Synthesis and evaluation of carbocyanine dyes as PRMT inhibitors and imaging agents

Synthesis and photo-induced anticancer activity of new 2-phenylethenyl-1H-benzo[e]indole dyes

Herein, a series of new 1,1,2-trimethyl-1H-benzo[e]indole dyes was prepared via Knoevenagel condensation reaction between 1,1,2-trimethyl-1H-benzo[e]indole and benzaldehydes, and characterized using various spectroscopic methods. The obtained compounds showed cytotoxic properties in G361 melanoma cell line upon irradiation with 414 nm blue light at submicromolar doses. The mechanism of action of the most potent compound 15 was further investigated. The treatment induced substantial generation of reactive oxygen species, leading to DNA damage followed by cell death depending on the concentration of the photosensitizer compound and the irradiation intensity.

Overview of PRMT1 modulators: Inhibitors and degraders

Protein arginine methyltransferase 1 (PRMT1) is pivotal in executing normal cellular functions through its catalytic action on the methylation of arginine side chains on protein substrates. Emerging research has revealed a correlation between the dysregulation of PRMT1 expression and the initiation and progression of tumors, significantly influence on patient prognostication, attributed to the essential role played by PRMT1 in a number of biological processes, including transcriptional regulation, signal transduction or DNA repair. Therefore, PRMT1 emerged as a promising therapeutic target for anticancer drug discovery in the past decade. In this review, we first summarize the structure and biological functions of PRMT1 and its association with cancer. Next, we focus on the recent advances in the design and development of PRMT1 modulators, including isoform-selective PRMT1 inhibitors, pan type I PRMT inhibitors, PRMT1-based dual-target inhibitors, and PRMT1-targeting PROTAC degraders, from the perspectives of rational design, pharmacodynamics, pharmacokinetics, and clinical status. Finally, we discuss the challenges and future directions for PRMT1-based drug discovery for cancer therapy.

Biomimetic NIR-II fluorescent proteins created from chemogenic protein-seeking dyes for multicolor deep-tissue bioimaging

Near-infrared-I/II fluorescent proteins (NIR-I/II FPs) are crucial for in vivo imaging, yet the current NIR-I/II FPs face challenges including scarcity, the requirement for chromophore maturation, and limited emission wavelengths (typically < 800 nm). Here, we utilize synthetic protein-seeking NIR-II dyes as chromophores, which covalently bind to tag proteins (e.g., human serum albumin, HSA) through a site-specific nucleophilic substitution reaction, thereby creating proof-of-concept biomimetic NIR-II FPs. This chemogenic protein-seeking strategy can be accomplished under gentle physiological conditions without catalysis. Proteomics analysis identifies specific binding site (Cys 477 on DIII). NIR-II FPs significantly enhance chromophore brightness and photostability, while improving biocompatibility, allowing for high-performance NIR-II lymphography and angiography. This strategy is universal and applicable in creating a wide range of spectrally separated NIR-I/II FPs for real-time visualization of multiple biological events. Overall, this straightforward biomimetic approach holds the potential to transform fluorescent protein-based bioimaging and enables in-situ albumin targeting to create NIR-I/II FPs for deep-tissue imaging in live organisms.

Site-specific albumin tagging with NIR-II fluorogenic dye for high-performance and super-stable bioimaging

Synthetic near-infrared-II (NIR-II) dyes are promising for deep tissue imaging, yet they are generally difficult to target a given biomolecule with high specificity. Furthermore, the interaction mechanism between albumin and cyanine molecules, which is usually regarded as uncertain "complexes" such as crosslinked nanoparticles, remains poorly understood. Methods: Here, we propose a new class of NIR-II fluorogenic dyes capable of site-specific albumin tagging for in situ albumin seeking/targeting or constructing high-performance cyanine@albumin probes. We further investigate the interaction mechanism between NIR-II fluorogenic dyes and albumin. Results: We identify CO-1080 as an optimal dye structure that produces a stable/bright NIR-II cyanine@albumin probe. CO-1080 exhibits maximum supramolecular binding affinity to albumin while catalyzing their covalent attachment. The probe shows exact binding sites located on Cys476 and Cys101, as identified by proteomic analysis and docking modeling. Conclusion: Our cyanine@albumin probe substantially improves the pharmacokinetics of its free dye counterpart, enabling high-performance NIR-II angiography and lymphography. Importantly, the site-specific labeling tags between NIR-II fluorogenic dyes and albumin occur under mild conditions, offering a specific and straightforward synthesis strategy for NIR-II fluorophores in the fields of targeting bioimaging and imaging-guided surgery.

