CITED2 and NCOR2 in anti-oestrogen resistance and progression of breast cancer. Br J Cancer. 2009;101:1824-1832. [PMID: 19904269 PMCID: PMC2788259 DOI: 10.1038/sj.bjc.6605423]

Oestrogen receptor positive breast cancer and its embedded mechanism: breast cancer resistance to conventional drugs and related therapies, a review

Traditional medication and alternative therapies have long been used to treat breast cancer. One of the main problems with current treatments is that there is an increase in drug resistance in the cancer cells owing to genetic differences such as mutational changes, epigenetic changes and miRNA (microRNA) alterations such as miR-1246, miR-298, miR-27b and miR-33a, along with epigenetic modifications, such as Histone3 acetylation and CCCTC-Binding Factor (CTCF) hypermethylation for drug resistance in breast cancer cell lines. Certain forms of conventional drug resistance have been linked to genetic changes in genes such as ABCB1, AKT, S100A8/A9, TAGLN2 and NPM. This review aims to explore the current approaches to counter breast cancer, the action mechanism, along with novel therapeutic methods endowing potential drug resistance. The investigation of novel therapeutic approaches sheds light on the phenomenon of drug resistance including genetic variations that impact distinct forms of oestrogen receptor (ER) cancer, genetic changes, epigenetics-reported resistance and their identification in patients. Long-term effective therapy for breast cancer includes selective oestrogen receptor modulators, selective oestrogen receptor degraders and genetic variations, such as mutations in nuclear genes, epigenetic modifications and miRNA alterations in target proteins. Novel research addressing combinational therapies including maytansine, photodynamic therapy, guajadiol, talazoparib, COX2 inhibitors and miRNA 1246 inhibitors have been developed to improve patient survival rates.

ZNF703 mRNA-Targeting Antisense Oligonucleotide Blocks Cell Proliferation and Induces Apoptosis in Breast Cancer Cell Lines

The luminal B molecular subtype of breast cancers (BC) accounts for more than a third of BCs and is associated with aggressive clinical behavior and poor prognosis. The use of endocrine therapy in BC treatment has significantly contributed to the decrease in the number of deaths in recent years. However, most BC patients with prolonged exposure to estrogen receptor (ER) selective modulators such as tamoxifen develop resistance and become non-responsive over time. Recent studies have implicated overexpression of the ZNF703 gene in BC resistance to endocrine drugs, thereby highlighting ZNF703 inhibition as an attractive modality in BC treatment, especially luminal B BCs. However, there is no known inhibitor of ZNF703 due to its nuclear association and non-enzymatic activity. Here, we have developed an antisense oligonucleotide (ASO) against ZNF703 mRNA and shown that it downregulates ZNF703 protein expression. ZNF703 inhibition decreased cell proliferation and induced apoptosis. Combined with cisplatin, the anti-cancer effects of ZNF703-ASO9 were improved. Moreover, our work shows that ASO technology may be used to increase the number of targetable cancer genes.

Immune Classification and Immune Landscape Analysis of Triple-Negative Breast Cancer

Background: To classify triple-negative breast cancer (TNBC) immunotyping using the public database, analyze the differences between subtypes in terms of clinical characteristics and explore the role and clinical significance of immune subtypes in TNBC immunotherapy.

Methods: We downloaded TNBC data from the cBioPortal and GEO databases. The immune genes were grouped to obtain immune gene modules and annotate their biological functions. Log-rank tests and Cox regression were used to evaluate the prognosis of immune subtypes (IS). Drug sensitivity analysis was also performed for the differences among immune subtypes in immunotherapy and chemotherapy. In addition, dimension reduction analysis based on graph learning was utilized to reveal the internal structure of the immune system and visualize the distribution of patients.

Results: Significant differences in prognosis were observed between subtypes (IS1, IS2, and IS3), with the best in IS3 and the worst in IS1. The sensitivity of IS3 to immunotherapy and chemotherapy was better than the other two subtypes. In addition, Immune landscape analysis found the intra-class heterogeneity of immune subtypes and further classified IS3 subtypes (IS3A and IS3B). Immune-related genes were divided into seven functional modules (The turquoise module has the worst prognosis). Five hub genes (RASSF5, CD8A, ICOS, IRF8, and CD247) were screened out as the final characteristic genes related to poor prognosis by low expression.

Conclusions: The immune subtypes of TNBC were significantly different in prognosis, gene mutation, immune infiltration, drug sensitivity, and heterogeneity. We validated the independent role of immune subtypes in tumor progression and immunotherapy for TNBC. This study provides a new perspective for personalized immunotherapy and the prognosis evaluation of TNBC patients in the future.

High-throughput proteomics of breast cancer interstitial fluid: identification of tumor subtype-specific serologically relevant biomarkers

Despite significant advancements in breast cancer (BC) research, clinicians lack robust serological protein markers for accurate diagnostics and tumor stratification. Tumor interstitial fluid (TIF) accumulates aberrantly externalized proteins within the local tumor space, which can potentially gain access to the circulatory system. As such, TIF may represent a valuable starting point for identifying relevant tumor-specific serological biomarkers. The aim of the study was to perform comprehensive proteomic profiling of TIF to identify proteins associated with BC tumor status and subtype. A liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of 35 TIFs of three main subtypes: luminal (19), Her2 (4), and triple-negative (TNBC) (12) resulted in the identification of > 8800 proteins. Unsupervised hierarchical clustering segregated the TIF proteome into two major clusters, luminal and TNBC/Her2 subgroups. High-grade tumors enriched with tumor infiltrating lymphocytes (TILs) were also stratified from low-grade tumors. A consensus analysis approach, including differential abundance analysis, selection operator regression, and random forest returned a minimal set of 24 proteins associated with BC subtypes, receptor status, and TIL scoring. Among them, a panel of 10 proteins, AGR3, BCAM, CELSR1, MIEN1, NAT1, PIP4K2B, SEC23B, THTPA, TMEM51, and ULBP2, was found to stratify the tumor subtype-specific TIFs. In particular, upregulation of BCAM and CELSR1 differentiates luminal subtypes, while upregulation of MIEN1 differentiates Her2 subtypes. Immunohistochemistry analysis showed a direct correlation between protein abundance in TIFs and intratumor expression levels for all 10 proteins. Sensitivity and specificity were estimated for this protein panel by using an independent, comprehensive breast tumor proteome dataset. The results of this analysis strongly support our data, with eight of the proteins potentially representing biomarkers for stratification of BC subtypes. Five of the most representative proteomics databases currently available were also used to estimate the potential for these selected proteins to serve as putative serological markers.

