Deficiency of Polη in Saccharomyces cerevisiae reveals the impact of transcription on damage-induced cohesion.

The structural maintenance of chromosome (SMC) complex cohesin mediates sister chromatid cohesion established during replication, and damage-induced cohesion formed in response to DSBs post-replication. The translesion synthesis polymerase Polη is required for damage-induced cohesion through a hitherto unknown mechanism. Since Polη is functionally associated with transcription, and transcription triggers de novo cohesion in Schizosaccharomyces pombe, we hypothesized that transcription facilitates damage-induced cohesion in Saccharomyces cerevisiae. Here, we show dysregulated transcriptional profiles in the Polη null mutant (rad30Δ), where genes involved in chromatin assembly and positive transcription regulation were downregulated. In addition, chromatin association of RNA polymerase II was reduced at promoters and coding regions in rad30Δ compared to WT cells, while occupancy of the H2A.Z variant (Htz1) at promoters was increased in rad30Δ cells. Perturbing histone exchange at promoters inactivated damage-induced cohesion, similarly to deletion of the RAD30 gene. Conversely, altering regulation of transcription elongation suppressed the deficient damage-induced cohesion in rad30Δ cells. Furthermore, transcription inhibition negatively affected formation of damage-induced cohesion. These results indicate that the transcriptional deregulation of the Polη null mutant is connected with its reduced capacity to establish damage-induced cohesion. This also suggests a linkage between regulation of transcription and formation of damage-induced cohesion after replication.

Clinico-pathological significance of TCGA classification and SWI/SNF proteins expression in undifferentiated/dedifferentiated endometrial carcinoma: A possible prognostic risk stratification.

BACKGROUND: Undifferentiated/dedifferentiated endometrial carcinoma (UEC/DDEC) is a heterogeneous entity, which may show any of the TCGA molecular signatures and loss of the switch/sucrose nonfermentable (SWI/SNF) proteins expression. AIM: To assess the clinico-pathological significance of the TCGA molecular groups and SWI/SNF proteins expression in UEC/DDEC, through a quantitative systematic review. METHODS: Electronic databases were searched for all studies assessing the TCGA molecular groups, i.e. POLE-mutant, mismatch repair-deficient (MMRd), p53-abnormal (p53abn) and no specific molecular profile (NSMP), and/or the SWI/SNF proteins (SMARCA4/BRG1, SMARCB1/INI1, ARID1B) expression in UEC/DDEC. Student t-test, Fisher's exact test and Kaplan-Meier survival analysis with long-rank test were used to assess differences among groups; a p-value<0.05 was considered significant. RESULTS: Eight studies were included in the systematic review. Among the TCGA groups, the mean patient age was significantly higher in the p53abn group than in the NSMP group (p = 0.048). The POLE-mutant group showed advanced FIGO stage (III-IV) significantly less commonly than the NSMP (p = 0.003) and MMRd (p = 0.008) groups, and a significantly better prognosis than the NSMP (p = 0.007), MMRd (p = 0.011) and p53abn (p = 0.045) groups.The SWI/SNF-deficient cases showed a significantly worse prognosis than the SWI/SNF-intact cases (p = 0.010), while no significant differences were found regarding patient age and FIGO stage. CONCLUSIONS: Among UEC/DDEC, POLE-mutant cases show good prognosis, while SWI/SNF-deficient cases show poor prognosis. The other TCGA molecular subtypes seem to be characterized by an intermediate biological behaviour. On this account, UEC/DDEC patients might be subdivided into three risk groups based on POLE and SWI/SNF status. Further studies are necessary in this field.

PoxCbh, a novel CENPB-type HTH domain protein, regulates cellulase and xylanase gene expression in Penicillium oxalicum.

