Identification of molecular targets associated with transformed diffuse large B cell lymphoma using highly purified tumor cells

Bifunctional Inhibitor Reveals NEK2 as a Therapeutic Target and Regulator of Oncogenic Pathways in Lymphoma

Expression of the serine/threonine kinase never in mitosis gene A (NIMA)-related kinase 2 (NEK2) is essential for entry into mitosis via its role in facilitating centrosome separation. Its overactivity can lead to tumorigenesis and drug resistance through the activation of several oncogenic pathways, including AKT. Although the cancer-enabling activities of NEK2 are documented in many malignancies, including correlations with poor survival in myeloma, breast, and non-small cell lung cancer, little is known about the role of NEK2 in lymphoma. Here, in tumors from patients with diffuse large B-cell lymphoma (DLBCL), the most common, aggressive non-Hodgkin lymphoma, we found a high abundance of NEK2 mRNA and protein associated with an inferior overall survival. Using our recently developed NEK2 inhibitor, NBI-961, we discovered that DLBCL cell lines and patient-derived cells exhibit a dependency on NEK2 for their viability. This compromised cell fitness was directly attributable to efficient NEK2 inhibition and proteasomal degradation by NBI-961. In a subset of particularly sensitive DLBCL cells, NBI-961 induced G2/mitosis arrest and apoptosis. In contrast, an existing indirect NEK2 inhibitor, INH154, did not prevent NEK2 autophosphorylation, induce NEK2 proteasomal degradation, or affect cell viability. Global proteomics and phospho-proteomics revealed that NEK2 orchestrates cell-cycle and apoptotic pathways through regulation of both known and new signaling molecules. We show the loss of NEK2-sensitized DLBCL to the chemotherapy agents, doxorubicin and vincristine, and effectively suppressed tumor growth in mice. These studies establish the oncogenic activity of NEK2 in DLBCL and set the foundation for development of anti-NEK2 therapeutic strategies in this frequently refractory and relapse-prone cancer.

Identification of a novel spirocyclic Nek2 inhibitor using high throughput virtual screening

NIMA Related Kinase 2 (Nek2) kinase is an attractive target for the development of therapeutic agents for several types of highly invasive cancers. Despite this, no small molecule inhibitor has advanced to the late clinical stages thus far. In this work, we have identified a novel spirocyclic inhibitor (V8) of Nek2 kinase, utilizing a high-throughput virtual screening (HTVS) approach. Using recombinant Nek2 enzyme assays, we show that V8 can inhibit Nek2 kinase activity (IC50 = 2.4 ± 0.2 µM) by binding to the enzyme's ATP pocket. The inhibition is selective, reversible and is not time dependent. To understand the key chemotype features responsible for Nek2 inhibition, a detailed structure-activity relationships (SAR) was performed. Using molecular models of the energy-minimized structures of Nek2-inhibitory complexes, we identify key hydrogen-bonding interactions, including two from the hinge-binding region, likely responsible for the observed affinity. Finally, using cell-based studies, we show that V8 attenuates (a) pAkt/PI3 Kinase signaling in a dose-dependent manner, and (b) proliferative and migratory phenotypes of highly aggressive human MDA-MB-231 breast and A549 lung cancer cell lines. Thus, V8 is an important novel lead compound for the development of highly potent and selective Nek2 inhibitory agents.

Bioinformatics analysis of the pathogenic link between Epstein-Barr virus infection, systemic lupus erythematosus and diffuse large B cell lymphoma

Epstein-Barr virus (EBV) is a risk factor for diffuse large B-cell lymphoma (DLBCL) and systemic lupus erythematosus (SLE). While prior research has suggested a potential correlation between SLE and DLBCL, the molecular mechanisms remain unclear. The present study aimed to explore the contribution of EBV infection to the pathogenesis of DLBCL in the individuals with SLE using bioinformatics approaches. The Gene Expression Omnibus database was used to compile the gene expression profiles of EBV-infected B cells (GSE49628), SLE (GSE61635), and DLBCL (GSE32018). Altogether, 72 shared common differentially expressed genes (DEGs) were extracted and enrichment analysis of the shared genes showed that p53 signaling pathway was a common feature of the pathophysiology. Six hub genes were selected using protein-protein interaction (PPI) network analysis, including CDK1, KIF23, NEK2, TOP2A, NEIL3 and DEPDC1, which showed preferable diagnostic values for SLE and DLBCL and involved in immune cell infiltration and immune responses regulation. Finally, TF-gene and miRNA-gene regulatory networks and 10 potential drugs molecule were predicted. Our study revealed the potential molecular mechanisms by which EBV infection contribute to the susceptibility of DLBCL in SLE patients for the first time and identified future biomarkers and therapeutic targets for SLE and DLBCL.

