Role of YY1 in the pathogenesis of prostate cancer and correlation with bioinformatic data sets of gene expression

DEAD/H-box helicase 11 is transcriptionally activated by Yin Yang-1 and accelerates oral squamous cell carcinoma progression

Oral squamous cell carcinoma (OSCC) is the most common oral malignancy. DEAD/H-box helicase 11 (DDX11), a DNA helicase, has been implicated in the progression of several cancers. Yet, the precise function of DDX11 in OSCC is poorly understood. The DDX11 expression in OSCC cells and normal oral keratinocytes was evaluated in the Gene Expression Omnibus database (GSE146483 and GSE31853). SCC-4 and CAL-27 cells expressing doxycycline-inducible DDX11 or DDX11 shRNA were generated by lentiviral infection. The role of DDX11 in OSCC cells was determined by 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay, colony formation assay, flow cytometry assay, TUNEL staining, and western blot. The effects of DDX11 on tumor growth were explored in a xenograft nude mouse model. The relationship between DDX11 and transcription factor Yin Yang-1 (YY1) was researched using the dual luciferase report assay and chromatin immunoprecipitation assay. DDX11 expression was significantly upregulated in OSCC cells. Knockdown of DDX11 inhibited cell proliferation, induced cell cycle arrest, and suppressed PI3K-AKT pathway, while DDX11 overexpression showed opposite effects. The number of apoptotic cells was increased in DDX11 silenced cells. DDX11 upregulation or knockdown accelerated or suppressed tumor growth in vivo, respectively. Moreover, the YY1 bound and activated the DDX11 promoter, resulting in increasing DDX11 expression. Forced expression DDX11 reversed the anticancer effects of YY1 silencing on OSCC cells. DDX11 has tumor-promoting function in OSCC and is transcriptionally regulated by YY1, indicating that DDX11 may serve as a potential target for the OSCC treatment.

Dissecting the roles and clinical potential of YY1 in the tumor microenvironment

Yin-Yang 1 (YY1) is a member of the GLI-Kruppel family of zinc finger proteins and plays a vital dual biological role in cancer as an oncogene or a tumor suppressor during tumorigenesis and tumor progression. The tumor microenvironment (TME) is identified as the “soil” of tumor that has a critical role in both tumor growth and metastasis. Many studies have found that YY1 is closely related to the remodeling and regulation of the TME. Herein, we reviewed the expression pattern of YY1 in tumors and summarized the function and mechanism of YY1 in regulating tumor angiogenesis, immune and metabolism. In addition, we discussed the potential value of YY1 in tumor diagnosis and treatment and provided a novel molecular strategy for the clinical diagnosis and treatment of tumors.

LncNAP1L6 activates MMP pathway by stabilizing the m6A-modified NAP1L2 to promote malignant progression in prostate cancer

Malignant progression such as bone metastasis, which is associated with pathologic fractures, pain and reduced survival frequently occurs in prostate cancer (PCa) patients at advanced stages. Accumulating evidence has supported that long non-coding RNAs (lncRNAs) participate in multiple biological processes. Nevertheless, the functions of most lncRNAs in PCa malignant progression remain largely unclear. Our current study is to elucidate the influence of lncRNA lncNAP1L6 on PCa malignant progression and uncover the possible regulatory mechanism. Firstly, RT-qPCR analysis was to detect lncNAP1L6 expression and suggested that lncNAP1L6 was markedly upregulated in PCa cells. Functional assays manifested that silencing of lncNAP1L6 hampered cell migration, invasion, and epithelial-mesenchymal transition (EMT) while overexpression of lncNAP1L6 exacerbated cell migration, invasion and EMT. In addition, mechanism assays were to determine the latent regulatory mechanism of lncNAP1L6. It turned out that METTL14/METTL3 complex mediated m6A methylation of NAP1L2 mRNA. Besides, lncNAP1L6 recruited HNRNPC to m6A-modified NAP1L2, leading to stabilization of NAP1L2 mRNA. Moreover, NAP1L6 interacted with YY1 to promote the transcription of MMP2 and MMP9 and activate MMP signaling pathway. In summary, lncNAP1L6 was identified as an oncogene in PCa, which revealed that lncNAP1L6 might be used as potential therapeutic target in PCa.

Protein signatures to distinguish aggressive from indolent prostate cancer

BACKGROUND

Distinguishing men with aggressive from indolent prostate cancer is critical to decisions in the management of clinically localized prostate cancer. Molecular signatures of aggressive disease could help men overcome this major clinical challenge by reducing unnecessary treatment and allowing more appropriate treatment of aggressive disease.

METHODS

We performed a mass spectrometry-based proteomic analysis of normal and malignant prostate tissues from 22 men who underwent surgery for prostate cancer. Prostate cancer samples included Grade Groups (3-5), with 8 patients experiencing recurrence and 14 without evidence of recurrence with a mean of 6.8 years of follow-up. To better understand the biological pathways underlying prostate cancer aggressiveness, we performed a systems biology analysis and gene enrichment analysis. Proteins that distinguished recurrent from nonrecurrent cancer were chosen for validation by immunohistochemical analysis on tissue microarrays containing samples from a larger cohort of patients with recurrent and nonrecurrent prostate cancer.