Serine synthesis influences tamoxifen response in ER+ human breast carcinoma

Estrogen receptor-positive breast cancer (ER+ BC) is the most common form of breast carcinoma accounting for approximately 70% of all diagnoses. Although ER-targeted therapies have improved survival outcomes for this BC subtype, a significant proportion of patients will ultimately develop resistance to these clinical interventions, resulting in disease recurrence. Phosphoserine aminotransferase 1 (PSAT1), an enzyme within the serine synthetic pathway (SSP), has been previously implicated in endocrine resistance. Therefore, we determined whether expression of SSP enzymes, PSAT1 or phosphoglycerate dehydrogenase (PHGDH), affects the response of ER+ BC to 4-hydroxytamoxifen (4-OHT) treatment. To investigate a clinical correlation between PSAT1, PHGDH, and endocrine resistance, we examined microarray data from ER+ patients who received tamoxifen as the sole endocrine therapy. We confirmed that higher PSAT1 and PHGDH expression correlates negatively with poorer outcomes in tamoxifen-treated ER+ BC patients. Next, we found that SSP enzyme expression and serine synthesis were elevated in tamoxifen-resistant compared to tamoxifen-sensitive ER+ BC cells in vitro. To determine relevance to endocrine sensitivity, we modified the expression of either PSAT1 or PHGDH in each cell type. Overexpression of PSAT1 in tamoxifen-sensitive MCF-7 cells diminished 4-OHT inhibition on cell proliferation. Conversely, silencing of either PSAT1 or PHGDH resulted in greater sensitivity to 4-OHT treatment in LCC9 tamoxifen-resistant cells. Likewise, the combination of a PHGDH inhibitor with 4-OHT decreased LCC9 cell proliferation. Collectively, these results suggest that overexpression of serine synthetic pathway enzymes contribute to tamoxifen resistance in ER+ BC, which can be targeted as a novel combinatorial treatment option.

Heregulin Drives Endocrine Resistance by Altering IL-8 Expression in ER-Positive Breast Cancer

Sustained HER2/HER3 signaling due to the overproduction of the HER3 ligand heregulin (HRG) is proposed as a key contributor to endocrine resistance in estrogen receptor-positive (ER+) breast cancer. The molecular mechanisms linking HER2 transactivation by HRG-bound HER3 to the acquisition of a hormone-independent phenotype in ER+ breast cancer is, however, largely unknown. Here, we explored the possibility that autocrine HRG signaling drives cytokine-related endocrine resistance in ER+ breast cancer cells. We used human cytokine antibody arrays to semi-quantitatively measure the expression level of 60 cytokines and growth factors in the extracellular milieu of MCF-7 cells engineered to overexpress full-length HRGβ2 (MCF-7/HRG cells). Interleukin-8 (IL-8), a chemokine closely linked to ER inaction, emerged as one the most differentially expressed cytokines. Cytokine profiling using structural deletion mutants lacking both the N-terminus and the cytoplasmic-transmembrane region of HRGβ2-which is not secreted and cannot transactivate HER2-or lacking a nuclear localization signal at the N-terminus-which cannot localize at the nucleus but is actively secreted and transactivates HER2-revealed that the HRG-driven activation of IL-8 expression in ER+ cells required HRG secretion and transactivation of HER2 but not HRG nuclear localization. The functional blockade of IL-8 with a specific antibody inversely regulated ERα-driven transcriptional activation in endocrine-sensitive MCF-7 cells and endocrine-resistant MCF-7/HRG cells. Overall, these findings suggest that IL-8 participates in the HRG-driven endocrine resistance program in ER+/HER2- breast cancer and might illuminate a potential clinical setting for IL8- or CXCR1/2-neutralizing antibodies.

Role of CITED2 in stem cells and cancer

Cbp/P300 interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2) is a transcription co-factor that interacts with several other transcription factors and co-factors, and serves critical roles in fundamental cell processes, including proliferation, apoptosis, differentiation, migration and autophagy. The interacting transcription factors or co-factors of CITED2 include LIM homeobox 2, transcription factor AP-2, SMAD2/3, peroxisome proliferator-activated receptor γ, oestrogen receptor, MYC, Nucleolin and p300/CBP, which regulate downstream gene expression, and serve important roles in the aforementioned fundamental cell processes. Emerging evidence has demonstrated that CITED2 serves an essential role in embryonic and adult tissue stem cells, including hematopoietic stem cells and tendon-derived stem/progenitor cells. Additionally, CITED2 has been reported to function in different types of cancer. Although the functions of CITED2 in different tissues vary depending on the interaction partner, altered CITED2 expression or altered interactions with transcription factors or co-factors result in alterations of fundamental cell processes, and may affect stem cell maintenance or cancer cell survival. The aim of this review is to summarize the molecular mechanisms of CITED2 function and how it serves a role in stem cells and different types of cancer based on the currently available literature.

CITED2 and the modulation of the hypoxic response in cancer

CITED2 (CBP/p300-interacting transactivator with Glu/Asp-rich C-terminal domain, 2) is a ubiquitously expressed protein exhibiting a high affinity for the CH1 domain of the transcriptional co-activators CBP/p300, for which it competes with hypoxia-inducible factors (HIFs). CITED2 is particularly efficient in the inhibition of HIF-1α-dependent transcription in different contexts, ranging from organ development and metabolic homeostasis to tissue regeneration and immunity, being also potentially involved in various other physiological processes. In addition, CITED2 plays an important role in inhibiting HIF in some diseases, including kidney and heart diseases and type 2-diabetes. In the particular case of cancer, CITED2 either functions by promoting or suppressing cancer development depending on the context and type of tumors. For instance, CITED2 overexpression promotes breast and prostate cancers, as well as acute myeloid leukemia, while its expression is downregulated to sustain colorectal cancer and hepatocellular carcinoma. In addition, the role of CITED2 in the maintenance of cancer stem cells reveals its potential as a target in non-small cell lung carcinoma and acute myeloid leukemia, for example. But besides the wide body of evidence linking both CITED2 and HIF signaling to carcinogenesis, little data is available regarding CITED2 role as a negative regulator of HIF-1α specifically in cancer. Therefore, comprehensive studies exploring further the interactions of these two important mediators in cancer-specific models are sorely needed and this can potentially lead to the development of novel targeted therapies.