The essential transcription factor PoxCxrA is required for cellulase and xylanase gene expression in the filamentous fungus Penicillium oxalicum that is potentially applied in biotechnological industry as a result of the existence of the integrated cellulolytic and xylolytic system. However, the regulatory mechanism of cellulase and xylanase gene expression specifically associated with PoxCxrA regulation in fungi is poorly understood. In this study, the novel regulator PoxCbh (POX06865), containing a centromere protein B-type helix-turn-helix domain, was identified through screening for the PoxCxrA regulon under Avicel induction and genetic analysis. The mutant ∆PoxCbh showed significant reduction in cellulase and xylanase production, ranging from 28.4% to 59.8%. Furthermore, PoxCbh was found to directly regulate the expression of important cellulase and xylanase genes, as well as the known regulatory genes PoxNsdD and POX02484, and its expression was directly controlled by PoxCxrA. The PoxCbh-binding DNA sequence in the promoter region of the cellobiohydrolase 1 gene cbh1 was identified. These results expand our understanding of the diverse roles of centromere protein B-like protein, the regulatory network of cellulase and xylanase gene expression, and regulatory mechanisms in fungi.

GINS2 was regulated by lncRNA XIST/miR-23a-3p to mediate proliferation and apoptosis in A375 cells.

Melanoma ranks second in aggressive tumors, and the occurrence of metastasis in melanoma results in a persistent drop in the survival rate of patients. Therefore, it is very necessary to find a novel therapeutic method for treating melanoma. It has been reported that lncRNA XIST could promote the tumorigenesis of melanoma. However, the mechanism by which lncRNA XIST regulates the progression of melanoma remains unclear. The proliferation of A375 cells was measured by clonal formation. Cell viability was detected by MTT assay. Flow cytometry was performed to detect cell apoptosis and cycle. The level of GINS2, miR-23a-3p, and lncRNA XIST was investigated by qRT-PCR. Protein level was detected by Western blot, and the correctness of prediction results was confirmed by Dual luciferase. In present study, GINS2 and lncRNA XIST were overexpressed in melanoma, while miR-23a-3p was downregulated. Silencing of GINS2 or overexpression of miR-23a-3p reversed cell growth and promoted apoptosis in A375 cells. Mechanically, miR-23a-3p directly targeted GINS2, and XIST regulated GINS2 level though mediated miR-23a-3p. Moreover, XIST exerted its function on cell proliferation, cell viability, and promoted the cell apoptosis of A375 cells though miR-23a-3p/GINS2 axis. LncRNA XIST significantly promoted the tumorigenesis of melanoma via sponging miR-23a-3p and indirectly targeting GINS2, which can be a potential new target for treating melanoma.

Preliminary Findings on Proline-Rich Protein 14 as a Diagnostic Biomarker for Parkinson's Disease.

The nuclear envelope component proline-rich protein 14 (PRR14) is involved in the nuclear morphological alteration and activation of the mTOR (mammalian target of rapamycin) signaling pathway, and has been repeatedly shown to be upregulated in patients with Parkinson's disease (PD). The aim of this study was to explore whether PRR14 can be used as a potential biomarker for the diagnosis of PD. We compared PRR14 expression in PD patients and normal controls in gene expression omnibus (GEO) data. Quantitative enzyme-linked immunosorbent assay (ELISA) was used to detect PRR14 expression in PD patients and age- and sex-matched controls. The relationship between serum PRR14 and clinical phenotype was evaluated using correlation analysis and logistic regression. The expression of PRR14 in whole blood, substantia nigra, and medial substantia nigra was significantly higher in PD patients than in the healthy control group. Compared to plasma, serum was more suitable for the detection of PRR14. Furthermore, serum PRR14 level in PD patients was significantly higher than that in age- and sex-matched controls. The area under the curve for serum PRR14 level in the ability to identify PD versus age- and sex-matched controls was 0.786. In addition, serum PRR14 level was found to correlate with constipation in PD patients. Our findings demonstrate for the first time that serum PRR14 is a potential biomarker for PD.

SMARCD3 is a potential prognostic marker and therapeutic target in CAFs.