Transcriptome Analysis of Diffuse Large B-Cell Lymphoma Cells Inducibly Expressing MyD88 L265P Mutation Identifies Upregulated CD44, LGALS3, NFKBIZ, and BATF as Downstream Targets of Oncogenic NF-κB Signaling

During innate immune responses, myeloid differentiation primary response 88 (MyD88) functions as a critical signaling adaptor protein integrating stimuli from toll-like receptors (TLR) and the interleukin-1 receptor (IL-1R) family and translates them into specific cellular outcomes. In B cells, somatic mutations in MyD88 trigger oncogenic NF-κB signaling independent of receptor stimulation, which leads to the development of B-cell malignancies. However, the exact molecular mechanisms and downstream signaling targets remain unresolved. We established an inducible system to introduce MyD88 to lymphoma cell lines and performed transcriptomic analysis (RNA-seq) to identify genes differentially expressed by MyD88 bearing the L265P oncogenic mutation. We show that MyD88L265P activates NF-κB signaling and upregulates genes that might contribute to lymphomagenesis, including CD44, LGALS3 (coding Galectin-3), NFKBIZ (coding IkBƺ), and BATF. Moreover, we demonstrate that CD44 can serve as a marker of the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL) and that CD44 expression is correlated with overall survival in DLBCL patients. Our results shed new light on the downstream outcomes of MyD88L265P oncogenic signaling that might be involved in cellular transformation and provide novel therapeutical targets.

miR-145-5p exerts anti-tumor effects in diffuse large B-cell lymphoma by regulating S1PR1/STAT3/AKT pathway

To investigate the molecular mechanism of miR-145-5p in diffuse large B-cell lymphoma (DLBCL) tissues and cells. The tissues from patients with DLBCL were collected for RT-qPCR or immunohistochemistry. Cell viability, proliferation, migration, invasion, the relationship between miR-145-5p and S1PR1, and proteins related pathway were detected using CCK-8, BrdU staining, Transwell assay, dual luciferase report assay, and western blotting, respectively. The results showed that miR-145-5p was down-regulated and positively correlated with the survival of DLBCL patients. Overexpression of miR-145-5p inhibited cell proliferation, migration, and invasion in cell model. miR-145-5p directly targeted S1PR1. miR-145-5p down-regulated S1PR1, p-AKT/AKT, and p-STAT3 expression. The reduction of miR-145-5p-induced cell movement was reversed by S1PR1 overexpression. Moreover, S1PR1-induced addition of cell growth was clearly alleviated in LY294002 or S3I-201 treated cells. S1PR1 was up-regulated in the tissues of DLBCL patients. In conclusion, miR-145-5p regulated DLBCL cell growth and movement through suppressing S1PR1/STAT3/AKT pathway.

High expression of NEK2 promotes gastric cancer progression via activating AKT signaling

Never in mitosis gene A-related kinase 2 (NEK2) has been recognized as an oncogene involved in the initiation and progression of various human cancers. However, our knowledge is still lacking in regard to the function of NEK2 in gastric cancer, the most common cancer in Eastern Asia associated with poor prognosis. Therefore, in the present study, we investigated the association of NEK2 with gastric cancer. We found that the development of gastric cancer is associated with NEK2 overexpression, particularly in patients with large tumor size and lymph node metastasis. We also provided evidence that NEK2 overexpression binds to and inhibits protein phosphatase 1 (PP1), which subsequently activates AKT and the downstream oncogenic pathways. As a result, via AKT/HIF1α axis, the glucose metabolism is reprogrammed towards aerobic glycolysis to provide rapid energy for the growth of gastric cancer cells. Moreover, the autophagic activity is suppressed via AKT/mTOR axis, leading to impaired response to cancer treatment and enhanced cell survival. In contrast, inactivating AKT by NEK2 silencing decreases aerobic glycolysis and promotes autophagic cell death, which eventually inhibits the growth of gastric cancer cell. All these results revealed that NEK2 promotes gastric cancer progression via activating AKT-mediated signaling pathways, which expanded our knowledge on gastric cancer pathogenesis and also provided novel target for clinical treatment.