Circulating miR-3197 and miR-2116-5p as novel biomarkers for diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of vision loss among older adults. The goal of this case-control study was to identify circulating miRNAs for the diagnosis of DR. The miRNeasy Serum/Plasma Kit was used to extract serum miRNAs. The μParaflo™ MicroRNA microarray was used to detect the expression levels of the miRNAs. The miRWalk algorithm was applied to predict the target genes of the miRNAs, which were further confirmed by the dual luciferase reporter gene system in HEK293T cells. A microarray was performed between 5 DR cases and 5 age-, sex-, body mass index-, and duration of diabetes-matched type 2 diabetic (T2DM) controls. The quantitative reverse transcription polymerase chain reaction technique was used to validate the differentially expressed circulating miRNAs in 45 DR cases and 45 well-matched controls. Receiver operating characteristic (ROC) curve analysis was used to evaluate the performance of the circulating miRNAs as diagnostic biomarkers for DR. Our microarray analysis screened out miR-2116-5p and miR-3197 as significantly up-regulated in DR cases compared with the controls. Furthermore, two miRNAs were validated in the 45 DR cases and 45 controls. The ROC analysis suggested that both miR-3197 and miR-2116-5p distinguished DR cases from controls. An additional dual-luciferase reporter gene assay confirmed that notch homolog 2 (NOTCH2) was the target gene of miR-2116-5p. Both miR-3197 and miR-2116-5p were identified as promising diagnostic biomarkers for DR. Future research is still needed to explore the molecular mechanisms of miR-3197 and miR-2116-5p in the pathogenesis of DR.

An estrogen receptor (ER)-related signature in predicting prognosis of ER-positive breast cancer following endocrine treatment

Quite a few estrogen receptor (ER)‐positive breast cancer patients receiving endocrine therapy are at risk of disease recurrence and death. ER‐related genes are involved in the progression and chemoresistance of breast cancer. In this study, we identified an ER‐related gene signature that can predict the prognosis of ER‐positive breast cancer patient receiving endocrine therapy. We collected RNA expression profiling from Gene Expression Omnibus database. An ER‐related signature was developed to separate patients into high‐risk and low‐risk groups. Patients in the low‐risk group had significantly better survival than those in the high‐risk group. ROC analysis indicated that this signature exhibited good diagnostic efficiency for the 1‐, 3‐ and 5‐year disease‐relapse events. Moreover, multivariate Cox regression analysis demonstrated that the ER‐related signature was an independent risk factor when adjusting for several clinical signatures. The prognostic value of this signature was validated in the validation sets. In addition, a nomogram was built and the calibration plots analysis indicated the good performance of this nomogram. In conclusion, combining with ER status, our results demonstrated that the ER‐related prognostic signature is a promising method for predicting the prognosis of ER‐positive breast cancer patients receiving endocrine therapy.

Aberrant expression of CITED2 promotes prostate cancer metastasis by activating the nucleolin-AKT pathway

Despite many efforts to develop hormone therapy and chemotherapy, no effective strategy to suppress prostate cancer metastasis has been established because the metastasis is not well understood. We here investigate a role of CBP/p300-interacting transactivator with E/D-rich carboxy-terminal domain-2 (CITED2) in prostate cancer metastasis. CITED2 is highly expressed in metastatic prostate cancer, and its expression is correlated with poor survival. The CITED2 gene is highly activated by ETS-related gene that is overexpressed due to chromosomal translocation. CITED2 acts as a molecular chaperone to guide PRMT5 and p300 to nucleolin, thereby activating nucleolin. Informatics and experimental data suggest that the CITED2-nucleolin axis is involved in prostate cancer metastasis. This axis stimulates cell migration through the epithelial-mesenchymal transition and promotes cancer metastasis in a xenograft mouse model. Our results suggest that CITED2 plays a metastasis-promoting role in prostate cancer and thus could be a target for preventing prostate cancer metastasis.

Complex polymorphisms in endocytosis genes suggest alpha-cyclodextrin as a treatment for breast cancer

Most breast cancer deaths are caused by metastasis and treatment options beyond radiation and cytotoxic drugs, which have severe side effects, and hormonal treatments, which are or become ineffective for many patients, are urgently needed. This study reanalyzed existing data from three genome-wide association studies (GWAS) using a novel computational biostatistics approach (muGWAS), which had been validated in studies of 600-2000 subjects in epilepsy and autism. MuGWAS jointly analyzes several neighboring single nucleotide polymorphisms while incorporating knowledge about genetics of heritable diseases into the statistical method and about GWAS into the rules for determining adaptive genome-wide significance. Results from three independent GWAS of 1000-2000 subjects each, which were made available under the National Institute of Health's "Up For A Challenge" (U4C) project, not only confirmed cell-cycle control and receptor/AKT signaling, but, for the first time in breast cancer GWAS, also consistently identified many genes involved in endo-/exocytosis (EEC), most of which had already been observed in functional and expression studies of breast cancer. In particular, the findings include genes that translocate (ATP8A1, ATP8B1, ANO4, ABCA1) and metabolize (AGPAT3, AGPAT4, DGKQ, LPPR1) phospholipids entering the phosphatidylinositol cycle, which controls EEC. These novel findings suggest scavenging phospholipids as a novel intervention to control local spread of cancer, packaging of exosomes (which prepare distant microenvironment for organ-specific metastases), and endocytosis of β1 integrins (which are required for spread of metastatic phenotype and mesenchymal migration of tumor cells). Beta-cyclodextrins (βCD) have already been shown to be effective in in vitro and animal studies of breast cancer, but exhibits cholesterol-related ototoxicity. The smaller alpha-cyclodextrins (αCD) also scavenges phospholipids, but cannot fit cholesterol. An in-vitro study presented here confirms hydroxypropyl (HP)-αCD to be twice as effective as HPβCD against migration of human cells of both receptor negative and estrogen-receptor positive breast cancer. If the previous successful animal studies with βCDs are replicated with the safer and more effective αCDs, clinical trials of adjuvant treatment with αCDs are warranted. Ultimately, all breast cancer are expected to benefit from treatment with HPαCD, but women with triple-negative breast cancer (TNBC) will benefit most, because they have fewer treatment options and their cancer advances more aggressively.

