DDX27 regulates oral squamous cell carcinoma development through targeting CSE1L

THE HEADINGS AIMS

DEAD-box helicase 27 (DDX27), a member of the DEAD-Box nucleic acid helicase family, holds an elusive role in oral squamous cell carcinoma (OSCC). This study aims to unravel the regulatory functions of DDX27 in OSCC and explore its downstream targets.

MATERIALS AND METHODS

A commercial oral squamous cell carcinoma (OSCC) tissue microarray (TMA) was utilized. We analyzed differentially expressed genes in OSCC through the GEO database. Target gene silencing was achieved using the shRNA-mediated lentivirus method. Coexpedia analysis identified co-expressed genes associated with DDX27. Additionally, a Co-Immunoprecipitation (Co-IP) experiment confirmed the protein interaction between DDX27 and CSE1L. Xenograft tumor models were employed to evaluate DDX27's role in OSCC tumor formation.

KEY FINDINGS

Elevated DDX27 expression in OSCC correlated with a higher pathological grade. DDX27 knockdown resulted in decreased cell proliferation, increased apoptosis, inhibited cell migration, and induced G2/M phase cell cycle arrest, as well as impaired tumor outgrowth. Coexpedia analysis identified STAU1, NELFCD, and CSE1L as top co-expressed genes. Lentiviral vectors targeting STAU1, NELFCD, and CSE1L revealed that silencing CSE1L significantly impaired cell growth, indicating it as a downstream target of DDX27. Cell rescue experiments demonstrated that increased DDX27 levels ameliorated cell proliferation, attenuated apoptosis, and CSE1L depletion blocked cell development induced by DDX27 overexpression.

SIGNIFICANCES

This study highlighted DDX27 as a potential therapeutic target for OSCC treatment, shedding light on its crucial role in OSCC development. Targeting DDX27 or its downstream effector, CSE1L, holds promise for innovative OSCC therapies.

The role of CSE1L silencing in the regulation of proliferation and apoptosis via the AMPK/mTOR signaling pathway in chronic myeloid leukemia

OBJECTIVES

Chromosome segregation 1-like (CSE1L) is abundant and strongly expressed in solid tumors. However, the expression and role of CSE1L in chronic myeloid leukemia(CML) remain largely unknown.

MATERIALS AND METHODS

The relative expression levels of CSE1L in bone marrow granulocytes from patients with primary CML and non-hematologic controls were measured by flow cytometry. Cell counting kit-8 analysis, DNA Content Quantitation Assay, and Annexin V-PE/7-AAD staining were applied to assess the effects of CSE1L knockdown on cell proliferation, cell cycle progression, and apoptosis.

RESULTS

Elevated expression of CSE1L was detected in bone marrow granulocytes of patients with primary CML. In the CML cell line K562 cells, CSE1L knockdown impaired cell proliferation blocked the cell cycle shift from G0/G1 phase to the S phase, and promoted apoptosis. Knockdown of CSE1L reduced Bcl-2 protein expression and increased Bax protein expression. Meanwhile, knockdown of CSE1L enhanced the expression of phospho-AMPK protein and decreased the expression of phospho-mTOR protein. The expression of total AMPK and mTOR proteins was not affected. In addition, CSE1L expression levels were decreased in imatinib-treated K562 cells.

CONCLUSIONS

CSE1L plays a pivotal role in K562 cell survival and growth. These functions may be partially dependent on the AMPK/mTOR signaling pathway to achieve. In addition, CSE1L may have had a future impact on the treatment of CML patients.

The Ubiquitin-Proteasome System Participates in Sperm Surface Subproteome Remodeling during Boar Sperm Capacitation

