Multiplex GPCR Assay in Reverse Transfection Cell Microarrays

G protein-coupled receptors (GPCRs) are a superfamily of proteins that include some of the most important drug targets in the pharmaceutical industry. Despite the success of this group of drugs, there remains a need to identify GPCR-targeted drugs with greater selectivity, to develop screening assays for validated targets, and to identify ligands for orphan receptors. To address these challenges, the authors have created a multiplexed GPCR assay that measures greater than 3000 receptor: ligand interactions in a single microplate. The multiplexed assay is generated by combining reverse transfection in a 96-well plate format with a calcium flux readout. This assay quantitatively measures receptor activation and inhibition and permits the determination of compound potency and selectivity for entire families of GPCRs in parallel. To expand the number of GPCR targets that may be screened in this system, receptors are cotransfected with plasmids encoding a promiscuous G protein, permitting the analysis of receptors that do not normally mobilize intracellular calcium upon activation. The authors demonstrate the utility of reverse transfection cell microarrays to GPCR-targeted drug discovery with examples of ligand selectivity screening against a panel of GPCRs as well as dose-dependent titrations of selected agonists and antagonists.

A comparison of health-related quality of life of patients with primary and recurrent varicose veins

Aim: To determine whether recurrent varicose veins affect patient quality of life. The health-related quality of life (HRQL) scores of patients with recurrent varicose veins were compared with those of patients presenting with primary varicose vein disease.

Methods: HRQL among patients attending outpatient appointments for recurrent and primary varicose veins was measured using the Aberdeen Varicose Vein Questionnaire (AVVQ) and the Short Form-36 General Health Survey (SF-36).

Results: Questionnaires were given to 211 patients (150 primary, 61 recurrent), and 194 (133 primary, 61 recurrent) completed them. For the AVVQ, patients with recurrent varicose veins had significantly worse symptom scores compared with those with primary disease (24.87 ± 12.28 vs 17.77 ± 9.68, Mann-Whitney, P <0.01). The SF-36 recorded significantly worse HRQL (Mann-Whitney, P <0.05) for patients with recurrent varicose veins compared with those with primary varicose veins in all but one of the eight domains (role limitation attributed to emotional problems, RE, P = 0.073).

Conclusion: Varicose vein recurrence is associated with a significantly worse HRQL than is found among patients with primary varicose veins.

Randomized clinical trial of varicose vein surgery with compression versus compression alone for the treatment of venous ulceration

Objectives: No randomized controlled trials exist to show whether varicose vein surgery improves healing of venous ulcers. In this study we investigated whether superficial venous surgery gave additional benefit to compression therapy in terms of healing rate, time to healing and quality of life of patients with venous ulcers.

Methods: A total of 121 consecutive patients with venous ulceration were identified, of which 45 were unfit/unwilling to be included. The remaining 76 (aged 38-89, 39 female) were randomized to receive either four-layer bandaging ( n =39) or superficial venous surgery (long and short saphenous with or without perforator surgery) and four-layer bandaging ( n =37). Ulcer healing and health-related quality of life (HRQL) were assessed.

Results: The healing rate was 64% (25/39) in the compression treatment group and 68% (25/37) in the surgical treatment group. This difference was not statistically significant (Pearson 2 P=0.75). There was no significant difference between the time to ulcer healing in the two treatment groups (log rank statistic=0.69, P value=0.41): median time 83 days for surgery vs 98 days for compression. After adjusting for duration of ulcer, size of ulcer and previous deep vein thrombosis, there was still no significant difference between time to healing for the two treatment groups (adjusted hazard ratio=0.79, 95% confidence interval 0.45-1.39). There was no difference in HRQL between the two groups, using the scores of a disease-specific questionnaire (CXVUQ).

Conclusions: This study suggests that for venous ulceration, superficial venous surgery gives no additional benefit to compression therapy from the point of view of healing rate and quality of life.