OBJECTIVE: Screening for novel prognostic biomarkers and potential therapeutic targets from colorectal cancer microenvironment. RESULTS: 372 genes were overexpressed in colorectal cancer microenvironment, five of which that had the most prognostic powers were enriched in Epithelial-Mesenchymal Transition and cell cycle pathways. For the first time, we showed that SMARCD3 was mainly expressed in CAFs and could be a novel prognostic marker and potential therapeutic target. Function analyses indicated that MSARCD3 might promote CAFs activation and colorectal cancer metastasis through SMARCD3-WNT5A/TGF-ß-MAPK14-SMARCD3 positive feedback loop. Signaling map of SMARCD3 was constructed and several potential drugs that could regulate SMARCD3 were also presented. CONCLUSIONS: SMARCD3 is a novel prognostic biomarker and potential therapeutic target of colorectal cancer, which may promote cancer metastasis through activation of CAFs. METHODS: Colorectal cancer microenvironment related genes were screened based on immune and stromal scores. Function enrichment analyses were performed to show the underlying mechanistic insights of these tumor microenvironment related genes. Kaplan-Meier survival analysis was used for evaluating the prognostic power. Gene-Pathway interaction network analysis and cellular heterogeneity analysis of tumor microenvironment were also performed. Gene set enrichment analysis was performed for signal gene pathway analysis. Protein data from The Cancer Genome Atlas were used for validation.

Expression of SMARCD1 interacts with age in association with asthma control on inhaled corticosteroid therapy.

BACKGROUND: Global gene expression levels are known to be highly dependent upon gross demographic features including age, yet identification of age-related genomic indicators has yet to be comprehensively undertaken in a disease and treatment-specific context. METHODS: We used gene expression data from CD4+ lymphocytes in the Asthma BioRepository for Integrative Genomic Exploration (Asthma BRIDGE), an open-access collection of subjects participating in genetic studies of asthma with available gene expression data. Replication population participants were Puerto Rico islanders recruited as part of the ongoing Genes environments & Admixture in Latino Americans (GALA II), who provided nasal brushings for transcript sequencing. The main outcome measure was chronic asthma control as derived by questionnaires. Genomic associations were performed using regression of chronic asthma control score on gene expression with age in years as a covariate, including a multiplicative interaction term for gene expression times age. RESULTS: The SMARCD1 gene (SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily D member 1) interacted with age to influence chronic asthma control on inhaled corticosteroids, with a doubling of expression leading to an increase of 1.3 units of chronic asthma control per year (95% CI [0.86, 1.74], p = 6 × 10- 9), suggesting worsening asthma control with increasing age. This result replicated in GALA II (p = 3.8 × 10- 8). Cellular assays confirmed the role of SMARCD1 in glucocorticoid response in airway epithelial cells. CONCLUSION: Focusing on age-dependent factors may help identify novel indicators of asthma medication response. Age appears to modulate the effect of SMARCD1 on asthma control with inhaled corticosteroids.

PRR14 overexpression promotes cell growth, epithelial to mesenchymal transition and metastasis of colon cancer via the AKT pathway.

BACKGROUND: PRR14 (Proline rich protein 14) was firstly identified for its ability to specify and localize heterochromatin during cell cycle progression. Aberrant expression of PRR14 is associated with the tumorigenesis and progression of lung cancer. However, its involvement in colon cancer remains unknown. Herein, we report the role of PRR14 in colon cancer. METHODS: Colon cancer tissue microarray was used to analyze and compare the expression of PRR14 among some clinicopathological characteristics of colon cancer. HCT116 and RKO cells were transfected with siRNA to downregulate PRR14 expression. The roles of PRR14 in proliferation, migration and invasion of the cell lines were determined using cell counting kit-8, colony formation assay, wound healing assay and transwell assays respectively. The expression of PRR14 was measured using immunofluorescence, qRT- PCR and western blot. Epithelial-mesenchymal transition (EMT) markers were determined by western blot. RESULTS: PRR14 was highly expressed in colon cancer tissues, and the expression level was correlated with tumor size, distant metastasis and Tumor Node Metastasis stages. Functional study revealed that downregulation of PRR14 inhibited colon cancer cells growth, migration and invasion. Furthermore, knockdown of PRR14 inhibited epithelial-mesenchymal transition (EMT) process, cell cycle-associated proteins expression and p-AKT level. CONCLUSION: PRR14 may promote the progression and metastasis of colon cancer, and may be a novel prognostic and therapeutic marker for the disease.