Integrative analysis to identify oncogenic gene expression changes associated with copy number variations of enhancer in ovarian cancer

Enhancers are short regulatory regions (50-1500 bp) of DNA that control the tissue-specific activation of gene expression by long distance interaction with targeting gene regions. Recently, genome-wide identification of enhancers in diverse tissues and cell lines was achieved using high-throughput sequencing. Enhancers have been associated with malfunctions in cancer development resulting from point mutations in regulatory regions. However, the potential impact of copy number variations (CNVs) on enhancer regions is unknown. To learn more about the relationship between enhancers and cancer, we integrated the CNVs data on enhancers and explored their targeting gene expression pattern in high-grade ovarian cancer. Using human enhancer-gene interaction data with 13,691 interaction pairs between 7,905 enhancers and 5,297 targeting genes, we found that the 2,910 copy number gain events of enhancer are significantly correlated with the up-regulation of targeting genes. We further identified that a number of highly mutated super-enhancers, with concordant gene expression change on their targeting genes. We also identified 18 targeting genes by super-enhancers with prognostic significance for ovarian cancer, such as the tumour suppressor CDKN1B. We are the first to report that abundant copy number variations on enhancers could change the expression of their targeting genes which would be valuable for the design of enhancer-based cancer treatment strategy.

RNA-Seq技术及其在胃肠肿瘤研究中的应用现状

转录组是特定的细胞或组织在特定的时间或状态下转录出来的RNA集合, 转录组研究能够从整体水平研究基因功能以及基因结构, 并能很好的显示处于表达状态的基因数量和活跃程度. 作为转录组学新一代高通量测序技术之一, RNA-Seq技术能够更为快速、准确地为人们提供更多的生物体转录信息, 在生物医学研究中已经得到广泛应用. 随着全球胃肠肿瘤发病率的逐年提高, RNA-Seq技术在胃肠肿瘤研究领域进行全转录组测序分析的应用越来越多, 并取得了一些新的进展. 本文将就RNA-Seq技术原理、优势及其在胃肠肿瘤研究中的具体应用进行论述.

Knockdown of Cbp/P300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 inhibits cell division and increases apoptosis in gastric cancer

BACKGROUND

Cbp/P300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2) is a pleiotropic protein associated with numerous cell functions, including transcription and differentiation. The role of CITED2 has been investigated in a number of malignancies; however, the roles of this protein in gastric cancers remain unclear. Therefore, we determined the role of CITED2 in gastric cancers.

MATERIALS AND METHODS

Gastric cancer cell lines (MKN74, MKN28, 7901, and AGS) were used to assess CITED2 transcript levels. Messenger RNA levels were determined using quantitative polymerase chain reaction. Lentiviral vectors containing CITED2 small interfering RNA were used to knockdown CITED2 expression. Cell proliferation was assessed with fluorescent imaging and 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide assays. Apoptosis and cell cycle stages were assessed through flow cytometry, and formation of colonies was determined using a fluorescent microscope.

RESULTS

All cell lines tested in this study expressed CITED2. The cell line expressing the highest levels of CITED2 (MKN74) showed significant knockdown of endogenous CITED2 expression on lentiviral infection. Cell proliferation was shown to be lower in CITED2 knockdown MKN74 cells. G1/S-phase cell cycle arrest was observed on silencing of CITED2 in MKN74 cells. A significant increase in apoptosis was observed on CITED2 knock down in MKN74 cells, while colony forming ability was significantly inhibited after knock down of CITED2.

CONCLUSIONS

CITED2 supports gastric cancer cell colony formation and proliferation while inhibiting apoptosis making it a potential gene therapy target for gastric cancer.

CITED2 in breast carcinoma as a potent prognostic predictor associated with proliferation, migration and chemoresistance

CITED2 (Cbp/p300‐interacting transactivator, with Glu/Asp‐rich carboxy‐terminal domain, 2) is a member of the CITED family and is involved in various cellular functions during development and differentiation. Mounting evidence suggests the importance of CITED in the progression of human malignancies, but the significance of CITED2 protein has not yet been examined in breast carcinoma. Therefore, in the present study, we examined the clinical significance and the biological functions of CITED2 in breast carcinoma by immunohistochemistry and in vitro study. CITED2 immunoreactivity was detected in breast carcinoma tissues, and it was significantly higher compared to those in morphologically normal mammary glands. CITED2 immunoreactivity was significantly associated with stage, pathological T factor, lymph node metastasis, histological grade, HER2 and Ki‐67, and inversely correlated with estrogen receptor. Moreover, the immunohistochemical CITED2 status was significantly associated with increased incidence of recurrence and breast cancer‐specific death of the breast cancer patients, and multivariate analyses demonstrated CITED2 status as an independent worse prognostic factor for disease‐free and breast cancer‐specific survival. Subsequent in vitro experiments showed that CITED2 expression significantly increased proliferation activity and migration property in MCF‐7and S KBR‐3 breast carcinoma cells. Moreover, CITED2 caused chemoresistance to epirubicin and 5‐fluorouracil, but not paclitaxel, in these cells, and it inhibited p53 accumulation after 5‐fluorouracil treatment in MCF‐7 cells. These results suggest that CITED2 plays important roles in the progression and chemoresistance of breast carcinoma and that CITED2 status is a potent prognostic factor in breast cancer patients.

Quantitative proteomic analyses of mammary organoids reveals distinct signatures after exposure to environmental chemicals

Common environmental contaminants such as bisphenols and phthalates and persistent contaminants such as polychlorinated biphenyls are thought to influence tissue homeostasis and carcinogenesis by acting as disrupters of endocrine function. In this study we investigated the direct effects of exposure to bisphenol A (BPA), mono-n-butyl phthalate (Pht), and polychlorinated biphenyl 153 (PCB153) on the proteome of primary organotypic cultures of the mouse mammary gland. At low-nanomolar doses each of these agents induced distinct effects on the proteomes of these cultures. Although BPA treatment produced effects that were similar to those induced by estradiol, there were some notable differences, including a reduction in the abundance of retinoblastoma-associated protein and increases in the Rho GTPases Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division cycle protein CDC42. Both Pht and PCB153 induced changes that were distinct from those induced by estrogen, including decreased levels of the transcriptional corepressor C-terminal binding protein 1. Interestingly, the three chemicals appeared to alter the abundance of distinct splice forms of many proteins as well as the abundance of several proteins that regulate RNA splicing. Our combined results indicate that the three classes of chemical have distinct effects on the proteome of normal mouse mammary cultures, some estrogen-like but most estrogen independent, that influence diverse biological processes including apoptosis, cell adhesion, and proliferation.