Myeloid translocation genes differentially regulate colorectal cancer programs

Myeloid translocation genes (MTGs), originally identified as chromosomal translocations in acute myelogenous leukemia, are transcriptional corepressors that regulate hematopoietic stem cell programs. Analysis of The Cancer Genome Atlas (TCGA) database revealed that MTGs were mutated in epithelial malignancy and suggested that loss of function might promote tumorigenesis. Genetic deletion of MTGR1 and MTG16 in the mouse has revealed unexpected and unique roles within the intestinal epithelium. Mtgr1^−/− mice have progressive depletion of all intestinal secretory cells, and Mtg16^−/− mice have a decrease in goblet cells. Furthermore, both Mtgr1^−/− and Mtg16^−/− mice have increased intestinal epithelial cell proliferation. We thus hypothesized that loss of MTGR1 or MTG16 would modify Apc^1638/+-dependent intestinal tumorigenesis. Mtgr1^−/− mice, but not Mtg16^−/− mice, had a 10-fold increase in tumor multiplicity. This was associated with more advanced dysplasia, including progression to invasive adenocarcinoma, and augmented intratumoral proliferation. Analysis of ChIP-seq datasets for MTGR1 and MTG16 targets indicated that MTGR1 can regulate Wnt and Notch signaling. In support of this, immunohistochemistry and gene expression analysis revealed that both Wnt and Notch signaling pathways were hyperactive in Mtgr1^−/− tumors. Furthermore, in human colorectal cancer (CRC) samples MTGR1 was downregulated at both the transcript and protein level. Overall our data indicates that MTGR1 has a context dependent effect on intestinal tumorigenesis.

Novel Oxindole Sulfonamides and Sulfamides: EPZ031686, the First Orally Bioavailable Small Molecule SMYD3 Inhibitor

SMYD3 has been implicated in a range of cancers; however, until now no potent selective small molecule inhibitors have been available for target validation studies. A novel oxindole series of SMYD3 inhibitors was identified through screening of the Epizyme proprietary histone methyltransferase-biased library. Potency optimization afforded two tool compounds, sulfonamide EPZ031686 and sulfamide EPZ030456, with cellular potency at a level sufficient to probe the in vitro biology of SMYD3 inhibition. EPZ031686 shows good bioavailability following oral dosing in mice making it a suitable tool for potential in vivo target validation studies.

Structure and Property Guided Design in the Identification of PRMT5 Tool Compound EPZ015666

The recent publication of a potent and selective inhibitor of protein methyltransferase 5 (PRMT5) provides the scientific community with in vivo-active tool compound EPZ015666 (GSK3235025) to probe the underlying pharmacology of this key enzyme. Herein, we report the design and optimization strategies employed on an initial hit compound with poor in vitro clearance to yield in vivo tool compound EPZ015666 and an additional potent in vitro tool molecule EPZ015866 (GSK3203591).

Mode instability thresholds for Tm-doped fiber amplifiers pumped at 790 nm

We use a detailed numerical model of stimulated thermal Rayleigh scattering to compute mode instability thresholds in Tm(3+)-doped fiber amplifiers. The fiber amplifies 2040 nm light using a 790 nm pump. The cross-relaxation process is strong, permitting power efficiencies of 60%. The predicted instability thresholds are compared with those in similar Yb(3+)-doped fiber amplifiers with 976 nm pump and 1060 nm signal, and are found to be higher, even though the heat load is much higher in Tm-doped amplifiers. The higher threshold in the Tm-doped fiber is attributed to its longer signal wavelength, and to stronger gain saturation, due in part to cross-relaxation heating.

Abstract IA27: Tazemetostat, an EZH2 inhibitor and potential therapeutic for non-Hodgkin lymphoma

Cell fate decisions, such as whether to self-renew or to differentiate, are regulated in large part by epigenetic mechanisms. Dysregulation of epigenetic machinery, such as histone methyltransferases, in certain progenitor cell contexts can promote increased self-renewal, decreased differentiation and ultimately oncogenesis. For example, EZH2, the histone H3K27 methyltransferase, has been implicated in a diverse set of cancer indications. As the catalytic subunit of the polycomb repressive complex 2 (PRC2), EZH2 is responsible for the initiation of gene silencing during embryonic development and in maintenance of pluripotency in certain adult stem cell settings. On the other hand, EZH2 activity is downregulated in the majority of adult somatic cells to facilitate the expression of lineage-specific gene programs, leading to differentiation. Thus, inappropriate activation of EZH2 can contribute to oncogenic signaling by potentiating “stem-like” programs in certain contexts.