CBX1 is a direct target of miR-205-5p and contributes to the progression of pituitary tumor.

MicroRNAs (miRs) are crucial regulators for tumorigenesis through negatively regulating their target genes expression in the manner of 3'-untranslated region (3'-UTR) binding. MiR-205-5p has been reported to function as a tumor suppressor in several cancer types. The aim of this study was to investigate the role of miR-205-5p/chromobox homolog 1 (CBX1) axis in human pituitary tumors. The expression of miR-205-5p was firstly examined by quantitative real-time PCR and the results revealed that miR-205-5p expression was declined in pituitary cell lines compared with normal cell line. Overexpression of miR-205-5p effectively decreased cell proliferation and cell migration. Based on the results of bioinformatic analysis, luciferase reporter assay, and western blot, we identified CBX1 as a direct target of miR-205-5p. Notably, overexpression of CBX1 promoted cell proliferation and migration. The effects of miR-205-5p overexpression on cell proliferation and migration can be reversed by CBX1 overexpression. Based on these findings, we deducted that miR-205-5p inhibits the cell proliferation and migration through directly targeting CBX1.

Oncogene c-MYC Controls the Expression of PHF10 Subunit of PBAF Chromatin Remodeling Complex in SW620 Cell Line.

The PBAF(SWI/SNF) multiprotein complex, which changes the chromatin structure, is widely involved in the regulation of eukaryotic gene expression. A specific component of this complex is the PHF10 protein, which is involved in recruiting this complex to chromatin. We showed that the PHF10 expression in cells of different lines is activated by the c-MYC oncogene. Since PHF10 stimulates cell proliferation, its c-MYC-dependent activation in cancer cells should lead to an increase in their proliferation rate.

Suppression of respiratory growth defect of mitochondrial phosphatidylserine decarboxylase deficient mutant by overproduction of Sfh1, a Sec14 homolog, in yeast.

Interorganelle phospholipid transfer is critical for eukaryotic membrane biogenesis. In the yeast Saccharomyces cerevisiae, phosphatidylserine (PS) synthesized by PS synthase, Pss1, in the endoplasmic reticulum (ER) is decarboxylated to phosphatidylethanolamine (PE) by PS decarboxylase, Psd1, in the ER and mitochondria or by Psd2 in the endosome, Golgi, and/or vacuole, but the mechanism of interorganelle PS transport remains to be elucidated. Here we report that Sfh1, a member of Sec14 family proteins of S. cerevisiae, possesses the ability to enhance PE production by Psd2. Overexpression of SFH1 in the strain defective in Psd1 restored its growth on non-fermentable carbon sources and increased the intracellular and mitochondrial PE levels. Sfh1 was found to bind various phospholipids, including PS, in vivo. Bacterially expressed and purified Sfh1 was suggested to have the ability to transport fluorescently labeled PS between liposomes by fluorescence dequenching assay in vitro. Biochemical subcellular fractionation suggested that a fraction of Sfh1 localizes to the endosome, Golgi, and/or vacuole. We propose a model that Sfh1 promotes PE production by Psd2 by transferring phospholipids between the ER and endosome.

Overexpression of the cohesin-core subunit SMC1A contributes to colorectal cancer development.

