Clinical and biological impact of cyclin-dependent kinase subunit 2 in esophageal squamous cell carcinoma

Biological functions and therapeutic potential of CKS2 in human cancer

The incidence of cancer is increasing worldwide and is the most common cause of death. Identification of novel cancer diagnostic and prognostic biomarkers is important for developing cancer treatment strategies and reducing mortality. Cyclin-dependent kinase subunit 2 (CKS2) is involved in cell cycle and proliferation processes, and based on these processes, CKS2 was identified as a cancer gene. CKS2 is expressed in a variety of tissues in the human body, but its abnormal expression is associated with cancer in a variety of systems. CKS2 is generally elevated in cancer, plays a role in almost all aspects of cancer biology (such as cell proliferation, invasion, metastasis, and drug resistance) through multiple mechanisms regulating certain important genes, and is associated with clinicopathological features of patients. In addition, CKS2 expression patterns are closely related to cancer type, stage and other clinical variables. Therefore, CKS2 is considered as a tool for cancer diagnosis and prognosis and may be a promising tumor biomarker and therapeutic target. This article reviews the biological function, mechanism of action and potential clinical significance of CKS2 in cancer, in order to provide a new theoretical basis for clinical molecular diagnosis, molecular targeted therapy and scientific research of cancer.

Prognostic significance of cyclin-dependent kinase subunit 2 (CKS2) in malignant tumours: a meta-analysis and bioinformatic analysis

OBJECTIVES

This study aimed to systematically elucidate the prognostic significance of cyclin-dependent kinase subunit 2 (CKS2) expression in various cancers and its correlation with their clinicopathological characteristics.

DESIGN

In this meta-analysis and bioinformatic analysis, articles were identified through searches of multiple databases and meta-analysed according to the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols. Data from The Cancer Genome Atlas were examined using UCSC Xena tools to further confirm the prognostic effect of CKS2.

DATA SOURCES

The PubMed, Embase, Web of Science and Cochrane Library databases were searched for articles published from their inception to 1 January 2023, using a combination of subject terms and free words, including 'CKS2', 'cancer', 'tumor', 'neoplasm', 'carcinoma', 'malignancy' and 'prognosis'.

ELIGIBILITY CRITERIA

The analysis included cohort or case-control studies, reported in English, with malignancy diagnoses confirmed by pathological methods, available HRs and 95% CIs for overall survival (OS) or extractable Kaplan-Meier curves, and a sample size of ≥20 patients. Reviews, commentaries, letters, conference reports, case reports, in vitro and animal studies, studies of CKS2 gene variants, studies with sample cases from public databases and studies with unavailable survival or duplicated data were excluded.

DATA EXTRACTION AND SYNTHESIS

Two researchers independently screened the articles, extracted the data and evaluated the quality of included studies using the Newcastle-Ottawa Scale. Meta-analysis and bioinformatic analyses were performed using the STATA and R software, respectively.

RESULTS

The analysis included 13 retrospective studies encompassing 1348 cases across 10 cancer types. Nine studies involving 1124 patients examined the correlation between CKS2 expression levels and OS. A fixed-effects model analysis revealed a significant association between high CKS2 expression and reduced OS (HR=2.27, 95% CI=1.87 to 2.77, p<0.001). Furthermore, high CKS2 expression was significantly associated with advanced tumour stage (relative risk (RR) = 1.82, 95% CI=1.57 to 2.11, p<0.001), lymph node metastasis (RR=1.68, 95% CI=1.38 to 2.04, p<0.001), larger tumour size (RR=1.60, 95% CI=1.27 to 2.03, p<0.001) and lower differentiation grade (RR=1.57, 95% CI=1.29 to 1.90, p<0.001). CKS2 expression levels were not significantly correlated with patients' age (RR=1.11, 95% CI=0.99 to 1.26, p=0.071) or sex (RR=0.98, 95% CI=0.90 to 1.07, p=0.653). An assessment of the articles showed no significant publication bias, confirming the robustness of these findings. The bioinformatic analysis further confirmed CKS2 upregulation in the examined cancer types and its association with poor OS in glioma (HR=1.97, 95% CI=1.78 to 2.18, p=3.70×10-42), liver hepatocellular carcinoma (HR=1.56, 95% CI=1.31 to 1.86, p=3.50×10-7) and lung adenocarcinoma (HR=1.27, 95% CI=1.10 to 1.48, p=1.70×10-3).

CONCLUSIONS

Elevated CKS2 expression is associated with poor prognosis in a subset of malignant tumours, highlighting its potential as a prognostic marker.

PROSPERO REGISTRATION NUMBER

CRD42023394038.