Transition-Metal-Free Synthesis of 2-Substituted Benzo[cd]Indoles via the Reaction of 1-Halo-8-lithionaphthalenes with Nitriles

A simple and effective organolithium approach to the synthesis of 2-substituted benzo[cd]indoles from peri-dihalonaphthalenes and nitriles has been developed. The reaction proceeds via a surprisingly easy intramolecular aromatic nucleophilic substitution facilitated by the "clothespin effect". The discovered transformation provides good isolated yields, allows usage of an extensive range of nitriles, and demonstrates a good substituents tolerance. UV-absorption and NMR spectra of the obtained benzo[cd]indoles and their protonated forms demonstrated exclusive protonation to the indole nitrogen atom even in the presence of two NMe2 groups in positions 5 and 6 (i. e. "proton sponge" moiety).

Chemical probes and methods for the study of protein arginine methylation

Protein arginine methylation is a widespread post-translational modification (PTM) in eukaryotic cells. This chemical modification in proteins functionally modulates diverse cellular processes from signal transduction, gene expression, and DNA damage repair to RNA splicing. The chemistry of arginine methylation entails the transfer of the methyl group from S-adenosyl-l-methionine (AdoMet, SAM) onto a guanidino nitrogen atom of an arginine residue of a target protein. This reaction is catalyzed by about 10 members of protein arginine methyltransferases (PRMTs). With impacts on a variety of cellular processes, aberrant expression and activity of PRMTs have been shown in many disease conditions. Particularly in oncology, PRMTs are commonly overexpressed in many cancerous tissues and positively correlated with tumor initiation, development and progression. As such, targeting PRMTs is increasingly recognized as an appealing therapeutic strategy for new drug discovery. In the past decade, a great deal of research efforts has been invested in illuminating PRMT functions in diseases and developing chemical probes for the mechanistic study of PRMTs in biological systems. In this review, we provide a brief developmental history of arginine methylation along with some key updates in arginine methylation research, with a particular emphasis on the chemical aspects of arginine methylation. We highlight the research endeavors for the development and application of chemical approaches and chemical tools for the study of functions of PRMTs and arginine methylation in regulating biology and disease.

Improved pentamethine cyanine nanosensors for optoacoustic imaging of pancreatic cancer

Optoacoustic imaging is a new biomedical imaging technology with clear benefits over traditional optical imaging and ultrasound. While the imaging technology has improved since its initial development, the creation of dedicated contrast agents for optoacoustic imaging has been stagnant. Current exploration of contrast agents has been limited to standard commercial dyes that have already been established in optical imaging applications. While some of these compounds have demonstrated utility in optoacoustic imaging, they are far from optimal and there is a need for contrast agents with tailored optoacoustic properties. The synthesis, encapsulation within tumor targeting silica nanoparticles and applications in in vivo tumor imaging of optoacoustic contrast agents are reported.

Cyanine Nanocage Activated by Near-IR Light for the Targeted Delivery of Cyclosporine A to Traumatic Brain Injury Sites

More than 2.8 million annually in the United States are afflicted with some form of traumatic brain injury (TBI), where 75% of victims have a mild form of TBI (MTBI). TBI risk is higher for individuals engaging in physical activities or involved in accidents. Although MTBI may not be initially life-threatening, a large number of these victims can develop cognitive and physical dysfunctions. These late clinical sequelae have been attributed to the development of secondary injuries that can occur minutes to days after the initial impact. To minimize brain damage from TBI, it is critical to diagnose and treat patients within the first or "golden" hour after TBI. Although it would be very helpful to quickly determine the TBI locations in the brain and direct the treatment selectively to the affected sites, this remains a challenge. Herein, we disclose our novel strategy to target cyclosporine A (CsA) into TBI sites, without the need to locate the exact location of the TBI lesion. Our approach is based on TBI treatment with a cyanine dye nanocage attached to CsA, a known therapeutic agent for TBI that is associated with unacceptable toxicities. In its caged form, CsA remains inactive, while after near-IR light photoactivation, the resulting fragmentation of the cyanine nanocage leads to the selective release of CsA at the TBI sites.