High expression of NEK2 promotes lung cancer progression and drug resistance and is regulated by mutant EGFR

Activating mutations within the tyrosine kinase (TK) domain of epidermal growth factor receptor (EGFR) gene are observed in 10 ~ 30% of the patients diagnosed with non-small cell lung cancer (NSCLC), and are causally related to NSCLC initiation and progression. Treatments with tyrosine kinase inhibitors (TKIs) targeting EGFR significantly improve the outcome of NSCLC patients with EGFR mutation, but are often associated with drug resistance, which is the main cause of treatment failure and cancer relapse. In the present study, by screening the transcriptome of NSCLC patients, we found that EGFR activation is highly correlated with the up-regulation of mitotic regulator, never in mitosis gene A-related kinase 2 (NEK2). NEK2 overexpression is associated with the poor survival of EGFR-mutant patients but not the wild-type patients. Further functional validation revealed that EGFR mutation induces NEK2 expression by activating ERK signaling pathway. Elevated NEK2 level promotes the rapid cell cycle progression and favors the rapid proliferation of EGFR-mutant NSCLC cells. Of note, NEK2 overexpression also impairs the efficacy of TKI treatment via inhibiting apoptosis, while depleting NEK2 suppresses cell growth and restored the sensitivity of TKI in NSCLC cells. Taken together, our study revealed that NEK2 is an oncogene regulated by EGFR mutation and is involved in disease progression and treatment response in NSCLC with EGFR mutation. These findings will pave the road for optimizing personalized treatment strategies to overcome drug resistance and improve the prognosis of lung cancer patients with EGFR mutation.

Acetylene Group, Friend or Foe in Medicinal Chemistry

The use of an acetylene (ethynyl) group in medicinal chemistry coincides with the launch of the Journal of Medicinal Chemistry in 1959. Since then, the acetylene group has been broadly exploited in drug discovery and development. As a result, it has become recognized as a privileged structural feature for targeting a wide range of therapeutic target proteins, including MAO, tyrosine kinases, BACE1, steroid receptors, mGlu5 receptors, FFA1/GPR40, and HIV-1 RT. Furthermore, a terminal alkyne functionality is frequently introduced in chemical biology probes as a click handle to identify molecular targets and to assess target engagement. This Perspective is divided into three parts encompassing: (1) the physicochemical properties of the ethynyl group, (2) the advantages and disadvantages of the ethynyl group in medicinal chemistry, and (3) the impact of the ethynyl group on chemical biology approaches.

Highly preserved consensus gene modules in human papilloma virus 16 positive cervical cancer and head and neck cancers

In this study, we investigated the consensus gene modules in head and neck cancer (HNC) and cervical cancer (CC). We used a publicly available gene expression dataset, GSE6791, which included 42 HNC, 14 normal head and neck, 20 CC and 8 normal cervical tissue samples. To exclude bias because of different human papilloma virus (HPV) types, we analyzed HPV16-positive samples only. We identified 3824 genes common to HNC and CC samples. Among these, 977 genes showed high connectivity and were used to construct consensus modules. We demonstrated eight consensus gene modules for HNC and CC using the dissimilarity measure and average linkage hierarchical clustering methods. These consensus modules included genes with significant biological functions, including ATP binding and extracellular exosome. Eigengen network analysis revealed the consensus modules were highly preserved with high connectivity. These findings demonstrate that HPV16-positive head and neck and cervical cancers share highly preserved consensus gene modules with common potentially therapeutic targets.