Global trends and hotspots in Cyclin-dependent Kinase Subunit 2 research from 1999 to 2022: A bibliometric and visualized analysis

BACKGROUND

Cyclin-dependent Kinase Subunit 2 is a protein closely related to the regulation of the cell cycle. In recent years, there has been an increasing number of research articles on this topic. However, there is a lack of comprehensive synthesis and evaluation in the field of CKS2 research. This study aims to summarize and visualize the literature distribution, research hotspots, and development trends of CKS2 based on bibliometric methods.

METHODS

Publications from 1999 to 2022 were extracted from the Web of Science. Citespace was used to analyze the relevant information of each article.

RESULTS

A total of 138 publications focused on CKS2 showed a positive growth trend from 1999 to 2022 and were published by 27 countries. The most prolific countries are China and the USA. The most prolific institution is Scripps Research Institute. The most prolific author is Steven I. Reed from Scripps Research Institute. The most cited article is published by Todd R Golub. The most cited author is Hanna-Stina Martinsson-Ahlzen. The journal with the most published articles is International Journal of Oncology. The high frequency keywords suggest that expression and function of CKS2 in cancer are dominated topics. The clusters and burst words suggest that expression and function of CKS2 still active in the future.

CONCLUSION SUBSECTIONS

The results of this bibliometric analysis provide information on the state and trends in CKS2 from 1999 to 2022. It is helpful for scholars to pinpoint hot issues and discover new areas of study.

Aberrant expression of CKS2 induced by ELK1 contributes to malignant progression of pancreatic cancer

Cyclin-dependent kinase subunit 2 (CKS2) has been reported to promote various malignancies. This study investigated the functional role of CKS2 in pancreatic cancer (PC). An analysis of abnormally expressed genes and their prognostic value for PC was performed by using the Gene Expression Profiling Interactive Analysis (GEPIA) database and performing immunohistochemical staining on 64 samples of tumor tissue. CCK-8 assays, EdU staining, colony formation assays, flow cytometry, and a xenograft tumor model were used to analyze the biological function of CKS2 in PC. Our results revealed that CKS2 was expressed at significantly higher levels in PC tissues than in adjacent normal tissues, and a high level of CKS2 expression was associated with a poor prognosis for patients with PC. Moreover, functional assays revealed that CKS2 knockdown suppressed cell proliferation, induced cell cycle S phase, G2/M phase arrest, and apoptosis in vitro, and also reduced tumor growth in vivo. In addition, CKS2 knockdown increased the levels of Bax, caspase-3, P53, P21, and GADD45α expression, but decreased Bcl-2, Cyclin B1, CDK1, Cyclin A, and Cdc25C expression. CKS2 overexpression produced the opposite effects of CKS2 knockdown. Furthermore, we found that ELK1 protein regulated transcription of the CKS2 gene. In conclusion, our findings suggest that CKS2 expression is regulated by ELK1, which could possibly serve as prognostic indicator and therapeutic target for PC.

Identification of Potential Biomarkers Using Integrative Approach: A Case Study of ESCC

This paper presents a consensus-based approach that incorporates three microarray and three RNA-Seq methods for unbiased and integrative identification of differentially expressed genes (DEGs) as potential biomarkers for critical disease(s). The proposed method performs satisfactorily on two microarray datasets (GSE20347 and GSE23400) and one RNA-Seq dataset (GSE130078) for esophageal squamous cell carcinoma (ESCC). Based on the input dataset, our framework employs specific DE methods to detect DEGs independently. A consensus based function that first considers DEGs common to all three methods for further downstream analysis has been introduced. The consensus function employs other parameters to overcome information loss. Differential co-expression (DCE) and preservation analysis of DEGs facilitates the study of behavioral changes in interactions among DEGs under normal and diseased circumstances. Considering hub genes in biologically relevant modules and most GO and pathway enriched DEGs as candidates for potential biomarkers of ESCC, we perform further validation through biological analysis as well as literature evidence. We have identified 25 DEGs that have strong biological relevance to their respective datasets and have previous literature establishing them as potential biomarkers for ESCC. We have further identified 8 additional DEGs as probable potential biomarkers for ESCC, but recommend further in-depth analysis.