Current trends in pyrrole and porphyrin-derived nanoscale materials for biomedical applications

This article is written to provide an up-to-date review of pyrrole-based biomedical materials. Porphyrins and other tetrapyrrolic molecules possess unique magnetic, optical and other photophysical properties that make them useful for bioimaging and therapy. This review touches briefly on some of the synthetic strategies to obtain porphyrin- and tetrapyrrole-based nanoparticles, as well as the variety of applications in which crosslinked, self-assembled, porphyrin-coated and other nanoparticles are utilized. We explore examples of these nanoparticles' applications in photothermal therapy, drug delivery, photodynamic therapy, stimuli response, fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, computed tomography and positron emission tomography. We anticipate that this review will provide a comprehensive summary of pyrrole-derived nanoparticles and provide a guideline for their further development.

RhIII -Catalyzed Double Dehydrogenative Coupling of Free 1-Naphthylamines with α,β-Unsaturated Esters

The Rh^III -catalyzed, consecutive double C-H oxidative coupling of free 1-naphthylamine and α,β-unsaturated esters through C-H/C-H and C-H/N-H bonds is reported. The one step reaction leads to the formation of biologically important alkylidene-1,2-dihydrobenzo[cd]indoles scaffolds. This efficient process is much more synthetically convenient and useful than others because the starting materials, such as 1-naphthylamine derivatives are readily available and the free amine serves as a directing group.

High-Yielding Water-Soluble Asymmetric Cyanine Dyes for Labeling Applications

A simple and efficient microwave-assisted synthesis of asymmetric pentamethine cyanine dyes with various functional groups was developed, which allows high-yielding results. The synthesized dyes are modifiable and suitable for single-molecule imaging in biological and medical sciences by application of click chemistry or classic esterification and amidation.

PRMT6 Promotes Lung Tumor Progression via the Alternate Activation of Tumor-Associated Macrophages

Increased expression of protein arginine methyl transferase 6 (PRMT6) correlates with worse prognosis in lung cancer cases. To interrogate the in vivo functions of PRMT6 in lung cancer, we developed a tamoxifen-inducible lung-targeted PRMT6 gain-of-function mouse model, which mimics PRMT6 amplification events in human lung tumors. Lung-targeted overexpression of PRMT6 accelerated cell proliferation de novo and potentiated chemical carcinogen (urethane)-induced lung tumor growth. To explore the molecular mechanism/s by which PRMT6 promotes lung tumor growth, we used proteomics-based approaches and identified interleukin-enhancer binding protein 2 (ILF2) as a novel PRMT6-associated protein. Furthermore, by using a series of in vitro gain-of-function and loss-of-function experiments, we defined a new role for the PRMT6-ILF2 signaling axis in alternate activation of tumor-associated macrophages (TAM). Interestingly, we have also identified macrophage migration inhibitory factor, which has recently been shown to regulate alternate activation of TAMs, as an important downstream target of PRMT6-ILF2 signaling. Collectively, our findings reveal a previously unidentified noncatalytic role for PRMT6 in potentiating lung tumor progression via the alternate activation of TAMs. IMPLICATIONS: This is the first study to demonstrate an in vivo role for PRMT6 in lung tumor progression via the alternate activation of TAMs.

Second Generation G-Quadruplex Stabilizing Trimethine Cyanines

G-Quadruplex DNA has been recognized as a highly appealing target for the development of new selective chemotherapeutics, which could result in markedly reduced toxicity toward normal cells. In particular, the cyanine dyes that bind selectively to G-quadruplex structures without targeting duplex DNA have attracted attention due to their high amenability to structural modifications that allows fine-tuning of their biomolecular interactions. We have previously reported pentamethine and symmetric trimethine cyanines designed to effectively bind G-quadruplexes through end stacking interactions. Herein, we are reporting a second generation of drug candidates, the asymmetric trimethine cyanines. These have been synthesized and evaluated for their quadruplex binding properties. Incorporating a benz[c,d]indolenine heterocyclic unit increased overall quadruplex binding, and elongating the alkyl length increases the quadruplex-to-duplex binding specificity.

Thermo- and photo-stable symmetrical benzo[cd]indolenyl-substituted heptamethine cyanine dye carrying a tetrakis(pentafluorophenyl)borate that absorbs only near-infrared light over 1000 nm

Thermo- and photo-stable NIR dyes absorbing only NIR light of over 1000 nm have been investigated.

