EZH2 inhibition decreases p38 signaling and suppresses breast cancer motility and metastasis

EZH2 represses mesenchymal genes and upholds the epithelial state of breast carcinoma cells

Emerging studies support that the polycomb repressive complex 2 (PRC2) regulates phenotypic changes of carcinoma cells by modulating their shifts among metastable states within the epithelial and mesenchymal spectrum. This new role of PRC2 in cancer has been recently proposed to stem from the ability of its catalytic subunit EZH2 to bind and modulate the transcription of mesenchymal genes during epithelial-mesenchymal transition (EMT) in lung cancer cells. Here, we asked whether this mechanism is conserved in other types of carcinomas. By combining TGF-β-mediated reversible induction of epithelial to mesenchymal transition and inhibition of EZH2 methyltransferase activity, we demonstrate that EZH2 represses a large set of mesenchymal genes and favours the residence of breast cancer cells towards the more epithelial spectrum during EMT. In agreement, analysis of human patient samples supports that EZH2 is required to efficiently repress mesenchymal genes in breast cancer tumours. Our results indicate that PRC2 operates through similar mechanisms in breast and lung cancer cells. We propose that PRC2-mediated direct transcriptional modulation of the mesenchymal gene expression programme is a conserved molecular mechanism underlying cell dissemination across human carcinomas.

EZH2-H3K27me3 mediated KRT14 upregulation promotes TNBC peritoneal metastasis

Triple-Negative Breast Cancer (TNBC) has a poor prognosis and adverse clinical outcomes among all breast cancer subtypes as there is no available targeted therapy. Overexpression of Enhancer of zeste homolog 2 (EZH2) has been shown to correlate with TNBC's poor prognosis, but the contribution of EZH2 catalytic (H3K27me3) versus non-catalytic EZH2 (NC-EZH2) function in TNBC progression remains elusive. We reveal that selective hyper-activation of functional EZH2 (H3K27me3) over NC-EZH2 alters TNBC metastatic landscape and fosters its peritoneal metastasis, particularly splenic. Instead of H3K27me3-mediated repression of gene expression; here, it promotes KRT14 transcription by attenuating binding of repressor SP1 to its promoter. Further, KRT14 loss significantly reduces TNBC migration, invasion, and peritoneal metastasis. Consistently, human TNBC metastasis displays positive correlation between H3K27me3 and KRT14 levels. Finally, EZH2 knockdown or H3K27me3 inhibition by EPZ6438 reduces TNBC peritoneal metastasis. Altogether, our preclinical findings suggest a rationale for targeting TNBC with EZH2 inhibitors.

EZH2 T367 phosphorylation activates p38 signaling through lysine methylation to promote breast cancer progression

Triple-negative breast cancers (TNBCs) are frequently poorly differentiated with high propensity for metastasis. Enhancer of zeste homolog 2 (EZH2) is the lysine methyltransferase of polycomb repressive complex 2 that mediates transcriptional repression in normal cells and in cancer through H3K27me3. However, H3K27me3-independent non-canonical functions of EZH2 are incompletely understood. We reported that EZH2 phosphorylation at T367 by p38α induces TNBC metastasis in an H3K27me3-independent manner. Here, we show that cytosolic EZH2 methylates p38α at lysine 139 and 165 leading to enhanced p38α stability and that p38 methylation and activation require T367 phosphorylation of EZH2. Dual inhibition of EZH2 methyltransferase and p38 kinase activities downregulates pEZH2-T367, H3K27me3, and p-p38 pathways in vivo and reduces TNBC growth and metastasis. These data uncover a cooperation between EZH2 canonical and non-canonical mechanisms and suggest that inhibition of these pathways may be a potential therapeutic strategy.

Autologous treatment for ALS with implication for broad neuroprotection

Background

Amyotrophic lateral sclerosis (ALS) is characterized by a progressive loss of motor neurons (MNs), leading to paralysis, respiratory failure and death within 2–5 years of diagnosis. The exact mechanisms of sporadic ALS, which comprises 90% of all cases, remain unknown. In familial ALS, mutations in superoxide dismutase (SOD1) cause 10% of cases.

Methods

ALS patient-derived human-induced pluripotent stem cells (ALS hiPSCs, harboring the SOD1^AV4 mutation), were differentiated to MNs (ALS-MNs). The neuroprotective effects of conditioned medium (CM) of hESCs (H9), wt hiPSCs (WTC-11) and the ALS iPSCs, on MN apoptosis and viability, formation and maintenance of neurites, mitochondrial activity and expression of inflammatory genes, were examined. For in vivo studies, 200 μl of CM from the ALS iPSCs (CS07 and CS053) was injected subcutaneously into the ALS model mice (transgenic for the human SOD1^G93A mutation). Animal agility and strength, muscle innervation and mass, neurological score, onset of paralysis and lifespan of the ALS mice were assayed. After observing significant disease-modifying effects, the CM was characterized biochemically by fractionation, comparative proteomics, and epigenetic screens for the dependence on pluripotency. CM of fibroblasts that were differentiated from the wt hiPSCs lacked any neuroprotective activity and was used as a negative control throughout the studies.

Results

The secretome of PSCs including the ALS patient iPSCs was neuroprotective in the H₂O₂ model. In the model with pathogenic SOD1 mutation, ALS iPSC-CM attenuated all examined hallmarks of ALS pathology, rescued human ALS-MNs from denervation and death, restored mitochondrial health, and reduced the expression of inflammatory genes. The ALS iPSC-CM also improved neuro-muscular health and function, and delayed paralysis and morbidity in ALS mice. Compared side by side, cyclosporine (CsA), a mitochondrial membrane blocker that prevents the leakage of mitochondrial DNA, failed to avert the death of ALS-MNs, although CsA and ALS iPSC-CM equally stabilized MN mitochondria and attenuated inflammatory genes. Biochemical characterization, comparative proteomics, and epigenetic screen all suggested that it was the interactome of several key proteins from different fractions of PSC-CM that delivered the multifaceted neuroprotection.

Conclusions

This work introduces and mechanistically characterizes a new biologic for treating ALS and other complex neurodegenerative diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40035-022-00290-5.

The transcriptional elongation factor CTR9 demarcates PRC2-mediated H3K27me3 domains by altering PRC2 subtype equilibrium

CTR9 is the scaffold subunit in polymerase-associated factor complex (PAFc), a multifunctional complex employed in multiple steps of RNA Polymerase II (RNAPII)-mediated transcription. CTR9/PAFc is well known as an evolutionarily conserved elongation factor that regulates gene activation via coupling with histone modifications enzymes. However, little is known about its function to restrain repressive histone markers. Using inducible and stable CTR9 knockdown breast cancer cell lines, we discovered that the H3K27me3 levels are strictly controlled by CTR9. Quantitative profiling of histone modifications revealed a striking increase of H3K27me3 levels upon loss of CTR9. Moreover, loss of CTR9 leads to genome-wide expansion of H3K27me3, as well as increased recruitment of PRC2 on chromatin, which can be reversed by CTR9 restoration. Further, CTR9 depletion triggers a PRC2 subtype switch from the less active PRC2.2, to the more active PRC2.1 with higher methyltransferase activity. As a consequence, CTR9 depletion generates vulnerability that renders breast cancer cells hypersensitive to PRC2 inhibitors. Our findings that CTR9 demarcates PRC2-mediated H3K27me3 levels and genomic distribution provide a unique mechanism that explains the transition from transcriptionally active chromatin states to repressive chromatin states and sheds light on the biological functions of CTR9 in development and cancer.