BACKGROUND: Cancer cells are characterized by chromosomal instability (CIN) and it is thought that errors in pathways involved in faithful chromosome segregation play a pivotal role in the genesis of CIN. Cohesin forms a large protein ring that binds DNA strands by encircling them. In addition to this central role in chromosome segregation, cohesin is also needed for DNA repair, gene transcription regulation and chromatin architecture. Though mutations in both cohesin and cohesin-regulator genes have been identified in many human cancers, the contribution of cohesin to cancer development is still under debate. METHODS: Normal mucosa, early adenoma, and carcinoma samples deriving from 16 subjects affected by colorectal cancer (CRC) were analyzed by OncoScan for scoring both chromosome gains and losses (CNVs) and loss of heterozygosity (LOH). Then the expression of SMC1A was analyzed by immunochemistry in 66 subjects affected by CRC. The effects of SMC1A overexpression and mutated SMC1A were analyzed in vivo using immunocompromised mouse models. Finally, we measured global gene expression profiles in induced-tumors by RNA-seq. RESULTS: Here we showed that SMC1A cohesin core gene was present as extra-copies, mutated, and overexpressed in human colorectal carcinomas. We then demonstrated that cohesin overexpression led to the development of aggressive cancers in immunocompromised mice through gene expression dysregulation. CONCLUSION: Collectively, these results support a role of defective cohesin in the development of human colorectal cancer.

PRR11 and SKA2 gene pair is overexpressed and regulated by p53 in breast cancer.

Our previous study found that two novel cancer-related genes, PRR11 and SKA2, constituted a classic gene pair that was regulated by p53 and NF-Y in lung cancer. However, their role and regulatory mechanism in breast cancer remain elusive. In this study, we found that the expression levels of PRR11 and SKA2 were upregulated and have a negative prognotic value in breast cancer. Loss-of-function experiments showed that RNAi-mediated knockdown of PRR11 and/or SKA2 inhibited proliferation, migration, and invasion of breast cancer cells. Mechanistic experiments revealed that knockdown of PRR11 and/or SKA2 caused dysregulation of several downstream genes, including CDK6, TPM3, and USP12, etc. Luciferase reporter assays demonstrated that wild type p53 significantly repressed the PRR11-SKA2 bidirectional promoter activity, but not NF-Y. Interestingly, NF-Y was only essential for and correlated with the expression of PRR11, but not SKA2. Consistently, adriamycin-induced (ADR) activation of endogenous p53 also caused significant repression of the PRR11 and SKA2 gene pair expression. Notably, breast cancer patients with lower expression levels of either PRR11 or SKA2, along with wild type p53, exhibited better disease-free survival compared to others with p53 mutations and/or higher expression levels of either PRR11 or SKA2. Collectively, our study indicates that the PRR11 and SKA2 transcription unit might be an oncogenic contributor and might serve as a novel diagnostic and therapeutic target in breast cancer. [BMB Reports 2019; 52(2): 157-162].

A Muscle-Specific Enhancer RNA Mediates Cohesin Recruitment and Regulates Transcription In trans.

The enhancer regions of the myogenic master regulator MyoD give rise to at least two enhancer RNAs. Core enhancer eRNA (CEeRNA) regulates transcription of the adjacent MyoD gene, whereas DRReRNA affects expression of Myogenin in trans. We found that DRReRNA is recruited at the Myogenin locus, where it colocalizes with Myogenin nascent transcripts. DRReRNA associates with the cohesin complex, and this association correlates with its transactivating properties. Despite being expressed in undifferentiated cells, cohesin is not loaded on Myogenin until the cells start expressing DRReRNA, which is then required for cohesin chromatin recruitment and maintenance. Functionally, depletion of either cohesin or DRReRNA reduces chromatin accessibility, prevents Myogenin activation, and hinders muscle cell differentiation. Thus, DRReRNA ensures spatially appropriate cohesin loading in trans to regulate gene expression.

CRL7SMU1 E3 ligase complex-driven H2B ubiquitylation functions in sister chromatid cohesion by regulating SMC1 expression.

