Genetic Polymorphisms of CCDC26 rs891835, rs6470745, and rs55705857 in Glioma Risk: A Systematic Review and Meta-analysis.

A genetic component is accepted in the etiology of the glioma. Evidence from candidate genes studies and GWAS reveal that CCDC26 gene could increase the risk of glioma. We performed a systematic review and up-to-date meta-analysis to explore if polymorphisms of CCDC26 gene (rs891835, rs6470745, and rs55705857) may be a susceptibility factor in developing glioma. An online search in PubMed, Web of Science, and SCOPUS up to September 2018 was performed. The pooled odds ratios were evaluated by fixed effects model and random effects model. Analyses of the overall sample and ethnic sub-groups were performed. In all the analyses, the allelic, additive, dominant, and recessive models were used. We found an association between all polymorphisms evaluated and an increased risk for glioma in the overall population in all the models studied. In sub-group analysis, we found that rs891835 and rs6470745 increased the risk of glioma in Europeans and Caucasians. On the other hand, the rs891835 polymorphism did not reveal any statistical association in Chinese population. Taken into consideration the limitations of this study, the present findings suggest a possible participation of rs891835, rs6470745, and rs55705857 as risk factors to develop glioma. Furthermore, it is possible that the involvement of CCDC26 variants depends on ethnicity. However, we recommend to perform further studies to have conclusive outcomes.

Australian genome-wide association study confirms higher female risk for adult glioma associated with variants in the region of CCDC26.

BACKGROUND: Glioma accounts for approximately 80% of malignant adult brain cancer and its most common subtype, glioblastoma, has one of the lowest 5-year cancer survivals. Fifty risk-associated variants within 34 glioma genetic risk regions have been found by genome-wide association studies (GWAS) with a sex difference reported for 8q24.21 region. We conducted an Australian GWAS by glioma subtype and sex. METHODS: We analyzed genome-wide data from the Australian Genomics and Clinical Outcomes of Glioma (AGOG) consortium for 7 573 692 single nucleotide polymorphisms (SNPs) for 560 glioma cases and 2237 controls of European ancestry. Cases were classified as glioblastoma, non-glioblastoma, astrocytoma or oligodendroglioma. Logistic regression analysis was used to assess the associations of SNPs with glioma risk by subtype and by sex. RESULTS: We replicated the previously reported glioma risk associations in the regions of 2q33.3 C2orf80, 2q37.3 D2HGDH, 5p15.33 TERT, 7p11.2 EGFR, 8q24.21 CCDC26, 9p21.3 CDKN2BAS, 11q21 MAML2, 11q23.3 PHLDB1, 15q24.2 ETFA, 16p13.3 RHBDF1, 16p13.3 LMF1, 17p13.1 TP53, 20q13.33 RTEL, and 20q13.33 GMEB2 (P < .05). We also replicated the previously reported sex difference at 8q24.21 CCDC26 (P = .0024) with the association being nominally significant for both sexes (P < .05). CONCLUSIONS: Our study supports a stronger female risk association for the region 8q24.21 CCDC26 and highlights the importance of analyzing glioma GWAS by sex. A better understanding of sex differences could provide biological insight into the cause of glioma with implications for prevention, risk prediction and treatment.

Long Noncoding RNA CCDC26 Promotes Thyroid Cancer Malignant Progression via miR-422a/EZH2/Sirt6 Axis.