The molecular mechanisms and therapeutic potential of EZH2 in breast cancer

Due to its high occurrence and mortality rate, breast cancer has been studied from various aspects as one of the cancer field's hot topics in the last decade. Epigenetic alterations are spoused to be highly effective in breast cancer development. Enhancer of zeste homolog 2 (EZH2) is an enzymatic epi-protein that takes part in most vital cell functions by its different action modes. EZH2 is suggested to be dysregulated in specific breast cancer types, particularly in advanced stages. Mounting evidence revealed that EZH2 overexpression or dysfunction affects the pathophysiology of breast cancer. In this review, we discuss biological aspects of the EZH2 molecule with a focus on its newly identified action mechanisms. We also highlight how EZH2 plays an essential role in breast cancer initiation, progression, metastasis, and invasion, which emerged as a worthy target for treating breast cancer in different approaches.

AP-2α-Mediated Activation of E2F and EZH2 Drives Melanoma Metastasis

In melanoma metastasis, the role of the AP-2α transcription factor, which is encoded by TFAP2A, is controversial as some findings have suggested tumor suppressor activity while other studies have shown high TFAP2A expression in node-positive melanoma associated with poor prognosis. Here we demonstrate that AP-2α facilitates melanoma metastasis through transcriptional activation of genes within the E2F pathway including EZH2. A BioID screen found that AP-2α interacts with members of the nucleosome remodeling and deacetylase (NuRD) complex. Loss of AP-2α removed activating chromatin marks in the promoters of EZH2 and other E2F target genes through activation of the NuRD repression complex. In melanoma cells, treatment with tazemetostat, an FDA-approved and highly specific EZH2 inhibitor, substantially reduced anchorage-independent colony formation and demonstrated heritable antimetastatic effects, which were dependent on AP-2α. Single-cell RNA sequencing analysis of a metastatic melanoma mouse model revealed hyperexpansion of Tfap2a ^High/E2F-activated cell populations in transformed melanoma relative to progenitor melanocyte stem cells. These findings demonstrate that melanoma metastasis is driven by the AP-2α/EZH2 pathway and suggest that AP-2α expression can be used as a biomarker to predict responsiveness to EZH2 inhibitors for the treatment of advanced melanomas. SIGNIFICANCE: AP-2α drives melanoma metastasis by upregulating E2F pathway genes including EZH2 through inhibition of the NuRD repression complex, serving as a biomarker to predict responsiveness to EZH2 inhibitors.

Disruption of YY1-EZH2 Interaction Using Synthetic Peptides Inhibits Breast Cancer Development

Simple Summary

Both Yin Yang 1 (YY1) and enhancer of zeste homolog 2 (EZH2) are oncogenes with overexpressed statuses in cancers. As a transcription factor, YY1 recruits EZH2 through its oncoprotein binding (OPB) domain to repress gene expression. In this study, we identified the interaction domain of YY1 on EZH2 protein with amino acids 493–519, named the YY1 protein binding (YPB) domain. Synthetic peptides using YPB and OPB domain sequences effectively blocked endogenous YY1-EZH2 interaction. Functionally, YPB and OPB peptides could efficiently inhibit the proliferation of breast cancer cells, promote their apoptosis, and reduce tumor growth in a xenograft mouse model. Using chromatin immunoprecipitation DNA sequencing (ChIP-seq) analysis, we discovered that YPB and OPB peptides could interfere with H3K27 trimethylation of multiple genes. Eventually, we identified that YPB and OPB peptides primarily targeted the PTENP1 gene and validated its importance in the anticancer activity of the two peptides.

Abstract

Enhancer of zeste homolog 2 (EZH2) is a methyltransferase to mediate lysine 27 trimethylation in histone H3 (i.e., H3K27me3) and repress gene expression. In solid tumors, EZH2 promotes oncogenesis and is considered a therapeutic target. As a transcription factor, Yin Yang 1 (YY1) recruits EZH2 through its oncoprotein binding (OPB) domain to establish gene repression. In this study, we mapped the YY1 protein binding (YPB) domain on EZH2 to a region of 27 amino acids. Both YPB and OPB domain synthetic peptides could disrupt YY1EZH2 interaction, markedly reduce breast cancer cell viability, and efficiently inhibit tumor growth in a xenograft mouse model. We analyzed MDA-MB-231 cells treated with YPB, OPB, and control peptides by chromatin immunoprecipitation DNA sequencing (ChIP-seq) using an antibody against H3K27me3. YPB and OPB treatments altered H3K27me3 on 465 and 1137 genes, respectively, compared to the control. Of these genes, 145 overlapped between the two peptides. Among them, PTENP1, the PTEN pseudogene, showed reduced H3K27me3 signal when treated by either YPB or OPB peptide. Consistently, the two peptides enhanced both PTENP1 and PTEN expression with concomitantly reduced AKT activation. Further studies validated PTENP1′s contribution to the anticancer activity of YPB and OPB peptides.

Noncanonical Functions of the Polycomb Group Protein EZH2 in Breast Cancer

Enhancer of Zeste Homologue 2 (EZH2) is the catalytic subunit of the polycomb repressive complex 2 (PRC2) that is critical for determining cell identity. An epigenetic writer, EZH2 has a well-defined role in transcriptional repression by depositing trimethyl marks on lysine 27 of histone H3. However, there is mounting evidence that histone methyltransferases like EZH2 exert histone methyltransferase-independent functions. The relevance of these functions to breast cancer progression and their regulatory mechanisms are only beginning to become understood. Here, we review the current understanding of EZH2 H3K27me3-independent, noncanonical, functions and their regulation in breast cancer.

Inhibition of EZH2 Catalytic Activity Selectively Targets a Metastatic Subpopulation in Triple-Negative Breast Cancer

Epigenetic changes are increasingly being appreciated as key events in breast cancer progression. However, breast cancer subtype-specific epigenetic regulation remains poorly investigated. Here we report that EZH2 is a leading candidate of epigenetic modulators associated with the TNBC subtype and that it predicts poor overall survival in TNBC patients. We demonstrate that specific pharmacological or genetic inhibition of EZH2 catalytic activity impairs distant metastasis. We further define a specific EZH2^high population with enhanced invasion, mammosphere formation, and metastatic potential that exhibits marked sensitivity to EZH2 inhibition. Mechanistically, EZH2 inhibition differentiates EZH2^high basal cells to a luminal-like phenotype by derepressing GATA3 and renders them sensitive to endocrine therapy. Furthermore, dissection of human TNBC heterogeneity shows that EZH2^high basal-like 1 and mesenchymal subtypes have exquisite sensitivity to EZH2 inhibition compared with the EZH2^low luminal androgen receptor subtype. These preclinical findings provide a rationale for clinical development of EZH2 as a targeted therapy against TNBC metastasis.

MiR-146a Regulates Migration and Invasion by Targeting NRP2 in Circulating-Tumor Cell Mimicking Suspension Cells

Cancer metastasis is the primary cause of cancer-related death and metastatic cancer has circulating-tumor cells (CTCs), which circulate in the bloodstream before invading other organs. Thus, understanding the precise role of CTCs may provide new insights into the metastasis process and reduce cancer mortality. However, the molecular characteristics of CTCs are not well understood due to a lack of number of CTCs. Therefore, suspension cells were generated from MDA-MB-468 cells to mimic CTCs, and we investigate the microRNA (miRNA)-dependent molecular networks and their role in suspension cells. Here, we present an integrated analysis of mRNA and miRNA sequencing data for suspension cell lines, through comparison with adherent cells. Among the differentially regulated miRNA–mRNAs axes, we focus on the miR-146a-Neuropilin2 (NRP2) axis, which is known to influence tumor aggressiveness. We show that miR-146a directly regulates NRP2 expression and inhibits Semaphorin3C (SEMA3C) signaling. Functional studies reveal that miR-146a represses SEMA3C-induced invasion and proliferation by targeting NRP2. Finally, high-NRP2 is shown to be associated with poor outcomes in breast cancer patients. This study identifies the key role of the miR-146a–NRP2 signaling axis that is critical for the regulation of migration and invasion in CTC-mimicking cells.