Sperm capacitation is a complex process endowing biological and biochemical changes to a spermatozoon for a successful encounter with an oocyte. The present study focused on the role of the ubiquitin-proteasome system (UPS) in the remodeling of the sperm surface subproteome. The sperm surface subproteome from non-capacitated and in vitro capacitated (IVC) porcine spermatozoa, with and without proteasomal inhibition, was selectively isolated. The purified sperm surface subproteome was analyzed using high-resolution, quantitative liquid chromatography-mass spectrometry (LC-MS) in four replicates. We identified 1680 HUGO annotated proteins, out of which we found 91 to be at least 1.5× less abundant (p < 0.05) and 141 to be at least 1.5× more abundant (p < 0.05) on the surface of IVC spermatozoa. These proteins were associated with sperm capacitation, hyperactivation, metabolism, acrosomal exocytosis, and fertilization. Abundances of 14 proteins were found to be significantly different (p < 0.05), exceeding a 1.5-fold abundance between the proteasomally inhibited (100 µM MG132) and vehicle control (0.2% ethanol) groups. The proteins NIF3L1, CSE1L, NDUFB7, PGLS, PPP4C, STK39, and TPRG1L were found to be more abundant; while BPHL, GSN, GSPT1, PFDN4, STYXL1, TIMM10, and UBXN4 were found to be less abundant in proteasomally inhibited IVC spermatozoa. Despite the UPS having a narrow range of targets, it modulated sperm metabolism and binding by regulating susceptible surface proteins. Changes in CSE1L, PFDN4, and STK39 during in vitro capacitation were confirmed using immunocytochemistry, image-based flow cytometry, and Western blotting. The results confirmed the active participation of the UPS in the extensive sperm surface proteome remodeling that occurs during boar sperm capacitation. This work will help us to identify new pharmacological mechanisms to positively or negatively modulate sperm fertilizing ability in food animals and humans.

Aberrantly Expressed Hsa_circ_0060762 and CSE1L as Potential Peripheral Blood Biomarkers for ALS

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive adult-onset neurodegenerative disease that is often diagnosed with a delay due to initial non-specific symptoms. Therefore, reliable and easy-to-obtain biomarkers are an absolute necessity for earlier and more accurate diagnostics. Circular RNAs (circRNAs) have already been proposed as potential biomarkers for several neurodegenerative diseases. In this study, we further investigated the usefulness of circRNAs as potential biomarkers for ALS. We first performed a microarray analysis of circRNAs on peripheral blood mononuclear cells of a subset of ALS patients and controls. Among the differently expressed circRNA by microarray analysis, we selected only the ones with a host gene that harbors the highest level of conservation and genetic constraints. This selection was based on the hypothesis that genes under selective pressure and genetic constraints could have a major role in determining a trait or disease. Then we performed a linear regression between ALS cases and controls using each circRNA as a predictor variable. With a False Discovery Rate (FDR) threshold of 0.1, only six circRNAs passed the filtering and only one of them remained statistically significant after Bonferroni correction: hsa_circ_0060762 and its host gene CSE1L. Finally, we observed a significant difference in expression levels between larger sets of patients and healthy controls for both hsa_circ_0060762 and CSE1L. CSE1L is a member of the importin β family and mediates inhibition of TDP-43 aggregation; the central pathogenicity in ALS and hsa_circ_0060762 has binding sites for several miRNAs that have been already proposed as biomarkers for ALS. In addition, receiver operating characteristics curve analysis showed diagnostic potential for CSE1L and hsa_circ_0060762. Hsa_circ_0060762 and CSE1L thus represent novel potential peripheral blood biomarkers and therapeutic targets for ALS.

Dual RNA-Seq of H5N1 Avian Influenza Virus and Host Cell Transcriptomes Reveals Novel Insights Into Host-Pathogen Cross Talk

H5N1 avian influenza virus (AIV) is a highly pathogenic influenza virus that poses a substantial threat to poultry production and public health. A comprehensive understanding of host-pathogen interactions for AIV requires knowledge of gene expression changes in both the pathogen and the host upon infection. We report the use of dual RNA sequencing technology to uncover trends in gene expression in H5N1 AIV and chickens (DF1 cells) during the course of infection. The expression of all viral genes increased continuously from 0 to 20 h post infection. We also identified 2,762 differentially expressed host genes during infection. Pathway analysis found that genes related to the signaling pathways of DNA replication, T cell activation, NF-kappa B signaling pathway, and RNA degradation were significantly enriched. We demonstrated that the cis-acting lncRNA MSTRG.14019.1 targeted CSE1L and may affect virus replication. This study provides a more comprehensive and detailed understanding of host-virus interactions at the RNA level during the course of H5N1 AIV infection.

Role of CSE1L expression in determining recurrence and survival of laryngeal tumors

PURPOSE

The correlation of CSE1L (human chromosomal segregation 1-like) staining intensity with disease-free survival, disease recurrence and development of distant metastases in Advanced Laryngeal Tumors.