Expression Profile and Molecular Basis of Cyclin-Dependent Kinases Regulatory Subunit 2 in Endometrial Carcinoma Detected by Diversified Methods

Purpose: Our purpose was to systematically appraise the clinicopathological significance and explore the molecular bases of CKS2 in endometrial carcinoma. Patients and Methods: We measured the clinicopathological significance of CKS2 using diverse methods of public RNA-seq, microarrays, and in-house tissue microarrays to investigate the molecular basis of CKS2 in endometrial carcinoma through upstream transcriptional analysis, immune infiltration correlation analysis, and co-expression analysis. Results: Both the analysis for public RNA-seq plus the microarray data and in-house tissue microarray confirmed the significant overexpression of CKS2 in a total of 1,021 endometrial carcinoma samples compared with 279 non-cancer endometrium samples (SMD = 2.10, 95% CI = 0.72-3.48). The upregulated CKS2 was significantly related to the lymph node metastasis and advanced clinical grade of endometrial carcinoma patients (p < 0.001). Mutation types such as amplification and mRNA occurred with high frequency in the CKS2 gene in endometrial carcinoma patients. A series of miRNAs and transcription factors, such as hsa-miR-26a, hsa-miR-130a, hsa-miR-30, E2F4, MAX, and GABPA, were predicted to regulate the transcription and expression of CKS2. Significant links were found between CKS2 expression and the infiltration level of B cells, CD4⁺ T cells, and neutrophils in endometrial carcinoma. CKS2-coexpressed genes were actively involved in pathways such as the mitotic cell cycle process, PID aurora B pathway, and prolactin signaling pathway. Conclusion: The overexpressed CKS2 showed positive correlations with the clinical progression of endometrial carcinoma and was associated with various cancer-related biological processes and pathways, showing potential as a promising clinical biomarker for endometrial carcinoma.

Clinicopathological value of the upregulation of cyclin-dependent kinases regulatory subunit 2 in osteosarcoma

Background

Cyclin-dependent kinase subunit 2 (CKS2) is a member of cyclin dependent kinase subfamily and the relationship between CKS2 and osteosarcoma (OS) remains to be further analyzed.

Methods

80 OS and 41 non-tumor tissue samples were arranged to perform immunohistochemistry (IHC) to evaluate CKS2 expression between OS and non-tumor samples. The standard mean deviation (SMD) was calculated based on in-house IHC and tissue microarrays, and exterior high-throughput datasets for further verification of CKS2 expression trend in OS. The effect of CKS2 expression on clinicopathological parameters of OS patients, and single-cell in OS tissues was analyzed through public high-throughput datasets and functional enrichment analysis was conducted for co-expression genes of CKS2 in accordance with weighted correlation network analysis.

Results

A total of 217 OS samples and 87 non-tumor samples (including tissue and cell line) were obtained from in-house IHC, microarrays and exterior high-throughput datasets. The analysis of integrated expression status demonstrated up-regulation of CKS2 in OS (SMD = 1.57, 95%CI [0.27–2.86]) and the significant power of CKS2 expression in distinguishing OS samples from non-tumor samples (AUC = 0.97 95%CI [0.95–0.98]). Clinicopathological analysis of GSE21257 indicated that OS patients with higher CKS2 expression was more likely to suffer OS metastasis. Although Kaplan–Meier curves showed no remarkable difference of overall survival rate between OS patients with high and low-CKS2, CKS2 was found up-regulated in proliferating osteosarcoma cells. Co-expression genes of CKS2 were mainly assembled in function and pathways such as cell cycle, cell adhesion, and intercellular material transport.

Conclusions

In summary, up-regulation of CKS2 expression in OS tissue was found through multiple technical approaches. In addition, scRNA-seq and co-expression analysis showed that CKS2 may have an impact on important biological process linked with cell cycle, cell adhesion, and intercellular material transport. Present study on CKS2 in OS indicated a promising prospect for CKS2 as a biomarker for OS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01234-8.

CKS2 Overexpression Correlates with Prognosis and Immune Cell Infiltration in Lung Adenocarcinoma: A Comprehensive Study based on Bioinformatics and Experiments

Objective: Cyclin-dependent kinase regulatory subunit 2 (CKS2) plays a vital role in regulation of the cell cycle and cancer progression. However, the role of CKS2 in lung adenocarcinoma (LUAD) remains unkonwn. Here, we examined the prognostic value and biological functions of CKS2 in LUAD by using omics data of 1,235 LUAD samples from TCGA, GEO, and our own cohort as well as data of in vitro experiments.

Methods: Kaplan-Meier was conducted to evaluate the prognostic value of CKS2 expression. The association between CKS2 expression level and tumor immune infiltration was explored using the single-sample Gene Set Enrichment Analysis (ssGSEA) and TIMER database. Functional enrichment analyses were performed to annotate the biological functions of CKS2 in LUAD. Furthermore, a series of in vitro experiments and immunohistochemistry were performed for validation.

Results: CKS2 overexpression was correlated with the advanced stage, TP53 status, PD-L1 expression, and DNA hypomethylation. Moreover, patients with LUAD and high CKS2 expression exhibited poor overall survival. Functional enrichment analysis indicated that CKS2 was involved in cell division, cell cycle, DNA replication. Experiments in vitro indicated that CKS2 knockdown decreased the invasion and proliferation of LUAD cells and facilitated their apoptosis. ssGSEA and TIMER analysis revealed a negative correlation between CKS2 expression and the immune cell infiltration.