Subcellular localization of EZH2 phosphorylated at T367 stratifies metaplastic breast carcinoma subtypes

BACKGROUND

Metaplastic carcinoma is an aggressive, triple-negative breast cancer (TNBC) with differentiation towards squamous, spindle, or mesenchymal cell types. The molecular underpinnings of the histological subtypes are unclear. Our lab discovered a cytoplasmic function of EZH2, a transcriptional repressor, whereby pEZH2 T367 binds to cytoplasmic proteins in TNBC cells and enhances invasion and metastasis. Here, we investigated the expression and subcellular localization of pEZH2 T367 protein in metaplastic carcinomas.

METHODS

Thirty-five metaplastic carcinomas (17 squamous, 10 mesenchymal, and 8 spindle) were evaluated and immunostained with anti-pEZH2 T367. We analyzed staining intensity (score 1-4), subcellular localization (nuclear/cytoplasmic), and localization within the tumor (center/invasive edge). Protein expression of pEZH2 T367-binding partners was measured from a quantitative multiplex proteomics analysis performed in our lab.

RESULTS

Cytoplasmic pEZH2 T367 was significantly upregulated in squamous (14 of 17, 82%) compared to mesenchymal (4 of 10, 40%) and spindle (2 of 6, 33%) subtypes (p = 0.011). Twenty-five of 34 (73%) tumors with available tumor-normal interface showed accentuated cytoplasmic pEZH2 T367 at the infiltrative edge. Cytoplasmic pEZH2 T367 was upregulated in 9 of 10 (90%) tumors with lymph node metastasis (p = 0.05). Bioinformatics analyses identified an EZH2 protein network in metaplastic carcinomas (p value: < 1.0e-16). Using quantitative proteomics, we found significantly increased expression of cytoplasmic EZH2-binding partners in squamous compared to spindle and mesenchymal subtypes.

CONCLUSIONS

pEZH2 T367 expression and subcellular localization may be useful to distinguish metaplastic carcinoma subtypes. pEZH2 T367 may play a role in the histological diversity and behavior of these tumors.

EZH2-mediated Epigenetic Silencing of miR-29/miR-30 targets LOXL4 and contributes to Tumorigenesis, Metastasis, and Immune Microenvironment Remodeling in Breast Cancer

Enhancer of Zeste Homolog 2 (EZH2), a key epigenetic regulator, is involved in breast cancer progression and metastasis. LOXL4 is increasingly recognized as an important player in cancer progression. To date, how EZH2 regulates LOXL4 in the progression of breast cancer remains unclear.

Methods: We evaluated the association between LOX family proteins and EZH2 in invasive breast carcinoma through the starBase v2.0 analysis, and its correlation with breast tumorigenesis using the Oncomine dataset. We then applied miRcode data combined with gene expression omnibus (GEO) data to screen candidate miRNAs mediating the regulation of LOXL4 by EZH2. We explored the regulatory mechanism of EZH2, miR-29b/miR-30d, and LOXL4 in breast cancer cells by qRT-PCR, Western blotting, cell proliferation, colony formation, and wound healing assays, xenograft experiments, dual-luciferase reporter assay, and chromatin immunoprecipitation. All statistical tests were two-sided.

Results: Inhibition of EZH2 or LOXL4, or miR-29b/miR-30d overexpression, decreased breast cancer cell proliferation, migration, and metastasis in vitro and in vivo. LOXL4 was identified as a direct target of miR-29b and miR-30d. EZH2 inhibition enhanced miR-30d and miR-29b transcription via promoter binding activity, leading to the reduced expression of LOXL4. Immunohistochemical analysis of human breast cancer specimens and flow cytometry analysis of tumor-infiltrating macrophages in mice showed a positive association of EZH2 with LOXL4 expression and macrophage infiltration.

Conclusions: Our findings identified EZH2-miR-29b/miR-30d-LOXL4 signaling pathway was involved in breast tumorigenesis, and suggested that the epigenetic modulation represents a potential therapeutic target for breast cancer by controlling macrophage activation.

MiR-33a functions as a tumor suppressor in triple-negative breast cancer by targeting EZH2

Background

Increasing reports have confirmed that microRNAs play an important role in breast cancer progression, particularly in triple-negative breast cancer (TNBC). The aim of our study was to investigate the role of miR-33a in TNBC progression.

Methods

PCR assays were performed to detect miR-33a and EZH2 expression in TNBC tissues, adjacent nontumor tissues and cell lines. Western blot, CCK8, Transwell, cell colony formation and EdU cell proliferation, cell cycle analysis and luciferase reporter assays were used to determine the regulation of miR-33a/EZH2 in TNBC progression.

Results

MiR-33a was significantly downregulated in TNBC tissues and cell lines. MiR-33a overexpression in TNBC cells significantly inhibited cell growth and mobility and induced G1 cell cycle arrest. The luciferase reporter assay revealed that EZH2 is a direct target of miR-33a and that it was upregulated in TNBC tissues and cell lines. There was a negative correlation between miR-33a and EZH2 expression in TNBC tissues. EZH2 knockdown exerted similar inhibitory effects, while ectopic expression of EZH2 showed suppressive effects on malignant behaviors induced by miR-33a overexpression in TNBC cells.

Conclusions

These findings revealed that miR-33a is a tumor-suppressive miRNA in TNBC and can inhibit proliferation and mobility and induce G1 cell cycle arrest by directly targeting EZH2.

p38α/S1P/SREBP2 activation by the SAM-competitive EZH2 inhibitor GSK343 limits its anticancer activity but creates a druggable vulnerability in hepatocellular carcinoma

Enhancer of zeste homolog 2 (EZH2) mediates epigenetic gene silencing via tri-methylation of histone H3 lysine 27 (H3K27-me3). Increased expression of EZH2 is frequently detected in various cancers including hepatocellular carcinoma (HCC), which is associated with the silencing of tumor suppressor genes. S-adenosyl-L-methionine (SAM)-competitive EZH2 inhibitors fall into the major category of EZH2 inhibitors for cancer therapy. In this study, microarray analyses found that induction of genes related to cholesterol homeostasis is a common effect of SAM-competitive EZH2 inhibitors in cancer cells. As a representative, GSK343 induced lipid accumulation which promoted cancer cell survival. GSK343 selectively activated sterol regulatory element-binding protein 2 (SREBP2), but not SREBP1, in HCC cells. Inhibition of SREBP2 by siRNA reduced cell viability and enhanced the anticancer effect of GSK343. Cancer genomics analysis indicated that SREBP2 upregulation was associated with the poor overall survival of HCC patients. Mechanistically, GSK343-induced SREBP2 activation was unrelated to its original ability to compete with SAM and inhibit EZH2 activity. Instead, GSK343 activated SREBP2 in p38α- and site-1 protease (S1P)-dependent manners. Inhibition of p38α and S1P by SB-202190 and PF-429242, respectively, enhanced the in vitro anticancer activity of GSK343, thereby creating a vulnerability for treating HCC.