Mechanisms and Inhibitors of Histone Arginine Methylation

Histone methylation plays an important regulatory role in chromatin restructuring and RNA transcription. Arginine methylation that is enzymatically catalyzed by the family of protein arginine methyltransferases (PRMTs) can either activate or repress gene expression depending on cellular contexts. Given the strong correlation of PRMTs with pathophysiology, great interest is seen in understanding molecular mechanisms of PRMTs in diseases and in developing potent PRMT inhibitors. Herein, we reviewed key research advances in the study of biochemical mechanisms of PRMT catalysis and their relevance to cell biology. We highlighted how a random binary, ordered ternary kinetic model for PRMT1 catalysis reconciles the literature reports and endorses a distributive mechanism that the enzyme active site utilizes for multiple turnovers of arginine methylation. We discussed the impacts of histone arginine methylation and its biochemical interplays with other key epigenetic marks. Challenges in developing small-molecule PRMT inhibitors were also discussed.

Listening to membrane potential: photoacoustic voltage-sensitive dye recording

Voltage-sensitive dyes (VSDs) are designed to monitor membrane potential by detecting fluorescence changes in response to neuronal or muscle electrical activity. However, fluorescence imaging is limited by depth of penetration and high scattering losses, which leads to low sensitivity in vivo systems for external detection. By contrast, photoacoustic (PA) imaging, an emerging modality, is capable of deep tissue, noninvasive imaging by combining near-infrared light excitation and ultrasound detection. Here, we show that voltage-dependent quenching of dye fluorescence leads to a reciprocal enhancement of PA intensity. We synthesized a near-infrared photoacoustic VSD (PA-VSD), whose PA intensity change is sensitive to membrane potential. In the polarized state, this cyanine-based probe enhances PA intensity while decreasing fluorescence output in a lipid vesicle membrane model. A theoretical model accounts for how the experimental PA intensity change depends on fluorescence and absorbance properties of the dye. These results not only demonstrate PA voltage sensing but also emphasize the interplay of both fluorescence and absorbance properties in the design of optimized PA probes. Together, our results demonstrate PA sensing as a potential new modality for recording and external imaging of electrophysiological and neurochemical events in the brain.

Inhibitors of Protein Methyltransferases and Demethylases

Post-translational modifications of histones by protein methyltransferases (PMTs) and histone demethylases (KDMs) play an important role in the regulation of gene expression and transcription and are implicated in cancer and many other diseases. Many of these enzymes also target various nonhistone proteins impacting numerous crucial biological pathways. Given their key biological functions and implications in human diseases, there has been a growing interest in assessing these enzymes as potential therapeutic targets. Consequently, discovering and developing inhibitors of these enzymes has become a very active and fast-growing research area over the past decade. In this review, we cover the discovery, characterization, and biological application of inhibitors of PMTs and KDMs with emphasis on key advancements in the field. We also discuss challenges, opportunities, and future directions in this emerging, exciting research field.

Transient Kinetics Define a Complete Kinetic Model for Protein Arginine Methyltransferase 1

Protein arginine methyltransferases (PRMTs) are the enzymes responsible for posttranslational methylation of protein arginine residues in eukaryotic cells, particularly within the histone tails. A detailed mechanistic model of PRMT-catalyzed methylation is currently lacking, but it is essential for understanding the functions of PRMTs in various cellular pathways and for efficient design of PRMT inhibitors as potential treatments for a range of human diseases. In this work, we used stopped-flow fluorescence in combination with global kinetic simulation to dissect the transient kinetics of PRMT1, the predominant type I arginine methyltransferase. Several important mechanistic insights were revealed. The cofactor and the peptide substrate bound to PRMT1 in a random manner and then followed a kinetically preferred pathway to generate the catalytic enzyme-cofactor-substrate ternary complex. Product release proceeded in an ordered fashion, with peptide dissociation followed by release of the byproduct S-adenosylhomocysteine. Importantly, the dissociation rate of the monomethylated intermediate from the ternary complex was much faster than the methyl transfer. Such a result provided direct evidence for distributive arginine dimethylation, which means the monomethylated substrate has to be released to solution and rebind with PRMT1 before it undergoes further methylation. In addition, cofactor binding involved a conformational transition, likely an open-to-closed conversion of the active site pocket. Further, the histone H4 peptide bound to the two active sites of the PRMT1 homodimer with differential affinities, suggesting a negative cooperativity mechanism of substrate binding. These findings provide a new mechanistic understanding of how PRMTs interact with their substrates and transfer methyl groups.