Conclusions: In summary, High CKS2 expression was associated with poor prognosis and low levels of infiltrating immune cells in LUAD as well as with malignant phenotypes. Therefore, CKS2 may be a promising prognostic biomarker and therapeutic target in LUAD.

CKS2 (CDC28 protein kinase regulatory subunit 2) is a prognostic biomarker in lower grade glioma: a study based on bioinformatic analysis and immunohistochemistry

Gliomas account for the highest cases of primary brain malignancies. Whereas previous studies have demonstrated the roles of CDC28 Protein Kinase Regulatory Subunit 2 (CKS2) in various cancer types, its functions in lower grade gliomas (LGGs) remain elusive. This study aimed to profile the expression and functions of CKS2 in LGG. Multiple online databases such as The Cancer Genome Atlas (TCGA), the Chinese Glioma Genome Atlas (CGGA), Gene Expression Profiling Interactive Analysis 2nd edition (GEPIA2), Tumor Immune Estimation Resource 2nd edition (TIMER2.0) as well as Gene Expression Omnibus (GEO) were used in this study. Immunohistochemistry (IHC) was performed to evaluate CKS2 protein expression. Our data demonstrated upregulation of CKS2 in LGG tissues at both mRNA and protein level, especially in grade III gliomas. Similarly, there was increased expression of CKS2 in isocitrate dehydrogenase 1 (IDH1) wildtype gliomas. In addition, increased DNA copy number and DNA hypomethylation might be associated with the upregulation of the CKS2 in LGG. Using the Kaplan–Meier survival analysis and the Cox regression analysis, CKS2 was shown to be independently associated with poor prognosis of LGG patients. Receiver operating characteristic (ROC) analysis revealed that CKS2 could effectively predict the 1-, 3- and 5-year survival rates of LGG patients. Enrichment analyses revealed that CKS2 was mainly involved in the regulation of the cell cycle in LGG. Taken together, our study demonstrated that CKS2 might be a candidate prognostic biomarker for LGG and could predict the survival rates of LGG patients.

Abbreviations: LGG: lower grade glioma; CKS2: CDC28 protein kinase regulatory subunit 2; TCGA: The Cancer Genome Atlas; CGGA: the Chinese Glioma Genome Atlas; GEO: Gene Expression Omnibus; GEPIA: Gene Expression Profiling Interactive Analysis; TIMER: Tumor Immune Estimation Resource; IHC: immunohistochemistry; qRT-PCR: quantitative real-time polymerase chain reaction; PBS: phosphate buffered saline; DAB: diaminobenzidine tetrachloride; OS: overall survival; CAN: copy number alteration; IDH: Isocitrate dehydrogenase; GSEA: Gene Set Enrichment Analysis; DEG: differentially expressed gene; KEGG: Kyoto encyclopedia of genes and genomes; GO: Gene ontology; BP: biological process; CC: cellular component; MF: molecular function; NES: normalized enrichment score; NOM: nominal; FDR: false discovery rate

LINC00657/miR-26a-5p/CKS2 ceRNA network promotes the growth of esophageal cancer cells via the MDM2/p53/Bcl2/Bax pathway

LncRNA LINC00657 has oncogenic or anti-carcinoma roles in different cancers, and yet its detailed molecular mechanism in esophageal cancer (EC) remains unclear. In addition, competitive endogenous RNA (ceRNA) regulatory lncRNA–miRNA–mRNA networks are critical for tumorigenesis and progression. Hence, the present study explored the roles of LINC00657 in EC and identified its relevant ceRNA network. We first detected the expression of LINC00657 in EC. Then, we applied starBase and TargetScan websites to find miR-26a-5p binding to LINC00657 and obtain CKS2 as a target of miR-26a-5p. The roles of LINC00657, miR-26a-5p or CKS2 in the proliferation, migration, invasion, and apoptosis of EC cells were respectively assessed by CCK-8, wound healing assay, transwell invasion assay, and flow cytometry. The changes of the MDM2/p53/Bcl2/Bax pathway were measured via Western blot. The results revealed that LINC00657 showed an aberrant high expression in EC cells, which promoted the growth of EC cells. Additionally, LINC00657 functioned as a sponge of miR-26a-5p, and LINC00657 negatively mediated miR-26a-5p to regulate the growth of EC cells. Furthermore, CKS2 was observed as a direct target of miR-26a-5p, and CKS2 controlled the growth of EC cells via the MDM2/p53/Bcl2/Bax pathway. Moreover, there was a positive correlation between LINC00657 and CKS2. LINC00657 knockdown inhibited CKS2 expression to suppress the proliferation, migration, and invasion of EC cells and induced apoptosis via regulating the MDM2/p53/Bcl2/Bax pathway. Collectively, LINC00657/miR-26a-5p/CKS2 ceRNA network could promote the progression of EC, which is good for understanding the molecular mechanism of EC and offers novel biomarkers for EC diagnosis and therapy.