METHODS

Specimens of patients with advanced glottic larynx cancer (T3, T4) were evaluated for nuclear CSE1L staining intensity. According to mild, moderate and severe CSE1L staining, patients were compared in terms of disease-free survival, disease recurrence and development of distant metastases.

RESULTS

17 of the 57 patients died within 5 years, distant metastases developed in 5 patients, and recurrence in 5 patients. Of the 17 patients who died within 5 years, 10(%59) showed severe staining with CSE1L, 6 (%35) showed moderate staining, and only 1 (%6) patient showed mild staining. 4 (%80) out of 5 patients who developed distant metastases were those with moderate staining with CSE1L. Metastases did not develop in any patient who stained poorly with CSE1L. 2 (%40) of the 5 patients who developed relapse were patients with severe staining with CSE1L, while 3 (%60) were patients with moderate staining with CSE1L. No recurrence was observed in any patient with mild staining with CSE1L.

CONCLUSION

CSE1L will help in demonstrating the increased risk of distant metastasis, increased recurrence probability and shortened life expectancy of advanced laryngeal carcinoma.

CSE1L silencing impairs tumor progression via MET/STAT3/PD-L1 signaling in lung cancer

CSE1L is involved in the cancer progression of several types of cancer. Its expression status, potential oncogenic role and underlying mechanism in lung cancer, however, are unclear. Here, we investigated CSE1L expression in primary lung adenocarcinoma based on multiple datasets and then investigated its oncologic role in lung cancer. We also examined the potential molecular mechanisms of CSE1L in cancer progression. CSE1L levels were increased in cancer as compared to normal lung tissues. CSE1L expression was higher in poorly-differentiated late stage and lymph node positive metastatic tumors. Higher CSE1L level was correlated with worse patient outcome. Knockdown of CSE1L using siRNAs impaired cell proliferation, invasion, migration and induced cell apoptosis. Mechanistically, MET, STAT3 and PD-L1 proteins were decreased upon CSE1L silencing. These results suggest that CSE1L may affect tumor progression through MET/STAT3/PD-L1 signaling. CSE1L may have potential as a biomarker and therapeutic target for lung cancer.

The microRNA-451a/chromosome segregation 1-like axis suppresses cell proliferation, migration, and invasion and induces apoptosis in nasopharyngeal carcinoma

MicroRNA-451a (miR-451a) has been implicated in the initiation and progression of multiple cancers. However, the regulatory mechanisms underlying its function in nasopharyngeal carcinoma (NPC) are poorly understood. Thus, we investigated in detail the role of the microRNA-451a/chromosome segregation 1-like (miR-45a/CSE1L) axis and its regulatory mechanism in NPC. We examined the levels of miR-451a and CSE1L in NPC, and assessed the effects of miR-451a and CSE1L on NPC by cell functional experiments. Furthermore, we elucidated the direct regulatory effect of miR-451a on CSE1L by the luciferase reporter assay, RNA pull-down assay, and RNA immunoprecipitation and validated our observations by calculating the Pearson's correlation coefficient. We found that miR-451a was down-regulated in NPC cells, and its over-expression attenuated cell proliferation, migration, and invasion, and tumor growth in 5-8 F and SUNE-1 cells and promoted apoptosis. Moreover, CSE1L was the direct gene target of miR-451a, and its over-expression abrogated miR-451a-dependent inhibition of malignancy in 5-8 F and SUNE-1 cells. The Pearson's correlation coefficient indicated a negative correlation between CSE1L and miR-451a. miR-451a serves as a tumor suppressor and targets CSE1L. miR-451a suppresses CSE1L expression, thereby reducing proliferation, invasion, and migration and increasing apoptosis of NPC cells.

CSE1L promotes nuclear accumulation of transcriptional coactivator TAZ and enhances invasiveness of human cancer cells