Protein Arginine Methylation and Citrullination in Epigenetic Regulation

The post-translational modification of arginine residues represents a key mechanism for the epigenetic control of gene expression. Aberrant levels of histone arginine modifications have been linked to the development of several diseases including cancer. In recent years, great progress has been made in understanding the physiological role of individual arginine modifications and their effects on chromatin function. The present review aims to summarize the structural and functional aspects of histone arginine modifying enzymes and their impact on gene transcription. We will discuss the potential for targeting these proteins with small molecules in a variety of disease states.

In Vivo Detection of Mitochondrial Dysfunction Induced by Clinical Drugs and Disease-Associated Genes Using a Novel Dye ZMJ214 in Zebrafish

Mitochondrial dysfunction has been implicated in various drug-induced toxicities and genetic disorders. Recently, the zebrafish has emerged as a versatile animal model for both chemical and genetic screenings. Taking advantage of its transparency, various in vivo fluorescent imaging methods have been developed to identify novel functions of chemicals and genes in zebrafish. However, there have not been fluorescent probes that can detect mitochondrial membrane potential in living zebrafish. In this study, we identified a novel cyanine dye called ZMJ214 that detects mitochondrial membrane potential in living zebrafish from 4 to 8 days post fertilization and is administered by simple immersion. The fluorescence intensity of ZMJ214 in zebrafish was increased and decreased by oligomycin and FCCP, respectively, suggesting a positive correlation between ZMJ214 fluorescence and mitochondrial membrane potential. In vivo imaging of zebrafish stained with ZMJ214 allowed for the detection of altered mitochondrial membrane potential induced by the antidiabetic drug troglitazone and the antiepileptic drug tolcapone, both of which have been withdrawn from the market due to mitochondrial toxicity. In contrast, pioglitazone and entacapone, which are similar to troglitazone and tolcapone, respectively, and have been used commercially, did not cause a change in mitochondrial membrane potential in zebrafish stained with ZMJ214. Live imaging of zebrafish stained with ZMJ214 also revealed that knock-down of slc25a12, a mitochondrial carrier protein associated with autism, dysregulated the mitochondrial membrane potential. These results suggest that ZMJ214 can be a useful tool to identify chemicals and genes that cause mitochondrial dysfunction in vivo.

Small Molecule Inhibitors of Protein Arginine Methyltransferases

INTRODUCTION

Arginine methylation is an abundant posttranslational modification occurring in mammalian cells and catalyzed by protein arginine methyltransferases (PRMTs). Misregulation and aberrant expression of PRMTs are associated with various disease states, notably cancer. PRMTs are prominent therapeutic targets in drug discovery.

AREAS COVERED

The authors provide an updated review of the research on the development of chemical modulators for PRMTs. Great efforts are seen in screening and designing potent and selective PRMT inhibitors, and a number of micromolar and submicromolar inhibitors have been obtained for key PRMT enzymes such as PRMT1, CARM1, and PRMT5. The authors provide a focus on their chemical structures, mechanism of action, and pharmacological activities. Pros and cons of each type of inhibitors are also discussed.

EXPERT OPINION

Several key challenging issues exist in PRMT inhibitor discovery. Structural mechanisms of many PRMT inhibitors remain unclear. There lacks consistency in potency data due to divergence of assay methods and conditions. Physiologically relevant cellular assays are warranted. Substantial engagements are needed to investigate pharmacodynamics and pharmacokinetics of the new PRMT inhibitors in pertinent disease models. Discovery and evaluation of potent, isoform-selective, cell-permeable and in vivo-active PRMT modulators will continue to be an active arena of research in years ahead.

Benz[c,d]indolium-containing Monomethine Cyanine Dyes: Synthesis and Photophysical Properties

Asymmetric monomethine cyanines have been extensively used as probes for nucleic acids among other biological systems. Herein we report the synthesis of seven monomethine cyanine dyes that have been successfully prepared with various heterocyclic moieties such as quinoline, benzoxazole, benzothiazole, dimethyl indole, and benz[e]indole adjoining benz[c,d]indol-1-ium, which was found to directly influence their optical and energy profiles. In this study the optical properties vs. structural changes were investigated using nuclear magnetic resonance and computational approaches. The twisted conformation unique to monomethine cyanines was exploited in DNA binding studies where the newly designed sensor displayed an increase in fluorescence when bound in the DNA grooves compared to the unbound form.