DNA methylation of oestrogen-regulated enhancers defines endocrine sensitivity in breast cancer

Expression of oestrogen receptor (ESR1) determines whether a breast cancer patient receives endocrine therapy, but does not guarantee patient response. The molecular factors that define endocrine response in ESR1-positive breast cancer patients remain poorly understood. Here we characterize the DNA methylome of endocrine sensitivity and demonstrate the potential impact of differential DNA methylation on endocrine response in breast cancer. We show that DNA hypermethylation occurs predominantly at oestrogen-responsive enhancers and is associated with reduced ESR1 binding and decreased gene expression of key regulators of ESR1 activity, thus providing a novel mechanism by which endocrine response is abated in ESR1-positive breast cancers. Conversely, we delineate that ESR1-responsive enhancer hypomethylation is critical in transition from normal mammary epithelial cells to endocrine-responsive ESR1-positive cancer. Cumulatively, these novel insights highlight the potential of ESR1-responsive enhancer methylation to both predict ESR1-positive disease and stratify ESR1-positive breast cancer patients as responders to endocrine therapy.

The molecular factors influencing patient response to endocrine therapy are poorly understood. Here Stone et al. characterize the DNA methylome of endocrine response and show that methylation of oestrogen receptor-associated enhancers underpins endocrine sensitivity in human breast cancer.

New target genes in endometrial tumors show a role for the estrogen-receptor pathway in microsatellite-unstable cancers

Microsatellite instability (MSI) in tumors results in an accumulation of mutations in (target) genes. Previous studies suggest that the profile of target genes differs according to tumor type. This paper describes the first genome-wide search for target genes for mismatch repair-deficient endometrial cancers. Genes expressed in normal endometrium containing coding repeats were analyzed for mutations in tumors. We identified 44 possible genes of which seven are highly mutated (>15%). Some candidates were also found mutated in colorectal and gastric tumors. The most frequently mutated gene, NRIP1 encoding nuclear receptor-interacting protein 1, was silenced in an endometrial tumor cell line and expression microarray experiments were performed. Silencing of NRIP1 was associated with differences in the expression of several genes in the estrogen-receptor network. Furthermore, an enrichment of genes related to cell cycle (regulation) and replication was observed. We present a new profile of target genes, some of them tissue specific, whereas others seem to play a more general role in MSI tumors. The high-mutation frequency combined with the expression data suggest, for the first time, an involvement of NRIP1 in endometrial cancer development.

Transduction motif analysis of gastric cancer based on a human signaling network

To investigate signal regulation models of gastric cancer, databases and literature were used to construct the signaling network in humans. Topological characteristics of the network were analyzed by CytoScape. After marking gastric cancer-related genes extracted from the CancerResource, GeneRIF, and COSMIC databases, the FANMOD software was used for the mining of gastric cancer-related motifs in a network with three vertices. The significant motif difference method was adopted to identify significantly different motifs in the normal and cancer states. Finally, we conducted a series of analyses of the significantly different motifs, including gene ontology, function annotation of genes, and model classification. A human signaling network was constructed, with 1643 nodes and 5089 regulating interactions. The network was configured to have the characteristics of other biological networks. There were 57,942 motifs marked with gastric cancer-related genes out of a total of 69,492 motifs, and 264 motifs were selected as significantly different motifs by calculating the significant motif difference (SMD) scores. Genes in significantly different motifs were mainly enriched in functions associated with cancer genesis, such as regulation of cell death, amino acid phosphorylation of proteins, and intracellular signaling cascades. The top five significantly different motifs were mainly cascade and positive feedback types. Almost all genes in the five motifs were cancer related, including EPOR, MAPK14, BCL2L1, KRT18, PTPN6, CASP3, TGFBR2, AR, and CASP7. The development of cancer might be curbed by inhibiting signal transductions upstream and downstream of the selected motifs.

Endocrine Resistance in Breast Cancer

Around 70% of all breast cancers are estrogen receptor alpha positive and hence their development is highly dependent on estradiol. While the invention of endocrine therapies has revolusioned the treatment of the disease, resistance to therapy eventually occurs in a large number of patients. This paper seeks to illustrate and discuss the complexity and heterogeneity of the mechanisms which underlie resistance and the approaches proposed to combat them. It will also focus on the use and development of methods for predicting which patients are likely to develop resistance.

The SMRT coregulator enhances growth of estrogen receptor-α-positive breast cancer cells by promotion of cell cycle progression and inhibition of apoptosis

The SMRT coregulator functions as a dual coactivator and corepressor for estrogen receptor-α (ERα) in a gene-specific manner, and in several studies its elevated expression correlates with poor outcome for breast cancer patients. A specific role of SMRT in breast cancer progression has not been elucidated, but SMRT knock-down limits estradiol-dependent growth of MCF-7 breast cancer cells. In this study, small-interfering RNA (siRNA) and short-hairpin RNA (shRNA) approaches were used to determine the effects of SMRT depletion on growth of ERα-positive MCF-7 and ZR-75-1 breast cancer cells, as well as the ERα-negative MDA-MB-231 breast cancer line. Depletion of SMRT inhibited growth of ERα-positive cells grown in monolayer but had no effect on growth of the ERα-negative cells. Reduced SMRT levels also negatively impacted the anchorage-independent growth of MCF-7 cells as assessed by soft agar colony formation assays. The observed growth inhibitions were due to a loss of estradiol-induced progression through the G1/S transition of the cell cycle and increased apoptosis in SMRT-depleted compared with control cells. Gene expression analyses indicated that SMRT inhibits apoptosis by a coordinated regulation of genes involved in apoptosis. Functioning as a dual coactivator for anti-apoptotic genes and corepressor for pro-apoptotic genes, SMRT can limit apoptosis. Together these data indicate that SMRT promotes breast cancer progression through multiple pathways leading to increased proliferation and decreased apoptosis.

RNA-seq reveals determinants for irinotecan sensitivity/resistance in colorectal cancer cell lines

Irinotecan is a topoisomerase I inhibitor approved worldwide as a first- and second-line chemotherapy for advanced or recurrent colorectal cancer (CRC). Although irinotecan showed significant survival advantage for patients, a relatively low response rate and severe adverse effects demonstrated the urgent need for biomarkers searching to select the suitable patients who can benefit from irinotecan-based therapy and avoid the adverse effects. In present work, the irinotecan response (IC50 doses) of 20 CRC cell lines were correlated with the basal expression profiles investigated by RNA-seq to figure out genes responsible for irinotecan sensitivity/resistance. Genes negatively or positively correlated to irinotecan sensitivity were given after biocomputation, and 7 (CDC20, CTNNAL1, FZD7, CITED2, ABR, ARHGEF7, and RNMT) of them were validated in two CRC cell lines by quantitative real-time PCR, several of these 7 genes has been proposed to promote cancer cells proliferation and hence may confer CRC cells resistance to irinotecan. Our work might provide potential biomarkers and therapeutic targets for irinotecan sensitivity in CRC cells.

