Correlations between cytoplasmic CSE1L in neoplastic colorectal glands and depth of tumor penetration and cancer stage

Analysis of exportins expression unveils their prognostic significance in colon adenocarcinoma: insights from public databases

Colon cancer remains a significant health burden globally, necessitating deeper investigation. Identification and targeting of prognostic markers can significantly improve the current therapeutic approaches for colon cancer. The differential nuclear transport (import and export) of cellular proteins, plays an important role in tumor progression. Exportins, critical mediators of nuclear export, have emerged as potential players in cancer pathogenesis. However, their precise roles and prognostic significance in colon adenocarcinoma remain elusive. This study was designed to comprehensively analyse the expression and prognostic significance of all seven exportins in Colon Adenocarcinoma (COAD) using the online public database. We used public databases UALCAN, C-Bio portal, Human Protein Atlas (HPA), and DAVID, to investigate exportins in COAD patients. Kaplan-Meier plotter, Gene ontology (GO), TIMER, STRING, and KEGG were used to analyse data and draw conclusions. Our observations showed a significant correlation of exportins expression with clinical parameters, used to predict a patient's prognosis in general, such as advancing tumor stage, overall/relapse-free survival, and immune cell infiltrations. Mutation analysis showed the presence of amplifications, missense mutations in XPO2 and XPO4, and deep deletions in XPO7 genes contributing to disease progression and patients survival. This study highlights the potential use of exportins as novel prognostic biomarkers and therapeutic targets for colon adenocarcinoma progression and management.

Data mining identifies novel RNA-binding proteins involved in colon and rectal carcinomas

Colorectal adenocarcinoma (COREAD) is the second most deadly cancer and third most frequently encountered malignancy worldwide. Despite efforts in molecular subtyping and subsequent personalized COREAD treatments, multidisciplinary evidence suggests separating COREAD into colon cancer (COAD) and rectal cancer (READ). This new perspective could improve diagnosis and treatment of both carcinomas. RNA-binding proteins (RBPs), as critical regulators of every hallmark of cancer, could fulfill the need to identify sensitive biomarkers for COAD and READ separately. To detect new RBPs involved in COAD and READ progression, here we used a multidata integration strategy to prioritize tumorigenic RBPs. We analyzed and integrated 1) RBPs genomic and transcriptomic alterations from 488 COAD and 155 READ patients, 2) ∼ 10,000 raw associations between RBPs and cancer genes, 3) ∼ 15,000 immunostainings, and 4) loss-of-function screens performed in 102 COREAD cell lines. Thus, we unraveled new putative roles of NOP56, RBM12, NAT10, FKBP1A, EMG1, and CSE1L in COAD and READ progression. Interestingly, FKBP1A and EMG1 have never been related with any of these carcinomas but presented tumorigenic features in other cancer types. Subsequent survival analyses highlighted the clinical relevance of FKBP1A, NOP56, and NAT10 mRNA expression to predict poor prognosis in COREAD and COAD patients. Further research should be performed to validate their clinical potential and to elucidate their molecular mechanisms underlying these malignancies.

Upregulation of phosphatidylinositol glycan anchor biosynthesis class C is associated with unfavorable survival prognosis in patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common types of malignant tumor, and is the second highest cause of cancer-associated mortality, behind lung carcinoma. It is urgent to identify novel genes that can be used to confirm the diagnosis and prognosis of patients with HCC. The present study aimed to investigate the expression pattern of phosphatidylinositol glycan anchor biosynthesis class C (PIGC) in HCC and assess its clinical prognostic significance. Bioinformatics analyses were used to investigate PIGC mRNA expression levels in HCC and adjacent non-cancerous tissue samples. Furthermore, the present study detected the expression levels of PIGC protein in HCC and matched normal tissue samples via immunohistochemistry, and evaluated the prognostic significance of PIGC protein in HCC. The levels of PIGC mRNA and protein were found to be significantly higher in tissue from patients with HCC compared with non-cancerous liver tissue. The survival analysis showed that the expression levels of PIGC mRNA or protein were associated with the survival of patients with HCC. PIGC protein expression was significantly associated with Tumor-Node-Metastasis stage. A negative correlation between PIGC DNA methylation and mRNA expression was observed (Spearman r=-0.453). PIGC is an oncogene that is negatively regulated by DNA methylation, and high levels of PIGC mRNA or protein may predict an unfavorable prognosis in patients with HCC.