The transcriptional coactivator with PDZ-binding motif (TAZ) (WWTR1) induces epithelial-mesenchymal transition and enhances drug resistance in multiple cancers. TAZ has been shown to interact with transcription factors in the nucleus, but when phosphorylated, translocates to the cytoplasm and is degraded through proteasomes. Here, we identified a compound TAZ inhibitor 4 (TI-4) that shifted TAZ localization to the cytoplasm independently of its phosphorylation. We used affinity beads to ascertain a putative target of TI-4, chromosomal segregation 1 like (CSE1L), which is known to be involved in the recycling of importin α and as a biomarker of cancer malignancy. We found that TI-4 suppressed TAZ-mediated transcription in a CSE1L-dependent manner. CSE1L overexpression increased nuclear levels of TAZ, whereas CSE1L silencing delayed its nuclear import. We also found via the in vitro coimmunoprecipitation experiments that TI-4 strengthened the interaction between CSE1L and importin α5 and blocked the binding of importin α5 to TAZ. WWTR1 silencing attenuated CSE1L-promoted colony formation, motility, and invasiveness of human lung cancer and glioblastoma cells. Conversely, CSE1L silencing blocked TAZ-promoted colony formation, motility, and invasiveness in human lung cancer and glioblastoma cells. In human cancer tissues, the expression level of CSE1L was found to correlate with nuclear levels of TAZ. These findings support that CSE1L promotes the nuclear accumulation of TAZ and enhances malignancy in cancer cells.

FLVCR1 Predicts Poor Prognosis and Promotes Malignant Phenotype in Esophageal Squamous Cell Carcinoma via Upregulating CSE1L

Objective

Dysregulation of feline leukemia virus subgroup C receptor 1(FLVCR1) expression has been investigated in several tumors. However, the expression and role of FLVCR1 in esophageal squamous cell carcinoma (ESCC) remain largely unknown.

Methods

FLVCR1 expression in tissues was measured by immunohistochemical staining (IHC). Celigo assay, MTT assay, colony formation, caspase 3/7 activity analysis, wound healing assay, Transwell migration, and invasion assay were applied to assess the effects of FLVCR1 on ESCC tumorigenesis. Coimmunoprecipitation (Co-IP) and liquid chromatography-mass spectrometry (LC-MS) were used to identify protein interactions with FLVCR1. An in vivo imaging system (IVIS) was used to investigate the functions of FLVCR1 on the growth and metastatic capability of ESCC cells in a xenograft model and a tail vein metastasis model.

Results

Elevated expression of FLVCR1 was detected in ESCC tissues and predicted poor survival. Upregulated FLVCR1 was positively correlated with lymph node metastasis (N stage) and late tumor-node-metastasis (TNM) stage. FLVCR1 knockdown inhibited cell proliferation and colony formation ability, induced cell apoptosis, and repressed cell migration and invasion of ESCC in vitro. Inhibition of FLVCR1 markedly repressed tumorigenicity and metastasis of ESCC cells in vivo. Mechanistically, chromosome segregation 1–like (CSE1L) was identified to interact with FLVCR1 using a Co-IP assay. Moreover, the inhibitory effect of FLVCR1 knockdown on proliferation and migration was counteracted by the exogenous expression of CSE1L.

Conclusion

FLVCR1 plays a pivotal role in ESCC cell survival, growth, and migration. These functions may be partially dependent upon the protein interaction between FLVCR1 and CSE1L. In addition, FLVCR1 can be applied as a clinical prognostic marker for patients with ESCC.

CSE1L, as a novel prognostic marker, promotes pancreatic cancer proliferation by regulating the AKT/mTOR signaling pathway

Pancreatic cancer is one of the most aggressive tumors with poor prognosis and new targetable therapies are urgently required. CSE1L (chromosome segregation 1 like) is thought to play an important role in tumorigenesis and acts as a cancer therapeutic target. However, the biological function and the underlying mechanism of CSE1L in pancreatic cancer are still not fully explicit. In the present study, we found that high CSE1L expression was related to a worse prognosis in patients with pancreatic cancer according to data from the Cancer Genome Atlas (TCGA) database. Additionally, we found that CSE1L knockdown inhibited the proliferation of pancreatic cancer cells and promoted apoptosis, while CSE1L overexpression demonstrated the opposite phenomenon. Furthermore, we discovered that CSE1L might regulate pancreatic cancer proliferation through AKT signaling pathway. In summary, we reveal that CSE1L plays a crucial role in tumor growth and may serve as a potential prognostic and therapeutic target for pancreatic cancer.

