Inhibition of NF-kappaB signaling via tyrosine phosphorylation of Ymer

CCDC50, an essential driver involved in tumorigenesis, is a potential severity marker of diffuse large B cell lymphoma

Diffuse Large B Cell Lymphoma (DLBCL) is the most common form of blood cancer. Among the subtypes, the activated B-cell (ABC) subtype is typically more aggressive and associated with worse outcomes. However, the underlying mechanisms are not fully understood. In this study, we performed microarray analysis to identify potential ABC-DLBCL-associated genes. We employed Kaplan-Meier methods and cox univariate analysis to explore the prognostic value of the identified candidate gene Coiled-coil domain containing 50 (CCDC50). Additionally, we used DLBCL cell lines and mouse models to explore the functions and mechanisms of CCDC50. Finally, we isolated CCDC50-bearing exosomes from clinical patients to study the correlation between these exosomes and disease severity. Our results demonstrated that CCDC50 not only showed significantly positive correlations with ABC subtype, tumor stage and number of extranodal sites, but also suggested poor outcomes in DLBCL patients. We further found that CCDC50 promoted ABC-DLBCL proliferation in vitro and in vivo. Mechanistically, CCDC50 inhibited ubiquitination-mediated c-Myc degradation by stimulating the PI3K/AKT/GSK-3β pathway. Moreover, CCDC50 expression was positively correlated with c-Myc at protein levels in DLBCL patients. Additionally, in two clinical cohorts, the plasma CCDC50-positive exosomes differentiated DLBCL subtypes robustly (AUC > 0.80) and predicted disease severity effectively (p < 0.05). Our findings suggest that CCDC50 likely drives disease progression in ABC-DLBCL patients, and the CCDC50-bearing exosome holds great potential as a non-invasive biomarker for subtype diagnosis and prognosis prediction of DLBCL patients.

Insights into the pathophysiology of DFNA44 hearing loss associated with CCDC50 frameshift variants

Non-syndromic sensorineural hearing loss (SNHL) is the most common sensory disorder, and it presents a high genetic heterogeneity. As part of our clinical genetic studies, we ascertained a previously unreported mutation in CCDC50 [c.828_858del, p.(Asp276Glufs*40)] segregating with hearing impairment in a Spanish family with SNHL associated with the autosomal dominant deafness locus DFNA44, which is predicted to disrupt protein function. To gain insight into the mechanism behind DFNA44 mutations, we analysed two Ccdc50 presumed loss-of-function mouse mutants, which showed normal hearing thresholds up to 6 months of age, indicating that haploinsufficiency is unlikely to be the pathogenic mechanism. We then carried out in vitro studies on a set of artificial mutants and on the p.(Asp276Glufs*40) and p.(Phe292Hisfs*37) human mutations, and determined that only the mutants containing the six-amino-acid sequence CLENGL as part of their aberrant protein tail showed an abnormal distribution consisting of perinuclear aggregates of the CCDC50 protein (also known as Ymer). Therefore, we conclude that the CLENGL sequence is necessary to form these aggregates. Taken together, the in vivo and in vitro results obtained in this study suggest that the two identified mutations in CCDC50 exert their effect through a dominant-negative or gain-of-function mechanism rather than by haploinsufficiency.

CCDC50 suppresses NLRP3 inflammasome activity by mediating autophagic degradation of NLRP3

The NLRP3-directed inflammasome complex is crucial for the host to resist microbial infection and monitor cellular damage. However, the hyperactivation of NLRP3 inflammasome is implicated in pathogenesis of inflammatory diseases, including inflammatory bowel disease (IBD). Autophagy and autophagy-related genes are closely linked to NLRP3-mediated inflammation in these inflammatory disorders. Here, we report that CCDC50, a novel autophagy cargo receptor, negatively regulates NLRP3 inflammasome assembly and suppresses the cleavage of pro-caspase-1 and interleukin 1β (IL-1β) release by delivering NLRP3 for autophagic degradation. Transcriptome analysis showed that knockdown of CCDC50 results in upregulation of signaling pathways associated with autoinflammatory diseases. CCDC50 deficiency leads to enhanced proinflammatory cytokine response triggered by a wide range of endogenous and exogenous NLRP3 stimuli. Ccdc50-deficient mice are more susceptible to dextran sulfate (DSS)-induced colitis and exhibit more severe gut inflammation with elevated NLRP3 inflammasome activity. These results illustrate the physiological significance of CCDC50 in the pathogenicity of inflammatory diseases, suggesting protective roles of CCDC50 in keeping gut inflammation under control.