Cellular apoptosis susceptibility protein (CAS) suppresses the proliferation of breast cancer cells by upregulated cyp24a1

Breast cancer is the most common cancer in women. Although several studies demonstrated cellular apoptosis susceptibility protein (CAS) involved in the development of breast cancer, the underlying mechanisms of CAS regulating cell processes in the breast cancer remain elusive. In the present study, we explored the possible mechanism of CAS in contributing to the cell proliferation in the breast cancer cell line MCF-7. Knockdown of CAS led to the reduction of cell viability and proliferation. Furthermore, cell cycle was arrested in G0/G1 phase after knocking down CAS with the decrease of cyclinD1. In addition, RNA-seq analysis for the CAS knockdown cells demonstrated that total eleven genes were significantly altered (Fold changes > 2). Of note, the expression of cyp24a1 was dramatically increased in the shCAS cells compared to that of shNC cells as well as confirmed by quantitative real-time polymerase chain reaction (qPCR). These observations clarified the previous conflicting results on the cell fates of the breast cells regulated by CAS and provide new insight into the role of CAS in the development of breast cancer.

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.

Expression of CAS/CSE1L, the Cellular Apoptosis Susceptibility Protein, Correlates With Neoplastic Progression in Barrett's Esophagus

BACKGROUND

Identifying the molecular switch responsible for the neoplastic progression of Barrett's esophagus (BE) and initiation of adenocarcinoma (ADC) is clinically essential and it will have a profound impact on patient diagnosis, prognosis, and treatment. The cellular apoptosis susceptibility gene CAS/CSE1L is overexpressed in various cancers, including a rare report on esophageal ADC; however, its expression in BE neoplasia has not been addressed.

MATERIALS AND METHODS

We investigated the expression of the CAS/CSE1L protein immunohistochemically in 56 esophageal resection specimens for ADC arising in BE. For each specimen, a full representative section of the invasive ADC was selected to include, when possible, BE, low-grade dysplasia (LGD) and high-grade dysplasia (HGD). Samples were stained for CAS/CSE1L expression using a rabbit polyclonal antibody recognizing the N-terminus of human CAS/CSE1L. Protein expression levels were measured using the Allred semiquantitative scoring system. The data were evaluated using χ statistical analysis. Gene expression Omnibus was queried for CAS/CSE1L and BE neoplasia.

RESULTS

We found minimal to absent CAS/CSE1L in all BE tissue samples; however, CAS/CSE1L was upregulated in 60% of LGD and overexpressed in HGD and ADC. The results were statistically significant (P<0.05). The localization of CAS/CSE1L protein was nuclear in BE; it became nuclear and cytoplasmic in LGD and HGD, and predominantly cytoplasmic in ADC. A similar progressive increase was observed for CAS/CSE1L gene expression.

CONCLUSION

These findings show changes in CAS/CSE1L during BE progression. CAS/CSE1L may represent a potential marker for dysplasia/carcinoma.

Downregulation of G Protein-Coupled Estrogen Receptor (GPER) is Associated with Reduced Prognosis in Patients with Gastric Cancer