Targeting NEK2 attenuates glioblastoma growth and radioresistance by destabilizing histone methyltransferase EZH2

Accumulating evidence suggests that glioma stem cells (GSCs) are important therapeutic targets in glioblastoma (GBM). In this study, we identified NIMA-related kinase 2 (NEK2) as a functional binding protein of enhancer of zeste homolog 2 (EZH2) that plays a critical role in the posttranslational regulation of EZH2 protein in GSCs. NEK2 was among the most differentially expressed kinase-encoding genes in GSC-containing cultures (glioma spheres), and it was required for in vitro clonogenicity, in vivo tumor propagation, and radioresistance. Mechanistically, the formation of a protein complex comprising NEK2 and EZH2 in glioma spheres phosphorylated and then protected EZH2 from ubiquitination-dependent protein degradation in a NEK2 kinase activity-dependent manner. Clinically, NEK2 expression in patients with glioma was closely associated with EZH2 expression and correlated with a poor prognosis. NEK2 expression was also substantially elevated in recurrent tumors after therapeutic failure compared with primary untreated tumors in matched GBM patients. We designed a NEK2 kinase inhibitor, compound 3a (CMP3a), which efficiently attenuated GBM growth in a mouse model and exhibited a synergistic effect with radiotherapy. These data demonstrate a key role for NEK2 in maintaining GSCs in GBM by stabilizing the EZH2 protein and introduce the small-molecule inhibitor CMP3a as a potential therapeutic agent for GBM.

Targeting NEK2 as a promising therapeutic approach for cancer treatment

Never in Mitosis (NIMA) Related Kinase 2 (NEK2) plays a key role in regulating mitotic processes, including centrosome duplication and separation, microtubule stabilization, kinetochore attachment and spindle assembly checkpoint. NEK2 is aberrantly overexpressed in a wide variety of human cancers and has been implicated in various aspects of malignant transformation, including tumorigenesis, drug resistance and tumor progression. The close relationship between NEK2 and cancer has made it an attractive target for anticancer therapeutic development; however, the mechanisms of how NEK2 coordinates altered signaling to malignant transformation remains unclear. In this paper, we discuss the functional roles of NEK2 in cancer development; highlight some of the significant NEK2 signaling in cancer, and summarize recent advances in the development of NEK2 inhibitors.

NIMA-related kinase 2 regulates hepatocellular carcinoma cell growth and proliferation

NIMA-related kinase 2 (Nek2) is often upregulated in human cancer and is important in regulating the cell cycle and gene expression, and maintaining centrosomal structure and function. The present study aimed to investigate the expression pattern, clinical significance, and biological function of Nek2 in hepatocellular carcinoma (HCC). mRNA and protein levels of Nek2 were examined in HCC and corresponding normal liver tissues. The MTT and soft agar colony formation assays, and flow cytometry were employed to assess the roles of Nek2 in cell proliferation and growth. In addition, western blot analysis was performed to assess the expression of cell cycle- and proliferation-related proteins. The results revealed that Nek2 was upregulated in HCC tissues and cell lines. The clinical significance of Nek2 expression was also analyzed. Inhibiting Nek2 expression by siRNA suppressed cell proliferation, growth, and colony formation in hepatocellular carcinoma cell line HepG2 cells, induced cell cycle arrest in the G2/M phase by retarding the S-phase, and promoted apoptosis. Furthermore, Nek2 depletion downregulated β-catenin expression in HepG2 cells and diminished expression of Myc proto-oncogene protein (c-Myc), cyclins D1, B1, and E and cyclin-dependent kinase 1, whilst increasing protein levels of p27. This demonstrates that overexpression of Nek2 is associated with the malignant evolution of HCC. Targeting Nek2 may inhibit HCC cell growth and proliferation through the regulation of β-catenin by the Wnt/β-catenin pathway and therefore may be developed as a novel therapeutic strategy to treat HCC.