Nuclear export protein CSE1L interacts with P65 and promotes NSCLC growth via NF-κB/MAPK pathway

Non-small cell lung cancer (NSCLC) is characterized with high morbidity and mortality, mainly due to frequent recurrence and metastasis. However, the underlying molecular mechanisms of NSCLC tumorigenesis are largely unclear. Through data mining in the ONCOMINE and Gene Expression Omnibus (GEO) databases, the expression of CSE1L (chromosome segregation like 1 protein/CAS), an exportin, was identified to be significantly upregulated in NSCLC and positively associated with poor prognosis of patients. By use of in vitro and in vivo gain- and loss-of-function experiments, we found that CSE1L can promote NSCLC cell proliferation while inhibiting cell apoptosis. Through immunoprecipitation and mass spectrometry experiments, we demonstrated that CSE1L interacted with RELA (named as P65) and affected its location in the nucleus. Moreover, we found that one of the mechanisms by which CSE1L promotes proliferation and inhibits apoptosis is through activating the nuclear factor-κB (NF-κB)/mitogen-activated protein kinase (MAPK) signaling pathway. In summary, our findings indicated an oncogenic role of CSE1L in NSCLC tumorigenesis.

Circular RNA 0060745, a Novel circRNA, Promotes Colorectal Cancer Cell Proliferation and Metastasis Through miR-4736 Sponging

Purpose

Recent studies have shown that noncoding RNAs (ncRNAs) play essential roles in the development of a number of cancers. Circular RNAs (circRNAs) have been shown to contribute to the progression of colorectal cancer (CRC).

Methods

In this study, the expression levels of circular RNA 0060745 (circ_0060745), and microRNA 4736 (miR-4736) were measured using qRT-PCR. Kaplan–Meier survival analysis and receiver operating characteristic (ROC) analysis were used to evaluate the diagnostic value of circ_0060745. Transwell assay and cell counting kit-8 (CCK8) assay were used to determine the metastatic and proliferative capacity of CRC cells. The expression of chromosome segregation one like (CSE1L) was measured using Western blotting and immunohistochemistry (IHC). In addition, RNA pull-down assay and luciferase assay were performed to verify the targeted binding between miR-473,6 and circ_0060745, and between as miR-4736 and CSE1L.

Results

We showed that circ_0060745 was upregulated in CRC, and was associated with unfavorable clinicopathological characteristics. We also showed that circ_0060745 acted as an oncogene and promoted CRC cell proliferation and metastasis. Circ_0060745 was primarily located in the cytoplasm. Furthermore, miR-4736 was downregulated in CRC, was a downstream target of circ_0060745, and mediated proliferation and metastasis. We showed that circ_0060745 sequestered miR-4736, which resulted in CRC cell proliferation and metastasis. Finally, we showed that CSE1L, a downstream target of miR-4736, was upregulated in CRC and mediated suppression of proliferation and metastasis in CRC.

Conclusion

The results of this study showed that circ_0060745 promoted CRC cell proliferation and metastasis via modulation of miR-4736/CSE1L signaling. The Circ_0060745/miR-4736/CSE1L axis might be a novel target for the treatment of CRC.

LncRNA BANCR promotes tumorigenesis and enhances adriamycin resistance in colorectal cancer

Colorectal cancer (CRC) is the third most common malignancy in the United States. Chemotherapeutic resistance is a massive obstacle for cancer treatment. The roles and molecular basis of long non-coding RNA BRAF-activated noncoding RNA (BANCR) in CRC progression and adriamycin (ADR) resistance have not been extensively identified. In this study, we found that BANCR and CSE1L expressions were upregulated in CRC tumor tissues. Meanwhile, CSE1L expression was correlated with depth of CRC. BANCR silencing suppressed cell proliferation and invasion capacity, increased apoptotic rate and potentiated cell sensitivity to ADR. CSE1L downregulation triggered a reduction of cell proliferation and invasion ability, and an increase of apoptosis rate and cell sensitivity to ADR. CSE1L overexpression attenuated si-BANCR-mediated anti-proliferation, anti-invasion and pro-apoptosis effects in CRC cells. BANCR acted as a molecular sponge of miR-203 to sequester miR-203 away from CSE1L in CRC cells, resulting in the upregulation of CSE1L expression. CSE1L knockdown inhibited expressions of DNA-repair-related proteins (53BP1 and FEN1) in HCT116 cells. BANCR knockdown also inhibited tumor growth and enhanced ADR sensitivity in CRC mice model. In conclusion, BANCR knockdown suppressed CRC progression and strengthened chemosensitization of CRC cells to ADR possibly by regulating miR-203/CSE1L axis, indicating that BANCR might be a promising target for CRC treatment.