RESULTS

In all, 24,037 unique peptides (false discovery rate < 1%) corresponding to 3,313 distinct proteins were identified with absolute abundance ranges spanning seven orders of magnitude. Of these proteins, 115 showed significantly (p < 0.01) different levels in tissues from recurrent versus nonrecurrent cancers. Analysis of all differentially expressed proteins in recurrent and nonrecurrent cases identified several protein networks, most prominently one in which approximately 24% of the proteins in the network were regulated by the YY1 transcription factor (adjusted p < 0.001). Strong immunohistochemical staining levels of three differentially expressed proteins, POSTN, CALR, and CTSD, on a tissue microarray validated their association with shorter patient survival.

CONCLUSIONS

The protein signatures identified could improve understanding of the molecular drivers of aggressive prostate cancer and be used as candidate prognostic biomarkers.

Insights of RKIP-Derived Suppression of Prostate Cancer

Simple Summary

Despite an intensive research effort in the past few decades, prostate cancer (PC) remains a top cause of cancer death in men, particularly in the developed world. The major cause of fatality is the progression of local prostate cancer to metastasis disease. Treatment of patients with metastatic prostate cancer (mPC) is generally ineffective. Based on the discovery of mPC relying on androgen for growth, many patients with mPC show an initial response to the standard of care: androgen deprivation therapy (ADT). However, lethal castration resistant prostate cancers (CRPCs) commonly develop. It is widely accepted that intervention of metastatic progression of PC is a critical point of intervention to reduce PC death. Accumulative evidence reveals a role of RKIP in suppression of PC progression towards mPC. We will review current evidence and discuss the potential utilization of RKIP in preventing mPC progression.

Abstract

Prostate cancer (PC) is a major cause of cancer death in men. The disease has a great disparity in prognosis. Although low grade PCs with Gleason scores ≤ 6 are indolent, high-risk PCs are likely to relapse and metastasize. The standard of care for metastatic PC (mPC) remains androgen deprivation therapy (ADT). Resistance commonly occurs in the form of castration resistant PC (CRPC). Despite decades of research efforts, CRPC remains lethal. Understanding of mechanisms underpinning metastatic progression represents the overarching challenge in PC research. This progression is regulated by complex mechanisms, including those regulating PC cell proliferation, epithelial–mesenchymal transition (EMT), and androgen receptor (AR) signaling. Among this PC metastatic network lies an intriguing suppressor of PC metastasis: the Raf kinase inhibitory protein (RKIP). Clinically, the RKIP protein is downregulated in PC, and showed further reduction in mPC. In xenograft mouse models for PC, RKIP inhibits metastasis. In vitro, RKIP reduces PC cell invasion and sensitizes PC cells to therapeutic treatments. Mechanistically, RKIP suppresses Raf-MEK-ERK activation and EMT, and modulates extracellular matrix. In return, Snail, NFκB, and the polycomb protein EZH2 contribute to inhibition of RKIP expression. In this review, we will thoroughly analyze RKIP’s tumor suppression actions in PC.

Filtering of the Gene Signature as the Predictors of Cisplatin-Resistance in Ovarian Cancer

BACKGROUND

Gene expression profiling and prediction of drug responses based on the molecular signature indicate new molecular biomarkers which help to find the most effective drugs according to the tumor characteristics.

OBJECTIVES

In this study two independent datasets, GSE28646 and GSE15372 were subjected to meta-analysis based on Affymetrix microarrays.

MATERIAL AND METHODS

In-silico methods were used to determine differentially expressed genes (DEGs) in the previously reported sensitive and resistant A2780 cell lines to Cisplatin. Gene Fuzzy Scoring (GFS) and Principle Component Analysis (PCA) were then used to eliminate batch effects and reduce data dimension, respectively. Moreover, SVM method was performed to classify sensitive and resistant data samples. Furthermore, Wilcoxon Rank sum test was performed to determine DEGs. Following the selection of drug resistance markers, several networks including transcription factor-target regulatory network and miRNA-target network were constructed and Differential correlation analysis was performed on these networks.

RESULTS

The trained SVM successfully classified sensitive and resistant data samples. Moreover, Performing DiffCorr analysis on the sensitive and resistant samples resulted in detection of 27 and 25 significant (with correlation ≥|0.9|) pairs of genes that respectively correspond to newly constructed correlations and loss of correlations in the resistant samples.

CONCLUSIONS

Our results indicated the functional genes and networks in Cisplatin resistance of ovarian cancer cells and support the importance of differential expression studies in ovarian cancer chemotherapeutic agent responsiveness.