Cullin-RING-type E3 ligases (CRLs) control a broad range of biological processes by ubiquitylating numerous cellular substrates. However, the role of CRL E3 ligases in chromatid cohesion is unknown. In this study, we identified a new CRL-type E3 ligase (designated as CRL7SMU1 complex) that has an essential role in the maintenance of chromatid cohesion. We demonstrate that SMU1, DDB1, CUL7 and RNF40 are integral components of this complex. SMU1, by acting as a substrate recognition module, binds to H2B and mediates monoubiquitylation at the lysine (K) residue K120 through CRL7SMU1 E3 ligase complex. Depletion of CRL7SMU1 leads to loss of H2B ubiquitylation at the SMC1a locus and, thus, subsequently compromised SMC1a expression in cells. Knockdown of CRL7SMU1 components or loss of H2B ubiquitylation leads to defective sister chromatid cohesion, which is rescued by restoration of SMC1a expression. Together, our results unveil an important role of CRL7SMU1 E3 ligase in promoting H2B ubiquitylation for maintenance of sister chromatid cohesion during mitosis.This article has an associated First Person interview with the first author of the paper.

The potential predictive value of DEK expression for neoadjuvant chemoradiotherapy response in locally advanced rectal cancer.

BACKGROUND: Limited data are available regarding the ability of biomarkers to predict complete pathological response to neoadjuvant chemoradiotherapy in locally advanced rectal cancer. Complete response translates to better patient survival. DEK is a transcription factor involved not only in development and progression of different types of cancer, but is also associated with treatment response. This study aims to analyze the role of DEK in complete pathological response following chemoradiotherapy for locally advanced rectal cancer. METHODS: Pre-treated tumour samples from 74 locally advanced rectal-cancer patients who received chemoradiation therapy prior to total mesorectal excision were recruited for construction of a tissue microarray. DEK immunoreactivity from all samples was quantified by immunohistochemistry. Then, association between positive stained tumour cells and pathologic response to neoadjuvant treatment was measured to determine optimal predictive power. RESULTS: DEK expression was limited to tumour cells located in the rectum. Interestingly, high percentage of tumour cells with DEK positiveness was statistically associated with complete pathological response to neoadjuvant treatment based on radiotherapy and fluoropyrimidine-based chemotherapy and a marked trend toward significance between DEK positiveness and absence of treatment toxicity. Further analysis revealed an association between DEK and the pro-apoptotic factor P38 in the pre-treated rectal cancer biopsies. CONCLUSIONS: These data suggest DEK as a potential biomarker of complete pathological response to treatment in locally advanced rectal cancer.

CBX3/heterochromatin protein 1 gamma is significantly upregulated in patients with non-small cell lung cancer.

AIM: Lung cancer is typically categorized into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC comprises of the majority of lung cancer with a poor prognosis in advanced cases. Transcriptional profiling studies, including microarrays and RNA-sequencing studies, have significantly enriched our knowledge of gene expression patterns in NSCLC. A recent transcriptional profiling study identified high prevalence of CBX3/HP1-gamma upregulation in human NSCLC samples. CBX3/HP1-gamma is an isoform of the heterochromatin protein 1 family, which plays a role in heterochromatin formation and is linked to cancer. METHODS: We examined lung cancer samples from our hospital using immunohistochemistry for CBX3/HP1-gamma staining. We also analyzed publicly available databases of NSCLC transcriptional profiling to validate our results. RESULTS: We identified a high prevalence (77.2%) of samples with positive CBX3/HP1-gamma staining by immunohistochemistry in NSCLC patient samples. Independently, we queried a publicly available dataset (GSE40419) containing RNA-seq data from 77 patients. Upregulation of CBX3/HP1-gamma in tumor samples was present in 60.2% of the patients. A similar correlation was also observed in the The Cancer Genome Atlas (TCGA) database. Interestingly, we discovered a highly significant association between positive CBX3/HP1-gamma staining and EGFR mutation in our patient samples (40 of 42 patients, P < 0.001). Treatment of EGFR mutant NSCLC cell lines with the EGFR inhibitor gefitinib failed to yield a change in CBX/HP1-gamma expression, suggesting that CBX/HP1-gamma expression may be independent of EGFR downstream signaling. CONCLUSION: We report a significant upregulation of CBX3/HP1-gamma in NSCLC patients, and also a possible relationship between CBX3/HP1-gamma expression and EGFR mutation.