For example, during B cell maturation, EZH2 activity is critical for formation of the germinal center (GC) reaction. PRC2-mediated repression of certain target sets, such as cell cycle checkpoint genes and DNA damage response genes, allows germinal center B (GCB) cells to undergo clonal expansion and somatic hypermutation. In order for GCB cells to exit the germinal center reaction, EZH2 expression and activity must be attenuated – the failure to do so may contribute to oncogenic signaling in certain B cell lymphomas. We and others have previously reported on gain-of-function mutations in EZH2, involving residues such as Y646, A682 and A692. These lesions result in increased trimethylation of H3K27 on polycomb target genes, including those required for B cell maturation and exit from the germinal center reaction. Importantly, lymphoma cell lines bearing these mutations demonstrate robust antiproliferative phenotypes, both in culture and in subcutaneous xenograft models, in response to small molecule inhibitors of EZH2. Beyond these mutant EZH2 cell lines, there is evidence that small molecule inhibitors of EZH2 also have antiproliferative activity in GCB cell and non-GCB lymphomas with wild type (wt) EZH2. These data are consistent with the idea that EZH2 is a “lineage factor” for B cell maturation, and that certain B cell lymphomas may possibly become “addicted” to EZH2 through mechanisms other than gain-of-function mutations in said gene. In addition to these preclinical findings, a recent update from ongoing clinical trials reported objective responses to single-agent tazemetostat (an EZH2 inhibitor in clinical development) in both wild-type and mutant EZH2 non-Hodgkin lymphoma (NHL) patients.

The focus of this presentation will be the emerging translational landscape for tazemetostat (EPZ-6438), a small molecule inhibitor of EZH2, currently in phase II clinical trials for multiple oncology indications, including subsets of NHL. Data to be discussed will include preclinical efforts to understand the molecular mechanisms that determine GCB and non-GCB lymphoma response to EZH2 inhibition. Additionally, preclinical investigations evaluating the combination of tazemetostat with multiple therapeutic modalities will be presented. Finally, a brief overview of the early clinical observations of tazemetostat will be discussed.

Citation Format: Jesse J. Smith. Tazemetostat, an EZH2 inhibitor and potential therapeutic for non-Hodgkin lymphoma. [abstract]. In: Proceedings of the AACR Special Conference on Chromatin and Epigenetics in Cancer; Sep 24-27, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2016;76(2 Suppl):Abstract nr IA27.

Abstract C85: Identification of a novel potent selective SMYD3 inhibitor with oral bioavailability

SMYD3 (Set and Mynd Domain containing 3) is a lysine methyltransferase overexpressed in several cancer types including breast, prostrate, pancreatic, and lung, and this overexpression is associated with poor clinical prognosis. Genetic knockdown of SMYD3 by shRNA has been shown to decrease proliferation in a range of cancer cell lines suggesting that inhibition of SMYD3 may have therapeutic utility.

In this presentation we describe the discovery and optimization of a novel series of oxindole sulfonamides and sulfamides with SMYD3 inhibitory activity. One of these compounds, EPZ030456, has a SMYD3 biochemical IC50 of 4 nM and is active in cells with an IC50 of 48 nM in a trimethyl MAP3K2 (MEKK2) in-cell western (ICW) assay. The crystal structure of this compound was solved with SMYD3 and the nucleotide substrate, S-adenosylmethionine and shows the oxindole portion of the molecule extends into the SMYD3 lysine binding channel. EPZ030456 shows &lt; 30% inhibition at a 10 uM screening concentration against 17 histone methyltransferase targets tested, including SMYD2.

Further optimization within the series resulted in EPZ031686 which has similar potency to EPZ030456 with a biochemical IC50 of 3 nM and an ICW IC50 of 36 nM and in addition exhibits good bioavailability following oral dosing in mice. Hence, EPZ031686 is a suitable tool to study the role of SMYD3 in cancer and other therapeutic areas, using both in vitro and in vivo models.

Citation Format: Lorna H. Mitchell, Paula A. Boriack-Sjodin, Sherri Smith, Michael Thomenius, Nathalie Rioux, Michael Munchhof, James E. Mills, Christine Klaus, Jennifer Totman, Thomas V. Riera, Alejandra Raimondi, Suzanne L. Jacques, Megan Foley, Nigel J. Waters, Kevin W. Kuntz, Tim J. Wigle, Margaret Porter Scott, Robert A. Copeland, Jesse J. Smith, Richard Chesworth. Identification of a novel potent selective SMYD3 inhibitor with oral bioavailability. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C85.