Roles Played by YY1 in Embryonic, Adult and Cancer Stem Cells

Accumulating evidence strongly indicates that the presence of cancer stem cells (CSCs) leads to the emergence of worse clinical scenarios, such as chemo- and radiotherapy resistance, metastasis, and cancer recurrence. CSCs are a highly tumorigenic population characterized by self-renewal capacity and differentiation potential. Thus, CSCs establish a hierarchical intratumor organization that enables tumor adaptation to evade the immune response and resist anticancer therapy. YY1 functions as a transcription factor, RNA-binding protein, and 3D chromatin regulator. Thus, YY1 has multiple effects and regulates several molecular processes. Emerging evidence indicates that the development of lethal YY1-mediated cancer phenotypes is associated with the presence of or enrichment in cancer stem-like cells. Therefore, it is necessary to investigate whether and to what extent YY1 regulates the CSC phenotype. Since CSCs mirror the phenotypic behavior of stem cells, we initially describe the roles played by YY1 in embryonic and adult stem cells. Next, we scrutinize evidence supporting the contributions of YY1 in CSCs from a number of various cancer types. Finally, we identify new areas for further investigation into the YY1-CSCs axis, including the participation of YY1 in the CSC niche.

Loss of YY1 expression predicts unfavorable prognosis in stage III colorectal cancer

Background

Yin Yang 1 (YY1), the multifunctional transcription factor, has recently been assigned biological properties related to human malignancies. YY1 can facilitate both tumor suppression and tumor growth. The conflicting role of YY1 in human malignancies is not yet fully explained.

Objective

In this study, we determined the clinicopathologic significance and prognostic role of YY1 in stage III colorectal cancer (CRC).

Materials and Methods

YY1 expression was evaluated immunohistochemically in tissue microarray from 345 CRCs. YY1 expression was scored by the proportion of tumor cells with nuclear staining into 4 scores (0, none; 1+, ≤10%; 2+, 10 to ≤25%; 3+, >25%). A score of 0 and 1 were considered as loss of expression.

Results

Loss of YY1 expression was observed in 49 (14.2%) out of 345 CRCs and was associated with larger tumor size (P = 0.004), tumor deposit (P = 0.008), and higher pathologic tumor (pT) stage (P = 0.004). In stage III group, loss of YY1 expression was associated with larger tumor size (P = 0.027) and tumor deposit (P = 0.011). Kaplan-Meier survival curves revealed no significant difference between patients with YY1 loss and patients with intact YY1 in both cancer-specific survival and recurrence-free survival (P = 0.330 and P = 0.470, respectively). In American Joint Committee on Cancer (AJCC) stage subgroup, loss of YY1 expression was associated with poor recurrence-free survival in AJCC stage III CRC (P = 0.038).

Conclusion

Loss of YY1 expression was significantly associated with aggressive phenotypes and poor patient outcome in AJCC stage III CRC.

YY1 is a cis-regulator in the organoid models of high mammographic density

MOTIVATION

Our previous study has shown that ERBB2 is overexpressed in the organoid model of MCF10A when the stiffness of the microenvironment is increased to that of high mammographic density (MD). We now aim to identify key transcription factors (TFs) and functional enhancers that regulate processes associated with increased stiffness of the microenvironment in the organoid models of premalignant human mammary cell lines.

RESULTS

3D colony organizations and the cis-regulatory networks of two human mammary epithelial cell lines (184A1 and MCF10A) are investigated as a function of the increased stiffness of the microenvironment within the range of MD. The 3D colonies are imaged using confocal microscopy, and the morphometries of colony organizations and heterogeneity are quantified as a function of the stiffness of the microenvironment using BioSig3D. In a surrogate assay, colony organizations are profiled by transcriptomics. Transcriptome data are enriched by correlative analysis with the computed morphometric indices. Next, a subset of enriched data are processed against publicly available ChIP-Seq data using Model-based Analysis of Regulation of Gene Expression to predict regulatory transcription factors. This integrative analysis of morphometric and transcriptomic data predicted YY1 as one of the cis-regulators in both cell lines as a result of the increased stiffness of the microenvironment. Subsequent experiments validated that YY1 is expressed at protein and mRNA levels for MCF10A and 184A1, respectively. Also, there is a causal relationship between activation of YY1 and ERBB2 when YY1 is overexpressed at the protein level in MCF10A.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

The USP21/YY1/SNHG16 axis contributes to tumor proliferation, migration, and invasion of non-small-cell lung cancer

Deubiquitinases (DUBs) and noncoding RNAs have been the subjects of recent extensive studies regarding their roles in lung cancer, but the mechanisms involved are largely unknown. In our study, we used The Cancer Genome Atlas data set and bioinformatics analyses and identified USP21, a DUB, as a potential contributor to oncogenesis in non-small-cell lung cancer (NSCLC). We further demonstrated that USP21 was highly expressed in NSCLCs. We then conducted a series of in vitro and in vivo assays to explore the effect of USP21 on NSCLC progression and the underlying mechanism involved. USP21 promoted NSCLC cell proliferation, migration, and invasion and in vivo tumor growth by stabilizing a well-known oncogene, Yin Yang-1 (YY1), via mediating its deubiquitination. Furthermore, YY1 transcriptionally regulates the expression of SNHG16. Moreover, StarBase bioinformatics analyses predicted that miR-4500 targets SNHG16 and USP21. A series of in vitro experiments indicated that SNHG16 increased the expression of USP21 through miR-4500. In summary, the USP21/YY1/SNHG16 axis plays a role in promoting the progression of NSCLC. Therefore, the USP21/YY1/SNHG16/miR-4500 axis may be a potential therapeutic target in NSCLC treatment.