TBX2 interacts with heterochromatin protein 1 to recruit a novel repression complex to EGR1-targeted promoters to drive the proliferation of breast cancer cells

Early Growth Response 1 (EGR1) is a stress response transcription factor with multiple tumour suppressor roles in breast tissue, whose expression is often lost in breast cancers. We have previously shown that the breast cancer oncogene TBX2 (T-BOX2) interacts with EGR1 to co-repress EGR1-target genes including the breast tumour suppressor NDRG1. Here, we show the mechanistic basis of this TBX2 repression complex. We show that siRNA knockdown of TBX2, EGR1, Heterochromatin Protein 1 (HP1) isoforms and the generic HP1-associated corepressor protein KAP1 all resulted in growth inhibition of TBX2-expressing breast cancer cells. We show that TBX2 interacts with HP1 through a conserved HP1-binding motif in its N-terminus, which in turn leads to the recruitment of KAP1 and other associated proteins. Mutation of the TBX2 HP1 binding domain abrogates the TBX2-HP1 interaction and loss of repression of target genes such as NDRG1. Chromatin-immunoprecipitation (ChIP) assays showed that TBX2 establishes a repressive chromatin mark, specifically H3K9me3, around the NDRG1 proximal promoter coincident with the recruitment of the DNA methyltransferase DNMT3B and histone methyltransferase (HMT) complex components (G9A, Enhancer of Zeste 2 (EZH2) and Suppressor of Zeste 12 (SUZ12)). Knockdown of G9A, EZH2 or SUZ12 resulted in upregulation of TBX2/EGR1 co-regulated targets accompanied by a dramatic inhibition of cell proliferation. We show that a generic inhibitor of HMT activity, DzNep, phenocopies expression of an inducible dominant negative TBX2. Knockdown of TBX2, KAP1 or HP1 inhibited NDRG1 promoter decoration specifically with the H3K9me3 repression mark. Correspondingly, treatment with a G9A inhibitor effectively reversed TBX2 repression of NDRG1 and synergistically downregulated cell proliferation following TBX2 functional inhibition. These data demonstrate that TBX2 promotes suppression of normal growth control mechanisms through recruitment of a large repression complex to EGR1-responsive promoters leading to the uncontrolled proliferation of breast cancer cells.

A new view of the mammary epithelial hierarchy and its implications for breast cancer initiation and metastasis

The existence of mammary epithelial stem cell (MaSC) populations capable of mediating mammary gland development and homeostasis has been established for over a decade. A combination of lineage tracing and mammary gland transplantation studies has affirmed that MaSCs and their downstream progenitors are organized in a hierarchal manner; however, these techniques have failed to illuminate the complete spectrum of epithelial intermediate populations or their spatial and temporal relationships. The advent of single cell sequencing technology has allowed for characterization of highly heterogeneous tissues at high resolution. In the last two years, the remarkable advances in single cell RNA sequencing (scRNA-seq) technologies have been leveraged to address the heterogeneity of the mammary epithelium. These studies have afforded fresh insights into the transcriptional differentiation hierarchy and its chronology. Importantly, these data have led to a major conceptual shift in which the rigid boundaries separating stem, progenitor, and differentiated epithelial populations have been deconstructed, resulting in a new more fluid and flexible model of epithelial differentiation. The emerging view of the mammary epithelial hierarchy has important implications for mammary development, carcinogenesis, and metastasis, providing novel insights into the underlying cellular states that may promote malignant phenotypes.

EZH2 plays a crucial role in ischemia/reperfusion-induced acute kidney injury by regulating p38 signaling

OBJECTIVE AND DESIGN

Renal ischemia-reperfusion (IR)-induced acute kidney injury (AKI) remains a major challenge in clinic. The histone methyltransferases enhancer of zest homolog-2 (EZH2) is associated with the development of renal injury. However, the molecular mechanism has not been fully elucidated.

MATERIALS

AKI in C57BL/6 mice was generated by renal IR.

TREATMENTS

The 3-deazaneplanocin A (DZNeP), a selective EZH2 inhibitor, or vehicle was administrated in mice after IR. HK-2 cells were exposed to hypoxia-reoxygenation (H/R) stress.

METHODS

Apoptosis was detected by TUNEL assay or flow cytometry. EZH2, caspase-3, p38, F4/80⁺ macrophages, and CD3⁺ T cells were examined by immunohistochemistry or Western blot. Tumor necrosis factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, IL-6, and IL-18 were measured using RT-PCR.

RESULTS

Mice treated with DZNeP exhibited less severe renal dysfunction and tubular injury following IR. EZH2 inhibition decreased apoptotic cells while reducing activation of caspase-3 in kidneys under IR condition. Moreover, EZH2 inhibition impaired the recruitment of CD3⁺ T cells and F4/80⁺ cells in kidneys with IR. Administration of DZNeP suppressed the production of TNF-α, MCP-1, IL-6, and IL-18 in IR-treated kidneys. Of note, EZH2 inhibition reduced p38 phosphorylation in kidneys after IR. In H/R-treated HK-2 cells, DZNeP treatment or EZH2 knockdown reduced apoptosis. EZH2 inhibition inactivated p38 resulting in reduction of active caspase-3 and proinflammatory molecules. By contrast, EZH2 overexpression induced p38 phosphorylation, caspase-3 activation, and production of proinflammatory molecules, which was reversed by SB203580.

CONCLUSIONS

EZH2 plays a crucial role in IR-induced AKI via modulation of p38 signaling. Targeting EZH2/p38 signaling pathway may offer novel strategies to protect kidneys from acute kidney injury induced by ischemia-reperfusion.

MicroRNA-365 targets multiple oncogenes to inhibit proliferation, invasion, and self-renewal of aggressive endometrial cancer cells

Background

MicroRNA-365 (miR-365) has been reported to be a tumor suppressor miRNA. However, the role of miR-365 in progression of endometrial cancer (EC) has not been explored, in this study, we have found that re-expression of miRNA-365 inhibits cell proliferation, causes apoptosis and senescence.

Materials and methods

Overexpression of miR-365 attenuated cell migration and invasion, inhibited sphere-forming capacity, and enhanced the chemosensitivity to paclitaxel. In silico prediction tools identified the potential targets of miR-365.

Results

We identified EZH2 and FOS as targets of miR-365 and found that downregulating these genes imitated the tumor suppressive effect of miR-365. The outcomes of the study suggested that a reverse correlation existed between low miR-365 and overexpression of FOS and EZH2 in EC tissue specimens.

Conclusion

The study concludes that miR-365 acts as an important tumor suppressor and contributes by suppressing cell invasiveness, proliferation, and self-renewal in cancer cell lines by regulating multiple oncogenes. We establish that miR-365-EZH2/FOS pathway is an important target for treating EC.

Long noncoding RNA TALNEC2 plays an oncogenic role in breast cancer by binding to EZH2 to target p57KIP2 and involving in p-p38 MAPK and NF-κB pathways

We aimed to investigate the potential role and regulatory mechanism of long noncoding RNA tumor-associated lncRNA expressed in chromosome 2 (TALNEC2) in breast cancer. The expression of TALNEC2 in breast cancer tissues and cells were investigated. MCF-7 and MDA-MB-231 cells were transfected with small interfering RNA (siRNA) duplexes for targeting TALNEC2 (si-TALNEC2), enhancer of zeste homolog 2 (EZH2; si-EZH2) and p57^KIP2 (si-p57 ^KIP2 ), and their corresponding controls (si-NC). The viability, colony forming ability, cell cycle, apoptosis, and autophagy of transfected cells were assessed. The expressions of p-p38 mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) pathway-related proteins were investigated. The results showed that TALNEC2 was highly expressed in breast cancer tissues and cells. Knockdown of TALNEC2 significantly inhibited the malignant behaviors of MCF-7 and MDA-MB-231 cells, including inhibiting cell viability and colony forming, arresting cell cycle at G0/G1 phase, inducing cell apoptosis, and promoting cell autophagy. EZH2 was a TALNEC2 binding protein, which was upregulated in breast cancer tissues and cells and could negatively regulate p57 ^KIP2 . Effects of TALNEC2 knockdown on malignant behaviors of MCF-7 cells were reversed by p57 ^KIP2 knockdown. The expressions of p-p38, RelA, and RelB in MCF-7 cells were decreased after knockdown of TALNEC2 or EZH2, which were reversed by knockdown of p57 ^KIP2 concurrently. In conclusion, TALNEC2 may play an oncogenic role in breast cancer by binding to EZH2 to target p57 ^KIP2 . Activation of p-p38 MAPK and NF-κB pathways may be key mechanisms mediating the oncogenic role of TALNEC2 in breast cancer. TALNEC2 may serve as a promising target in the therapy of breast cancer.