Candidate luminal B breast cancer genes identified by genome, gene expression and DNA methylation profiling

Breast cancers (BCs) of the luminal B subtype are estrogen receptor-positive (ER+), highly proliferative, resistant to standard therapies and have a poor prognosis. To better understand this subtype we compared DNA copy number aberrations (CNAs), DNA promoter methylation, gene expression profiles, and somatic mutations in nine selected genes, in 32 luminal B tumors with those observed in 156 BCs of the other molecular subtypes. Frequent CNAs included 8p11-p12 and 11q13.1-q13.2 amplifications, 7q11.22-q34, 8q21.12-q24.23, 12p12.3-p13.1, 12q13.11-q24.11, 14q21.1-q23.1, 17q11.1-q25.1, 20q11.23-q13.33 gains and 6q14.1-q24.2, 9p21.3-p24,3, 9q21.2, 18p11.31-p11.32 losses. A total of 237 and 101 luminal B-specific candidate oncogenes and tumor suppressor genes (TSGs) presented a deregulated expression in relation with their CNAs, including 11 genes previously reported associated with endocrine resistance. Interestingly, 88% of the potential TSGs are located within chromosome arm 6q, and seven candidate oncogenes are potential therapeutic targets. A total of 100 candidate oncogenes were validated in a public series of 5,765 BCs and the overexpression of 67 of these was associated with poor survival in luminal tumors. Twenty-four genes presented a deregulated expression in relation with a high DNA methylation level. FOXO3, PIK3CA and TP53 were the most frequent mutated genes among the nine tested. In a meta-analysis of next-generation sequencing data in 875 BCs, KCNB2 mutations were associated with luminal B cases while candidate TSGs MDN1 (6q15) and UTRN (6q24), were mutated in this subtype. In conclusion, we have reported luminal B candidate genes that may play a role in the development and/or hormone resistance of this aggressive subtype.

The Ddx5 and Ddx17 RNA helicases are cornerstones in the complex regulatory array of steroid hormone-signaling pathways

Estrogen and androgen receptors (ER and AR) play key roles in breast and prostate cancers, respectively, where they regulate the transcription of large arrays of genes. The activities of ER and AR are controlled by large networks of protein kinases and transcriptional coregulators, including Ddx5 and its highly related paralog Ddx17. The Ddx5 and Ddx17 RNA helicases are also splicing regulators. Here, we report that Ddx5 and Ddx17 are master regulators of the estrogen- and androgen-signaling pathways by controlling transcription and splicing both upstream and downstream of the receptors. First, Ddx5 and Ddx17 are required downstream of ER and AR for the transcriptional and splicing regulation of a large number of steroid hormone target genes. Second, Ddx5 and Ddx17 act upstream of ER and AR by controlling the expression, at the splicing level, of several key regulators of ER and AR activities. Of particular interest, we demonstrate that Ddx5 and Ddx17 control alternative splicing of the GSK3β kinase, which impacts on both ER and AR protein stability. We also provide a freely available online resource which gives information regarding splicing variants of genes involved in the estrogen- and androgen-signaling pathways.

Cited2 in hematopoietic stem cell function

PURPOSE OF REVIEW

Transcription co-regulator Cited2 is essential for mouse development. Recent work has shown that Cited2 plays important roles in normal hematopoiesis in fetal liver and adult bone marrow. This review focuses on the function of Cited2 in the maintenance of hematopoietic stem cells (HSCs) and its potential role in the metabolic regulation of HSCs.

RECENT FINDINGS

Fetal liver cells from Cited2 null embryos give rise to reduced numbers of hematopoietic colonies and display significantly impaired hematopoietic reconstitution capacity. In adult mice, conditional deletion of Cited2 markedly reduces the number of HSCs and compromises hematopoietic reconstitution in mice receiving a transplant of Cited2 deficient bone marrow cells. Additional deletion of Ink4a/Arf or p53 in a Cited2-deficient background restores HSC functionality. Meanwhile, Cited2 deficient HSCs display loss of quiescence, which can be partially rescued by additional deletion of hypoxia inducible factor-1α.

SUMMARY

Cited2 is an essential regulator in fetal liver and adult hematopoiesis. Further studies into the function of Cited2 and the underlying mechanism in the metabolic regulation of HSCs will provide a better understanding of the connection between energy metabolism and HSC quiescence and self-renewal. Investigations of the pathologic role of Cited2 in leukemogenesis may yield useful information in developing effective therapeutic strategies.

CITED2 modulates estrogen receptor transcriptional activity in breast cancer cells

Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (CITED2) is a member of the CITED family of non-DNA binding transcriptional co-activators of the p300/CBP-mediated transcription complex. Previously, we identified CITED2 as being overexpressed in human breast tumors relative to normal mammary epithelium. Upon further investigation within the estrogen receptor (ER)-positive subset of these breast tumor samples, we found that CITED2 mRNA expression was elevated in those associated with poor survival. In light of this observation, we investigated the effect of elevated CITED2 levels on ER function. While ectopic overexpression of CITED2 in three ER-positive breast cancer cell lines (MCF-7, T47D, and CAMA-1) did not alter cell proliferation in complete media, growth was markedly enhanced in the absence of exogenous estrogen. Correspondingly, cells overexpressing CITED2 demonstrated reduced sensitivity to the growth inhibitory effects of the selective estrogen receptor modulator, 4-hydroxytamoxifen. Subsequent studies revealed that basal ER transcriptional activity was elevated in CITED2-overexpressing cells and was further increased upon the addition of estrogen. Similarly, basal and estrogen-induced expression of the ER-regulated genes trefoil factor 1 (TFF1) and progesterone receptor (PGR) was higher in cells overexpressing CITED2. Concordant with this observation, ChIP analysis revealed higher basal levels of CITED2 localized to the TFF-1 and PGR promoters in cells with ectopic overexpression of CITED2, and these levels were elevated further in response to estrogen stimulation. Taken together, these data indicate that CITED2 functions as a transcriptional co-activator of ER in breast cancer cells and that its increased expression in tumors may result in estrogen-independent ER activation, thereby reducing estrogen dependence and response to anti-estrogen therapy.