Therapies targeting a molecular feedback loop involved in tumor growth may prove valuable for treating non-small-cell lung cancer. Fangbao Ding, Jianbing Huang, and co-workers at Shanghai Jiao Tong University in Shanghai, China, have shown how an enzyme called USP21 promotes cancer cell proliferation and tumor growth in non-small-cell lung cancer. The team took cancerous and non-cancerous lung tissue samples from 42 patients, and analyzed the expression and behavior of USP21. The enzyme was highly expressed in cancerous tissues, where it stabilized a known gene with the potential to cause cancer called YY1. This gene also regulated the expression of a particular RNA molecule, which in turn worked to increase levels of USP21. This cyclical process encouraged the proliferation, migration and invasion of non-small-cell lung cancer cells, and may provide a future therapeutic target.

The Two Sides of YY1 in Cancer: A Friend and a Foe

Yin Yang 1 (YY1), a dual function transcription factor, is known to regulate transcriptional activation and repression of many genes associated with multiple cellular processes including cellular differentiation, DNA repair, autophagy, cell survival vs. apoptosis, and cell division. Owing to its role in processes that upon deregulation are linked to malignant transformation, YY1 has been implicated as a major driver of many cancers. While a large body of evidence supports the role of YY1 as a tumor promoter, recent reports indicated that YY1 also functions as a tumor suppressor. The mechanism by which YY1 brings out opposing outcome in tumor growth vs. suppression is not completely clear and some of the recent reports have provided significant insight into this. Likewise, the mechanism by which YY1 functions both as a transcriptional activator and repressor is not completely clear. It is likely that the proteins with which YY1 interacts might determine its function as an activator or repressor of transcription as well as its role as a tumor suppressor or promoter. Hence, a collection of YY1-protein interactions in the context of different cancers would help us gain an insight into how YY1 promotes or suppresses cancers. This review focuses on the YY1 interacting partners and its target genes in different cancer models. Finally, we discuss the possibility of therapeutically targeting the YY1 in cancers where it functions as a tumor promoter.

YY1 mediates TGF-β1-induced EMT and pro-fibrogenesis in alveolar epithelial cells

Pulmonary fibrosis is a chronic, progressive lung disease associated with lung damage and scarring. The pathological mechanism causing pulmonary fibrosis remains unknown. Emerging evidence suggests prominent roles of epithelial–mesenchymal transition (EMT) of alveolar epithelial cells (AECs) in myofibroblast formation and progressive pulmonary fibrosis. Our previous work has demonstrated the regulation of YY1 in idiopathic pulmonary fibrosis and pathogenesis of fibroid lung. However, the specific function of YY1 in AECs during the pathogenesis of pulmonary fibrosis is yet to be determined. Herein, we found the higher level of YY1 in primary fibroblasts than that in primary epithelial cells from the lung of mouse. A549 and BEAS-2B cells, serving as models for type II alveolar pulmonary epithelium in vitro, were used to determine the function of YY1 during EMT of AECs. TGF-β-induced activation of the pro-fibrotic program was applied to determine the role YY1 may play in pro-fibrogenesis of type II alveolar epithelial cells. Upregulation of YY1 was associated with EMT and pro-fibrotic phenotype induced by TGF-β treatment. Targeted knockdown of YY1 abrogated the EMT induction by TGF-β treatment. Enforced expression of YY1 can partly mimic the TGF-β-induced pro-fibrotic change in either A549 cell line or primary alveolar epithelial cells, indicating the induction of YY1 expression may mediate the TGF-β-induced EMT and pro-fibrosis. In addition, the translocation of NF-κB p65 from the cytoplasm to the nucleus was demonstrated in A549 cells after TGF-β treatment and/or YY1 overexpression, suggesting that NF-κB-YY1 signaling pathway regulates pulmonary fibrotic progression in lung epithelial cells. These findings will shed light on the better understanding of mechanisms regulating pro-fibrogenesis in AECs and pathogenesis of lung fibrosis.

Characterization of HMGB1/2 Interactome in Prostate Cancer by Yeast Two Hybrid Approach: Potential Pathobiological Implications

High mobility group box B (HMGB) proteins are pivotal in the development of cancer. Although the proteomics of prostate cancer (PCa) cells has been reported, the involvement of HMGB proteins and their interactome in PCa is an unexplored field of considerable interest. We describe herein the results of the first HMGB1/HMGB2 interactome approach to PCa. Libraries constructed from the PCa cell line, PC-3, and from patients’ PCa primary tumor have been screened by the yeast 2-hybrid approach (Y2H) using HMGB1 and HMGB2 baits. Functional significance of this PCa HMGB interactome has been validated through expression and prognosis data available on public databases. Copy number alterations (CNA) affecting these newly described HMGB interactome components are more frequent in the most aggressive forms of PCa: those of neuroendocrine origin or castration-resistant PCa. Concordantly, adenocarcinoma PCa samples showing CNA in these genes are also associated with the worse prognosis. These findings open the way to their potential use as discriminatory biomarkers between high and low risk patients. Gene expression of a selected set of these interactome components has been analyzed by qPCR after HMGB1 and HMGB2 silencing. The data show that HMGB1 and HMGB2 control the expression of several of their interactome partners, which might contribute to the orchestrated action of these proteins in PCa

hnRNPM, a potential mediator of YY1 in promoting the epithelial-mesenchymal transition of prostate cancer cells

BACKGROUND

With the popularity of serum prostate-specific antigen (PSA) screening, the number of newly diagnosed prostate cancer (PCa) patients is increasing. However, indolent or invasive PCa cannot be distinguished by PSA levels. Here, we mainly explored the role of heterogeneous nuclear ribonucleoprotein M (hnRNPM) in the invasiveness of PCa.