Nek2A/SuFu feedback loop regulates Gli-mediated Hedgehog signaling pathway

Suppressor of Fused (SuFu), one of the most conserved components of the Hedgehog (Hh) signaling, binds Gli transcription factors and impedes activation of target gene expression in mammalian cells. Despite the central importance of SuFu in the Hh pathway, little is known about SuFu regulation. In a previous study, we identified NIMA-related expressed kinase 2A (Nek2A) as a SuFu-interacting protein. Here, we show that Nek2A stabilizes SuFu through impairing ubiquitin/proteasome degradation of SuFu. In addition, Nek2A negatively regulates target genes of Hh signaling as well as Gli2 transcriptional activity. In turn, inhibition of Hh signaling by GANT61 diminishes mRNA and protein levels of Nek2A, and Hh agonist promotes transcription of NEK2A gene. Chromatin immunoprecipitation assays revealed that Gli1 and Gli2 directly bind to the promoter regions of NEK2A gene and induced its transcription. Thus, we uncovered one of the mechanisms by which Nek2A acts as a modulator of the Hh signaling pathway in the context of a novel negative-feedback loop, which may offer new insights into Gli-mediated Hh signaling regulation in development and human diseases.

Overexpression of NIMA-related kinase 2 is associated with progression and poor prognosis of prostate cancer

Background

The NIMA-related kinase 2 (NEK2) is a serine/threonine kinase that is involved in regulation of centrosome duplication and spindle assembly during mitosis. Dysregulation of these processes causes chromosome instability and aneuploidy, which are hallmark changes of many solid tumors. However, whether aberrant expression of NEK2 is associated with outcome of prostate cancer (PCa) patients remains to be determined.

Methods

Expression of NEK2 in human PCa cells and primary PCa tissues was assessed by quantitative RT-PCR. Expression of NEK2 in human PCa cells was depleted with siRNA. Effects of the depletion on cell proliferation, survival, and tumorigenicity were assessed both in vitro with cell cultures and in vivo with subcutaneous implantation of xenografts. In silico analyses of the online Taylor dataset were carried out to determine whether the expression level of NEK2 correlated with the clinicopathological characteristics of prostate cancer.

Results

Compared with benign human prostatic epithelial cells and tissues, the expression of NEK2 was elevated in human PCa cells and primary PCa tissues. Depleting NEK2 expression inhibited human PCa cell proliferation in vitro and xenograft growth in vivo. Expression level of NEK2 in PCa positively correlated with the Gleason score and pathologic stage of the patient.

Conclusion

The results suggest that overexpression of NEK2 has the potential to serve as a biomarker for PCa prognosis. Further validation with large sample pool is warrant.

Primary Central Nervous System (CNS) Lymphoma B Cell Receptors Recognize CNS Proteins

Primary lymphoma of the CNS (PCNSL) is a diffuse large B cell lymphoma confined to the CNS. To elucidate its peculiar organ tropism, we generated recombinant Abs (recAbs) identical to the BCR of 23 PCNSLs from immunocompetent patients. Although none of the recAbs showed self-reactivity upon testing with common autoantigens, they recognized 1547 proteins present on a large-scale protein microarray, indicating polyreactivity. Interestingly, proteins (GRINL1A, centaurin-α, BAIAP2) recognized by the recAbs are physiologically expressed by CNS neurons. Furthermore, 87% (20/23) of the recAbs, including all Abs derived from IGHV4-34 using PCNSL, recognized galectin-3, which was upregulated on microglia/macrophages, astrocytes, and cerebral endothelial cells upon CNS invasion by PCNSL. Thus, PCNSL Ig may recognize CNS proteins as self-Ags. Their interaction may contribute to BCR signaling with sustained NF-κB activation and, ultimately, may foster tumor cell proliferation and survival. These data may also explain, at least in part, the affinity of PCNSL cells for the CNS.