CKS2 modulates cell-cycle progression of tongue squamous cell carcinoma cells partly via modulating the cellular distribution of DUTPase

BACKGROUND

CKS2 (CDC28 Protein Kinase Regulatory Subunit 2) is a gene that encodes CKS2 protein that has been characterized as a binding partner of the catalytic subunit of the cyclin-dependent kinases. However, its expression profile and regulatory effects in tongue squamous cell carcinoma has not yet been explored.

METHODS

Bioinformatic analysis was conducted using bulk-seq data from The Cancer Genome Atlas and single-cell RNA-seq data from GSE103322. SCC9 and CAL27 cells were used as in vitro cell models for cellular and molecular studies.

RESULTS

CKS2 expression was significantly upregulated in tongue squamous cell carcinoma tissues (N = 128) compared with adjacent normal tissues (N = 13). Its upregulation was associated with significantly shorter disease-specific survival and progression-free survival. Cellular status estimation in tumor cells indicated that CKS2 expression was moderately and positively correlated with cell-cycle progression. CKS2 inhibition in SCC9 and CAL27 cells resulted in decreased proliferation, weakened colony formation capability, and cell-cycle arrest at the G2/M phase. Immunofluorescence staining and co-Immunoprecipitation (co-IP) assay confirmed co-localization and interaction between CKS2 and DUTPase. CKS2 knockdown did not alter DUTPase expression but reduced its nuclear distribution. Both CKS2 and DUT expression were moderately correlated with their gene-level copy number.

CONCLUSION

CKS2 expression is associated with unfavorable survival of patients with tongue squamous cell carcinoma. Inhibiting its expression could reduce tongue squamous cell carcinoma cell growth and induce G2/M arrest. CKS2 may interact with DUTPase and regulate its nuclear localization. Gene-level copy amplification might be an important mechanism of upregulated CKS2 and DUT in the tumor.

Identification of hub genes associated with esophageal cancer progression using bioinformatics analysis

The underlying causes of esophageal cancer (EC) are unknown. To explore the molecular mechanisms that lead to EC, gene expression profiles of large cohorts of patients with EC were obtained from The Cancer Genome Atlas and the Gene Expression Omnibus (GEO) databases (GSE5364, GSE20347 and GSE23400). The present study identified 83 upregulated and 22 downregulated genes between EC and normal tissue using R statistical software and the GEO2R web tool. The Database for Annotation, Visualization and Integrated Discovery was used to identify the associated pathways, and for functional annotation of the differentially expressed genes (DEGs). Protein-protein interactions of these DEGs were analyzed based on the Search Tool for the Retrieval of Interacting Genes database, and hub genes were visualized using Cytoscape software. An online Kaplan-Meier plotter survival analysis tool was utilized to evaluate the prognostic value of hub gene expression in patients with EC. Further analysis of an additional dataset from GEO (GSE21293) revealed that these genes were associated with infiltration and metastasis in EC. In addition, the Gene Expression Profiling Interactive Analysis tool was used to evaluate expression levels of hub genes in patients with EC for different pathological stages. The Ualcan analysis tool was used to evaluate the expression levels of hub genes for different histological types. Overall, ubiquitin conjugating enzyme E2 C, cyclin dependent kinase inhibitor 3, CDC28 protein kinase regulatory subunit 2, kinesin family member 20A (KIF20A) and RAD51 associated protein 1 (RAD51AP1) were upregulated in EC tissues compared with normal tissues, and upregulation of these genes was a poor prognostic factor for patients with EC, indicating that these genes may mediate EC cell infiltration and metastasis. Among the hub genes, KIF-20A had potential value for predicting the pathological stage of EC. KIF20A and RAD51AP1 were more informative biomarkers of esophageal squamous cell carcinoma. Further studies are required to explore the value of these genes in the treatment of EC.

Integrated Analysis To Identify Molecular Biomarkers Of High-Grade Serous Ovarian Cancer

Purpose

Ovarian cancer is the leading cause of gynecologic cancer-related death worldwide. Early diagnosis of ovarian cancer can significantly improve patient prognosis. Hence, there is an urgent need to identify key diagnostic and prognostic biomarkers specific for ovarian cancer. Because high-grade serous ovarian cancer (HGSOC) is the most common type of ovarian cancer and accounts for the majority of deaths, we identified potential biomarkers for the early diagnosis and prognosis of HGSOC.