BACKGROUND This study is aimed to investigate the prognostic significance of the expression of G protein-coupled estrogen receptor (GPER) in gastric cancer tissue using bioinformatics data and immunohistochemistry. MATERIAL AND METHODS Expression of GPER mRNA in gastric cancer tissues and normal adjacent tissues was investigated using data from The Cancer Genome Atlas (TCGA), the Gene Expression Omnibus (GEO), and Oncomine database. Kaplan-Meier Plotter identified the association between GPER mRNA and prognosis. Correlation between GPER mRNA and DNA methylation used the cBioPortal for Cancer Genomics and the MethHC website. Genes co-expressed with GPER were identified from The Cancer Genome Atlas Stomach Adenocarcinoma (TCGA-STAD) underwent FunRich analysis. Immunohistochemistry and Western blot evaluated GPER protein expression in tissue microarrays (TMAs) and gastric cancer cell lines. RESULTS GPER mRNA and protein levels were significantly lower in gastric cancer tissue and cells lined when compared with normal tissues and cells. The results from GSE15459 showed that patients with low levels of GPER mRNA had a reduced overall survival (OS) (P=0.013) and disease-free survival (DFS) (P=0.019). A negative correlation (r=-0.611) between GPER mRNA and DNA methylation was found using the cBioPortal and MethHC. Co-expressed epithelial-mesenchymal transformation (EMT) genes were enriched with GPER (P<0.0001). Cox regression analysis showed that GPER protein expression was an independent prognostic factor (P=0.035) CONCLUSIONS Downregulation of GPER predicts poor prognosis in gastric cancer. GPER may act as a tumor suppressor through the regulation of EMT in gastric cancer.

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.

Knockdown of CSE1L Gene in Colorectal Cancer Reduces Tumorigenesis in Vitro

Human cellular apoptosis susceptibility (chromosomal segregation 1-like, CSE1L) gene plays a role in nuclear-to-cytoplasm transport and chromosome segregation during mitosis, cellular proliferation, and apoptosis. CSE1L is involved in colon carcinogenesis. CSE1L gene expression was assessed with three data sets using Affymetrix U133 + gene chips on normal human colonic mucosa (NR), adenomas (ADs), and colorectal carcinoma (CRC). CSE1L protein expression in CRC, AD, and NR from the same patients was measured by immunohistochemistry using a tissue microarray. We evaluated CSE1L expression in CRC cells (HCT116, SW480, and HT29) and its biological functions. CSE1L mRNA was significantly increased in all AD and CRC compared with NR (P < 0.001 and P = 0.02, respectivly). We observed a change in CSE1L staining intensity and cellular localization by immunohistochemistry. CSE1L was significantly increased during the transition from AD to CRC when compared with NR in a CRC tissue microarray (P = 0.01 and P < 0.001). HCT116, SW480, and HT29 cells also expressed CSE1L protein. CSE1L knockdown by shRNA inhibited protein, resulting in decreased cell proliferation, reduced colony formation in soft agar, and induction of apoptosis. CSE1L protein is expressed early and across all stages of CRC development. shRNA knockdown of CSE1L was associated with inhibition of tumorigenesis in CRC cells. CSE1L may represent a potential target for treatment of CRC.

Quantitative analysis of gene expression in fixed colorectal carcinoma samples as a method for biomarker validation

Biomarkers have been described as the future of oncology. Modern proteomics provide an invaluable tool for the near-whole proteome screening for proteins expressed differently in neoplastic vs. healthy tissues. However, in order to select the most promising biomarkers, an independent method of validation is required. The aim of the current study was to propose a methodology for the validation of biomarkers. Due to material availability the majority of large scale biomarker studies are performed using formalin-fixed paraffin-embedded (FFPE) tissues, therefore these were selected for use in the current study. A total of 10 genes were selected from what have been previously described as the most promising candidate biomarkers, and the expression levels were analyzed with reverse transcription-quantitative polymerase chain reaction (RT-qPCR) using calibrator normalized relative quantification with the efficiency correction. For 6/10 analyzed genes, the results were consistent with the proteomic data; for the remaining four genes, the results were inconclusive. The upregulation of karyopherin α 2 (KPNA2) and chromosome segregation 1-like (CSE1L) in colorectal carcinoma, in addition to downregulation of chloride channel accessory 1 (CLCA1), fatty acid binding protein 1 (FABP1), sodium channel, voltage gated, type VII α subunit (SCN7A) and solute carrier family 26 (anion exchanger), member 3 (SLC26A3) was confirmed. With the combined use of proteomic and genetic tools, it was reported, for the first time to the best of our knowledge, that SCN7A was downregulated in colorectal carcinoma at mRNA and protein levels. It had been previously suggested that the remaining five genes served an important role in colorectal carcinogenesis, however the current study provided strong evidence to support their use as biomarkers. Thus, it was concluded that combination of RT-qPCR with proteomics offers a powerful methodology for biomarker identification, which can be used to analyze FFPE samples.

