81 results found
Zhang Y, Takahashi Y, Hong SP, et al., 2019, High-resolution label-free 3D mapping of extracellular pH of single living cells, Nature Communications, Vol: 10, ISSN: 2041-1723
Dynamic mapping of extracellular pH (pHe) at the single-cell level is critical for understanding the role of H+ in cellular and subcellular processes, with particular importance in cancer. While several pHe sensing techniques have been developed, accessing this information at the single-cell level requires improvement in sensitivity, spatial and temporal resolution. We report on a zwitterionic label-free pH nanoprobe that addresses these long-standing challenges. The probe has a sensitivity >0.01 units, 2 ms response time, and 50 nm spatial resolution. The technology was incorporated into a double-barrel nanoprobe integrating pH sensing with feedback-controlled distance sensing via Scanning Ion Conductance Microscopy. This allows for the simultaneous 3D topographical imaging and pHe monitoring of living cancer cells. These classes of nanoprobes were used for real-time high spatiotemporal resolution pHe mapping at the subcellular level and revealed tumour heterogeneity of the peri-cellular environments of melanoma and breast cancer cells.
Hong SP, Lombardo Y, Chan TE, et al., 2019, Single-cell transcriptomics reveals multi-step adaptations to endocrine therapy, Nature Communications, Vol: 10, ISSN: 2041-1723
Resistant tumours are thought to arise from the action of Darwinian selection on genetically heterogenous cancer cell populations. However, simple clonal selection is inadequate to describe the late relapses often characterising luminal breast cancers treated with endocrine therapy (ET), suggesting a more complex interplay between genetic and non-genetic factors. Here, we dissect the contributions of clonal genetic diversity and transcriptional plasticity during the early and late phases of ET at single-cell resolution. Using single-cell RNA-sequencing and imaging we disentangle the transcriptional variability of plastic cells and define a rare sub population of pre-adapted (PA) cells which undergoes further transcriptomic reprogramming and copy number changes to acquire full resistance. We find evidence for sub-clonal expression of a PA signature in primary tumours and for dominant expression in clustered circulating tumour cells. We propose a multi-step model for ET resistance development and advocate the use of stage-specific biomarkers.
Perone Y, Farrugia AJ, Rodriguez-Meira A, et al., 2019, SREBP1 drives keratin-80-dependent cytoskeletal changes and invasive behavior in endocrine-resistant ER alpha breast cancer (vol 10, 2115, 2019), NATURE COMMUNICATIONS, Vol: 10, ISSN: 2041-1723
Ottaviani S, Stebbing J, Frampton AE, et al., 2019, Author Correction: TGF-beta induces miR-100 and miR-125b but blocks let-7a through LIN28B controlling PDAC progression, Nature Communications, Vol: 10, ISSN: 2041-1723
Nguyen VTM, Barozzi I, Faronato M, et al., 2019, Author Correction: Differential epigenetic reprogramming in response to specific endocrine therapies promotes cholesterol biosynthesis and cellular invasion, Nature Communications, Vol: 10, ISSN: 2041-1723
Perone Y, Farrugia AJ, Meira AR, et al., 2019, SREBP1 drives Keratin 80-dependent cytoskeletal changes and invasive behavior in endocrine resistant ERα breast cancer, Nature Communications, Vol: 10, ISSN: 2041-1723
Approximately 30% of ERα breast cancer patients relapse with metastatic disease following adjuvant endocrine therapies. The connection between acquisition of drug resistance and invasive potential is poorly understood. In this study, we demonstrate that the type II keratin topological associating domain undergoes epigenetic reprogramming in aromatase inhibitors (AI)-resistant cells, leading to Keratin-80 (KRT80) upregulation. KRT80 expression is driven by de novo enhancer activation by sterol regulatory element-binding protein 1 (SREBP1). KRT80 upregulation directly promotes cytoskeletal rearrangements at the leading edge, increased focal adhesion and cellular stiffening, collectively promoting cancer cell invasion. Shearwave elasticity imaging performed on prospectively recruited patients confirms KRT80 levels correlate with stiffer tumors. Immunohistochemistry showed increased KRT80-positive cells at relapse and, using several clinical endpoints, KRT80 expression associates with poor survival. Collectively, our data uncover an unpredicted and potentially targetable direct link between epigenetic and cytoskeletal reprogramming promoting cell invasion in response to chronic AI treatment.