The role of CSE1L expression in cervical lymph node metastasis of larynx tumors

Introduction

According to international reports, 30–40% of all head and neck cancers are larynx cancers, comprising 1–2.5% of all cancer types. Cervical nodal involvement has been reported to be 40% and 65% in T3 and T4 cases, respectively. Five-year survival in patients with cervical lymph node metastasis has been demonstrated to be 50% lower compared to patients with no metastasis. Chromosome segregation like 1 protein; is a DNA fragment isolated by Brinkmann et al. in 1995 that corresponds to yeast chromosome segregation protein. Studies on the effect of chromosome segregation like 1 protein expression in head and neck tumors are rare and it has been shown that nuclear chromosome segregation like 1 protein is over-expressed in these studies where gastrointestinal and breast tumors over-expressed cytoplasmic chromosome segregation like 1 protein.

Objective

Chromosome segregation like 1 protein may regulate the proliferation and metastasis of T3–T4 glottic larynx cancer. The aim of this study is to show the relationship between chromosome segregation like 1 protein expression and cervical lymph node metastasis of T3–T4 glottic larynx cancer.

Methods

A total of 57 male patients who were operated for T3–T4 glottic cancer in a tertiary referral hospital was included in this study. There were 28 patients with cervical lymph node metastasis and 29 patients without lymph node metastasis. Immunohistochemistry was carried out on formalin-fixed, paraffin-embedded archival glottic larynx tumour tissue. According to the percentage of immunoreactive cells, chromosome segregation like 1 protein status was analyzed.

Results

Among the patients, who had no cervical lymph node metastasis, 15 patients showed weak nuclear staining, 12 patients showed moderate nuclear staining and only 2 patients showed high nuclear staining for chromosome segregation like 1 protein. Among the patients who had cervical lymph node metastasis, 18 patients showed high nuclear staining, 9 patients showed moderate staining and only one patient showed weak staining for chromosome segregation like 1 protein. None of the metastatic patients showed cytoplasmic staining and only one patient in the non-metastatic group showed cytoplasmic staining for chromosome segregation like 1 protein. There was a positive correlation between nuclear chromosome segregation like 1 protein expression and cervical lymph node metastasis (r = 0,668) and it was statistically significant (p < 0,001).

Conclusion

Chromosome segregation like 1 protein expression is correlated with lymph node metastasis in T3–T4 glottic cancers. This may change the approach to cervical node treatment in patients with glottic cancers in future.

CSE1L participates in regulating cell mitosis in human seminoma

Objectives

CSE1L has been reported to be highly expressed in various tumours. Testicular germ cell tumours are common among young males, and seminoma is the major type. However, whether CSE1L has functions in the seminoma is unclear.

Materials and methods

The expression of CSE1L was detected by immunohistochemistry in seminoma tissues and non‐tumour normal testis tissues from patients. CSE1L distribution during cell mitosis was determined by immunofluorescent staining with CSE1L, α‐tubulin and γ‐tubulin antibodies. The effects of Cse1L knockdown on cell proliferation and cell cycle progression were determined by Cell Counting Kit‐8 assay, flow cytometry, PH3 staining and bromodeoxyuridine incorporation assay.

Results

CSE1L was significantly enriched in the seminoma tissue compared with the non‐tumour normal testis tissue. CSE1L also co‐localized with α‐tubulin in the cells with a potential to divide. In the seminoma cell line TCam‐2, CSE1L was associated with the spindles and the centrosomes during cell division. The knockdown of CSE1L in TCam‐2 cells attenuated the cells’ proliferative capacity. Cell cycle assay revealed that the CSE1L‐deficient cells were mainly arrested in the G0/G1 phase and moderately delayed in the G2/M phase. The proportion of cells with multipolar spindle and abnormal spindle geometry was obviously increased by CSE1L expression silencing in the TCam‐2 cells.

Conclusions

Overall, these findings showed that CSE1L plays a pivotal role in maintaining cell proliferation and cell division in seminomas.