PURPOSE: Long noncoding RNAs are crucial regulators in thyroid cancer progression. However, the role of lncRNA CCDC26 in thyroid cancer remains unclear. Here, we aimed to explore the effect of CCDC26 on thyroid cancer progression and the underlying mechanism. MATERIALS AND METHODS: A total of 50 clinical thyroid cancer samples were studied in patients' samples, cultured cells, and nude mice before and after treatment using quantitative reverse transcription-PCR, CCK-8 assays, BrdU incorporation assays, Transwell assays, cell apoptosis analysis, luciferase reporter gene assay, RNA immunoprecipitation, Western blot analysis, and tumorigenicity analysis. RESULTS: CCDC26 expression was elevated in patients' thyroid cancer tissues and thyroid cancer cell lines. CCDC26 depletion remarkably reduced proliferation, invasion, and migration but induced apoptosis of thyroid cancer cells. Mechanically, miR-422a mimic remarkably reduced the luciferase activity of CCDC26 transfected cells but failed to affect cells transfected with CCDC26 containing the mutated miR-422a-binding site. RNA immunoprecipitation (RIP) assays showed that CCDC26 and miR-422a preferentially interacted with Ago2, but not IgG, in the micro-ribonucleoprotein complexes (miRNPs). CCDC26 depletion enhanced miR-422a expression and MiR-422a inhibitor reversed CCDC26 knockdown-induced inhibition of thyroid cancer progression in vitro. CCDC26 upregulated EZH2 and Sirt6 expression by sponging miR-422a in thyroid cancer cells. Tumorigenicity analysis in nude mice revealed that CCDC26 contributed to thyroid tumor growth via miR-422a/EZH2/Sirt6 axis in vivo. CONCLUSION: CCDC26 promotes thyroid cancer malignant progression via miR-422a/EZH2/Sirt6 axis. This finding provides new insights into the mechanism by which CCDC26 promotes malignant thyroid cancer development, advances our understanding of lncRNAs' association with thyroid cancer, and indicates that CCDC26 and miR-422a may serve as potential targets for thyroid cancer.

LncRNA CCDC26 Interacts with CELF2 Protein to Enhance Myeloid Leukemia Cell Proliferation and Invasion via the circRNA_ANKIB1/miR-195-5p/PRR11 Axis.

LncRNA CCDC26 is aberrantly expressed in myeloid leukemia (ML) and promotes myeloid leukemia progression, but the potential mechanism of CCDC26 in regulating ML progression is unclear. In this study, we observed that lncRNA CCDC26 was upregulated in both chronic and acute ML cell lines. LncRNA CCDC26 promoted the proliferation and invasion of K562 and HL-60 cells, which was determined by cell counting kit-8 test and Transwell invasion assay. Flow cytometry showed that lncRNA CCDC26 inhibited cell apoptosis. Bioinformatics and expression correlation analyses revealed that there was a potential interaction between CCDC26 and CUGBP Elav-like family member 2 (CELF2) protein, an RNA bind protein (RBP). Then the relationship between CCDC26 and the RBP CELF2 was identified by using RNA pull-down and RNA immunoprecipitation (RNA-IP) assays. Further analysis showed that overexpression of CCDC26 could noticeably upregulate circRNA_ANKIB1 expression via sponging CELF2. Subsequently, we found that overexpressed circRNA_ANKIB1 could significantly promote proline rich 11 (PRR11) protein expression by sponging miR-195a-5p. Moreover, PRR11 was also upregulated by CCDC26 and downregulated by CELF2. Mechanically, we uncovered that the miR-195a-5p inhibitor activated the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways through upregulating PRR11 protein expression. Furthermore, the inhibitors of AKT, p65-NF-κB, or Bcl-2 could inhibit the effect of the miR-195a-5p inhibitor on ML cell behaviors. In conclusion, lncRNA CCDC26 could upregulate PRR11 protein expression by sponging miR-195a-5p, thereby activating the PI3K/AKT and NF-κB pathways to enhance ML cell proliferation and invasion and suppress cell apoptosis.

lncRNA-CCDC26, as a novel biomarker, predicts prognosis in acute myeloid leukemia.

The aim of the present study was to examine the expression and clinical significance of long non-coding RNA (lncRNA)-CCDC26 in patients with acute myeloid leukemia (AML), and to investigate the potential functions of CCDC26. The Gene Expression Omnibus database and reverse transcription-quantitative polymerase chain reaction analysis were used to detect the expression levels of CCDC26 in patients with AML and healthy volunteers. Clinical data for 93 patients with AML were collected to analyze the clinical significance of CCDC26. Weighted gene co-expression network analysis (WGCNA), a protein-protein interaction (PPI) network, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were used to examine the functions of CCDC26. The expression levels of CCDC26 in the initially diagnosed and relapsed patients with AML were significantly upregulated compared with the control group. The upregulated expression level of CCDC26 in patients with AML was significantly associated with age, anemia, risk stratification and remission. Furthermore, patients with a high CCDC26 expression level had a poorer overall survival (P=0.0105). In addition, the area under the curve (AUC)1year and AUC2year of CCDC26 for overall survival were 0.722 and 0.686, respectively. WGCNA, PPI network and KEGG pathway analysis revealed that CCDC26 was involved in the regulation of a number of biological processes. lncRNA-CCDC26 may serve as a novel biomarker for monitoring the progression and predicting the clinical outcome of AML.