Perone Y, Rodríguez Meira A, Farruggia A, et al., 2019, OR34-2 SREBP1 Drives KRT80-Dependent Cytoskeletal Changes and Invasive Behaviour in Endocrine-Resistant ERα Breast Cancer, Journal of the Endocrine Society, Vol: 3
Varghese V, Magnani L, Harada N, et al., 2019, FOXM1 modulates 5-FU resistance in colorectal cancer through regulating TYMS expression, Scientific Reports, Vol: 9, ISSN: 2045-2322
Resistance to 5-Fluoruracil (5-FU) has been linked to elevated expression of the main target, thymidylate synthase (TYMS), which catalyses the de novo pathway for production of deoxythymidine monophosphate. The potent oncogenic forkhead box transcription factor, FOXM1 is is regulated by E2F1 which also controls TYMS. This study reveals a significant role of FOXM1 in 5-FU resistance. Overexpression and knock-down studies of FOXM1 in colon cancer cells suggest the importance of FOXM1 in TYMS regulation. ChIP and global ChIP-seq data also confirms that FOXM1 can also potentially regulate other 5-FU targets, such as TYMS, thymidine kinase 1 (TK-1) and thymidine phosphorylase (TYMP). In human colorectal cancer tissue specimens, a strong correlation of FOXM1 and TYMS staining was observed. Elevated FOXM1 and TYMS expression was also observed in acquired 5-FU resistant colon cancer cells (HCT116 5-FU Res). A synergistic effect was observed following treatment of CRC cells with an inhibitor of FOXM1, thiostrepton, in combination with 5-FU. The combination treatment decreased colony formation and migration, and induced cell cycle arrest, DNA damage, and apoptosis in CRC cell lines. In summary, this research demonstrated that FOXM1 plays a pivotal role in 5-FU resistance at least partially through the regulation of TYMS.
Ferrari N, Ranftl R, Chicherova I, et al., 2019, Dickkopf-3 links HSF1 and YAP/TAZ signalling to control aggressive behaviours in cancer-associated fibroblasts, Nature Communications, Vol: 10, ISSN: 2041-1723
Aggressive behaviours of solid tumours are highly influenced by the tumour microenvironment. Multiple signalling pathways can affect the normal function of stromal fibroblasts in tumours, but how these events are coordinated to generate tumour-promoting cancer-associated fibroblasts (CAFs) is not well understood. Here we show that stromal expression of Dickkopf-3 (DKK3) is associated with aggressive breast, colorectal and ovarian cancers. We demonstrate that DKK3 is a HSF1 effector that modulates the pro-tumorigenic behaviour of CAFs in vitro and in vivo. DKK3 orchestrates a concomitant activation of β-catenin and YAP/TAZ. Whereas β-catenin is dispensable for CAF-mediated ECM remodelling, cancer cell growth and invasion, DKK3-driven YAP/TAZ activation is required to induce tumour-promoting phenotypes. Mechanistically, DKK3 in CAFs acts via canonical Wnt signalling by interfering with the negative regulator Kremen and increasing cell-surface levels of LRP6. This work reveals an unpredicted link between HSF1, Wnt signalling and YAP/TAZ relevant for the generation of tumour-promoting CAFs.
Patten DK, Corleone G, Győrffy B, et al., 2018, Enhancers mapping uncovers phenotypic heterogeneity and evolution in patients with luminal breast cancer, Nature Medicine, Vol: 24, Pages: 1469-1480, ISSN: 1078-8956
The degree of intrinsic and interpatient phenotypic heterogeneity and its role in tumor evolution is poorly understood. Phenotypic drifts can be transmitted via inheritable transcriptional programs. Cell-type specific transcription is maintained through the activation of epigenetically defined regulatory regions including promoters and enhancers. Here we have annotated the epigenome of 47 primary and metastatic estrogen-receptor (ERα)-positive breast cancer clinical specimens and inferred phenotypic heterogeneity from the regulatory landscape, identifying key regulatory elements commonly shared across patients. Shared regions contain a unique set of regulatory information including the motif for transcription factor YY1. We identify YY1 as a critical determinant of ERα transcriptional activity promoting tumor growth in most luminal patients. YY1 also contributes to the expression of genes mediating resistance to endocrine treatment. Finally, we used H3K27ac levels at active enhancer elements as a surrogate of intra-tumor phenotypic heterogeneity to track the expansion and contraction of phenotypic subpopulations throughout breast cancer progression. By tracking the clonality of SLC9A3R1-positive cells, a bona fide YY1-ERα-regulated gene, we show that endocrine therapies select for phenotypic clones under-represented at diagnosis. Collectively, our data show that epigenetic mechanisms significantly contribute to phenotypic heterogeneity and evolution in systemically treated breast cancer patients.