Methods

Six datasets (GSE14001, GSE18520, GSE26712, GSE27651, GSE40595, and GSE54388) were downloaded from the Gene Expression Omnibus database for analysis. Differentially expressed genes (DEGs) between HGSOC and normal ovarian surface epithelium samples were screened via integrated analysis. Hub genes were identified by analyzing protein-protein interaction (PPI) network data. The online Kaplan-Meier plotter was utilized to evaluate the prognostic roles of these hub genes. The expression of these hub genes was confirmed with Oncomine datasets and validated by quantitative real-time PCR and Western blotting.

Results

A total of 103 DEGs in patients with HGSOC-28 upregulated genes and 75 downregulated genes-were successfully screened. Enrichment analyses revealed that the upregulated genes were enriched in cell division and cell proliferation and that the downregulated genes mainly participated in the Wnt signaling pathway and various metabolic processes. Ten hub genes were associated with HGSOC pathogenesis. Seven overexpressed hub genes were partitioned into module 1 of the PPI network, which was enriched in the cell cycle and DNA replication pathways. Survival analysis revealed that MELK, CEP55 and KDR expression levels were significantly correlated with the overall survival of HGSOC patients (P < 0.05). The RNA and protein expression levels of these hub genes were validated experimentally.

Conclusion

Based on an integrated analysis, we propose the further investigation of MELK, CEP55 and KDR as promising diagnostic and prognostic biomarkers of HGSOC.

Cyclin-Dependent Kinase Regulatory Subunit 2 Indicated Poor Prognosis and Facilitated Aggressive Phenotype of Hepatocellular Carcinoma

Cyclin-dependent kinase regulatory subunit 2 (CKS2) is a member of the cell cycle-dependent protein kinase subunit family, which is implicated as an oncogene in various malignancies. However, the clinical significance, oncogenic functions, and related mechanisms of CKS2 in hepatocellular carcinoma (HCC) remain largely unclear. In the present study, expression features and prognostic value of CKS2 were evaluated in the bioinformatic databases and HCC tissues. The effects of CKS2 on the malignant phenotypes of HCC cells were explored in vitro. According to the analyses of three bioinformatic databases, mRNA levels of CKS2 were elevated in HCC tissues compared with the normal tissues. Immunohistochemical assays found that high CKS2 expression was closely associated with liver cirrhosis (P = 0.019), poor differentiation (P = 0.02), portal vein invasion (P < 0.001), TNM stage (P = 0.019), tumor metastasis (P = 0.008), and recurrence (P = 0.003). The multivariate regression analyses suggested that CKS2 was an independent prognostic factor for overall survival (HR = 2.088, P = 0.014) and disease-free survival (HR = 2.511, P = 0.002) of HCC patients. Moreover, the bioinformatic analyses indicated that CKS2 might be associated with the malignant phenotypes in HCC progression. In addition, in vitro assays showed that CKS2 expression was higher in HCC cell lines than in normal liver cells. Knockdown of CKS2 remarkably repressed the proliferation, colony formation (P = 0.0003), chemoresistance, migration (P = 0.0047), and invasion (P = 0.0012) of HCC cells. Taken together, overexpression of CKS2 was significantly correlated with poor prognosis of HCC patients and the malignant phenotypes of HCC cells, suggesting that it was a novel prognostic biomarker and potential target of HCC.

Mitochondrial Function of CKS2 Oncoprotein Links Oxidative Phosphorylation with Cell Division in Chemoradioresistant Cervical Cancer

CDK regulatory subunit 2 (CKS2) has a nuclear function that promotes cell division and is a candidate biomarker of chemoradioresistance in cervical cancer. The underlying mechanisms are, however, not completely understood. We investigated whether CKS2 also has a mitochondrial function that augments tumor aggressiveness. Based on global gene expression data of two cervical cancer cohorts of 150 and 135 patients, we identified a set of genes correlated with CKS2 expression. Gene set enrichment analysis showed enrichment of mitochondrial cellular compartments, and the hallmarks oxidative phosphorylation (OXPHOS) and targets of the MYC oncogene in the gene set. By in situ proximity ligation assay, we showed that CKS2 formed complex with the positively correlated MYC target, mitochondrial single-stranded DNA binding protein SSBP1, in the mitochondrion of cervix tumor samples and HeLa and SiHa cervical cancer cell lines, indicating a role in mitochondrial DNA (mtDNA) replication and thereby OXPHOS. CDK1 was found to be part of the complex. Flow cytometry analyses of HeLa cells showed cell cycle regulation of the CKS2-SSBP1 complex consistent with mtDNA replication activity. Moreover, repression of mtDNA replication and OXPHOS by acute hypoxia decreased CKS2-SSBP1 complex abundance and expression of MYC targets. By immunohistochemistry, cytoplasmic CKS2 expression was found to add to the prognostic impact of nuclear CKS2 expression in patients, suggesting that the mitochondrial function promotes tumor aggressiveness. Our study uncovers a novel link between regulation of cell division by nuclear pathways and OXPHOS in the mitochondrion that involves CKS2 and promotes chemoradioresistance of cervical cancer.