CCDC26 knockdown enhances resistance of gastrointestinal stromal tumor cells to imatinib by interacting with c-KIT.

Accumulating evidence indicates that long noncoding RNAs (lncRNAs) are involved in diseases such as cancer. However, little is known about the role of lncRNAs in gastrointestinal stromal tumors (GIST). In the present study, we explored the biological function of the lncRNA coiled-coil domain-containing 26 (CCDC26) in imatinib resistance of GIST. We found that human GIST-882 cells with lower CCDC26 expression were less sensitive to imatinib compared with GIST-T1 cells with higher CCDC26 expression. CCDC26 expression decreased in a time-dependent manner in the presence of imatinib. Moreover, small interfering RNA (siRNA) knockdown of CCDC26 increased GIST cell sensitivity to imatinib. The RNA pull-down experiment showed that CCDC26 can interact with c-KIT and that CCDC26 knockdown can upregulate c-KIT expression. We also found that inhibiting c-KIT induced resistance to imatinib. Lastly, we proved that inhibiting c-KIT can reverse CCDC26 knockdown-mediated imatinib resistance in GIST. We suggest that CCDC26 knockdown can induce imatinib resistance in GIST cells by downregulating c-KIT expression. Our results provide a novel insight into imatinib resistance in GIST.

Expression Analysis of PVT1, CCDC26, and CCAT1 Long Noncoding RNAs in Acute Myeloid Leukemia Patients.

BACKGROUND: Recent evidence indicates that the PVT1, CCDC26, and CCAT1 long noncoding RNAs (lncRNAs) are involved in the leukemogenic process. This study quantified the expression levels of the PVT1, CCDC26, and CCAT1 lncRNAs in patients with acute myeloid leukemia (AML) and also correlated their expression levels with the clinicopathological features of the patients. MATERIALS AND METHODS: The expression levels of the PVT1, CCDC26, and CCAT1 lncRNAs were analyzed using quantitative reverse transcription-polymerase chain reaction of bone marrow specimens obtained from 86 AML patients, 48 AML-M3 patients, and 40 normal controls. RESULTS: No differences were found between the combined AML patient populations and the healthy controls with respect to the expression levels of PVT1, CCDC26, and CCAT1 (p = 0.35, p = 0.09, and p = 0.77, respectively). However, compared with the controls, the AML-M3 patients had higher PVT1 expression (p = 0.017). Furthermore, high-risk AML-M3 patients manifested higher expression levels of PVT1 than low- and intermediate-risk groups. In addition, distinctive CCDC26 and CCAT1 expression levels were observed among patients with different French-American-British subtypes (p = 0.001 for CCDC26 and p = 0.013 for CCAT1). Compared with the healthy controls, AML-M4 and M5 had higher CCAT1 expression (p = 0.04) and AML-M2 and AML-M4/M5 patients had higher CCDC26 expression (p < 0.001 and p = 0.02, respectively). In addition, different patterns of CCDC26 expression were found among the different cytogenetic risk subtypes (p = 0.005). Finally, patients with intermediate cytogenetic risk showed higher CCDC26 expression levels. CONCLUSION: The differential expression of the PVT1, CCDC26, and CCAT1 lncRNAs in different AML subtypes suggests that the deregulation of these transcripts may function in the multistep leukemogenic process and that they may serve as new therapeutic targets for this malignancy.

CCDC26 rs4295627 polymorphisms associated with an increased risk of glioma: A meta-analysis.