Ottaviani S, Stebbing J, Frampton AE, et al., 2018, TGF-beta induces miR-100 and miR-125b but blocks let-7a through LIN28B controlling PDAC progression, Nature Communications, Vol: 9, ISSN: 2041-1723
TGF-β/Activin induces epithelial-to-mesenchymal transition and stemness in pancreatic ductal adenocarcinoma (PDAC). However, the microRNAs (miRNAs) regulated during this response have remained yet undetermined. Here, we show that TGF-β transcriptionally induces MIR100HG lncRNA, containing miR-100, miR-125b and let-7a in its intron, via SMAD2/3. Interestingly, we find that although the pro-tumourigenic miR-100 and miR-125b accordingly increase, the amount of anti-tumourigenic let-7a is unchanged, as TGF-β also induces LIN28B inhibiting its maturation. Notably, we demonstrate that inactivation of miR-125b or miR-100 affects the TGF-β-mediated response indicating that these miRNAs are important TGF-β effectors. We integrate AGO2-RIP-seq with RNA-seq to identify the global regulation exerted by these miRNAs in PDAC cells. Transcripts targeted by miR-125b and miR-100 significantly overlap and mainly inhibit p53 and cell–cell junctions’ pathways. Together, we uncover that TGF-β induces an lncRNA, whose encoded miRNAs, miR-100, let-7a and miR-125b play opposing roles in controlling PDAC tumourigenesis.
Noberini R, Osti D, Miccolo C, et al., 2018, Extensive and systematic rewiring of histone post-translational modifications in cancer model systems, Nucleic Acids Research, Vol: 46, Pages: 3817-3832, ISSN: 0305-1048
Histone post-translational modifications (PTMs) generate a complex combinatorial code that regulates gene expression and nuclear functions, and whose deregulation has been documented in different types of cancers. Therefore, the availability of relevant culture models that can be manipulated and that retain the epigenetic features of the tissue of origin is absolutely crucial for studying the epigenetic mechanisms underlying cancer and testing epigenetic drugs. In this study, we took advantage of quantitative mass spectrometry to comprehensively profile histone PTMs in patient tumor tissues, primary cultures and cell lines from three representative tumor models, breast cancer, glioblastoma and ovarian cancer, revealing an extensive and systematic rewiring of histone marks in cell culture conditions, which includes a decrease of H3K27me2/me3, H3K79me1/me2 and H3K9ac/K14ac, and an increase of H3K36me1/me2. While some changes occur in short-term primary cultures, most of them are instead time-dependent and appear only in long-term cultures. Remarkably, such changes mostly revert in cell line- and primary cell-derived in vivo xenograft models. Taken together, these results support the use of xenografts as the most representative models of in vivo epigenetic processes, suggesting caution when using cultured cells, in particular cell lines and long-term primary cultures, for epigenetic investigations.