Molecular pathogenesis of esophageal squamous cell carcinoma: Identification of the antitumor effects of miR‑145‑3p on gene regulation

Although miR‑145‑5p (the guide strand of the miR‑145 duplex) is established as a tumor suppressive microRNA (miRNA or miR), the functional significance of miR‑145‑3p (the passenger strand of the miR‑145 duplex) in cancer cells and its targets remains obscure. In our continuing analysis of esophageal squamous cell carcinoma (ESCC) pathogenesis, the aim of the present study was to identify important oncogenes and proteins that are controlled by miR‑145‑3p. Overexpression of miR‑145‑3p significantly reduced cancer cell proliferation, migration and invasive abilities, and further increased apoptotic abilities. In ESCC cells, 30 possible oncogenic targets were identified that might be regulated by miR‑145‑3p. Among these targets, dehydrogenase/reductase member 2 (DHRS2) and myosin IB (MYO1B) were focused on to investigate their functional roles in ESCC cells. DHRS2 and MYO1B were directly regulated by miR‑145‑3p in ESCC cells by dual luciferase reporter assays. Aberrantly expressed DHRS2 and MYOIB were detected in ESCC clinical specimens, and their overexpression enhanced cancer cell aggressiveness. Genes regulated by antitumor miR‑145‑3p were closely associated with the molecular pathogenesis of ESCC. The approach based on antitumor miRNAs may contribute to the understanding of ESCC molecular pathogenesis.

Integrative analysis of gene expression profiles reveals specific signaling pathways associated with pancreatic duct adenocarcinoma

Background

Pancreatic duct adenocarcinoma (PDAC) remains a major health problem because conventional cancer treatments are relatively ineffective against it. Microarray studies have linked many genes to pancreatic cancer, but the available data have not been extensively mined for potential insights into PDAC. This study attempted to identify PDAC-associated genes and signaling pathways based on six microarray-based profiles of gene expression in pancreatic cancer deposited in the gene expression omnibus database.

Methods

Pathway network methods were used to analyze core pathways in six publicly available pancreatic cancer gene (GSE71989, GSE15471, GSE16515, GSE32676, GSE41368 and GSE28735) expression profiles. Genes potentially linked to PDAC were assessed for potential impact on survival time based on data in The Cancer Genome Atlas and International Cancer Genome Consortium databases, and the expression of one candidate gene (CKS2) and its association with survival was examined in 102 patients with PDAC from our hospital. Effects of CKS2 knockdown were explored in the PDAC cell lines BxPC-3 and CFPAC-1.

Results

The KEGG signaling pathway called “pathway in cancer” may play an important role in pancreatic cancer development and progression. Five genes (BIRC5, CKS2, ITGA3, ITGA6 and RALA) in this pathway were significantly associated with survival time in patients with PDAC. CKS2 was overexpressed in PDAC samples from our hospital, and higher CKS2 expression in these patients was associated with shorter survival time. CKS2 knockdown substantially inhibited PDAC cell proliferation in vitro.

Conclusions

Analysis integrating existing microarray datasets allowed identification of the “pathway in cancer” as an important signaling pathway in PDAC. This integrative approach may be powerful for identifying genes and pathways involved in cancer.

Electronic supplementary material

The online version of this article (10.1186/s40880-018-0289-9) contains supplementary material, which is available to authorized users.

Regulation of SPOCK1 by dual strands of pre-miR-150 inhibit cancer cell migration and invasion in esophageal squamous cell carcinoma

Analysis of our microRNA (miRNA) expression signatures of human cancers based on RNA sequencing have shown that both strands of pre-miR-150, miR-150-5p (the guide strand) and miR-150-3p (the passenger strand), are significantly reduced in cancer tissues. We have investigated the functional significance of both strands of pre-miR-150 in cancer cells. The aim of this study was to investigate the antitumor function of these miRNAs and how these miRNAs regulated oncogenic targets in esophageal squamous cell carcinoma (ESCC). Ectopic expression studies demonstrated that both strands of pre-miR-150 miRNA inhibited ESCC cancer cell migration and invasion, indicating that both miR-150-5p and miR-150-3p acted as antitumor miRNAs. A combination of genome-wide gene expression analyses and in silico database searches showed that SPOCK1 (SPARC/osteonectin, cwcv and kazal-like domains proteoglycan 1) was a candidate target of miR-150-5p and miR-150-3p in ESCC cells. Luciferase reporter assays showed that SPOCK1 was directly regulated by these miRNAs. Silencing of SPOCK1 by small interfering RNA inhibited cancer cell migration and invasion. Overexpression of SPOCK1/SPOCK1 was confirmed by real-time PCR methods and immunohistochemistry. Taken together, downregulation of both strands of pre-miR-150 and overexpression of SPOCK1 are involved in ESCC pathogenesis. The involvement of passenger strand miRNAs in the regulation of cancer cell aggressiveness is a novel concept in RNA research.