METHODS

Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis was used to detect the expressions of hnRNPM in PCa and benign prostate hyperplasia (BPH) tissues as well as in PCa cell lines. Immunohistochemistry was applied to detect the hnRNPM or Yin Yang 1 (YY1) expression in BPH, prostate adenocarcinoma (ADENO) and neuroendocrine prostate cancer (NEPC) tissues. After aberrant, the expression of hnRNPM in C4-2 and PC3 cells, the changes of cell migration and invasion were observed through wound-healing and transwell assays. We also predicted the transcription factor of hnRNPM through databases, then verified the association of hnRNPM and YY1 using chromatin immunoprecipitation (ChIP) and luciferase assays.

RESULTS

The expression level of hnRNPM is gradually reduced in BPH, ADENO, and NEPC tissues and it is less expressed in more aggressive PCa cell lines. Overexpression of hnRNPM can significantly reduce Twist1 expression, which inhibits the migration and invasion of PCa cells in vitro. In PCa cells, overexpression of YY1 can promote epithelial-mesenchymal transition by reducing hnRNPM expression. Furthermore, this effect caused by overexpression of YY1 can be partially attenuated by simultaneous overexpression of hnRNPM.

CONCLUSIONS

Our study demonstrates that hnRNPM negatively regulated PCa cell migration and invasion, and its expression can be transcriptionally inhibited by YY1. We speculated that hnRNPM may be a biomarker to assist in judging the aggressiveness of PCa.

Functional interplay between YY1 and CARM1 promotes oral carcinogenesis

Coactivator associated arginine methyltransferase 1 (CARM1) has been functionally implicated in maintenance of pluripotency, cellular differentiation and tumorigenesis; where it plays regulatory roles by virtue of its ability to coactivate transcription as well as to modulate protein function as an arginine methyltransferase. Previous studies establish an oncogenic function of CARM1 in the context of colorectal and breast cancer, which correlate to its overexpressed condition. However, the mechanism behind its deregulated expression in the context of cancer has not been addressed before. In the present study we uncover an oncogenic function of CARM1 in the context of oral cancer, where it was found to be overexpressed. We also identify YY1 to be a positive regulator of CARM1 gene promoter, where silencing of YY1 in oral cancer cell line could lead to reduction in expression of CARM1. In this context, YY1 showed concomitant overexpression in oral cancer patient samples compared to adjacent normal tissue. Cell line based experiments as well as xenograft study revealed pro-neoplastic functions of YY1 in oral cancer. Transcriptomics analysis as well as qRT-PCR validation clearly indicated pro-proliferative, pro-angiogenic and pro-metastatic role of YY1 in oral cancer. We also show that YY1 is a substrate of CARM1 mediated arginine methylation, where the latter could coactivate YY1 mediated reporter gene activation in vivo. Taken together, CARM1 and YY1 were found to regulate each other in a positive feedback loop to facilitate oral cancer progression.

YY1 negatively regulates the XAF1 gene expression in prostate cancer

XAF1 is a tumor suppressor gene with low or absent expression in cancer. Since transcriptional reactivation or ectopic-mediated expression of XAF1 inhibits tumor growth, it is of great interest to elucidate the molecular mechanisms leading to XAF1 silencing. YY1 is a transcription factor that acts as a repressor or an activator to modulate several cancer-associated cellular processes. Both YY1 and XAF1 have key roles in prostate cancer (PCa) progression and are associated with worse clinical outcomes. To assess whether YY1 regulates the transcriptional activation of the XAF1 gene, we performed gene-reporter assays coupled with site-directed mutagenesis, which showed that YY1 is able to mediate XAF1 silencing. Concordantly, ChIP-qPCR assays showed that YY1 interacts with the XAF1 promoter in PC3 cells that lacks XAF1 expression. This association was lost after exposure to epigenetic modulators that induce XAF1 expression. Further supporting the YY1's repressive role, we found transcriptional reactivation of the XAF1 gene by YY1 downregulation. As expected by previous reports showing that HDAC1 is needed for YY1-mediated repressive actions, we observed XAF1 re-expression after either inhibition or downregulation of the HDAC1 gene. Finally, expression data retrieved from the TCGA consortium showed that PCa samples presented lower XAF1 and higher HDAC expression levels than normal tissues. Thus, our results support a model in which YY1 is able to silence tumor suppressor genes such as XAF1 through HDAC1 in PCa.

