MB4-3 breakpoints. Among the patients, 25 (47.2%), 12 (22.6%) and 16 (30.2%) had the MB4-1, MB4-2 and MB4-3 breakpoints, respectively. When adjusted to the established prognostic variables including del(17p), ISS stage, serum LDH and serum calcium levels, the pooled MB4-2/MB4-3 subgroup remained a powerful independent adverse factor for PFS (P=0.013) and OS (P=0.029). Bortezomib-based therapy significantly improved the survival of the MB4-1 subgroup but could not overcome the negative effect of the MB4-2/MB4-3 breakpoints. Our results indicate that MB4-2/MB4-3 breakpoints with truncated forms of MMSET define a subset of t(4;14)^posMM with poor prognosis.

AKT-mediated stabilization of histone methyltransferase WHSC1 promotes prostate cancer metastasis

Loss of phosphatase and tensin homolog (PTEN) and activation of the PI3K/AKT signaling pathway are hallmarks of prostate cancer (PCa). However, these alterations alone are insufficient for cells to acquire metastatic traits. Here, we have shown that the histone dimethyl transferase WHSC1 critically drives indolent PTEN-null tumors to become metastatic PCa. In a PTEN-null murine PCa model, WHSC1 overexpression in prostate epithelium cooperated with Pten deletion to produce a metastasis-prone tumor. Conversely, genetic ablation of Whsc1 prevented tumor progression in PTEN-null mice. Molecular characterization revealed that increased AKT activity due to PTEN loss directly phosphorylates WHSC1 at S172, preventing WHSC1 degradation by CRL4Cdt2 E3 ligase. Increased WHSC1 expression transcriptionally upregulates expression of RICTOR, a pivotal component of mTOR complex 2 (mTORC2), to further enhance AKT activity. Therefore, the AKT/WHSC1/mTORC2 signaling cascade represents a vicious feedback loop that elicits unrestrained AKT signaling. Furthermore, we determined that WHSC1 positively regulates Rac1 transcription to increase tumor cell motility. The biological importance of a WHSC1-mediated signaling cascade is substantiated by patient sample analysis in which WHSC1 signaling is tightly correlated with disease progression and recurrence. Taken together, our findings highlight a pivotal link between an epigenetic regulator, WHSC1, and key intracellular signaling molecules, AKT, RICTOR, and Rac1, to drive PCa metastasis.