BACKGROUND: Gliomas are the most common primary brain tumor in adults. Many studies have revealed associations between the rs4295627 polymorphism in the coiled-coil domain containing 26 (CCDC26) gene and the risk of glioma. However, the conclusions are still unclear because some studies have reported inconsistent results. OBJECTIVES: The aim of the present meta-analysis was to determine the relationship and quantitatively evaluate the effect of the rs4295627 polymorphism on the risk of glioma. MATERIAL AND METHODS: Data was extracted from PubMed, EMBASE and Google Scholar, with the most recent search up to December, 2015. Odds ratios (OR) and their 95% CIs were used to evaluate the effect of CCDC26 rs4295627 polymorphisms on glioma. A test of heterogeneity and an assessment of publication bias were also performed. RESULTS: A total of 11 studies (8292 cases and 12,419 controls) were selected for this meta-analysis. Significant associations were observed in all genetic analysis models (G vs T: OR = 1.26, 95% CI = 1.12-1.43; GG vs TT: OR = 1.72, 95% CI = 1.24-2.39; GT vs TT: OR = 1.33, 95% CI = 1.24-1.42; GG + GT vs TT: OR = 1.36, 95% CI = 1.20-1.53; GG vs GT + TT: OR = 1.65, 95% CI = 1.18-2.29, respectively). CONCLUSION: The results of the present study clearly show that the G allele of the rs4295627 polymorphism significantly increases the risk of glioma. Nevertheless, well-designed large-scale studies are needed to further evaluate the effect of the rs4295627 polymorphism on different types or degrees of glioma in different ethnic groups as well as to measure the combined effects on glioma risk.

Long noncoding RNA CCDC26 as a potential predictor biomarker contributes to tumorigenesis in pancreatic cancer.

Pancreatic cancer (PC) is the fourth most common cancer worldwide and has the least patient survival rate of any cancer. Emerging studies have demonstrated that long noncoding RNAs (lncRNAs) were present in cancer patients and have shown great potential as powerful markers and therapeutic targets. However, little is known about the role of lncRNAs in PC. The present study aimed to investigate the expression pattern, clinical significance and biological function of lncRNA CCDC26 (CCDC26) in PC. With quantitative real-time PCR, we analyzed CCDC26 expression levels in 40 PC patients. We found that the CCDC26 expression was significantly higher in PC tissues than in normal tissues. CCDC26 levels were correlated with tumor size, tumor number, and reduced overall survival (OS). Univariate and multivariate analysis showed that CCDC26 expression is an independent prognostic factor of OS in patients with PC. Additionally, ROCAUC of CCDC26 was up to 0.663, implicating that CCDC26 could be a diagnostic marker for distinguishing PC from normal. Knockdown of CCDC26 expression by small interfering RNA significantly promoted growth arrest and apoptosis. Moreover, we found that the expression of CCDC26 was positively correlated with PCNA and Bcl2. Our data suggest that CCDC26 may be identified as a novel oncogene in PC, and responsible for growth and apoptosis of cancer cell, partly by regulating the PCNA and Bcl2 expression. This work provides a novel biomarker and therapeutic target of PC for cancer clinic in future.

An Updated and Comprehensive Meta-Analysis of Association Between Seven Hot Loci Polymorphisms from Eight GWAS and Glioma Risk.