Abstract C162: A medium-throughput single cell CRISPR-Cas9 assay to assess gene essentiality

Target selection for oncology and other indications is a critical step in the successful development of therapeutics, however it remains one of the most challenging areas of drug discovery. In fact, up to two-thirds of oncology relevant targets reported in literature have not been confirmed on follow-up studies, indicating that target validation in oncology is especially challenging. Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 gene editing of specific loci offers an alternative method to RNA interference and complements small molecule inhibitors for determining whether or not a cell line is dependent on a specific gene product for proliferation and/or survival. Importantly, CRISPR-Cas9 may be advantageous for some studies as it offers efficient and specific gene knock-out leading to complete loss of protein function. This may be especially useful for some target classes, including epigenetic targets, which appear to require near complete loss of protein function to observe phenotypes. In our initial studies using CRISPR-Cas9 to verify the essential nature of EZH2 (Enhancer of Zest 2) expression for the proliferation of SMARCB1/SNF5/INI1 mutant malignant rhabdoid tumor cell lines, we observed that the initial reduction in proliferation was lost over time. We hypothesized that in the few cells that retain proliferative capacity at least one allele of EZH2 remains functional, and this hypothesis suggests that carrying out CRISPR-Cas9 studies for individual target genes without analyzing single cell clones could produce misleading results. To verify this, we developed a medium throughput assay to analyze 10s-100s of single cell clones for target gene disruption using CRISPR-Cas9 gene knockout, followed by a restriction digest and fluorescent undigested fragment length analysis to successfully assess EZH2 allele status. Significantly, these data support our hypothesis that retention of one functional copy of EZH2 is required for the proliferation of EZH2-dependent cell lines and that this can be rapidly assessed by our assay. Thus, the assessment of zygosity of the gene of interest can be evaluated in a medium-throughput manner in single cell clones. The assay is thereby able to unambiguously indicate whether or not a specific gene is essential for survival and/or proliferation in a given cell line, and offers a unique approach for target validation using gene editing. Importantly, this approach should be applicable to any target of interest that is expected to affect cell proliferation or survival. Such data can aid in the development of more robust cancer therapeutics by increasing confidence in target selection.

Citation Format: Alexandra R. Grassian, Tim Scales, Sarah K. Knutson, Nicola J. McCarthy, Chris E. Lowe, Jon D. Moore, Robert A. Copeland, Heike Keilhack, Jesse J. Smith, Julie A. Wickendon, Scott Ribich. A medium-throughput single cell CRISPR-Cas9 assay to assess gene essentiality. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C162.

Abstract B78: CRISPR pooled screening identifies differential dependencies on epigenetic pathways

It has become clear in the past decade that dysregulation of epigenetic pathways is fundamental to many if not all tumors. Importantly, a number of epigenetic targeted therapies are now being tested in the clinic and are beginning to show promising efficacy. Identification of new targets for oncology therapeutics is critical, and the ideal target should: 1) be effective in a specific indication or genetically defined patient population; and 2) lead to a minimal amount of deleterious side effects in patients. Thus, target identification must be performed in a large number of cell lines to address both objectives and to ensure specific target dependence. However, it remains challenging to identify specific dependencies on epigenetic genes in preclinical models, which may result in part from the need for near complete loss of protein function for this class of enzymes to observe proliferation phenotypes, and this can be difficult to achieve with RNAi reagents. The advent of clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 technology enables the specific and complete knockout of the target protein and allows for observation of proliferation phenotypes that RNAi studies may not uncover. Additionally, the CRISPR-Cas9 system is amenable to pooled cell line screening which permits the quick and accurate examination of proliferation effects across many genes and many cell lines.