Roles of the CSE1L-mediated nuclear import pathway in epigenetic silencing

Epigenetic silencing can be mediated by various mechanisms, and many regulators remain to be identified. Here, we report a genome-wide siRNA screening to identify regulators essential for maintaining gene repression of a CMV promoter silenced by DNA methylation. We identified CSE1L (chromosome segregation 1 like) as an essential factor for the silencing of the reporter gene and many endogenous methylated genes. CSE1L depletion did not cause DNA demethylation. On the other hand, the methylated genes derepressed by CSE1L depletion largely overlapped with methylated genes that were also reactivated by treatment with histone deacetylase inhibitors (HDACi). Gene silencing defects observed upon CSE1L depletion were linked to its nuclear import function for certain protein cargos because depletion of other factors involved in the same nuclear import pathway, including KPNAs and KPNB1 proteins, displayed similar derepression profiles at the genome-wide level. Therefore, CSE1L appears to be critical for the nuclear import of certain key repressive proteins. Indeed, NOVA1, HDAC1, HDAC2, and HDAC8, genes known as silencing factors, became delocalized into cytosol upon CSE1L depletion. This study suggests that the cargo specificity of the protein nuclear import system may impact the selectivity of gene silencing.

CAS (CSE1L) signaling pathway in tumor progression and its potential as a biomarker and target for targeted therapy

CSE1L (chromosome segregation 1-like protein), also named as CAS (cellular apoptosis susceptibility protein), is highly expressed in most cancer types. CSE1L/CAS is a multiple functional protein that plays roles in apoptosis, cell survival, chromosome assembly, nucleocytoplasmic transport, microvesicle formation, and cancer metastasis; some of the functions are explicitly correlated. CSE1L is also a cancer serum biomarker. The phosphorylation of CAS is regulated by the extracellular signal-regulated kinase (ERK). The RAS/RAF/MAPK/ERK signaling pathways are the essential targets of most targeted cancer drugs, thus serum phosphorylated CSE1L may be a potential biomarker for monitoring drug resistance in targeted therapy. CSE1L can regulate Ras-induced ERK phosphorylation. CSE1L also regulates the expression and phosphorylation of CREB (cAMP response element binding protein) and MITF (microphthalmia-associated transcription factor) and is thus involved in the melanogenesis and progression of melanoma. CAS is an exosome/microvesicle membrane protein. Tumor cells consistently secrete microvesicles and tumor-derived microvesicles may be accumulated around tumors. Therefore, microvesicle membrane CSE1L may be a potential target for the development of high-efficacy antibody-drug conjugates (ADCs) for cancer therapy. This review will focus on CSE1L expression in cancers, its relationship to Ras/ERK and cAMP/PKA signaling pathways in melanoma development, its potential for the development of ADCs and tumor imaging reagents, and secretory phosphorylated CSE1L for monitoring the emergence of drug resistance in targeted cancer therapy.

CSE1L Links cAMP/PKA and Ras/ERK pathways and regulates the expressions and phosphorylations of ERK1/2, CREB, and MITF in melanoma cells

The Ras/ERK (extracellular signal-regulated protein kinase) and cAMP/PKA (protein kinase A) pathways are essential for the transcriptional activities of CREB (cAMP response element binding protein) and MITF (microphthalmia-associated transcription factor) in melanogenesis and the progression of melanoma. However, the interaction between Ras/ERK and cAMP/PKA pathways in the melanogenesis and progression of melanoma is not fully known. Here, we report that CSE1L (chromosome segregation 1-like protein) regulates cAMP/PKA-induced CREB and MITF expressions as well as Ras-induced ERK1/2 phosphorylation. IBMX, a cAMP/PKA activator, treatment induced CSE1L phosphorylation and augmented Ras-induced ERK1/2 phosphorylation. CSE1L knockdown by CSE1L shRNA expression vectors inhibited Ras-induced ERK1/2 phosphorylation and melanogenesis in melanoma cells. CSE1L overexpression increased phospho-CREB expression; CSE1L knockdown also inhibited Ras-induced phospho-CREB, MITF, and tyrosinase expressions, regardless of the presence of IBMX. This study identifies CSE1L links and controls the Ras/ERK and cAMP/PKA pathways in the melanogenesis of melanoma cells. Melanomas frequently develop drug resistance via paradoxical activation of Ras/Raf/MEK/ERK or alternatively activated Ras/ERK and cAMP/PKA pathways. Thus CSE1L may be a potential target for treating melanomas that harbor Ras mutations or are resistant to drugs targeting Raf/MEK/ERK. © 2015 Wiley Periodicals, Inc.