A regulatory mutant on TRIM26 conferring the risk of nasopharyngeal carcinoma by inducing low immune response

The major histocompatibility complex (MHC) is most closely associated with nasopharyngeal carcinoma (NPC), but the complexity of its genome structure has proven challenging for the discovery of causal MHC loci or genes. We conducted a targeted MHC sequencing in 40 Cantonese NPC patients followed by a two‐stage replication in 1065 NPC cases and 2137 controls of Southern Chinese descendent. Quantitative RT‐PCR analysis (qRT‐PCR) was used to detect gene expression status in 108 NPC and 43 noncancerous nasopharyngeal (NP) samples. Luciferase reporter assay and chromatin immunoprecipitation (ChIP) were used to assess the transcription factor binding site. We discovered that a novel SNP rs117565607_A at TRIM26 displayed the strongest association (OR = 1.909, Pcombined = 2.750 × 10⁻¹⁹). We also observed that TRIM26 was significantly downregulated in NPC tissue samples with genotype AA/AT than TT. Immunohistochemistry (IHC) test also found the TRIM26 protein expression in NPC tissue samples with the genotype AA/AT was lower than TT. According to computational prediction, rs117565607 locus was a binding site for the transcription factor Yin Yang 1 (YY1). We observed that the luciferase activity of YY1 which is binding to the A allele of rs117565607 was suppressed. ChIP data showed that YY1 was binding with T not A allele. Significance analysis of microarray suggested that TRIM26 downregulation was related to low immune response in NPC. We have identified a novel gene TRIM26 and a novel SNP rs117565607_A associated with NPC risk by regulating transcriptional process and established a new functional link between TRIM26 downregulation and low immune response in NPC.

Diagnostic and prognostic relevance of CP2c and YY1 expression in hepatocellular carcinoma

Recent studies have demonstrated an oncogenic role of the transcription factor (TF) CP2c in hepatocellular carcinoma (HCC) based on a strong correlation between CP2c expression, tumor grade, and aggressiveness. We recently found that CP2c directly interacts with another TF, YY1, which is also overexpressed in multiple cancers, including HCC. To evaluate if these proteins are co-regulated in carcinogenesis, we analyzed the expression of CP2c and YY1 in HCC (n = 136) tissues and examined the correlation between their expression and clinicopathological characteristics of HCC. Receiver operating characteristic analysis exhibited the validity of CP2c and nuclear YY1 expression as a diagnostic factor in HCC tissues. High expression of CP2c was significantly correlated with patient age, and higher histological grade, American Joint Committee on Cancer (AJCC) stage, and small and large vessel invasion in HCC tissues, whereas high expression of nuclear YY1 was significantly associated with higher AJCC stage and small vessel invasion. In univariate and multivariate analyses, high expression of CP2c was significantly correlated with disease free survival (DFS), indicating that CP2c expression is an independent prognostic factor for DFS in HCC patients. Patients with high expression of both CP2c and nuclear YY1 usually had a shorter median survival time and worse DFS prognosis than other patients, suggesting that combined detection of CP2c and nuclear YY1 is a useful prognostic marker in HCC patients.

SFMBT2 (Scm-like with four mbt domains 2) negatively regulates cell migration and invasion in prostate cancer cells

Metastatic prostate cancer is the leading cause of morbidity and mortality in men. In this study, we found that expression level of SFMBT2 is altered during prostate cancer progression and has been associated with the migration and invasion of prostate cancer cells. The expression level of SFMBT2 is high in poorly metastatic prostate cancer cells compared to highly metastatic prostate cancer cells. We also found that SFMBT2 knockdown elevates MMP-2, MMP-3, MMP-9, and MMP-26 expression, leading to increased cell migration and invasion in LNCaP and VCaP cells. SFMBT2 interacts with YY1, RNF2, N-CoR and HDAC1/3, as well as repressive histone marks such as H3K9me2, H4K20me2, and H2AK119Ub which are associated with transcriptional repression. In addition, SFMBT2 knockdown decreased KAI1 gene expression through up-regulation of N-CoR gene expression. Expression of SFMBT2 in prostate cancer was strongly associated with clinicopathological features. Patients having higher Gleason score (≥ 8) had substantially lower SFMBT2 expression than patients with lower Gleason score. Moreover, tail vein or intraprostatic injection of SFMBT2 knockdown LNCaP cells induced metastasis. Taken together, our findings suggest that regulation of SFMBT2 may provide a new therapeutic strategy to control prostate cancer metastasis as well as being a potential biomarker of metastatic prostate cancer.

Expression of Yin Yang 1 in cervical cancer and its correlation with E-cadherin expression and HPV16 E6

The molecular mechanisms of normal cervical squamous epithelium advancing to cervical intraepithelial neoplasia (CIN) and eventually to cervical squamous cell carcinoma (CSCC) are largely unknown. This study explored abnormal expression of Yin Yang 1 (YY1) in cervical cancer and its correlation with the expression of E-cadherin and human papillomavirus (HPV) 16 E6. YY1, E-cadherin and HPV16 E6 expression were detected by immunohistochemistry in 90 cervical tissue specimens collected from 30 patients with hysteromyoma, 15 patients with CIN I, 15 patients with CIN II-III, and 30 patients with CSCC. The H-score method was employed to measure the expression of YY1, E-cadherin and HPV16 E6. Increased expression of YY1 and HPV16 E6, and the decreased expression levels of E-cadherin were strongly associated with malignant transformation of the cervical epithelium and the histological progression of CSCC. The expression of YY1 in cervical tissues was inversely correlated with E-cadherin expression, and positively correlated with HPV16 E6 expression. Expression of YY1 in CSCC tissues was not significantly correlated with tumor differentiation, but was significantly correlated with an advanced clinical stage of CSCC. These results suggest that up-regulation of YY1 is closely associated with the progression of CSCC, and YY1 may play an important role in the pathogenesis of cervical cancer by modulating the expression of E-cadherin and HPV16 E6.