Myostatin Promotes Osteoclastogenesis by Regulating Ccdc50 Gene Expression and RANKL-Induced NF-κB and MAPK Pathways

Myostatin is a crucial cytokine that is widely present in skeletal muscle and that negatively regulates the growth and development of muscle cells. Recent research has shown that myostatin might play an essential role in bone metabolism. In RAW264.7 cells and bone marrow monocytes (BMMCs), myostatin activates the expression of the II type receptor ActR II B. Here, we report that myostatin significantly promoted RANKL/M-CSF-induced osteoclastogenesis and activated NF-κB and MAPK pathways in vitro via the Ccdc50 gene. Overexpression of myostatin promoted osteoclastogenesis and osteoclastogenesis-related markers including c-Src, MMP9, CTR, CK, and NFATc1. Specifically, myostatin increased the phosphorylation of Smad2, which led to the activation of NF-κB and MAPK pathways to activate osteoclastogenesis. Ccdc50 was identified as a gene whose expression was highly decreased in osteoclastogenesis upon myostatin treatment, and it could inhibit the function of myostatin in osteoclastogenesis by blocking NF-κB and MAPKs pathways. Our study indicates that myostatin is a promising candidate target for inhibiting RANKL-mediated osteoclastogenesis and might participate in therapy for osteoporosis, and that the Ccdc50 gene plays a significant role in the regulatory process.

Coiled-coil domain containing 50-V2 protein positively regulates neurite outgrowth

The coiled-coil domain containing 50 (CCDC50) protein is a phosphotyrosine-dependent signalling protein stimulated by epidermal growth factor. It is highly expressed in neuronal cells in the central nervous system; however, the roles of CCDC50 in neuronal development are largely unknown. In this study, we showed that the depletion of CCDC50-V2 impeded the neuronal development process, including arbor formation, spine density development, and axonal outgrowth, in primary neurons. Mechanistic studies revealed that CCDC50-V2 positively regulated the nerve growth factor receptor, while it downregulated the epidermal growth factor receptor pathway. Importantly, JNK/c-Jun activation was found to be induced by the CCDC50-V2 overexpression, in which the interaction between CCDC50-V2 and JNK2 was also observed. Overall, the present study demonstrates a novel mechanism of CCDC50 function in neuronal development and provides new insight into the link between CCDC50 function and the aetiology of neurological disorders.

HnRNP A1 - mediated alternative splicing of CCDC50 contributes to cancer progression of clear cell renal cell carcinoma via ZNF395

BACKGROUND

Aberrant alternative splicing events play critical roles in carcinogenesis and progression of many cancers, while sparse studies regarding to alternative splicing are available for clear cell renal cell carcinoma (ccRCC). We identified that alternative splicing of coiled-coil domain containing 50 (CCDC50) was dysregulated in ccRCC, whereas the clinical significance of this splicing event and its splicing regulation mechanisms were still elusive.

METHODS

Bioinformatic algorithm was utilized to identify significant exon skipping events in ccRCC via exon sequencing data from The Cancer Genome Atlas. Semi-quantitative real-time polymerase chain reaction and western blot were used to validate the aberrant expression of different transcripts in renal cancer tissues, cell lines and corresponding noncancerous controls. Short hairpin RNA targeting CCDC50 and overexpressing plasmids for each transcript were introduced into ccRCC cell lines, followed by a series of in vitro and in vivo functional experiments. Moreover, a panel of splicing factors were identified and their roles on splicing regulation of CCDC50 precursor mRNA (pre-mRNA) were studied. Furthermore, RNAseq data were analyzed to elucidate downstream molecules of CCDC50. Two-way analysis of variance and unpaired Student t test were used in statistical analysis.

RESULTS

Pre-mRNA of CCDC50 generated two transcripts, full-length transcript (CCDC50-FL) and truncated transcript (CCDC50-S) with exon 6 skipped. CCDC50-S was overexpressed in ccRCC tissues and cell lines compared to noncancerous counterparts, but CCDC50-FL was only detected in noncancerous tissues and normal renal epithelial cells. Higher percent spliced-in index was associated with better survival in ccRCC patients. In vitro and in vivo functional experiments indicated that CCDC50-S transcript promoted the proliferation, migration, invasion and tumorigenesis of ccRCC, while CCDC50-FL exerted opposite tumor suppressive functions. Besides, we identified that heterogeneous nuclear ribonucleoprotein A1 (HnRNP A1) could promote the skipping of exon 6, which resulted in higher portion of CCDC50-S and oncogenic transformation. Moreover, zinc finger protein 395 (ZNF395) was identified as a downstream protein of CCDC50-S, and the interaction initiated oncogenic pathways which were involved in ccRCC progression.

CONCLUSIONS

Aberrant alternative splicing of CCDC50 is regulated by HnRNP A1 in ccRCC. This splicing event contributes to cancer progression through the downstream pathway involving ZNF395.