Atypical Ductal Lesions of the Breast: Criteria, Significance, and Laboratory Updates

Context.—

Atypical ductal hyperplasia (ADH) is a challenging diagnosis defined by cytologic and architectural features that carries an increased risk of subsequent carcinoma when diagnosed in isolation. In addition, ADH may secondarily involve benign breast lesions, wherein it carries variable clinical significance.

Objectives.—

To review the diagnostic criteria and clinical significance of ADH in isolation and as it involves benign breast lesions, and to review the evolving literature on its molecular signature.

Data Sources.—

Recently published studies that collectively examine ADH were reviewed.

Conclusions.—

Atypical ductal hyperplasia carries an increased risk of subsequent carcinoma in isolation and when it involves most benign breast lesions. Identifying which cases of ADH will be upgraded to carcinoma has been challenging, and new laboratory developments, such as EZH2 overexpression, may have a future role.

p38-mediated phosphorylation at T367 induces EZH2 cytoplasmic localization to promote breast cancer metastasis

Overexpression of EZH2 in estrogen receptor negative (ER-) breast cancer promotes metastasis. EZH2 has been mainly studied as the catalytic component of the Polycomb Repressive Complex 2 (PRC2) that mediates gene repression by trimethylating histone H3 at lysine 27 (H3K27me3). However, how EZH2 drives metastasis despite the low H3K27me3 levels observed in ER- breast cancer is unknown. Here we show that in human invasive carcinomas and distant metastases, cytoplasmic EZH2 phosphorylated at T367 is significantly associated with ER- disease and low H3K27me3 levels. p38-mediated EZH2 phosphorylation at T367 promotes EZH2 cytoplasmic localization and potentiates EZH2 binding to vinculin and other cytoskeletal regulators of cell migration and invasion. Ectopic expression of a phospho-deficient T367A-EZH2 mutant is sufficient to inhibit EZH2 cytoplasmic expression, disrupt binding to cytoskeletal regulators, and reduce EZH2-mediated adhesion, migration, invasion, and development of spontaneous metastasis. These results point to a PRC2-independent non-canonical mechanism of EZH2 pro-metastatic function.

ZRANB1 Is an EZH2 Deubiquitinase and a Potential Therapeutic Target in Breast Cancer

Although EZH2 enzymatic inhibitors have shown antitumor effects in EZH2-mutated lymphoma and ARID1A-mutated ovarian cancer, many cancers do not respond because EZH2 can promote cancer independently of its histone methyltransferase activity. Here we identify ZRANB1 as the EZH2 deubiquitinase. ZRANB1 binds, deubiquitinates, and stabilizes EZH2. Depletion of ZRANB1 in breast cancer cells results in EZH2 destabilization and growth inhibition. Systemic delivery of ZRANB1 small interfering RNA (siRNA) leads to marked antitumor and antimetastatic effects in preclinical models of triple-negative breast cancer (TNBC). Intriguingly, a small-molecule inhibitor of ZRANB1 destabilizes EZH2 and inhibits the viability of TNBC cells. In patients with breast cancer, ZRANB1 levels correlate with EZH2 levels and poor survival. These findings suggest the therapeutic potential for targeting the EZH2 deubiquitinase ZRANB1.

GSK3β inactivation promotes the oncogenic functions of EZH2 and enhances methylation of H3K27 in human breast cancers

During the process of tumorigenesis, inactivation of tumor suppressors is a critical step. EZH2, a histone methyltransferase, promotes cell growth and migration through catalyzing trimethylation of histone H3 at Lys 27 (H3K27me3) and plays an important role in tumorigenesis. Its expression can be controlled by phosphorylation. However, the regulation of EZH2 activity by tumor suppressor kinase is not well understood. In this study, we show that glycogen synthase kinase 3 beta (GSK3β) negatively regulates H3K27 trimethylation. We also validate that GSKβ physically interacts with EZH2, and their interaction occurs in the cytosol. GSK3β phosphorylates EZH2 at Ser363 and Thr367 in vitro, and activating GSK3β upregulates Thr367 phosphorylationin vivo. Cells expressing GSK3β-non-phosphorylatable mutant EZH2 have higher H3K27 trimethylation and enhanced ability of cell migration and anchorage-independent growth. Inactivation of GSK3β as measured by its phosphorylation at Ser9 is positively correlated with higher level of H3K27 trimethylation in tumor tissues from breast cancer patients. Our study indicated that GSK3β phosphorylates EZH2 at Ser363 and Thr367, resulting in reduced H3K27 trimethylation and biological activity of EZH2 in breast cancer.

The matricellular protein CCN6 (WISP3) decreases Notch1 and suppresses breast cancer initiating cells

Increasing evidence supports that the epithelial to mesenchymal transition (EMT) in breast cancer cells generates tumor initiating cells (TICs) but the contribution of the tumor microenvironment to these programs needs further elucidation. CCN6 (WISP3) is a secreted matrix-associated protein (36.9 kDa) of the CCN family (named after CTGF, Cyr61 and Nov) that is reduced or lost in invasive carcinomas of the breast with lymph node metastasis and in inflammatory breast cancer. CCN6 exerts breast cancer growth and invasion inhibitory functions, but the mechanisms remain to be defined. In the present study we discovered that ectopic CCN6 overexpression in triple negative (TN) breast cancer cells and in cells derived from patients is sufficient to induce a mesenchymal to epithelial transition (MET) and to reduce TICs. In vivo, CCN6 overexpression in the TIC population of MDA-MB-231 cells delayed tumor initiation, reduced tumor volume, and inhibited the development of metastasis. Our studies reveal a novel CCN6/Slug signaling axis that regulates Notch1 signaling activation, epithelial cell phenotype and breast TICs, which requires the conserved thrombospondin type 1 (TSP1) motif of CCN6. The relevance of these data to human breast cancer is highlighted by the finding that CCN6 protein levels are inversely correlated with Notch1 intracellular activated form (NICD1) in 69.5% of invasive breast carcinomas. These results demonstrate that CCN6 regulates epithelial and mesenchymal states transition and TIC programs, and pinpoint one responsible mechanism.

EZH2-mediated repression of GSK-3β and TP53 promotes Wnt/β-catenin signaling-dependent cell expansion in cervical carcinoma

Enhancer of zeste homolog 2 (EZH2), a catalytic core component of the Polycomb repressive complex 2 (PRC2), stimulates the silencing of target genes through histone H3 lysine 27 trimethylation (H3K27me3). Recent findings have indicated EZH2 is involved in the development and progression of various human cancers. However, the exact mechanism of EZH2 in the promotion of cervical cancer is largely unknown. Here, we show that EZH2 expression gradually increases during the progression of cervical cancer. We identified a significant positive correlation between EZH2 expression and cell proliferation in vitro and tumor formation in vivo by the up-regulation or down-regulation of EZH2 using CRISPR-Cas9-mediated gene editing technology and shRNA in HeLa and SiHa cells. Further investigation indicated that EZH2 protein significantly accelerated the cell cycle transition from the G0/G1 to S phase. TOP/FOP-Flash reporter assay revealed that EZH2 significantly activated Wnt/β-catenin signaling and the target genes of Wnt/β-catenin pathway were up-regulated, including β-catenin, cyclin D1, and c-myc. Moreover, dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays confirmed that EZH2 inhibited the expression of glycogen synthase kinase-3β (GSK-3β) and TP53 through physically interacting with motifs in the promoters of the GSK-3β and TP53 genes. Additionally, blockage of the Wnt/β-catenin pathway resulted in significant inhibition of cell proliferation, and activation of the Wnt/β-catenin pathway resulted in significant enhancement of cell proliferation, as induced by EZH2. Taken together, our data demonstrate that EZH2 promotes cell proliferation and tumor formation in cervical cancer through activating the Wnt/β-catenin pathway by epigenetic silencing via GSK-3β and TP53.