High expression of cytoplasmic phosphorylated CSE1L in malignant melanoma but not in benign nevi: phosphorylated CSE1L for the discrimination between melanoma and benign nevi

Melanoma is difficult to treat when it has metastasized. Discrimination between melanoma and benign nevi in melanocytic lesions is crucial for identifying melanomas and consequently improving melanoma treatment and prognosis. The chromosome segregation 1-like (CSE1L) protein has been implicated in cancer progression and is regulated by phosphorylation by extracellular signal-regulated kinase 1/2 (ERK1/2) signaling, a critical pathway in melanoma progression. We studied phosphorylated CSE1L expression in human melanoma and benign nevi specimens. Immunohistochemistry with tissue microarray using antibody against phosphorylated CSE1L showed that melanomas exhibited considerable staining for phosphorylated CSE1L (100%, 34/34), whereas the benign nevi showed only faint staining (0%, 0/34). Melanomas mainly exhibited cytoplasmic phospho-CSE1L distribution, whereas the benign nevi mainly exhibited nuclear phospho-CSE1L distribution. Moreover, immunohistochemistry with anti-CSE1L antibody revealed that CSE1L mainly exhibited cytoplasmic/nuclear distribution and nuclear distribution was the dominant. Immunofluorescence with B16F10 melanoma cells showed cytoplasmic distribution of phospho-CSE1L and nuclear distribution of CSE1L. Our results indicated that nuclear CSE1L is mainly non-phosphorylated CSE1L and is involved in gene regulation and cytoplasmic CSE1L is mainly phosphorylated CSE1L and is involved in cytoplasmic signaling regulation in melanocytic tumorigenesis. Furthermore, immunohistochemical analysis of cytoplasmic phospho-CSE1L may aid in the diagnosis of melanoma.

AKT activation drives the nuclear localization of CSE1L and a pro-oncogenic transcriptional activation in ovarian cancer cells

The human homolog of the yeast cse1 gene (CSE1L) is over-expressed in ovarian cancer. CSE1L forms complex with Ran and importin-α and has roles in nucleocytoplasmic traffic and gene expression. CSE1L accumulated in the nucleus of ovarian cancer cell lines, while it was localized also in the cytoplasm of other cancer cell lines. Nuclear localization depended on AKT, which was constitutively active in ovarian cancer cells, as the CSE1L protein translocated to the cytoplasm when AKT was inactivated. Moreover, the expression of a constitutively active AKT forced the translocation of CSE1L from the cytoplasm to the nucleus in other cancer cells. Nuclear accrual of CSE1L was associated to the nuclear accumulation of the phosphorylated Ran Binding protein 3 (RanBP3), which depended on AKT as well. Also in samples of human ovarian cancer, AKT activation was associated to nuclear accumulation of CSE1L and phosphorylation of RanBP3. Expression profiling of ovarian cancer cells after CSE1L silencing showed that CSE1L was required for the expression of genes promoting invasion and metastasis. In agreement, CSE1L silencing impaired motility and invasiveness of ovarian cancer cells. Altogether these data show that in ovarian cancer cells activated AKT by affecting RanBP3 phosphorylation determines the nuclear accumulation of CSE1L and likely the nuclear concentration of transcription factors conveying pro-oncogenic signals.

CSE1L modulates Ras-induced cancer cell invasion: correlation of K-Ras mutation and CSE1L expression in colorectal cancer progression

BACKGROUND

Ras plays an important role in colorectal cancer progression. CSE1L (chromosome segregation 1-like) gene maps to 20q13, a chromosomal region that correlates with colorectal cancer development. We investigated the association of CSE1L with Ras in colorectal cancer progression.

METHODS

The effect of CSE1L on metastasis-stimulating activity of Ras was studied in an animal model with tumor cells expressing CSE1L-specific shRNA and v-H-Ras. CSE1L expression was evaluated by the immunohistochemical analysis of 127 surgically resected colorectal tumors. K-Ras mutations were analyzed by direct sequencing.

RESULTS

CSE1L knockdown reduced Ras-induced metastasis of B16F10 melanoma cells in C57BL/6 mice. v-H-Ras expression altered the cellular trafficking of CSE1L and increased CSE1L secretion. Most colorectal tumors were positive for CSE1L staining (98.4%, 125 of 127). Colorectal tumors with K-Ras mutation or high cytoplasmic CSE1L expression were correlated with T status (depth of tumor penetration; P = .004), stage (P = .004), and lymph node metastasis (P = .019).

CONCLUSIONS

CSE1L may be a target for treating Ras-associated tumors. Analysis of K-Ras mutation and CSE1L expression may provide valuable clinical and pathological information to aid in the determination of treatment options for colorectal cancer.