To examine the specific dependencies of cell lines on epigenetic pathways, we have used pooled CRISPR-Cas9 screening to interrogate over 600 epigenetic-related genes in a panel of more than 60 cells lines. The performance of the screen is highly consistent and able to reproduce findings that have been previously reported. We observe that CRISPR pooled screening is highly effective at identifying targets which are known to be required for cell proliferation either in all cell lines or in a genetically-defined subset of cell lines. We also identify new epigenetic-related genes required for the proliferation of almost all the cell lines tested, and have termed these “pan-essential” epigenetic genes. Intriguingly, these pan-essential genes represent members of almost all classes of epigenetic pathways, including histone methyltransferases, histone acetylases and deacetylases, chromatin remodeling factors, regulators of mRNA splicing, DNA helicases and others. This is an important set of genes to identify, as they represent targets which are likely to induce broad clinical toxicity if inhibited in patients, yet may be identified as potential targets in pre-clinical interrogation which does not fully examine proliferation dependencies in a sufficiently broad panel of cell lines.

Importantly, we also identify a variety of epigenetic targets which induce altered proliferation in a subset of cell lines tested. These include epigenetic-related genes from many classes, including histone methyltransferases. Notably, for certain genes, trends are emerging that indicate a specific genetic marker(s) which may predict dependence on these epigenetic targets. These genes represent highly promising targets for epigenetic therapeutics in a variety of oncology indications.

Citation Format: Alexandra R. Grassian, Julian Fowler, Igor Feldman, Thomas Riera, Darren Harvey, Allison E. Drew, Richard Chesworth, Robert A. Copeland, Heike Keilhack, Jesse J. Smith, Scott Ribich. CRISPR pooled screening identifies differential dependencies on epigenetic pathways. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B78.

Abstract 5383: DOT1L inhibitor EPZ-5676 synergizes with cytarabine and azacitidine in preclinical models of MLL-rearranged leukemia

EPZ-5676 is a small molecule inhibitor of the histone methyltransferase DOT1L currently in clinical development and represents a first in class novel therapeutic agent for the treatment of MLL-rearranged (MLL-r) leukemia. In preclinical studies, EPZ-5676 selectively inhibited intracellular histone H3K79 methylation, downstream target gene expression and demonstrated complete tumor regression in a MLL-r leukemia xenograft model. We previously reported synergistic and durable anti-proliferative activity when EPZ-5676 was combined with current AML standard of care drugs, cytarabine and daunorubicin in MLL-r leukemia models MOLM-13 (MLL-AF9) and MV4-11 (MLL-AF4). Combination benefit was also observed when MLL-r cells were treated with cytarabine, prior to co-treatment with EPZ-5676. Additionally, both cytarabine and the DNA methyltransferase inhibitor azacitidine, displayed synergistic anti-leukemic activity in MLL-r rearranged cells in a 7 day co-treatment model (7 days of continuous treatment with EPZ-5676 and second agent; see Klaus et al, JPET, 2014). In this report we discuss results of investigating additional treatment schedules using EPZ-5676 in combination with azacitidine in MLL-r cells. Cells were pretreated with azacitidine at nanomolar concentrations known to reverse promoter DNA-hypermethylation and alter the chromatin state (Tsai et al., Cancer Cell, 2012). We found treating MV4-11 and MOLM-13 cells once daily for three consecutive days followed by sequential treatment with EPZ-5676 elicited a synergistic anti-proliferative effect using the Chou-Talalay method (Chou, Pharmacol Rev., 2006). Results of studies to investigate the mechanism of this synergistic cell killing, including evaluation of differentiation markers and Annexin V staining will be reported. To determine if combinations of EPZ-5676 with cytarabine or azacitidine were tolerable and efficacious in vivo, nude rats implanted subcutaneously with MV4-11 tumors were treated using a range of doses and schedules. Azacitidine and cytarabine were delivered by intraperitoneal injection once daily for 14 days at their respective maximum tolerated doses of 2 and 200 mg/kg. Dosing at the established MTD, these agents inhibited the subcutaneous MV4-11 tumor growth by 50% compared to vehicle controls. Efficacy results from the EPZ-5676 combination studies with cytarabine or azacitidine will be presented. In summary, our results indicate that EPZ-5676 in combination with cytarabine or azacitidine revealed a synergistic effect, regardless of the treatment schedule used in preclinical models of MLL-r leukemia. Tolerable in vivo rat combination doses for EPZ-5676 with both cytarabine and azacitidine have been determined in support of potential future assessment of these combinations in MLL-r leukemia patients.