miR‑218 inhibits the proliferation of human glioma cells through downregulation of Yin Yang 1

Malignant glioma is the most common cancer type of the nervous system and the mechanisms driving the occurrence and development remain unclear, preventing effective treatment of this disease. Therefore, novel and efficient therapies for glioma are required. MicroRNAs (miRNAs) are small non‑coding RNAs that act as oncogenes or tumor suppressors in human cancer. In the present study, it was confirmed that Yin Yang‑1 (YY1), a transcription factor that is part of the polycomb group protein (PcG) family, is a direct target of miR‑218 in human glioma cells. It was demonstrated that YY1 promoted glioma cell proliferation and miR‑218 could inhibit glioma cell proliferation by targeting YY1, and indirectly reduced the degradation of p53. Together the results indicate that miR‑218 functions as a tumor suppressor in human glioma and suggest that overexpression of miR‑218 may be a potential strategy for the treatment of human glioma in the future.

Prognostic significance of high YY1AP1 and PCNA expression in colon adenocarcinoma

To investigate the relationship between YY1AP1 and various clinicopathological features of colon adenocarcinoma (COAD), we conducted immunohistochemical (IHC) analyses of human tissue microarrays. We found that YY1AP1 protein expression was significantly higher in tumor tissue of the colon and liver, and was significantly lower in tumor tissue of the kidney. An analysis that employed the SurvExpress database indicated that increased expression of YY1AP1 mRNA was significantly associated with the overall survival of COAD patients. To clarify the validity of YY1AP1 or PCNA as determined by the IHC analysis was performed on 59 paired samples from COAD and adjacent normal tissue. Statistically significant differences of immunoreactivity for YY1AP1 or PCNA protein expression was observed between COAD tissue and adjacent normal tissue. High protein expression levels of YY1AP1 and PCNA were also found to be significantly correlated with M-class and distant metastasis. We also determined that YY1AP1 was correlated with PCNA expression in COAD samples, and Kaplan-Meier survival curves indicated that YY1AP1 protein expression was significantly associated with poor survival. Finally, a univariate analysis demonstrated that YY1AP1 protein expression was related to YY1AP1 score, and multivariate analysis revealed that the YY1AP1 protein expression level was an independent risk factor of overall COAD survival. Taken together, our findings indicate that YY1AP1 expression plays an important role in the tumorigenesis and progression of COAD and could serve as a clinical prognostic indicator for COAD.

DNA methylation-based chromatin compartments and ChIP-seq profiles reveal transcriptional drivers of prostate carcinogenesis

BACKGROUND

Profiles of DNA methylation of many tissues relevant in human disease have been obtained from microarrays and are publicly available. These can be used to generate maps of chromatin compartmentalization, demarcating open and closed chromatin across the genome. Additionally, large sets of genome-wide transcription factor binding profiles have been made available thanks to ChIP-seq technology.

METHODS

We have identified genomic regions with altered chromatin compartmentalization in prostate adenocarcinoma tissue relative to normal prostate tissue, using DNA methylation microarray data from The Cancer Genome Atlas. DNA binding profiles from the Encyclopedia of DNA Elements (ENCODE) ChIP-seq studies have been systematically screened to find transcription factors with inferred DNA binding sites located in discordantly open/closed chromatin in malignant tissue (compared with non-cancer control tissue). We have combined this with tests for corresponding up-/downregulation of the transcription factors' putative target genes to obtain an integrated measure of cancer-specific regulatory activity to identify likely transcriptional drivers of prostate cancer.

RESULTS

Generally, we find that the degree to which transcription factors preferentially bind regions of chromatin that become more accessible during prostate carcinogenesis is significantly associated to the level of systematic upregulation of their targets, at the level of gene expression. Our approach has yielded 11 transcription factors that show strong cancer-specific transcriptional activation of targets, including the novel candidates KAT2A and TRIM28, alongside established drivers of prostate cancer MYC, ETS1, GABP and YY1.

CONCLUSIONS

This approach to integrated epigenetic and transcriptional profiling using publicly available data represents a cheap and powerful technique for identifying potential drivers of human disease. In our application to prostate adenocarcinoma data, the fact that well-known drivers are amongst the top candidates suggests that the discovery of novel candidate drivers may unlock pathways to future medicines. Data download instructions and code to reproduce this work are available at GitHub under 'edcurry/PRAD-compartments'.