Expression of EZH2 in endometrial carcinoma and its effects on proliferation and invasion of endometrial carcinoma cells

Expression of enhancer of zeste homolog 2 (EZH2) has been implicated in cancer pathology, but research on its mechanistic activity is limited. The present study sought to assess the levels expression of EZH2 in patients with endometrial carcinoma (EC) and to explore the effects of EZH2 downregulation on the biological behavior of endometrial carcinoma RL-952 cells. Samples were obtained from a total of 104 patients with EC and an immunohistochemical assay was used to detect the expression of EZH2 in cancer and adjacent tissues. The relationship between the expression of EZH2 and the clinicopathological features was analyzed. Endometrial carcinoma RL-952 cells were transfected with chemically synthesized siRNA to conduct targeting inhibition of EZH2 expression. The expression levels of EZH2 protein were detected by immunoblotting. MTT and Transwell assays were used to detect the changes of cell proliferation and invasion after EZH2 downregulation. Of the 104 cases of endometrial carcinoma samples, 71 cases showed positive expression of EZH2, with an expression rate of 68.27%. In 104 cases of adjacent tissue samples, 25 cases showed positive expression of EZH2, with an expression rate of 24.03%. The expression of EZH2 in endometrial carcinoma tissue was significantly higher than that in adjacent tissue (P<0.05). The expression of EZH2 in endometrial carcinoma tissue was not correlated with the menopausal status and age of patients (P>0.05), but was correlated with the histological grade, depth of tumor invasion, lymph node metastasis and TNM stage (P<0.05). The expression of E2H2 was significantly downregulated by si-E2H2 and the proliferation and invasion abilities of cells were significantly reduced after EZH2 downregulation (P<0.05). EZH2 is closely related to the development of endometrial carcinoma and can enhance the proliferative activity of endometrial carcinoma RL-952 cells and promote cell invasion.

miR-21 modulates the effect of EZH2 on the biological behavior of human lung cancer stem cells in vitro

Non-small-cell lung cancer has a high mortality rate and poor prognosis. Therefore, novel therapeutic approaches are urgently needed to enhance patient survival rates. In this study, we investigated the effects of miR-21 and EZH2 on the biological behavior of human lung cancer stem cells in vitro. We found increased expression of EZH2 and miR-21 in LCSCs, and miR-21 overexpression increased EZH2 levels in LCSCs. In addition, EZH2 and miR-21 knockdown increased the sensitivity of LCSCs to chemo- and radiation therapy, and exogenous EZH2 expression rescued the effects of anti-miR-21. Cell proliferation was reduced by 39.2% and 69.7% in the presence of radio- or chemotherapy combined with anti-miR-21 transfection, respectively. The downstream molecules included Cdc2, cyclin B1, and Bcl-2, which are involved in the regulation of cell cycle and apoptosis and which could themselves be reduced or enhanced by changes in miR-21 and EZH2 levels in LCSCs. This study demonstrates the direct relationship between miR-21 and EZH2 which was increased by 43% after the application of the miR-21 mimic. Above data indicates that these two molecules can influence the biological behavior of LCSCs by altering their corresponding targets. Our findings support the potential roles of miR-21 and EZH2 in improving the therapeutic efficacy of clinical lung cancer treatments.

Metastatic biomarkers in synovial sarcoma

Synovial sarcoma (SS) is an aggressive soft tissue sarcoma (STS) that typically occurs in the extremities near a joint. Metastatic disease is common and usually occurs in the lungs and lymph nodes. Surgical management is the mainstay of treatment with chemotherapy and radiation typically used as adjuvant treatment. Although chemotherapy has a positive impact on survival, the prognosis is poor if metastatic disease occurs. The biology of sarcoma invasion and metastasis remain poorly understood. Chromosomal translocation with fusion of the SYT and SSX genes has been described and is currently used as a diagnostic marker, although the full impact of the fusion is unknown. Multiple biomarkers have been found to be associated with SS and are currently under investigation regarding their pathways and mechanisms of action. Further research is needed in order to develop better diagnostic screening tools and understanding of tumor behavior. Development of targeted therapies that reduce metastatic events in SS, would dramatically improve patient prognosis.

Osteoprotegerin mediates tumor-promoting effects of Interleukin-1beta in breast cancer cells

Background

It is widely recognized that inflammation promotes breast cancer invasion and metastasis. Given the complex nature of the breast tumor inflammatory microenvironment, much remains to be understood of the molecular mechanisms that govern these effects. We have previously shown that osteoprotegerin knockdown in breast cancer cells resulted in reduced invasion and metastasis. Here we present novel insight into the role of osteoprotegerin in inflammation-driven tumor progression in breast cancer by investigating the link between osteoprotegerin, macrophages and the potent pro-inflammatory cytokine Interleukin-1beta.

Methods

We used human breast cancer cell lines to investigate the effects of Interleukin-1beta treatment on osteoprotegerin secretion as measured by ELISA. We analyzed public datasets containing human breast cancer genome-wide mRNA expression data to reveal a significant and positive correlation between osteoprotegerin mRNA expression and the mRNA expression of Interleukin-1beta and of monocyte chemoattractant protein CC-chemokine ligand 2. Osteoprotegerin, Interleukin-1beta and CC-chemokine ligand 2 mRNA levels were also examined by qPCR on cDNA from normal and cancerous human breast tissue. We determined the effect of Interleukin-1beta–producing macrophages on osteoprotegerin expression by co-culturing breast cancer cells and differentiated THP-1 macrophages. Immunohistochemistry was performed on human breast tumor tissue microarrays to assess macrophage infiltration and osteoprotegerin expression. To demonstrate that osteoprotegerin mediated functional effects of Interleukin-1beta we performed cell invasion studies with control and OPG siRNA knockdown on Interleukin-1beta-treated breast cancer cells.

Results

We report that Interleukin-1beta induces osteoprotegerin secretion, independent of breast cancer subtype and basal osteoprotegerin levels. Co-culture of breast cancer cells with Interleukin-1beta-secreting macrophages resulted in a similar increase in osteoprotegerin secretion in breast cancer cells as Interleukin-1beta treatment. Macrophage infiltration correlates with osteoprotegerin secretion in human breast tumor tissue samples. We show that osteoprotegerin secretion is regulated by Interleukin-1beta in a p38- and p42/44-dependent manner. We also demonstrate that osteoprotegerin knockdown represses Interleukin-1beta expression, Interleukin-1beta-mediated breast cancer cell invasion and MMP3 expression.

Conclusions

These data indicate a novel role for osteoprotegerin as a mediator of inflammation- promoted breast cancer progression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0606-y) contains supplementary material, which is available to authorized users.

Tranilast Inhibits Genes Functionally Involved in Cell Proliferation, Fibrosis, and Epigenetic Regulation and Epigenetically Induces miR-29c Expression in Leiomyoma Cells

Tranilast (N-3,4-dimethoxycinnamoyl anthranilic acid) is an antiallergic agent with inhibitory effects on cell proliferation and extracellular matrix production. Here we assess the effect of tranilast on the expression of miR-29c and genes functionally involved in cell proliferation, fibrosis, and epigenetic regulation in isolated leiomyoma smooth muscle cells (LSMC). Tranilast significantly inhibited the rate of LSMC proliferation, which was associated with downregulation of cell cycle progression genes cyclin D1 (CCND1) and cyclin-dependent kinase 2 (CDK2) expression at messenger RNA and protein levels ( P < .05). Tranilast also suppressed the expression of collagen type I (COL1), collagen type III alpha 1 chain (COL3A1), the profibrotic cytokine, transforming growth factor β-3 (TGF-β3), DNA (cytosine-5)-methyltransferase 1 (DNMT1), and enhancer of zeste homolog 2 (EZH2), which regulate epigenetic status of gene promoters ( P < .05). Tranilast also significantly induced the expression of cellular and secreted miR-29c through downregulation of methylation status of miR-29c promoter ( P < .05). In addition, tranilast suppressed the activity of luciferase reporter containing 3'UTR of COL3A1 and CDK2, which are downstream targets of miR-29c ( P < .05). Knockdown of miR-29c expression attenuated the inhibitory effects of tranilast on COL3A1 and CDK2 protein expression ( P < .05). Collectively, these findings suggest that tranilast could have therapeutic potential as an inhibitory agent for leiomyoma growth and its associated symptoms.