Eight genome-wide association studies (GWASs) found that seven loci (rs2736100, rs4295627, rs4977756, rs498872, rs11979158, rs2252586, rs6010620) polymorphisms could elevate the risk of glioma, one of the most common types of primary brain cancer in adults. However, the replication studies about these seven loci obtained inconsistent results. In order to derive a more accurate estimation about the relationship between the selected single-nucleotide polymorphism (SNP) and susceptibility to glioma, we conducted a meta-analysis containing all eligible published case control studies to evaluate the association. An overall literature search was conducted using the database of PubMed, Science Direct, China national knowledge infrastructure (CNKI), and Embase. Seventeen articles with 25 studies were included in the meta-analysis. Glioma risk (odds ratio, OR; 95 % confidential interval, 95 %CI) was estimated with the random-effect model or the fixed-effects model. STATA 12.0 was applied to analyze all statistical data. Results showed that seven hot loci were all associated with increased risk of glioma (rs2736100, OR = 1.28, 95 %CI = 1.23-1.32; rs4295627, OR = 1.34, 95 %CI = 1.21-1.47; rs4977756, OR = 1.24, 95 %CI = 1.20-1.28; rs498872, OR = 1.24, 95 %CI = 1.15-1.33; rs6010620, OR = 1.29, 95 %CI = 1.24-1.35; rs11979158: OR = 1.18, 95 %CI = 1.10-1.25; rs2252586: OR = 1.18, 95 %CI = 1.10-1.25). Additionally, subgroup analysis by stages of glioma found that variation of rs11979158 had stronger relationship with high-grade (OR = 1.32, 95 %CI = 1.19-1.45) than low-grade glioma (OR = 1.12, 95 % CI = 1.03-1.21). Similarly, stratified analysis of rs2252586 by stages revealed the similar trend, with OR of 1.26 (95 %CI = 1.17-1.35) in high-grade glioma and OR of 1.15 (95 %CI = 1.08-1.22) in low-grade glioma. In summary, the present study showed that mutations of the seven loci could elevate the risk of glioma significantly. However, more other factors that could be related with glioma should be considered in further studies.

CCDC26 rs4295627 polymorphism and glioma risk: a meta-analysis.

Several studies have examined the association of CCDC26 rs4295627 polymorphism and glioma risk. However, the results were conflicting. Thus, a meta-analysis was conducted. We searched for relevant studies up to Dec 2014 in both English and Chinese through the PubMed/MEDLINE, EMBASE, the China National Knowledge Infrastructure (CNKI) platforms, WanFang and VIP database. Overall, 14 studies with 17419 cases and 28465 controls were selected for final meta-analysis. CCDC26 rs4295627 polymorphism was significantly associated with an increased risk of glioma (OR = 1.25, 95% CI 1.15-1.36, P < 0.00001). Interestingly, CCDC26 rs4295627 polymorphism might decrease the risk of glioma in Asians (OR = 0.92, 95% CI 0.82-1.03, P = 0.15). However, Caucasians with CCDC26 rs4295627 polymorphism showed an increased risk of glioma (OR = 1.33, 95% CI 1.25-1.46, P < 0.00001). Subgroup analysis was performed by histology. Significant associations were observed among astrocytoma patients (OR = 1.31, 95% CI 1.17-1.47, P < 0.00001) and oligodendroglioma patients (OR = 1.79, 95% CI 1.47-2.17, P < 0.00001). No significant association was found between this polymorphism and glioblastoma risk (OR = 0.11, 95% CI 0.92-1.33, P = 0.28). This meta-analysis suggested that CCDC26 rs4295627 polymorphism was a risk factor for glioma.

Downregulation of lncRNA CCDC26 contributes to imatinib resistance in human gastrointestinal stromal tumors through IGF-1R upregulation

Imatinib is the first line of therapy for patients with metastatic or gastrointestinal stromal tumors (GIST). However, drug resistance limits the long-term effect of imatinib. Long non-coding RNAs (lncRNAs) are emerging as key players in regulating drug resistance in cancer. In this study, we investigated the association between lncRNA CCDC26 and IGF-1R in GIST and their involvement in drug resistance. Considering the key role of lncRNAs in drug resistance in cancer, we hypothesized that IGF-1R is regulated by lncRNAs. The expression of a series of reported drug resistance-related lncRNAs, including CCDC26, ARF, H19, NBR2, NEAT1, and HOTAIR, in GIST cells treated with imatinib H19 was examined at various time-points by qRT-PCR. Based on our results and published literature, CCDC26, a strongly down-regulated lncRNA following imatinib treatment, was chosen as our research target. GIST cells with high expression of CCDC26 were sensitive to imatinib treatment while knockdown of CCDC26 significantly increased the resistance to imatinib. Furthermore, we found that CCDC26 interacted with c-KIT by RNA pull down, and that CCDC26 knockdown up-regulated the expression of IGF-1R. Moreover, IGF-1R inhibition reversed CCDC26 knockdown-mediated imatinib resistance in GIST. These results indicated that treatments targeting CCDC26-IGF-1R axis would be useful in increasing sensitivity to imatinib in GIST.