Regulation of MMP13 by antitumor microRNA-375 markedly inhibits cancer cell migration and invasion in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive malignancies. Recently developed molecular targeted therapies are not available for patients with ESCC. After curative surgical resection, patients frequently suffer distant metastasis and recurrence. Exploration of novel ESCC metastatic pathways may lead to the development of new treatment protocols for this disease. Accordingly, we have sequentially identified microRNA (miRNA)-mediated metastatic pathways in several cancers. Our past studies of miRNA expression signatures have shown that microRNA-375 (miR-375) is frequently reduced in several types of cancers, including ESCC. In the present study, we aimed to investigate novel miR-375-mediated metastatic pathways in ESCC cells. The expression of miR-375 was downregulated in ESCC tissues, and ectopic expression of this miRNA markedly inhibited cancer cell migration and invasion, suggesting that miR-375 acted as an antimetastatic miRNA in ESCC cells. Our strategies for miRNA target searching demonstrated that matrix metalloproteinase 13 (MMP13) was directly regulated by miR-375 in ESCC cells. Overexpression of MMP13 was observed in ESCC clinical tissues, and the expression of MMP13 promoted cancer cell aggressiveness. Moreover, oncogenic genes, including CENPF, KIF14 and TOP2A, were shown to be regulated downstream of MMP13. Taken together, these findings demonstrated that the antitumor miR-375/oncogenic MMP13 axis had a pivotal role in ESCC aggressiveness. These results provide novel insights into the potential mechanisms of ESCC pathogenesis.

Depletion of Cks1 and Cks2 expression compromises cell proliferation and enhance chemotherapy-induced apoptosis in HepG2 cells

The present study explored the oncogenic roles of overexpressed Cks1 and Cks2 in human hepatocellular carcinoma cells. Gene expression of Cks1 and Cks2 in HepG2 cells was disrupted by siRNA or increased by cDNA transfection. Cell proliferation was assayed by CCK-8 analysis and cell counting. Cisplatin-induced apoptosis after transfection was measured by flow cytometry using Annexin V/propidium iodide (PI) double staining. Cell cycle changes after transfection were determined by flow cytometry with PI staining. Protein levels of Akt and GSK-3β were measured after transfection. The results revealed that HepG2 proliferation was decreased by depletion of endogenous Cks1 or Cks2, and increased by overexpression of Cks1 or Cks2. HepG2 apoptosis increased concordantly with the decline of Cks1 or Cks2 expression. Overexpression of Cks1 or Cks2 prevented cell apoptosis. Protein levels of p-Akt and p-GSK-3β were downregulated after RNA interference of Cks1 or Cks2. In conclusion, Cks1 and Cks2 promoted proliferation and prevented apoptosis of HepG2 cells. The Akt/GSK-3β-related PI3K/Akt signaling pathway may be a key signaling pathway that is involved in the regulation of cell growth and cell death.

CKS2 in human cancers: Clinical roles and current perspectives (Review)

Cyclin-dependent kinase subunit 2 (CKS2) is indicated in the processes of cell cycle and cell proliferation. Through these processes, CKS2 is identified as a cancer gene, but its role has not been well reviewed. The aim of the present study was to summarize the clinicopathological significance and the molecular mechanisms of CKS2 in human cancers. Its expression was upregulated in the majority of the types of cancer studied. CKS2 was shown to have a function in cancers of the digestive tract, genital tract, thyroid, nerve and certain other types of cancer. CKS2 can promote progression of certain cancers via positive control of proliferation, invasion and migration. Downregulation of CKS2 induces cancer cell apoptosis. CKS2 can change a multitude of cellular mechanisms in cancer pathogenesis by regulating the gene translation of numerous validated targets, such as p53, CDK1, cyclin A, cyclin B1, caspase-3 and Bax. In addition, the molecular mechanism that causes aberrant expression of CKS2 was epigenetic modification of miR-26a and the Y-box-binding protein 1 (YB-1) gene. In conclusion, CKS2 is commonly elevated in cancer, most likely due to its ability to promote cancer cell growth, invasion and migration through regulating certain significant genes. Understanding the mechanisms by which CKS2 is involved with cancer pathogenesis will be useful in the development of tumor therapy for patients with cancer.