Galectin expression in cancer diagnosis and prognosis: A systematic review

Galectins are a family of proteins that bind to specific glycans thereby deciphering the information captured within the glycome. In the last two decades, several galectin family members have emerged as versatile modulators of tumor progression. This has initiated the development and preclinical assessment of galectin-targeting compounds. With the first compounds now entering clinical trials it is pivotal to gain insight in the diagnostic and prognostic value of galectins in cancer as this will allow a more rational selection of the patients that might benefit most from galectin-targeted therapies. Here, we present a systematic review of galectin expression in human cancer patients. Malignant transformation is frequently associated with altered galectin expression, most notably of galectin-1 and galectin-3. In most cancers, increased galectin-1 expression is associated with poor prognosis while elevated galectin-9 expression is emerging as a marker of favorable disease outcome. The prognostic value of galectin-3 appears to be tumor type dependent and the other galectins require further investigation. Regarding the latter, additional studies using larger patient cohorts are essential to fully unravel the diagnostic and prognostic value of galectin expression. Furthermore, to better compare different findings, consensus should be reached on how to assess galectin expression, not only with regard to localization within the tissue and within cellular compartments but also regarding alternative splicing and genomic variations. Finally, linking galectin expression and function to aberrant glycosylation in cancer cells will improve our understanding of how these versatile proteins can be exploited for diagnostic, prognostic and even therapeutic purposes in cancer patients.

Diffuse large B-cell lymphoma classification system that associates normal B-cell subset phenotypes with prognosis

PURPOSE

Current diagnostic tests for diffuse large B-cell lymphoma use the updated WHO criteria based on biologic, morphologic, and clinical heterogeneity. We propose a refined classification system based on subset-specific B-cell-associated gene signatures (BAGS) in the normal B-cell hierarchy, hypothesizing that it can provide new biologic insight and diagnostic and prognostic value.

PATIENTS AND METHODS

We combined fluorescence-activated cell sorting, gene expression profiling, and statistical modeling to generate BAGS for naive, centrocyte, centroblast, memory, and plasmablast B cells from normal human tonsils. The impact of BAGS-assigned subtyping was analyzed using five clinical cohorts (treated with cyclophosphamide, doxorubicin, vincristine, and prednisone [CHOP], n = 270; treated with rituximab plus CHOP [R-CHOP], n = 869) gathered across geographic regions, time eras, and sampling methods. The analysis estimated subtype frequencies and drug-specific resistance and included a prognostic meta-analysis of patients treated with first-line R-CHOP therapy.

RESULTS

Similar BAGS subtype frequencies were assigned across 1,139 samples from five different cohorts. Among R-CHOP-treated patients, BAGS assignment was significantly associated with overall survival and progression-free survival within the germinal center B-cell-like subclass; the centrocyte subtype had a superior prognosis compared with the centroblast subtype. In agreement with the observed therapeutic outcome, centrocyte subtypes were estimated as being less resistant than the centroblast subtype to doxorubicin and vincristine. The centroblast subtype had a complex genotype, whereas the centrocyte subtype had high TP53 mutation and insertion/deletion frequencies and expressed LMO2, CD58, and stromal-1-signature and major histocompatibility complex class II-signature genes, which are known to have a positive impact on prognosis.

CONCLUSION

Further development of a diagnostic platform using BAGS-assigned subtypes may allow pathogenetic studies to improve disease management.

Role of NEK2A in human cancer and its therapeutic potentials

Chromosome instability (CIN) has been identified as a common feature of most human cancers. A number of centrosomal kinases are thought to cause CIN in cancer cells. Part of those centrosomal kinases exhibit elevated expression in a wide variety of tumours and cancer cell lines. Additionally, critical roles in many aspects of cancer cell growth, proliferation, metastasis, and drug resistance have been assigned to some of these centrosomal kinases, such as polo-like kinase 1 (PLk1) and Aurora-A kinase. Recent studies from our group and others revealed that a centrosomal kinase, Never in Mitosis (NIMA) Related Kinase 2A (NEK2A), is frequently upregulated in multiple types of human cancers. Uncontrolled activity of NEK2A activates several oncogenic pathways and ABC transporters, thereby leading to CIN, cancer cell proliferation, metastasis, and enhanced drug resistance. In this paper, we highlight recent findings on the aberrant expression and functional significance of NEK2A in human cancers and emphasize their significance for therapeutic potentials.