Magnani L, Frige G, Gadaleta RM, et al., 2017, Corrigendum: Acquired CYP19A1 amplification is an early specific mechanism of aromatase inhibitor resistance in ER alpha metastatic breast cancer, Nature Genetics, Vol: 49, Pages: 970-970, ISSN: 1061-4036
Magnani L, Frige G, Gadaleta RM, et al., 2017, Acquired CYP19A1 amplification is an early specific mechanism of aromatase inhibitor resistance in ERα metastatic breast cancer, Nature Genetics, Vol: 49, Pages: 444-450, ISSN: 1546-1718
Tumor evolution is shaped by many variables, potentially involving external selective pressures induced by therapies1. After surgery, estrogen receptor (ERα) positive breast cancer (BCa) patients are treated with adjuvant endocrine therapy2including selective estrogen receptor modulators (SERMs) and/or aromatase inhibitors (AIs)3. However, over 20% of patients relapse within 10 years and eventually progress to incurable metastatic disease4. Here we demonstratethat the choice of therapy has a fundamental influence on the genetic landscape of relapsed diseases: in this study, 21.5% of AI-treated, relapsed patients had acquiredCYP19A1gene (aromatase) amplification (CYP19A1amp). Relapsed patients also developed numerous mutations targeting key breast cancer genes including ESR1 and CYP19A1. Strikingly, CYP19A1amp cells also emerge in vitrobut only in AI resistant models. CYP19A1 amplification causesincreased aromatase activity and estrogen-independent ERα binding to target genesresulting inCYP19A1amp cells displaying decreased sensitivity to AI treatment. Collectively these data suggest that AI treatment itself selects for acquiredCYP19A1 amplification and promotes local autocrine estrogen signalling in AI resistant metastatic patients.
Magnani L, Patten DK, 2017, Fundamental pathways in breast cancer 3: Estrogen biology, Breast Cancer: Innovations in Research and Management, Pages: 19-26, ISBN: 9783319488462
© Springer International Publishing AG 2017. Over the last two decades, it has become evident that breast cancer should be considered as a family of diseases rather than as a unique malignancy. Pathological, molecular, and genetic analysis have revealed the existence of five to ten main subgroups [1-3]. Over 70% of all patients are generally classified by the tumor dependencies on estrogenic compounds . These dependencies are principally mediated by the nuclear receptor estrogen receptor a (ERa) [5, 6]. For all these reasons, ERa remains the key driver in the majority of breast cancers and is commonly used as a molecular biomarker for stratification while serving as the main target for systemic adjuvant chemotherapy. In this chapter I will discuss the molecular mechanisms of ERa activation focusing on integrative analysis that have recently exposed the intimate link between ERa and chromatin structure.
Harrod A, Fulton J, Nguyen VTM, et al., 2016, Genomic modelling of the ESR1 Y537S mutation for evaluating function and new therapeutic approaches for metastatic breast cancer, Oncogene, Vol: 36, Pages: 2286-2296, ISSN: 1476-5594
Drugs that inhibit estrogen receptor-α (ER) activity have been highlysuccessful in treating and reducing breast cancer progression in ER-positivedisease. However, resistance to these therapies presents a major clinicalproblem. Recent genetic studies have shown that mutations in the ER geneare found in >20% of tumours that progress on endocrine therapies.Remarkably, the great majority of these mutations localise to just a few aminoacids within or near the critical helix 12 region of the ER hormone bindingdomain, where they are likely to be single allele mutations. Understandinghow these mutations impact on ER function is a prerequiste for identifyingmethods to treat breast cancer patients featuring such mutations. Towardsthis end, we used CRISPR-Cas9 genome editing to make a single alleleknockin of the most commonly mutated amino acid residue, tyrosine 537, inthe estrogen-responsive MCF7 breast cancer cell line. Genomic analysesusing RNA-seq and ER ChIP-seq demonstrated that the Y537S mutationpromotes constitutive ER activity globally, resulting in estrogen-independentgrowth. MCF7-Y537S cells were resistant to the anti-estrogen tamoxifen andfulvestrant. Further, we show that the basal transcription factor TFIIH isconstitutively recruited by ER-Y537S, resulting in ligand-independentphosphorylation of Serine 118 (Ser118) by the TFIIH kinase, CDK7. TheCDK7 inhibitor, THZ1 prevented Ser118 phosphorylation and inhibited growthof MCF7-Y537S cells. These studies confirm the functional importance of ERmutations in endocrine resistance, demonstrate the utility of knockinmutational models for investigating alternative therapeutic approaches andhighlight CDK7 inhibition as a potential therapy for endocrine resistant breastcancer mediated by ER mutations.