Citation Format: Christine R. Klaus, Scott R. Daigle, Vivek Chopra, Jeffrey A. Keats, Carly T. Campbell, Dorothy Iwanowicz, Edward J. Olhava, Margaret P. Scott, Roy M. Pollock, Robert A. Copeland, Jesse J. Smith, Jorge DiMartino, Stephen J. Blakemore, Alejandra Raimondi. DOT1L inhibitor EPZ-5676 synergizes with cytarabine and azacitidine in preclinical models of MLL-rearranged leukemia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5383. doi:10.1158/1538-7445.AM2015-5383

Abstract 2701: Characterization of acquired EPZ-5676 resistance in cell line models of MLL rearranged leukemia

DOT1L inhibitor EPZ-5676 is currently under Phase 1 clinical trial investigation in relapsed/refractory patients with acute leukemia, including those with an MLL-rearrangement (MLL-r). Early clinical results, including complete remissions, support ongoing clinical development and preclinical investigation into mechanisms precipitating EPZ-5676 treatment induced resistance. MLL-r cell lines KOPN-8 (MLL-ENL) and NOMO-1 (MLL-AF9) were exposed to an EPZ-5676 concentration above the pre-determined 14 day proliferation assay IC90. Initial treatment of the cell lines led to the expected inhibition of H3K79 dimethylation (H3K79me2) and MLL-r target genes HOXA9 and MEIS1 as outlined in previous work (Daigle et al, Cancer Cell 2011). Resistance to EPZ-5676 in both cell lines emerged following three weeks of continued treatment with EPZ-5676 and was defined by increased growth rates in the presence of inhibitor. Mechanisms of resistance for both cell lines were investigated using RNASeq and ChIPSeq on parental and resistant cell line pools. Our analysis identified common characteristics between the resistant cell lines, but mechanisms by which they became resistant differed. Global H3K79me2 inhibition was maintained in both refractory cell lines, yet ChIP-seq analysis of resistant pools identified specific loci with H3K79me2 recovery in KOPN-8 cells. In resistant KOPN-8 cells recovery of H3K79me2 was concentrated at the HOXA locus and other MLL-r target genes (e.g. MEIS1 and RUNX2), with the remainder of actively transcribed genes maintaining H3K79me2 inhibition at levels observed in parental cells. In contrast, resistant NOMO-1 cells did not recover H3K79me2 at any actively transcribed genes, including those of the MLL-r signature. Only resistant KOPN-8 cells regained expression of the MLL-r target genes HOXA9 and MEIS1. Of note both resistant NOMO-1 and KOPN-8 cell lines had 8 and 40 fold upregulation of the ABCB1 (MDR1, P-gp) tranporter respectively when compared to a matched control cell line. To explore the role of drug efflux transporter ABCB1 on resistance, we treated cells with Valspodar, a known inhibitor of ABCB1. Following treatment with 1 μM Valspodar, KOPN-8 cells showed decreased cell growth similar to the naïve control cell line. Supporting the presence of an alternative resistance mechanism in NOMO-1 cells in addition to MDR1 upregulation, NOMO-1 cells remained resistant upon Valspodar treatment. Detailed gene expression and pathway analysis will be presented supporting mechanisms of treatment emergent resistance to EPZ-5676. In summary, we have identified two mechanisms of EPZ-5676 resistance in MLL-r cell lines, one mechanism dependent on and the other independent of ABCB1. Further refinement of these mechanisms will aid in providing hypotheses for testing mechanisms of EPZ-5676 treatment emergent resistance in patients and may support designing future rational clinical combinations.

Citation Format: Scott R. Daigle, Carly T. Campbell, Nigel J. Waters, Edward J. Olhava, Robert A. Copeland, Stephen J. Blakemore, Roy M. Pollock, Jesse J. Smith. Characterization of acquired EPZ-5676 resistance in cell line models of MLL rearranged leukemia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2701. doi:10.1158/1538-7445.AM2015-2701

Aryl Pyrazoles as Potent Inhibitors of Arginine Methyltransferases: Identification of the First PRMT6 Tool Compound

A novel aryl pyrazole series of arginine methyltransferase inhibitors has been identified. Synthesis of analogues within this series yielded the first potent, selective, small molecule PRMT6 inhibitor tool compound, EPZ020411. PRMT6 overexpression has been reported in several cancer types suggesting that inhibition of PRMT6 activity may have therapeutic utility. Identification of EPZ020411 provides the field with the first small molecule tool compound for target validation studies. EPZ020411 shows good bioavailability following subcutaneous dosing in rats making it a suitable tool for in vivo studies.