Bridging cancer biology with the clinic: relative expression of a GRHL2-mediated gene-set pair predicts breast cancer metastasis

Identification and characterization of crucial gene target(s) that will allow focused therapeutics development remains a challenge. We have interrogated the putative therapeutic targets associated with the transcription factor Grainy head-like 2 (GRHL2), a critical epithelial regulatory factor. We demonstrate the possibility to define the molecular functions of critical genes in terms of their personalized expression profiles, allowing appropriate functional conclusions to be derived. A novel methodology, relative expression analysis with gene-set pairs (RXA-GSP), is designed to explore the potential clinical utility of cancer-biology discovery. Observing that Grhl2-overexpression leads to increased metastatic potential in vitro, we established a model assuming Grhl2-induced or -inhibited genes confer poor or favorable prognosis respectively for cancer metastasis. Training on public gene expression profiles of 995 breast cancer patients, this method prioritized one gene-set pair (GRHL2, CDH2, FN1, CITED2, MKI67 versus CTNNB1 and CTNNA3) from all 2717 possible gene-set pairs (GSPs). The identified GSP significantly dichotomized 295 independent patients for metastasis-free survival (log-rank tested p = 0.002; severe empirical p = 0.035). It also showed evidence of clinical prognostication in another independent 388 patients collected from three studies (log-rank tested p = 3.3e–6). This GSP is independent of most traditional prognostic indicators, and is only significantly associated with the histological grade of breast cancer (p = 0.0017), a GRHL2-associated clinical character (p = 6.8e–6, Spearman correlation), suggesting that this GSP is reflective of GRHL2-mediated events. Furthermore, a literature review indicates the therapeutic potential of the identified genes. This research demonstrates a novel strategy to integrate both biological experiments and clinical gene expression profiles for extracting and elucidating the genomic impact of a novel factor, GRHL2, and its associated gene-sets on the breast cancer prognosis. Importantly, the RXA-GSP method helps to individualize breast cancer treatment. It also has the potential to contribute considerably to basic biological investigation, clinical tools, and potential therapeutic targets.

Cancer epigenetics: a perspective on the role of DNA methylation in acquired endocrine resistance

Epigenetic mechanisms, including DNA methylation, are responsible for determining and maintaining cell fate, stably differentiating the various tissues in our bodies. Increasing evidence shows that DNA methylation plays a significant role in cancer, from the silencing of tumor suppressors to the activation of oncogenes and the promotion of metastasis. Recent studies also suggest a role for DNA methylation in drug resistance. This perspective article discusses how DNA methylation may contribute to the development of acquired endocrine resistance, with a focus on breast cancer. In addition, we discuss DNA methylome profiling and how recent developments in this field are shedding new light on the role of epigenetics in endocrine resistance. Hormone ablation is the therapy of choice for hormone-sensitive breast tumors, yet as many as 40% of patients inevitably relapse, and these hormone refractory tumors often have a poor prognosis. Epigenetic studies could provide DNA methylation biomarkers to predict and diagnose acquired resistance in response to treatment. Elucidation of epigenetic mechanisms may also lead to the development of new treatments that specifically target epigenetic abnormalities or vulnerabilities in cancer cells. Expectations must be tempered by the fact that epigenetic mechanisms of endocrine resistance remain poorly understood, and further study is required to better understand how altering epigenetic pathways with therapeutics can promote or inhibit endocrine resistance in different contexts. Going forward, DNA methylome profiling will become increasingly central to epigenetic research, heralding a network-based approach to epigenetics that promises to advance our understanding of the etiology of cancer in ways not previously possible.

Elevated nuclear expression of the SMRT corepressor in breast cancer is associated with earlier tumor recurrence

Silencing mediator of retinoic acid and thyroid hormone receptor (SMRT), also known as nuclear corepressor 2 (NCOR2) is a transcriptional corepressor for multiple members of the nuclear receptor superfamily of transcription factors, including estrogen receptor-α (ERα). In the classical model of corepressor action, SMRT binds to antiestrogen-bound ERα at target promoters and represses ERα transcriptional activity and gene expression. Herein SMRT mRNA and protein expression was examined in a panel of 30 breast cancer cell lines. Expression of both parameters was found to vary considerably amongst lines and the correlation between protein and mRNA expression was very poor (R (2) = 0.0775). Therefore, SMRT protein levels were examined by immunohistochemical staining of a tissue microarray of 866 patients with stage I-II breast cancer. Nuclear and cytoplasmic SMRT were scored separately according to the Allred score. The majority of tumors (67 %) were negative for cytoplasmic SMRT, which when detected was found at very low levels. In contrast, nuclear SMRT was broadly detected. There was no significant difference in time to recurrence (TTR) according to SMRT expression levels in the ERα-positive tamoxifen-treated patients (P = 0.297) but the difference was significant in the untreated patients (P = 0.01). In multivariate analysis, ERα-positive tamoxifen-untreated patients with high nuclear SMRT expression (SMRT 5-8, i.e., 2nd to 4th quartile) had a shorter TTR (HR = 1.94, 95 % CI, 1.24-3.04; P = 0.004) while there was no association with SMRT expression for ERα-positive tamoxifen-treated patients. There was no association between SMRT expression and overall survival for patients, regardless of whether they received tamoxifen. Thus while SMRT protein expression was not predictive of outcome after antiestrogen therapy, it may have value in predicting tumor recurrence in patients not receiving adjuvant tamoxifen therapy.

Differential copy number aberrations in novel candidate genes associated with progression from in situ to invasive ductal carcinoma of the breast

Only a minority of intraductal carcinomas of the breast give rise to stromally invasive disease. We microdissected 206 paraffin blocks representing 116 different cases of low-grade ductal carcinoma in situ (DCIS). Fifty-five were pure DCIS (PD) cases without progression to invasive carcinoma. Sixty-one cases had a small invasive component. DNA was extracted from microdissected sections and hybridized to high-density bacterial artificial chromosome arrays. Array comparative genomic hybridization analysis of 118 hybridized DNA samples yielded data on 69 samples that were suitable for further statistical analysis. This cohort included 20 pure DCIS cases, 25 mixed DCIS (MD), and 24 mixed invasive carcinoma samples. PD cases had a higher frequency of DNA copy number changes than MD cases, and the latter had similar DNA profiles compared to paired invasive carcinomas. Copy number changes on 13 chromosomal arms occurred at different rates in PD versus MD lesions. Eight of 19 candidate genes residing at those loci were confirmed to have differential copy number changes by quantitative PCR. NCOR2/SMRT and NR4A1 (both on 12q), DYNLRB2 (16q), CELSR1, UPK3A, and ST13 (all on 22q) were more frequently amplified in PD. Moreover, NCOR2, NR4A1, and DYNLRB2 showed more frequent copy number losses in MD. GRAP2 (22q) was more often amplified in MD, whereas TAF1C (16q) was more commonly deleted in PD. A multigene model comprising these candidate genes discriminated between PD and MD lesions with high accuracy. These findings suggest that the propensity to invade the stroma may be encoded in the genome of intraductal carcinomas.