Menyhárt O, Harami-Papp H, Sukumar S, et al., 2016, Guidelines for the selection of functional assays to evaluate the hallmarks of cancer, Biochimica et Biophysica Acta-Reviews on Cancer, Vol: 1866, Pages: 300-319, ISSN: 0304-419X
The hallmarks of cancer capture the most essential phenotypic characteristics of malignant transformation and progression. Although numerous factors involved in this multi-step process are still unknown to date, an ever-increasing number of mutated/altered candidate genes are being identified within large-scale cancer genomic projects. Therefore, investigators need to be aware of available and appropriate techniques capable of determining characteristic features of each hallmark.We review the methods tailored to experimental cancer researchers to evaluate cell proliferation, programmed cell death, replicative immortality, induction of angiogenesis, invasion and metastasis, genome instability, and reprogramming of energy metabolism. Selecting the ideal method is based on the investigator's goals, available equipment and also on financial constraints. Multiplexing strategies enable a more in-depth data collection from a single experiment — obtaining several results from a single procedure reduces variability and saves time and relative cost, leading to more robust conclusions compared to a single end point measurement. Each hallmark possesses characteristics that can be analyzed by immunoblot, RT-PCR, immunocytochemistry, immunoprecipitation, RNA microarray or RNA-seq. In general, flow cytometry, fluorescence microscopy, and multiwell readers are extremely versatile tools and, with proper sample preparation, allow the detection of a vast number of hallmark features. Finally, we also provide a list of hallmark-specific genes to be measured in transcriptome-level studies.Although our list is not exhaustive, we provide a snapshot of the most widely used methods, with an emphasis on methods enabling the simultaneous evaluation of multiple hallmark features.
Perone Y, Magnani L, 2016, Going off the grid: ERα breast cancer beyond estradiol, Journal of Molecular Endocrinology, Vol: 57, Pages: F1-F5, ISSN: 1479-6813
Novel studies have linked cholesterol biosynthesis to drug resistance in luminal breast cancer. Structural data suggest that cholesterol metabolites, including 27-hydroxycholesterol (27-HC), can act as ERα ligands in these cells. Additionally, hypercholesterolemia has now been linked to breast cancer progression. The focus of this review is to briefly summarize these recent finding and discuss how epigenetic reprogramming is definitively connected to endogenous cholesterol biosynthesis. We elaborate on how these data support a working model in which cholesterol biosynthesis promotes autocrine, pro- invasive signaling via activation of a series of closely related transcription factors. Importantly, we discuss how this mechanism of resistance is specifically associated with aromatase inhibitors. Finally, we examine how the field is now considering the development of anti-cholesterol therapeutics and companion biomarkers to stratify and treat ERα breast cancer patients. In particular, we review recent progress in pharmaceutical strategies targeting the cholesterol molecular machinery in primary and secondary breast cancers.
Patel H, Abduljabbar R, Lai CF, et al., 2016, CDK7, cyclin H and MAT1 is elevated in breast cancer and is prognostic in estrogen receptor- positive breast cancer, Clinical Cancer Research, Vol: 22, Pages: 5929-5938, ISSN: 1557-3265
PURPOSE: CDK-activation kinase (CAK) is required for the regulation of the cell-cycle and is a trimeric complex consisting of Cyclin Dependent Kinase 7 (CDK7), Cyclin H and the accessory protein, MAT1. CDK7 also plays a critical role in regulating transcription, primarily by phosphorylating RNA polymerase II, as well as transcription factors such as estrogen receptor-alpha(ERalpha).). Deregulation of cell cycle and transcriptional control is aare general featurefeatures of cancertumor cells, highlighting the potential for the use of CDK7 inhibitors as novel cancer therapeutics in cancer. EXPERIMENTAL DESIGN: mRNA and protein expression of CDK7 and its essential co-factors cyclinH and MAT1, were evaluated in breast cancer samples to determine if their levels are altered in cancer. Immunohistochemical staining of >900 breast cancers was used to determine the association with clinicopathological features and patient outcome. RESULTS: We show that expression of CDK7, cyclinH and MAT1 are all closely linked at the mRNA and protein level and their expression is elevated in breast cancer compared with the normal breast tissue. Intriguingly, CDK7 expression was inversely proportional to tumour grade and size and outcome analysis showed an association between CAK levels and better outcome. Moreover, CDK7 expression was positively associated with ERalpha expression and in particular with phosphorylation of ERalpha at serine 118, a site important for ERalpha transcriptional activity. CONCLUSIONS: Expression of components of the CAK complex, CDK7, MAT1 and Cyclin H are elevated in breast cancer and correlates with ERalpha.. Like ERalpha, CDK7 expression is inversely proportional to poor prognostic factors and survival.