The mechanism of cancer drug addiction in ALK-positive T-Cell lymphoma

Rational new strategies are needed to treat tumors resistant to kinase inhibitors. Mechanistic studies of resistance provide fertile ground for development of new approaches. Cancer drug addiction is a paradoxical resistance phenomenon, well-described in MEK-ERK-driven solid tumors, in which drug-target overexpression promotes resistance but a toxic overdose of signaling if inhibitor is withdrawn. This can permit prolonged control of tumors through intermittent dosing. We and others showed previously that cancer drug addiction arises also in the hematologic malignancy ALK-positive anaplastic large-cell lymphoma (ALCL) resistant to ALK-specific tyrosine kinase inhibitors (TKIs). This is driven by overexpression of the fusion kinase NPM1-ALK, but the mechanism by which ALK overactivity drives toxicity upon TKI withdrawal remained obscure. Here we reveal the mechanism of ALK-TKI addiction in ALCL. We interrogated the well-described mechanism of MEK/ERK pathway inhibitor addiction in solid tumors and found it does not apply to ALCL. Instead, phosphoproteomics and confirmatory functional studies revealed STAT1 overactivation is the key mechanism of ALK-TKI addiction in ALCL. Withdrawal of TKI from addicted tumors in vitro and in vivo leads to overwhelming phospho-STAT1 activation, turning on its tumor-suppressive gene-expression program and turning off STAT3’s oncogenic program. Moreover, a novel NPM1-ALK-positive ALCL PDX model showed significant survival benefit from intermittent compared to continuous TKI dosing. In sum, we reveal for the first time the mechanism of cancer-drug addiction in ALK-positive ALCL and the benefit of scheduled intermittent dosing in high-risk patient-derived tumors in vivo.

Identification of subtype specific miRNA-mRNA functional regulatory modules in matched miRNA-mRNA expression data: multiple myeloma as a case

Identification of miRNA-mRNA modules is an important step to elucidate their combinatorial effect on the pathogenesis and mechanisms underlying complex diseases. Current identification methods primarily are based upon miRNA-target information and matched miRNA and mRNA expression profiles. However, for heterogeneous diseases, the miRNA-mRNA regulatory mechanisms may differ between subtypes, leading to differences in clinical behavior. In order to explore the pathogenesis of each subtype, it is important to identify subtype specific miRNA-mRNA modules. In this study, we integrated the Ping-Pong algorithm and multiobjective genetic algorithm to identify subtype specific miRNA-mRNA functional regulatory modules (MFRMs) through integrative analysis of three biological data sets: GO biological processes, miRNA target information, and matched miRNA and mRNA expression data. We applied our method on a heterogeneous disease, multiple myeloma (MM), to identify MM subtype specific MFRMs. The constructed miRNA-mRNA regulatory networks provide modular outlook at subtype specific miRNA-mRNA interactions. Furthermore, clustering analysis demonstrated that heterogeneous MFRMs were able to separate corresponding MM subtypes. These subtype specific MFRMs may aid in the further elucidation of the pathogenesis of each subtype and may serve to guide MM subtype diagnosis and treatment.

Cytoplasmic ezrin and moesin correlate with poor survival in head and neck squamous cell carcinoma

Members of the 4.1 superfamily of proteins, including ezrin, moesin, merlin, and willin regulate many normal physiologic processes such as cellular shape, motility, and proliferation. In addition, they contribute both to tumor development and tumor progression. We reported previously that strong cytoplasmic ezrin expression was independently associated with poorer patient survival. One hundred and thirty-one histologically confirmed primary head and neck squamous cell carcinomas were examined prospectively for cancer progression and survival at a large health care center in the Bronx, NY, USA. Immunohistochemical analysis of ezrin, moesin, merlin, and willin expression in tissue microarray samples of primary head and neck squamous cell carcinoma revealed a significant association of increased cytoplasmic ezrin with poor cancer survival. Global RNA analyses suggest that cancers with high cytoplasmic ezrin have a more invasive phenotype. This study supports our previous findings associating cytoplasmic ezrin with more aggressive behavior and poorer outcome and indicates the need for a multi-institutional study to validate the use of cytoplasmic ezrin as a biomarker for treatment planning in head and neck squamous cell carcinoma.

Gene knockdown studies revealed CCDC50 as a candidate gene in mantle cell lymphoma and chronic lymphocytic leukemia

The two B-cell non-Hodgkin's lymphoma entities, chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL), show recurrent chromosomal gains of 3q25-q29, 12q13-q14 and 18q21-q22. The pathomechanisms affected by these aberrations are not understood. The aim of this study was to identify genes, located within these gained regions, which control cell death and cell survival of MCL and CLL cancer cells. Blood samples collected from 18 patients with CLL and 6 patients with MCL, as well as 6 cell lines representing both malignancies were analyzed by gene expression profiling. By a comparison of genomic DNA and gene expression, 72 candidate genes were identified. We performed a limited RNA interference screening with these candidates to identify genes affecting cell survival. CCDC50 (coiled coil domain containing protein 50), SERPINI2 and SMARCC2 mediated a reduction of cell viability in primary CLL cells as well as in cell lines. Gene knockdown and a nuclear factor kappa B (NFkappaB) reporter gene assay revealed that CCDC50 is required for survival in MCL and CLL cells and controls NFkappaB signaling.