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.

Does CSE1L Overexpression Affect Distant Metastasis Development in Breast Cancer?

BACKGROUND

CSE1L (chromosome segregation 1-like) is the human homologue to the yeast gene CSE1, and is related to invasion and metastasis in cancer progression. The aim of this study was to investigate the potential role of CSE1L expression in distant metastasis of breast cancer.

PATIENTS AND METHODS

A total of 71 breast cancer patients were included in this study. Clinical characteristics and CSE1L status were evaluated. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded archival breast tumor tissue. The results of CSE1L staining were analyzed according to the percentage of immunoreactive cells.

RESULTS

34 patients had distant metastasis and 37 did not. The mean age of the patients was 50.5 ± 12.1 years. Age, tumor size, and hormone receptor status were similar in patients with distant metastasis and in those without. A statistically significant relationship was found between nuclear CSE1L expression and distant metastasis of breast cancer. Lymph node metastasis and nuclear grade were other factors affecting distant metastasis.

CONCLUSION

There is a relationship between nuclear CSE1L overexpression and distant metastasis in breast cancer. CSE1L status may therefore become a valuable prognostic tool in the future.

Early decline in serum phospho-CSE1L levels in vemurafenib/sunitinib-treated melanoma and sorafenib/lapatinib-treated colorectal tumor xenografts

Background

Although targeted therapies have improved the clinical outcomes of cancer treatment, tumors resistance to targeted drug are often detected too late and cause mortality. CSE1L is secreted from tumor and its phosphorylation is regulated by ERK1/2. ERK1/2 is located downstream of various growth factor receptors and kinases, the targets of most targeted drugs. Serum phospho-CSE1L may be a marker for monitoring the efficacy of targeted therapy.

Methods

We used mice tumor xenograft model to study the assay of serum phosphorylated CSE1L for early detecting the efficacy of targeted drugs. The phosphorylation status of CSE1L in vemurafenib and sorafenib treated tumor cells were assayed by immunoblotting with antibody against phosphorylated CSE1L.

Results

Ras activation increased phospho-CSE1L expression in B16F10 melanoma cells. Vemurafenib and sorafenib treatment did not significantly reduce the total CSE1L levels; however, they inhibited ERK1/2 and CSE1L phosphorylation in A375 melanoma cells and HT-29 colorectal cancer cells. In the melanoma xenograft model, serum phospho-CSE1L level declined 5 days after vemurafenib/sunitinib treatment and 3 days after sorafenib/lapatinib treatment in the HT-29 colon cancer xenograft model. Vemurafenib/sunitinib and sorafenib/lapatinib treatments resulted in tumor regression.

Conclusions

Our results indicated that serum phospho-CSE1L is useful for early detecting the efficacy of targeted therapy in initial treatment and for monitoring emerging secondary drug resistance to facilitate timely therapeutic decision making.

The relationship between CSE1L expression and axillary lymph node metastasis in breast cancer

AIM

CSE1L is the human homologue to the yeast gene CSE1 and CSE1L is a gene related to cancer progression. Thus, CSE1L may regulate the invasion and metastasis of breast cancer. The aim of this study is to show the relationship between CSE1L and axillary lymph node metastasis.

METHODS

Sixty-six breast cancer patients were evaluated according to patient and tumor characteristics. Immunohistochemistry was carried out on formalin-fixed, paraffin-embedded archival breast tumor tissues. The results of CSE1L staining were analyzed according to the percentage of immunoreactive cells.

RESULTS

There were 29 patients without axillary lymph node metastasis and 37 patients with nodal metastasis. The mean age of the patients was 50.6 ± 11.3 years. Age, tumor size, nuclear grade and hormone receptor status were similar in the axillary lymph node positive and negative groups. There was a statistically significant relationship between cytoplasmic CSE1L expression and axillary lymph node metastasis. However, nuclear CSE1L expression did not have any effect on axillary lymph node metastasis.

CONCLUSIONS

Cytoplasmic CSE1L overexpression may be a valuable tool for prognosis of breast cancer in future.

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.