Bhat-Nakshatri P, Goswami CP, Badve S, et al., 2016, Molecular insights of pathways resulting from two common PIK3CA mutations in breast cancer, Cancer Research, Vol: 76, Pages: 3989-4001, ISSN: 1538-7445
The phosphatidylinositol 3-kinase (PI3K) pathway is activated in ~70% of breast cancers. PIK3CA gene mutations or amplifications that affect the PI3K p110α subunit account for activation of this pathway in 20-40% of cases, particularly in estrogen-receptor alpha (ERα)-positive breast cancers. AKT family of kinases, AKT1-3, are the downstream targets of PI3K and these kinases activate ERα. Although several inhibitors of PI3K have been developed, none has proven effective in the clinic, partly due to an incomplete understanding of the selective routing of PI3K signaling to specific AKT isoforms. Accordingly, we investigated in this study the contribution of specific AKT isoforms in connecting PI3K activation to ERα signaling, and we also assessed the utility of using the components of PI3K-AKT isoform-ERα signaling axis as predictive biomarkers of response to PI3K inhibitors. Using a variety of physiologically relevant model systems with defined natural or knock-in PIK3CA mutations and/or PI3K hyperactivation, we show that PIK3CA-E545K mutations (found in ~20% of PIK3CA-mutant breast cancers), but not PIK3CA-H1047R mutations (found in 55% of PIK3CA-mutant breast cancers), preferentially activate AKT1. Our findings argue that AKT1 signaling is needed to respond to estrogen and PI3K inhibitors in breast cancer cells with PIK3CA-E545K mutation, but not in breast cancer cells with other PIK3CA mutations. This study offers evidence that personalizing treatment of ER-positive breast cancers to PI3K inhibitor therapy may benefit from an analysis of PIK3CA-E545K-AKT1-estrogen signaling pathways.
Zhang Y, Clausmeyer J, Babakinejad B, et al., 2016, Spearhead Nanometric Field-Effect Transistor Sensors for Single-Cell Analysis., ACS Nano, Vol: 10, Pages: 3214-3221, ISSN: 1936-086X
Nanometric field-effect-transistor (FET) sensors are made on the tip of spear-shaped dual carbon nanoelectrodes derived from carbon deposition inside double-barrel nanopipettes. The easy fabrication route allows deposition of semiconductors or conducting polymers to comprise the transistor channel. A channel from electrodeposited poly pyrrole (PPy) exhibits high sensitivity toward pH changes. This property is exploited by immobilizing hexokinase on PPy nano-FETs to give rise to a selective ATP biosensor. Extracellular pH and ATP gradients are key biochemical constituents in the microenvironment of living cells; we monitor their real-time changes in relation to cancer cells and cardiomyocytes. The highly localized detection is possible because of the high aspect ratio and the spear-like design of the nano-FET probes. The accurately positioned nano-FET sensors can detect concentration gradients in three-dimensional space, identify biochemical properties of a single living cell, and after cell membrane penetration perform intracellular measurements.
Magnani L, Louloupi A, Zwart W, 2016, Histone Posttranslational Modifications in Breast Cancer and Their Use in Clinical Diagnosis and Prognosis, Epigenetic Biomarkers and Diagnostics, Pages: 467-477, ISBN: 9780128018996
© 2016 Elsevier Inc. All rights reserved. Epigenetic regulation plays a key role in normal physiology and disease. In breast cancer, multiple epigenetic regulators have been found to be causally involved in tumorigenesis and treatment resistance. Since treatment resistance in breast cancer is commonly observed, epigenetic modifiers may represent promising targets for pharmaceutical intervention. Multiple epigenetic modifiers are currently being targeted in clinical trials with varying success rates. Yet, biological roles of epigenetic modifiers are complex and lack tissue specificity, which may diminish any therapeutic window. Is epigenetic profiling the "new black" of biomarker discovery in breast cancer? and would epigenetic drugs yield the new "silver bullet" in breast cancer treatment, or are we dealing with a "red herring"?