Protein pathway activation mapping reveals molecular networks associated with antiestrogen resistance in breast cancer cell lines

Previously, we have identified a panel of breast cancer antiestrogen resistance (BCAR) genes. Several of these genes have clinical relevance because mRNA or protein levels associate with tamoxifen resistance or tumor aggressiveness. We postulated that changes in activation status of protein signaling networks induced by BCAR genes may provide better insight into the mechanisms underlying antiestrogen resistance. Key signal transduction pathways were analyzed for changes in activation or expression using reverse-phase protein microarrays probed with 78 antibodies against signaling proteins with known roles in tumorigenesis. We used ZR-75-1-derived cell lines transduced with AKT1, AKT2, BCAR1, BCAR3, BCAR4, EGFR, GRB7, HRAS, HRAS(v12) or HEF1 and MCF7-derived cell lines transduced with BCAR3, BCAR4 or EGFR. In the antiestrogen-resistant cell lines, we observed increased phosphorylation of several pathways involved in cell proliferation and survival. All tamoxifen-resistant cell lines contained high levels of phosphorylated AKT and its biochemically linked substrates Forkhead box O1/3. The activation of ERBB2, ERBB3 and the downstream modulators focal adhesion kinase and SHC were activated in cells with overexpression of BCAR4. Remarkable differences were observed for the levels of activated AMPK alpha1, cyclins, STAT5, STAT6, ERK1/2 and BCL2. The comparison of the cell signaling networks in estrogen-dependent and -independent cell lines revealed biochemically linked kinase-substrate markers that comprised systemically activated signaling pathways involved in tamoxifen resistance. Our results show that this model provides insights into the molecular and cellular mechanisms of breast cancer progression and antiestrogen resistance. This knowledge may help the development of novel targeted treatments.

HIF-1α deletion partially rescues defects of hematopoietic stem cell quiescence caused by Cited2 deficiency

Cited2 is a transcriptional modulator involved in various biologic processes including fetal liver hematopoiesis. In the present study, the function of Cited2 in adult hematopoiesis was investigated in conditional knockout mice. Deletion of Cited2 using Mx1-Cre resulted in increased hematopoietic stem cell (HSC) apoptosis, loss of quiescence, and increased cycling, leading to a severely impaired reconstitution capacity as assessed by 5-fluorouracil treatment and long-term transplantation. Transcriptional profiling revealed that multiple HSC quiescence- and hypoxia-related genes such as Egr1, p57, and Hes1 were affected in Cited2-deficient HSCs. Because Cited2 is a negative regulator of HIF-1, which is essential for maintaining HSC quiescence, and because we demonstrated previously that decreased HIF-1α gene dosage partially rescues both cardiac and lens defects caused by Cited2 deficiency, we generated Cited2 and HIF-1α double-knockout mice. Additional deletion of HIF-1α in Cited2-knockout BM partially rescued impaired HSC quiescence and reconstitution capacity. At the transcriptional level, deletion of HIF-1α restored expression of p57 and Hes1 but not Egr1 to normal levels. Our results suggest that Cited2 regulates HSC quiescence through both HIF-1-dependent and HIF-1-independent pathways.

Knockdown of CITED2 using short-hairpin RNA sensitizes cancer cells to cisplatin through stabilization of p53 and enhancement of p53-dependent apoptosis

CITED2 is a transcriptional modulator which has been implicated in human oncogenesis. In the present study, we examined whether CITED2 is also involved in the resistance of cancer cells to the chemotherapeutic drug cisplatin. We first observed that knockdown of CITED2 using short-hairpin RNA sensitized non-tumorigenic HEK293 cells to cisplatin. Sensitization to cisplatin following knockdown of CITED2 was also observed in cervical carcinoma HeLa cells and in cisplatin-resistant HeLa cells, thereby showing that acquired cisplatin resistance could be reversed by CITED2 knockdown. This sensitization response was dependent on the status of p53 since efficient sensitization was observed in p53-positive hepatocellular carcinoma (HCC) Sk-Hep-1 cells, whereas a negligible response was produced in the two p53-defective cell lines HCC Mahlavu and lung cancer H1299. In contrast, overexpression of CITED2 decreased sensitivity of HEK293 cells to cisplatin, while moderate resistance was produced in HeLa cells. Overexpression of CITED2 also decreased sensitivity to cisplatin in p53-defective H1299 cells when exogenous p53 expression was re-introduced. We observed that knockdown of CITED2-induced CBP/p300-mediated p53 acetylation (Lys373) in HEK293 cells, thereby leading to a decrease of p53 ubiquitination and subsequent accumulation of the p53 protein. Notably, the effects of CITED2 knockdown on p53 accumulation and the increase of p53's target Bax were more pronounced after treatment with cisplatin. Based on these results, we propose that a combination of cisplatin and CITED2 shRNA may represent an effective treatment against p53-sensitive cancer cells.

Decreased expression of EZH2 is associated with upregulation of ER and favorable outcome to tamoxifen in advanced breast cancer

The purpose of this study is to investigate EZH2 in a large series of breast cancer patients for its prognostic and predictive value, and to evaluate its functional role in treatment response in vitro. EZH2 levels were measured using quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) in primary breast cancer specimens and related to clinicopathologic factors and disease outcome. EZH2 expression was downregulated with siRNAs in MCF7, to assess expression alterations of putative EZH2 downstream genes and to determine cell numbers after treatment with the anti-estrogen ICI 164384. In 688 lymph node-negative patients who did not receive adjuvant systemic therapy, EZH2 was not significantly correlated with metastasis-free survival (MFS). In 278 patients with advanced disease treated with first-line tamoxifen monotherapy, the tertile with highest EZH2 levels was associated with the lowest clinical benefit (OR = 0.48; P = 0.02) and with a shorter progression-free survival (PFS) in both univariate (HR = 1.80; P < 0.001) and multivariate analysis, including traditional factors (HR = 1.61; P = 0.004). In vitro, EZH2 silencing in MCF7 caused a 38% decrease in cell numbers (P < 0.001) whereas ICI 164384 treatment resulted in a 25% decrease (P < 0.001) compared to controls. Combining EZH2 silencing with ICI treatment reduced cell numbers with 67% (P < 0.001) compared to control conditions. EZH2 downregulation was associated with an almost two-fold upregulation of the estrogen receptor alpha (ER) (P = 0.001). In conclusion, EZH2 has no prognostic value in breast cancer. High levels of EZH2 are associated with poor outcome to tamoxifen therapy in advanced breast cancer. Downregulated EZH2 leads to upregulation of the ER and better response to anti-estrogens.