Breast Cancer and African Ancestry: Lessons Learned at the 10-Year Anniversary of the Ghana-Michigan Research Partnership and International Breast Registry

Women with African ancestry in western, sub-Saharan Africa and in the United States represent a population subset facing an increased risk of being diagnosed with biologically aggressive phenotypes of breast cancer that are negative for the estrogen receptor, the progesterone receptor, and the HER2/neu marker. These tumors are commonly referred to as triple-negative breast cancer. Disparities in breast cancer incidence and outcome related to racial or ethnic identity motivated the establishment of the International Breast Registry, on the basis of partnerships between the Komfo Anokye Teaching Hospital in Kumasi, Ghana, the University of Michigan Comprehensive Cancer Center in Ann Arbor, Michigan, and the Henry Ford Health System in Detroit, Michigan. This research collaborative has featured educational training programs as well as scientific investigations related to the comparative biology of breast cancer in Ghanaian African, African American, and white/European American patients. Currently, the International Breast Registry has expanded to include African American patients throughout the United States by partnering with the Sisters Network (a national African American breast cancer survivors' organization) and additional sites in Ghana (representing West Africa) as well as Ethiopia (representing East Africa). Its activities are now coordinated through the Henry Ford Health System International Center for the Study of Breast Cancer Subtypes. Herein, we review the history and results of this international program at its 10-year anniversary.

Targeting Enhancer of Zeste Homolog 2 as a promising strategy for cancer treatment

Polycomb group proteins represent a global silencing system involved in development regulation. In specific, they regulate the transition from proliferation to differentiation, contributing to stem-cell maintenance and inhibiting an inappropriate activation of differentiation programs. Enhancer of Zeste Homolog 2 (EZH2) is the catalytic subunit of Polycomb repressive complex 2, which induces transcriptional inhibition through the tri-methylation of histone H3, an epigenetic change associated with gene silencing. EZH2 expression is high in precursor cells while its level decreases in differentiated cells. EZH2 is upregulated in various cancers with high levels associated with metastatic cancer and poor prognosis. Indeed, aberrant expression of EZH2 causes the inhibition of several tumor suppressors and differentiation genes, resulting in an uncontrolled proliferation and tumor formation. This editorial explores the role of Polycomb repressive complex 2 in cancer, focusing in particular on EZH2. The canonical function of EZH2 in gene silencing, the non-canonical activities as the methylation of other proteins and the role in gene transcriptional activation, were summarized. Moreover, mutations of EZH2, responsible for an increased methyltransferase activity in cancer, were recapitulated. Finally, various drugs able to inhibit EZH2 with different mechanism were described, specifically underscoring the effects in several cancers, in order to clarify the role of EZH2 and understand if EZH2 blockade could be a new strategy for developing specific therapies or a way to increase sensitivity of cancer cells to standard therapies.

MicroRNA-101 targets EZH2, MCL-1 and FOS to suppress proliferation, invasion and stem cell-like phenotype of aggressive endometrial cancer cells

MicroRNA-101 has been implicated as a tumor suppressor miRNA in human tumors. However, its potential functional impact and the underlying mechanisms in endometrial cancer progression have not been determined. Here, we report that in aggressive endometrial cancer cells, re-expression of microRNA-101 leads to inhibition of cell proliferation and induction of apoptosis and senescence. Ectopic overexpression of microRNA-101 attenuates the epithelial-mesenchymal transition-associated cancer cell migration and invasion, abrogates the sphere-forming capacity and enhances chemosensitivity to paclitaxel. Algorithm and microarray-based strategies identifies potential microRNA-101 targets. Among these, we validated EZH2, MCL-1 and FOS as direct targets of miR-101 and silencing of these genes mimics the tumor suppressive effects observed on promoting microRNA-101 function. Importantly, further results suggest an inverse correlation between low miR-101 and high EZH2, MCL-1 and FOS expression in EC specimens. We conclude that, as a crucial tumor suppressor, microRNA-101 suppresses cell proliferation, invasiveness and self-renewal in aggressive endometrial cancer cells via modulating multiple critical oncogenes. The microRNA-101-EZH2/MCL-1/FOS axis is a potential therapeutic target for endometrial cancer.

Histone methylation modifiers in cellular signaling pathways

Histone methyltransferases and demethylases epigenetically regulate gene expression by modifying histone methylation status in numerous cellular processes, including cell differentiation and proliferation. These modifiers also control methylation levels of various non-histone proteins, such as effector proteins that play critical roles in cellular signaling networks. Dysregulated histone methylation modifiers alter expression of oncogenes and tumor suppressor genes and change methylation states of effector proteins, frequently resulting in aberrant cellular signaling cascades and cellular transformation. In this review, we summarize the role of histone methylation modifiers in regulating the following signaling pathways: NF-κB, RAS/RAF/MEK/MAPK, PI3K/Akt, Wnt/β-catenin, p53, and ERα.

The Polycomb group protein RING1B is overexpressed in ductal breast carcinoma and is required to sustain FAK steady state levels in breast cancer epithelial cells

In early stages of metastasis malignant cells must acquire phenotypic changes to enhance their migratory behavior and their ability to breach the matrix surrounding tumors and blood vessel walls. Epigenetic regulation of gene expression allows the acquisition of these features that, once tumoral cells have escape from the primary tumor, can be reverted. Here we report that the expression of the Polycomb epigenetic repressor Ring1B is enhanced in tumoral cells that invade the stroma in human ductal breast carcinoma and its expression is coincident with that of Fak in these tumors. Ring1B knockdown in breast cancer cell lines revealed that Ring1B is required to sustain Fak expression in basal conditions as well as in Tgfβ-treated cells. Functionally, endogenous Ring1B is required for cell migration and invasion in vitro and for in vivo invasion of the mammary fat pad by tumoral cells. Finally we identify p63 as a target of Ring1B to regulate Fak expression: Ring1B depletion results in enhanced p63 expression, which in turns represses Fak expression. Importantly, Fak downregulation upon Ring1B depletion is dependent on p63 expression. Our findings provide new insights in the biology of the breast carcinoma and open new avenues for breast cancer prognosis and therapy.

Ubiquitin-conjugating enzyme Ubc13 controls breast cancer metastasis through a TAK1-p38 MAP kinase cascade

Metastatic spread is the leading cause of cancer mortality. Breast cancer (BCa) metastatic recurrence can happen years after removal of the primary tumor. Here we show that Ubc13, an E2 enzyme that catalyzes K63-linked protein polyubiquitination, is largely dispensable for primary mammary tumor growth but is required for metastatic spread and lung colonization by BCa cells. Loss of Ubc13 inhibited BCa growth and survival only at metastatic sites. Ubc13 was dispensable for transforming growth factor β (TGFβ)-induced SMAD activation but was required for activation of non-SMAD signaling via TGFβ-activating kinase 1 (TAK1) and p38, whose activity controls expression of numerous metastasis promoting genes. p38 activation restored metastatic activity to Ubc13-deficient cells, and its pharmacological inhibition attenuated BCa metastasis in mice, suggesting it is a therapeutic option for metastatic BCa.