Chen X, Jung JG, Shajahan-Haq AN, et al., 2015, ChIP-BIT: Bayesian inference of target genes using a novel joint probabilistic model of ChIP-seq profiles., Nucleic Acids Research, Vol: 44, ISSN: 1362-4962
Chromatin immunoprecipitation with massively parallel DNA sequencing (ChIP-seq) has greatly improved the reliability with which transcription factor binding sites (TFBSs) can be identified from genome-wide profiling studies. Many computational tools are developed to detect binding events or peaks, however the robust detection of weak binding events remains a challenge for current peak calling tools. We have developed a novel Bayesian approach (ChIP-BIT) to reliably detect TFBSs and their target genes by jointly modeling binding signal intensities and binding locations of TFBSs. Specifically, a Gaussian mixture model is used to capture both binding and background signals in sample data. As a unique feature of ChIP-BIT, background signals are modeled by a local Gaussian distribution that is accurately estimated from the input data. Extensive simulation studies showed a significantly improved performance of ChIP-BIT in target gene prediction, particularly for detecting weak binding signals at gene promoter regions. We applied ChIP-BIT to find target genes from NOTCH3 and PBX1 ChIP-seq data acquired from MCF-7 breast cancer cells. TF knockdown experiments have initially validated about 30% of co-regulated target genes identified by ChIP-BIT as being differentially expressed in MCF-7 cells. Functional analysis on these genes further revealed the existence of crosstalk between Notch and Wnt signaling pathways.
Nguyen VTM, Barozzi I, Faronato M, et al., 2015, Differential epigenetic reprogramming in response to specific endocrine therapies promotes cholesterol biosynthesis and cellular invasion, Nature Communications, Vol: 6, ISSN: 2041-1723
Endocrine therapies target the activation of the oestrogen receptor alpha (ERa) via distinctmechanisms, but it is not clear whether breast cancer cells can adapt to treatment usingdrug-specific mechanisms. Here we demonstrate that resistance emerges via drug-specificepigenetic reprogramming. Resistant cells display a spectrum of phenotypical changes withinvasive phenotypes evolving in lines resistant to the aromatase inhibitor (AI). Orthogonalgenomics analysis of reprogrammed regulatory regions identifies individual drug-inducedepigenetic states involving large topologically associating domains (TADs) and the activationof super-enhancers. AI-resistant cells activate endogenous cholesterol biosynthesis (CB)through stable epigenetic activation in vitro and in vivo. Mechanistically, CB sparks theconstitutive activation of oestrogen receptors alpha (ERa) in AI-resistant cells, partly via thebiosynthesis of 27-hydroxycholesterol. By targeting CB using statins, ERa binding is reducedand cell invasion is prevented. Epigenomic-led stratification can predict resistance to AI in asubset of ERa-positive patients.
Ali S, Periyasamy M, Patel H, et al., 2015, APOBEC3B mediated cytidine deamination is required for estrogen receptor action in breast cancer, Cell Reports, Vol: 13, Pages: 108-121, ISSN: 2211-1247
Estrogen receptor α (ERα) is the key transcriptional driver in a large proportion of breast cancers. We report that APOBEC3B (A3B) is required for regulation of gene expression by ER and acts by causing C-to-U deamination at ER binding regions. We show that these C-to-U changes lead to the generation of DNA strand breaks through activation of base excision repair (BER) and to repair by non-homologous end-joining (NHEJ) pathways. We provide evidence that transient cytidine deamination by A3B aids chromatin modification and remodelling at the regulatory regions of ER target genes that promotes their expression. A3B expression is associated with poor patient survival in ER+ breast cancer, reinforcing the physiological significance of A3B for ER action.
Xu Y, Zhang H, Van TMN, et al., 2015, LMTK3 represses tumor suppressor-like genes through chromatin remodeling in breast cancer, Cell Reports, Vol: 12, Pages: 837-849, ISSN: 2211-1247
LMTK3 is an oncogenic receptor tyrosine kinase (RTK) implicated in various types of cancer, including breast, lung, gastric, and colorectal cancer. It is localized in different cellular compartments, but its nuclear function has not been investigated so far. We mapped LMTK3 binding across the genome using ChIP-seq and found that LMTK3 binding events are correlated with repressive chromatin markers. We further identified KRAB-associated protein 1 (KAP1) as a binding partner of LMTK3. The LMTK3/KAP1 interaction is stabilized by PP1α, which suppresses KAP1 phosphorylation specifically at LMTK3-associated chromatin regions, inducing chromatin condensation and resulting in transcriptional repression of LMTK3-bound tumor suppressor-like genes. Furthermore, LMTK3 functions at distal regions in tethering the chromatin to the nuclear periphery, resulting in H3K9me3 modification and gene silencing. In summary, we propose a model where a scaffolding function of nuclear LMTK3 promotes cancer progression through chromatin remodeling.