Overexpression of the Nek2 kinase in colorectal cancer correlates with beta-catenin relocalization and shortened cancer-specific survival

The serine/threonine kinase Nek2 (NIMA-related kinase 2) regulates centrosome separation and mitotic progression, with overexpression causing induction of aneuploidy in vitro. Overexpression may also enable tumour progression through effects upon Akt signalling, cell adhesion markers and the Wnt pathway. The objective of this study was to examine Nek2 protein expression in colorectal cancer (CRC). Nek2 protein expression was examined in a panel of CRC cell lines using Western blotting and immunofluorescence microscopy. Nek2 and beta-catenin expression were examined by immunohistochemistry in a series of resected CRC, as well as their matched lymph node and liver metastases, and correlated with clinicopathological characteristics. Nek2 protein expression in all CRC lines examined was higher than in the immortalised colonocyte line HCEC. Nek2 overexpression was present in 86.4% of resected CRC and was significantly associated with advancing AJCC tumour stage and shortened cancer-specific survival. Elevated Nek2 expression was maintained within all matched metastases from overexpressing primary tumours. Nek2 overexpression was significantly associated with lower tumour membranous beta-catenin expression and higher cytoplasmic and nuclear beta-catenin accumulation. These data support a role for Nek2 in CRC progression and confirm potential for Nek2 inhibition as a therapeutic avenue in CRC.

Novel small molecules disrupting Hec1/Nek2 interaction ablate tumor progression by triggering Nek2 degradation through a death-trap mechanism

Hec1 (highly expressed in cancer 1) or Nek2 (NIMA-related kinase 2) is often overexpressed in cancers with poor prognosis. Both are critical mitotic regulators, and phosphorylation of Hec1 S165 by Nek2 is required for proper chromosome segregation. Therefore, inactivation of Hec1 and Nek2 by targeting their interaction with small molecules represents an ideal strategy for tackling these types of cancers. Here we showed that new derivatives of INH (inhibitor for Nek2 and Hec1 binding) bind to Hec1 at amino acids 394-408 on W395, L399 and K400 residues, effectively blocking Hec1 phosphorylation on S165 by Nek2, and killing cancer cells at the nanomolar range. Mechanistically, the D-box (destruction-box) region of Nek2 specifically binds to Hec1 at amino acids 408-422, immediately adjacent to the INH binding motif. Subsequent binding of Nek2 to INH-bound Hec1 triggered proteasome-mediated Nek2 degradation, whereas the Hec1 binding defective Nek2 mutant, Nek2 R361L, resisted INH-induced Nek2 degradation. This finding unveils a novel drug-action mechanism where the binding of INHs to Hec1 forms a virtual death-trap to trigger Nek2 degradation and eventually cell death. Furthermore, analysis of the gene expression profiles of breast cancer patient samples revealed that co-elevated expressions of Hec1 and Nek2 correlated with the shortest survival. Treatment of mice with this kind of tumor with INHs significantly suppressed tumor growth without obvious toxicity. Taken together, the new INH derivatives are suitable for translation into clinical application.

The centrosomal kinase NEK2 is a novel splicing factor kinase involved in cell survival

NEK2 is a serine/threonine kinase that promotes centrosome splitting and ensures correct chromosome segregation during the G2/M phase of the cell cycle, through phosphorylation of specific substrates. Aberrant expression and activity of NEK2 in cancer cells lead to dysregulation of the centrosome cycle and aneuploidy. Thus, a tight regulation of NEK2 function is needed during cell cycle progression. In this study, we found that NEK2 localizes in the nucleus of cancer cells derived from several tissues. In particular, NEK2 co-localizes in splicing speckles with SRSF1 and SRSF2. Moreover, NEK2 interacts with several splicing factors and phosphorylates some of them, including the oncogenic SRSF1 protein. Overexpression of NEK2 induces phosphorylation of endogenous SR proteins and affects the splicing activity of SRSF1 toward reporter minigenes and endogenous targets, independently of SRPK1. Conversely, knockdown of NEK2, like that of SRSF1, induces expression of pro-apoptotic variants from SRSF1-target genes and sensitizes cells to apoptosis. Our results identify NEK2 as a novel splicing factor kinase and suggest that part of its oncogenic activity may be ascribed to its ability to modulate alternative splicing, a key step in gene expression regulation that is frequently altered in cancer cells.