Molecular Mechanism underlying PRMT1 Dimerization for SAM Binding and Methylase Activity

Protein arginine methyltransferases (PRMTs) catalyze the posttranslational methylation of arginine, which is important in a range of biological processes, including epigenetic regulation, signal transduction, and cancer progression. Although previous studies of PRMT1 mutants suggest that the dimerization arm and the N-terminal region of PRMT1 are important for activity, the contributions of these regions to the structural architecture of the protein and its catalytic methylation activity remain elusive. Molecular dynamics (MD) simulations performed in this study showed that both the dimerization arm and the N-terminal region undergo conformational changes upon dimerization. Because a correlation was found between the two regions despite their physical distance, an allosteric pathway mechanism was proposed based on a network topological analysis. The mutation of residues along the allosteric pathways markedly reduced the methylation activity of PRMT1, which may be attributable to the destruction of dimer formation and accordingly reduced S-adenosyl-L-methionine (SAM) binding. This study provides the first demonstration of the use of a combination of MD simulations, network topological analysis, and biochemical assays for the exploration of allosteric regulation upon PRMT1 dimerization. These findings illuminate the results of mechanistic studies of PRMT1, which have revealed that dimer formation facilitates SAM binding and catalytic methylation, and provided direction for further allosteric studies of the PRMT family.

Exploration of cyanine compounds as selective inhibitors of protein arginine methyltransferases: synthesis and biological evaluation

Protein arginine methyltransferase 1 (PRMT1) is involved in many biological activities, such as gene transcription, signal transduction, and RNA processing. Overexpression of PRMT1 is related to cardiovascular diseases, kidney diseases, and cancers; therefore, selective PRMT1 inhibitors serve as chemical probes to investigate the biological function of PRMT1 and drug candidates for disease treatment. Our previous work found trimethine cyanine compounds that effectively inhibit PRMT1 activity. In our present study, we systematically investigated the structure–activity relationship of cyanine structures. A pentamethine compound, E-84 (compound 50), showed inhibition on PRMT1 at the micromolar level and 6- to 25-fold selectivity over CARM1, PRMT5, and PRMT8. The cellular activity suggests that compound 50 permeated the cellular membrane, inhibited cellular PRMT1 activity, and blocked leukemia cell proliferation. Additionally, our molecular docking study suggested compound 50 might act by occupying the cofactor binding site, which provided a roadmap to guide further optimization of this lead compound.

Virtual screening and biological evaluation of novel small molecular inhibitors against protein arginine methyltransferase 1 (PRMT1)

Protein arginine methylation is a common post-translational modification which is crucial for a variety of biological processes. Dysregulation of protein arginine methyltransferases (PRMTs) activity has been implicated in cancer and other serious diseases. Thus, small molecule inhibitors against PRMT have great potential for therapeutic development. Herein, through the combination of virtual screening and bioassays, six small molecular compounds were identified as PRMT1 inhibitors. Amongst them, the binding affinity of compounds DCLX069 and DCLX078 with PRMT1 was further validated by T1ρ and saturation transfer difference (STD) NMR experiments. Most important of all, both compounds effectively blocked cell proliferation in breast cancer, liver cancer and acute myeloid leukemia cell lines. The binding mode analysis from molecular docking simulations theoretically indicated that both inhibitors occupied the SAM binding pocket to exert the inhibitory effect. Taken together, our compounds enriched the structural scaffolds as PRMT1 inhibitors and afforded clues for further optimization.

Conference scene: 2nd cancer epigenetics conference

The GTC Cancer Summit: Novel Approaches to Drug Discovery was divided into two parallel tracks: the 2nd Cancer Epigenetics Conference, and the Protein Kinases and Drug Design Conference. The 2nd Cancer Epigenetics Conference focused on exciting changes in drug discovery that include an unprecedented private and public collaboration on drug discovery in epigenetics through the Structural Genomics Consortium (SGC), which has led to several major breakthroughs including: the development of small-molecule inhibitors that interfere with protein interactions, especially bromodomain-containing protein acetylation readers; the indirect but successful targeting of the elusive MYC oncogene; and the identification of epigenetic drugs that are disease-specific. Also reported were the development of clinically useful DNA methylation assays; cell, peptide and protein arrays for testing antibody- and protein-binding specificity; and tools for chromatin capture and DNA modification analysis. Several groups reported on the lack of specificity of some commercial, but unnamed, antibodies used for epigenetic studies.