Magnani L, Patten DK, Nguyen VTM, et al., 2015, The pioneer factor PBX1 is a novel driver of metastatic progression in ERα-positive breast cancer., Oncotarget, Vol: 6, Pages: 21878-24891, ISSN: 1949-2553
Over 30% of ERα breast cancer patients develop relapses and progress to metastatic disease despite treatment with endocrine therapies. The pioneer factor PBX1 translates epigenetic cues and mediates estrogen induced ERα binding. Here we demonstrate that PBX1 plays a central role in regulating the ERα transcriptional response to epidermal growth factor (EGF) signaling. PBX1 regulates a subset of EGF-ERα genes highly expressed in aggressive breast tumours. Retrospective stratification of luminal patients using PBX1 protein levels in primary cancer further demonstrates that elevated PBX1 protein levels correlate with earlier metastatic progression. In agreement, PBX1 protein levels are significantly upregulated during metastatic progression in ERα-positive breast cancer patients. Finally we reveal that PBX1 upregulation in aggressive tumours is partly mediated by genomic amplification of the PBX1 locus. Correspondingly, ERα-positive breast cancer patients carrying PBX1 amplification are characterized by poor survival. Notably, we demonstrate that PBX1 amplification can be identified in tumor derived-circulating free DNA of ERα-positive metastatic patients. Metastatic patients with PBX1 amplification are also characterized by shorter relapse-free survival. Our data identifies PBX1 amplification as a functional hallmark of aggressive ERα-positive breast cancers. Mechanistically, PBX1 amplification impinges on several critical pathways associated with aggressive ERα-positive breast cancer.
Faronato M, Nguyen VTM, Patten DK, et al., 2015, DMXL2 drives epithelial to mesenchymal transition in hormonal therapy resistant breast cancer through Notch hyper-activation, Oncotarget, Vol: 6, Pages: 22467-22479, ISSN: 1949-2553
The acquisition of endocrine therapy resistance in estrogen receptor α (ERα) breast cancer patients represents a major clinical problem. Notch signalling has been extensively linked to breast cancer especially in patients who fail to respond to endocrine therapy. Following activation, Notch intracellular domain is released and enters the nucleus where activates transcription of target genes. The numerous steps that cascade after activation of the receptor complicate using Notch as biomarker. Hence, this warrants the development of reliable indicators of Notch activity. DMXL2 is a novel regulator of Notch signalling not yet investigated in breast cancer. Here, we demonstrate that DMXL2 is overexpressed in a subset of endocrine therapy resistant breast cancer cell lines where it promotes epithelial to mesenchymal transition through hyper-activation of Notch signalling via V-ATPase dependent acidification. Following DMXL2 depletion or treatment with Bafilomycin A1, both EMT targets and Notch signalling pathway significantly decrease. We show for the first time that DMXL2 protein levels are significantly increased in ERα positive breast cancer patients that progress after endocrine therapy. Finally, we demonstrate that DMXL2 is a transmembrane protein with a potential extra-cellular domain. These findings identify DMXL2 as a novel, functional biomarker for ERα positive breast cancer.
Okamoto OK, Matheu A, Magnani L, 2015, Stem cells in translational cancer research, Stem Cells International, Vol: 2015, ISSN: 1687-9678
Nakshatri H, Goswami C, Badve S, et al., 2015, Divergent activation of AKT1 and AKT2 isoforms downstream of PI3K mutation impacts response of breast cancer cells to estradiol and PI3K inhibitors, 37th Annual CTRC-AACR San Antonio Breast Cancer Symposium, Publisher: AMER ASSOC CANCER RESEARCH, ISSN: 0008-5472
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