Epigenetic reprogramming in breast cancer: from new targets to new therapies

Breast cancer is the most commonly diagnosed cancer and the second leading cause of cancer death among women in the United States. Recently, interest has grown in the role of epigenetics in breast cancer development and progression. Epigenetic changes such as DNA methylation, histone modifications, and abnormal expression of non-coding RNAs emerged as novel biomarkers in breast cancer diagnosis, therapy, and prevention. This review focuses on the most recent mechanistic findings underlying epigenetic changes in breast cancer development and their role as predictors of breast cancer risk. The rapid progress in our understanding of epigenetic findings in breast cancer has opened new avenues for potential therapeutic approaches via identification of epigenetic targets. We highlight the development of novel epigenetically targeted drugs, relevant clinical trials in breast cancer patients, and recent approaches combining epigenetic agents with chemotherapy and/or endocrine therapy that may incrementally improve long-term outcomes in appropriately selected breast cancer patients. Biomarkers of response are needed, however, to identify patient subsets that are most likely to benefit from epigenetic treatment strategies.

Receptor-interacting protein kinase 2 promotes triple-negative breast cancer cell migration and invasion via activation of nuclear factor-kappaB and c-Jun N-terminal kinase pathways

Introduction

Metastasis is the main cause of breast cancer morbidity and mortality. Processes that allow for tumor cell migration and invasion are important therapeutic targets. Here we demonstrate that receptor-interacting protein kinase 2 (RIP2), a kinase known to be involved in inflammatory processes, also has novel roles in cancer cell migration and invasion.

Methods

A total of six breast cancer expression databases, including The Cancer Genome Atlas, were assessed for RIP2 expression among various clinical subtypes and its role as a prognostic biomarker. mRNA fluorescence in situ hybridization (FISH) for RIP2 was performed on 17 stage III breast cancers to determine if there was a correlation between RIP2 expression and lymph node involvement. RNA-interference was used to knock-down RIP2 expression in MDA-MB-231, Htb126, SUM149PT, MCF7, T47D, and HCC1428 cells. Cell migration and invasion were measured in vitro by scratch/wound healing and transwell migration assays. A xenograft mouse model was used to assess tumor growth and chemosensitivity to docetaxel in vivo in MDA-MB-231 cells with and without RIP2 small hairpin RNA knockdown. Western blot and immunofluorescence imaging were used to evaluate protein expressions.

Results

Interrogation of expression databases showed that RIP2 expression is significantly over-expressed in triple-negative breast cancers (TNBC: estrogen-receptor (ER) negative, progesterone-receptor (PR) negative, Her2/neu- (Her2) negative), compared to other clinical subtypes. High RIP2 expression correlates with worse progression-free survival using a combined breast cancer expression array dataset consisting of 946 patients. Multivariate analysis shows RIP2 as an independent prognostic biomarker. Knock-down of RIP2 significantly decreases migration in both scratch/wound healing and transwell migration assays in MDA-MB-231, Htb126, SUM149PT, MCF7, and T47D cells and is correlated with decreased Nuclear Factor-kappaB and c-Jun N-terminal kinase (JNK) activation. Finally, RIP2 knock-down leads to increased sensitivity to docetaxel and decreased tumor mass and lung metastases in a xenograft mouse model.

Conclusion

These results highlight RIP2 as a pro-metastasis kinase in patients with advanced breast cancer. These results also illustrate a novel role for this kinase in addition to its known role in inflammation, and suggest that targeting RIP2 may improve outcomes in advanced breast cancer patients, in which it is overexpressed.

Histone demethylase RBP2 is critical for breast cancer progression and metastasis

Metastasis is a major clinical challenge for cancer treatment. Emerging evidence suggests that aberrant epigenetic modifications contribute significantly to tumor formation and progression. However, the drivers and roles of such epigenetic changes in tumor metastasis are still poorly understood. Using bioinformatic analysis of human breast cancer gene-expression data sets, we identified histone demethylase RBP2 as a putative mediator of metastatic progression. By using both human breast cancer cells and genetically engineered mice, we demonstrated that RBP2 is critical for breast cancer metastasis to the lung in multiple in vivo models. Mechanistically, RBP2 promotes metastasis as a pleiotropic positive regulator of many metastasis genes, including TNC. In addition, RBP2 loss suppresses tumor formation in MMTV-neu transgenic mice. These results suggest that therapeutic targeting of RBP2 is a potential strategy for inhibition of tumor progression and metastasis.

IL-1β-induced activation of p38 promotes metastasis in gastric adenocarcinoma via upregulation of AP-1/c-fos, MMP2 and MMP9

Background

Interleukin-1β (IL-1β) has been implicated in the progression of gastric adenocarcinoma (GA); however, the molecular mechanisms of action of IL-1β in GA are poorly characterized. P38 and JNK are the major MAPK family members that regulate IL-1β signaling pathways. Here, we investigated the role of both p38 and JNK in IL-1β-induced GA cell migration, invasion and metastatic potential.

Methods

The effects of IL-1β-induced p38 and JNK activation in GA cells were determined using in vitro Transwell migration and invasion assays of MKN-45 and AGS cells, or an in vivo metastasis assay in nude mice. The IL-1β-induced p38 signaling pathway was further characterized in GA cells. Activation of the IL-1β/p38 signaling pathway was also assessed in human primary GA tissues by immunohistochemistry.

Results

IL-1β-induced activation of p38 increased GA cell migration and invasion in vitro and promoted the metastatic potential of GA cells in vivo; these effects were attenuated by p38 siRNA or the p38 inhibitor SB202190. MMP2 or MMP9 siRNAs and the MMP2/9 inhibitor BiPS also inhibited IL-1β-induced GA cell migration and invasion in vitro. IL-1β-induced p38 activation significantly increased MMP2 and MMP9 mRNA and protein expression and activity. Luciferase reporter assays demonstrated that the activator protein-1 (AP-1) and the AP-1 binding sites of the MMP9 promoter (−670/MMP9) were activated by IL-1β-induced p38 activation. Phospho-p38 was significantly upregulated in human GA tissues (compared to matched non-neoplastic tissues), and significantly associated with lymph node metastasis, and invasion beyond the serosa. Expression of phospho-p38 significantly correlated with IL-1β, MMP2, MMP9, and c-fos expression in both human GA tissues and GA cell metastases in the lungs of nude mice. IL-1β was also capable of activating JNK in GA cells, but activation of JNK was not associated with GA cell migration and invasion. Therefore, IL-1β-induced the migration and invasion in GA cells were regulated by p38, but not by JNK.

Conclusions

IL-1β-induced p38 activation and the IL-1β/p38/AP-1(c-fos)/MMP2 & MMP9 pathway play an important role in metastasis in GA; this pathway may provide a novel therapeutic target for GA.

Deregulation of the miRNAs expression in cervical cancer: human papillomavirus implications

MicroRNAs (miRNAs) are a class of small non coding RNAs of 18-25 nucleotides in length. The temporal or short-lived expression of the miRNAs modulates gene expression post transcriptionally. Studies have revealed that miRNAs deregulation correlates and is involved with the initiation and progression of human tumors. Cervical cancer (CC) displays notably increased or decreased expression of a large number of cellular oncogenic or tumor suppressive miRNAs, respectively. However, understanding the potential role of miRNAs in CC is still limited. In CC, the high-risk human papillomaviruses (HR-HPVs) infection can affect the miRNAs expression through oncoprotein E6 and E7 that contribute to viral pathogenesis, although other viral proteins might also be involved. This deregulation in the miRNAs expression has an important role in the hallmarks of CC. Interestingly, the miRNA expression profile in CC can discriminate between normal and tumor tissue and the extraordinary stability of miRNAs makes it suitable to serve as diagnostic and prognostic biomarkers of cancer. In this review, we will summarize the role of the HR-HPVs in miRNA expression, the role of miRNAs in the hallmarks of CC, and the use of miRNAs as potential prognostic biomarkers in CC.