LSD1-Mediated Epigenetic Reprogramming Drives CENPE Expression and Prostate Cancer Progression.

Androgen receptor (AR) signaling is a key driver of prostate cancer, and androgen-deprivation therapy (ADT) is a standard treatment for patients with advanced and metastatic disease. However, patients receiving ADT eventually develop incurable castration-resistant prostate cancer (CRPC). Here, we report that the chromatin modifier LSD1, an important regulator of AR transcriptional activity, undergoes epigenetic reprogramming in CRPC. LSD1 reprogramming in this setting activated a subset of cell-cycle genes, including CENPE, a centromere binding protein and mitotic kinesin. CENPE was regulated by the co-binding of LSD1 and AR to its promoter, which was associated with loss of RB1 in CRPC. Notably, genetic deletion or pharmacological inhibition of CENPE significantly decreases tumor growth. Our findings show how LSD1-mediated epigenetic reprogramming drives CRPC, and they offer a mechanistic rationale for its therapeutic targeting in this disease. Cancer Res; 77(20); 5479-90. ©2017 AACR.

DEK proto-oncogene is highly expressed in astrocytic tumors and regulates glioblastoma cell proliferation and apoptosis.

Astrocytic tumors are the most common neuroepithelial neoplasms with high relapse rate after surgery. Understanding the molecular mechanisms for astrocytic tumorigenesis and progression will lead to early diagnosis and effective treatment of astrocytic tumors. The DEK mRNA and protein expression in normal brain tissues and astrocytic tumors was quantified. To investigate DEK functions in tumor cells, DEK gene was silenced with siRNA in U251 glioblastoma cells. Cell proliferation, cell cycle and apoptosis were then measured. The expression and activity of key genes that regulate cell proliferation and apoptosis were also measured. We identified DEK as a high expressed gene in astrocytic tumor tissues. DEK expression level was positively correlated with the pathological grade of astrocytic tumors. Gene silencing of DEK in U251 glioblastomas inhibited cell proliferation and blocked cells at G0/G1 phase of cell cycle. DEK depletion also induced cell apoptosis, with up-regulated expression of P53 and P21 and down-regulated expression of Bcl-2 and C-myc. The Caspase-3 activity in U251 cells was also significantly increased after knockdown. Our results provided evidences that DEK regulates proliferation and apoptosis of glioblastomas. DEK gene silencing may induce apoptosis through P53-dependent pathway. Our data indicated DEK plays multiple roles to facilitate tumor growth and maintenance. It can be used as a potential target for astrocytic tumor diagnosis and gene therapy.

Hypoxia promotes chemotherapy resistance by down-regulating SKA1 gene expression in human osteosarcoma.

Drug resistance has always been the main problem in osteosarcoma treatment, and hypoxia seems to be one of the many causes for drug resistance. Therefore, in this study, we investigated how hypoxia triggers chemotherapy resistance in osteosarcoma. We first screened hypoxia- and normoxia- cultured osteosarcoma cells in silico to identify the differentially expressed genes specifically related to drug resistance. This led to the identification of spindle and kinetochore associated complex subunit 1 (SKA1) as a probable gene of interest. SKA1 was further overexpressed by a lentiviral vector into an osteosarcoma cell line to study its role in chemoresistance. Our data revealed that SKA1 overexpression reduced the expression of some multidrug resistance genes, and enhanced the sensitivity of two common chemotherapeutic drugs used in osteosarcoma patients, epirubicin (EPI) and ifosfamide (IFO). In addition, we also confirmed the role of SKA1 in EPI drug sensitivity in vivo. Taken together, our study indicated that hypoxia mediated downregulation of SKA1 expression increased the chemotherapy resistance in human osteosarcoma cells.