Identification of candidate B-lymphoma genes by cross-species gene expression profiling

Comparative genome-wide expression profiling of malignant tumor counterparts across the human-mouse species barrier has a successful track record as a gene discovery tool in liver, breast, lung, prostate and other cancers, but has been largely neglected in studies on neoplasms of mature B-lymphocytes such as diffuse large B cell lymphoma (DLBCL) and Burkitt lymphoma (BL). We used global gene expression profiles of DLBCL-like tumors that arose spontaneously in Myc-transgenic C57BL/6 mice as a phylogenetically conserved filter for analyzing the human DLBCL transcriptome. The human and mouse lymphomas were found to have 60 concordantly deregulated genes in common, including 8 genes that Cox hazard regression analysis associated with overall survival in a published landmark dataset of DLBCL. Genetic network analysis of the 60 genes followed by biological validation studies indicate FOXM1 as a candidate DLBCL and BL gene, supporting a number of studies contending that FOXM1 is a therapeutic target in mature B cell tumors. Our findings demonstrate the value of the "mouse filter" for genomic studies of human B-lineage neoplasms for which a vast knowledge base already exists.

Galectin-3 binds to CD45 on diffuse large B-cell lymphoma cells to regulate susceptibility to cell death

Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma and an aggressive malignancy. Galectin-3 (gal-3), the only antiapoptotic member of the galectin family, is overexpressed in DLBCL. While gal-3 can localize to intracellular sites, gal-3 is secreted by DLBCL cells and binds back to the cell surface in a carbohydrate-dependent manner. The major counterreceptor for gal-3 on DLBCL cells was identified as the transmembrane tyrosine phosphatase CD45. Removal of cell-surface gal-3 from CD45 with the polyvalent glycan inhibitor GCS-100 rendered DLBCL cells susceptible to chemotherapeutic agents. Binding of gal-3 to CD45 modulated tyrosine phosphatase activity; removal of endogenous cell-surface gal-3 from CD45 with GCS-100 increased phosphatase activity, while addition of exogenous gal-3 reduced phosphatase activity. Moreover, the increased susceptibility of DLBCL cells to chemotherapeutic agents after removal of gal-3 by GCS-100 required CD45 phosphatase activity. Gal-3 binding to a subset of highly glycosylated CD45 glycoforms was regulated by the C2GnT-1 glycosyltransferase, indicating that specific glycosylation of CD45 is important for regulation of gal-3-mediated signaling. These data identify a novel role for cell-surface gal-3 and CD45 in DLBCL survival and suggest novel therapeutic targets to sensitize DLBCL cells to death.

Irreversible Nek2 kinase inhibitors with cellular activity

A structure-based approach was used to design irreversible, cysteine-targeted inhibitors of the human centrosomal kinase, Nek2. Potent inhibition of Nek2 kinase activity in biochemical and cell-based assays required a noncatalytic cysteine residue (Cys22), located near the glycine-rich loop in a subset of human kinases. Elaboration of an oxindole scaffold led to our most selective compound, oxindole propynamide 16 (JH295). Propynamide 16 irreversibly inhibited cellular Nek2 without affecting the mitotic kinases, Cdk1, Aurora B, or Plk1. Moreover, 16 did not perturb bipolar spindle assembly or the spindle assembly checkpoint. To our knowledge, 16 is the first small molecule shown to inactivate Nek2 kinase activity in cells.

The basis and rational use of molecular genetic testing in mature B-cell lymphomas

An increasing number of neoplasms are associated with variably specific genetic abnormalities. This is best exemplified by hematological malignancies, in which there is a growing list of entities that are defined by their genetic lesion(s); this is not (yet) the case in mature B-cell lymphomas. However, enhanced insights into the pathogenesis of this large and diverse group of lymphomas have emerged with the ongoing unraveling of a plethora of fascinating genetic abnormalities. The purpose of this review is to synthesize well-recognized data and nascent discoveries in our understanding of the genetic basis of a spectrum of mature B-cell lymphomas, and how this may be applied to contemporary clinical practice. Despite the explosion of new and exciting knowledge in this arena, with the potential for enhanced diagnostic and prognostic strategies, it is essential to remain cognizant of the limitations (and complexity) of genetic investigations, so that assays can be developed and used both judiciously and rationally.