Inverse correlation between the metastasis suppressor RKIP and the metastasis inducer YY1: Contrasting roles in the regulation of chemo/immuno-resistance in cancer

Several gene products have been postulated to mediate inherent and/or acquired anticancer drug resistance and tumor metastasis. Among these, the metastasis suppressor and chemo-immuno-sensitizing gene product, Raf Kinase Inhibitor Protein (RKIP), is poorly expressed in many cancers. In contrast, the metastasis inducer and chemo-immuno-resistant factor Yin Yang 1 (YY1) is overexpressed in many cancers. This inverse relationship between RKIP and YY1 expression suggests that these two gene products may be regulated via cross-talks of molecular signaling pathways, culminating in the expression of different phenotypes based on their targets. Analyses of the molecular regulation of the expression patterns of RKIP and YY1 as well as epigenetic, post-transcriptional, and post-translational regulation revealed the existence of several effector mechanisms and crosstalk pathways, of which five pathways of relevance have been identified and analyzed. The five examined cross-talk pathways include the following loops: RKIP/NF-κB/Snail/YY1, p38/MAPK/RKIP/GSK3β/Snail/YY1, RKIP/Smurf2/YY1/Snail, RKIP/MAPK/Myc/Let-7/HMGA2/Snail/YY1, as well as RKIP/GPCR/STAT3/miR-34/YY1. Each loop is comprised of multiple interactions and cascades that provide evidence for YY1's negative regulation of RKIP expression and vice versa. These loops elucidate potential prognostic motifs and targets for therapeutic intervention. Chiefly, these findings suggest that targeted inhibition of YY1 by specific small molecule inhibitors and/or the specific induction of RKIP expression and activity are potential therapeutic strategies to block tumor growth and metastasis in many cancers, as well as to overcome anticancer drug resistance. These strategies present potential alternatives for their synergistic uses in combination with low doses of conventional chemo-immunotherapeutics and hence, increasing survival, reducing toxicity, and improving quality of life.

miR-34a inhibits the migration and invasion of esophageal squamous cell carcinoma by targeting Yin Yang-1

Esophageal squamous cell carcinoma (ESCC), one of the most common gastrointestinal tumors, is known for its high mortality rate. microRNAs (miRNAs) have been reported to play important regulatory roles in cancer metastasis and progression. miR-34a has been demonstrated to be associated with the development of and metastasis in certain types of cancer via various target genes, but its function and targets in ESCC are unknown. The aim of this study was to examine whether the expression of miR-34a was significantly decreased in ESCC tissues, compared with normal esophageal tissues using RT-PCR and western blot analysis. The results showed that miR-34a overexpression increased apoptosis and decreased clonogenic formation, but inhibited invasion and migration in ESCC cells by suppressing MMP-2 and -9 expression. Yin Yang-1 (YY1), a widely distributed transcription factor that belongs to the GLI-Kruppel class of zinc finger proteins, was found to be a direct target of miR-34a in ESCC cell lines. Rescue experiments indicated that the suppressive effect of miR-34a on invasion and migration was mediated by activating YY1 expression. Results of the present study showed that miR-34a is associated with ESCC migration and provides a potential therapeutic and diagnostic target for ESCC.

Prognostic significance of YY1 protein expression and mRNA levels by bioinformatics analysis in human cancers: a therapeutic target

Conventional therapeutic treatments for various cancers include chemotherapy, radiotherapy, hormonal therapy and immunotherapy. While such therapies have resulted in clinical responses, they were coupled with non-tumor specificity, toxicity and resistance in a large subset of the treated patients. During the last decade, novel approaches based on scientific knowledge on the biology of cancer were exploited and led to the development of novel targeted therapies, such as specific chemical inhibitors and immune-based therapies. Although these targeted therapies resulted in better responses and less toxicity, there still remains the problem of the inherent or acquired resistance. Hence, current studies are seeking additional novel therapeutic targets that can overcome several mechanisms of resistance. The transcription factor Yin Yang 1 (YY1) is a ubiquitous protein expressed in normal and cancer tissues, though the expression level is much higher in a large number of cancers; hence, YY1 has been considered as a potential novel prognostic biomarker and therapeutic target. YY1 has been reported to be involved in the regulation of drug/immune resistance and also in the regulation of EMT. Several excellent reviews have been published on YY1 and cancer (see below), and, thus, this review will update recently published reports as well as report on the analysis of bioinformatics datasets for YY1 in various cancers and the relationship between reported protein expression and mRNA levels. The potential clinical significance of YY1 is discussed.

The molecular mechanisms and therapeutic potential of microRNA-7 in cancer

INTRODUCTION

Increasing evidence supports that microRNAs (miRNAs) play crucial roles in cancer through post-transcriptional gene silencing of their target genes, therefore, more and more effort has been devoted to develop miRNA-targeting therapeutics in cancer. MicroRNA-7 (miR-7) has been characterized as a potential tumor suppressor and regulates diverse fundamental biological processes of cancer cells including initiation, proliferation, migration, invasion, survival and death by targeting a number of oncogenic signaling pathways.

AREAS COVERED

This review examines evidence of the biological responses of miR-7 in cancer, with an emphasis on its regulation of the vital oncogenic signaling pathways. It also discusses the rationale, strategies and challenges of miR-7 as a potential therapeutic target for cancer.

EXPERT OPINION

With the increasing understanding of molecular mechanisms of miR-7-mediated regulatory networks and the advancement of miRNA-based therapeutics, targeting miR-7 may be a potential and promising strategy for cancer therapy.