The early management of the burned patient in the Naval service

Burns represent a perpetual threat in military combat and are a pervasive threat in the land, maritime and air arenas. Therefore, it is imperative that military clinicians are well versed in managing burns in order to ensure optimal survival and recovery. This article aims to explore the epidemiology, pathophysiology, assessment and early management of the burned patient with a focus on the austere maritime environment and current military guidance.

EPZ011989, A Potent, Orally-Available EZH2 Inhibitor with Robust in Vivo Activity

Inhibitors of the protein methyltransferase Enhancer of Zeste Homolog 2 (EZH2) may have significant therapeutic potential for the treatment of B cell lymphomas and other cancer indications. The ability of the scientific community to explore fully the spectrum of EZH2-associated pathobiology has been hampered by the lack of in vivo-active tool compounds for this enzyme. Here we report the discovery and characterization of EPZ011989, a potent, selective, orally bioavailable inhibitor of EZH2 with useful pharmacokinetic properties. EPZ011989 demonstrates significant tumor growth inhibition in a mouse xenograft model of human B cell lymphoma. Hence, this compound represents a powerful tool for the expanded exploration of EZH2 activity in biology.

ERBB4 is over-expressed in human colon cancer and enhances cellular transformation

The ERBB4 receptor tyrosine kinase promotes colonocyte survival. Herein, we tested whether ERBB4's antiapoptotic signaling promotes transformation and colorectal tumorigenesis. ERBB4 alterations in a The Cancer Genome Atlas colorectal cancer (CRC) data set stratified survival, and in a combined Moffitt Cancer Center and Vanderbilt Medical Center CRC expression data set, ERBB4 message levels were increased at all tumor stages. Similarly, western blot and immunohistochemistry on additional CRC tissue banks showed elevated ERBB4 protein in tumors. ERBB4 was highly expressed in aggressive, dedifferentiated CRC cell lines, and its knockdown in LIM2405 cells reduced anchorage-independent colony formation. In nude mouse xenograft studies, ERBB4 alone was insufficient to induce tumor establishment of non-transformed mouse colonocytes, but its over-expression in cells harboring Apc(min) and v-Ha-Ras caused a doubling of tumor size. ERBB4-expressing xenografts displayed increased activation of survival pathways, including epidermal growth factor receptor and Akt phosphorylation and COX-2 expression, and decreased apoptotic signals. Finally, ERBB4 deletion from mouse intestinal epithelium impaired stem cell replication and in vitro enteroid establishment. In summary, we report that ERBB4 is over-expressed in human CRC, and in experimental systems enhances the survival and growth of cells driven by Ras and/or WNT signaling. Chronic ERBB4 over-expression in the context of, for example, inflammation may contribute to colorectal carcinogenesis. Tumors with high receptor levels are likely to have enhanced cell survival signaling through epidermal growth factor receptor, PI3K and COX-2. These results suggest ERBB4 as a novel therapeutic target in a subset of CRC.

Risk stratification by the Appendicitis Inflammatory Response score to guide decision-making in patients with suspected appendicitis

BACKGROUND

Current management of suspected appendicitis is hampered by the overadmission of patients with non-specific abdominal pain and a significant negative exploration rate. The potential benefits of risk stratification by the Appendicitis Inflammatory Response (AIR) score to guide clinical decision-making were assessed.

METHODS

During this 50-week prospective observational study at one institution, the AIR score was calculated for all patients admitted with suspected appendicitis. Appendicitis was diagnosed by histological examination, and patients were classified as having non-appendicitis pain if histological findings were negative or surgery was not performed. The diagnostic performance of the AIR score and the potential for risk stratification to reduce admissions, optimize imaging and prevent unnecessary explorations were quantified.

RESULTS

A total of 464 patients were included, of whom 210 (63·3 per cent) with non-appendicitis pain were correctly classified as low risk. However, 13 low-risk patients had appendicitis. Low-risk patients accounted for 48·1 per cent of admissions (223 of 464), 57 per cent of negative explorations (48 of 84) and 50·7 per cent of imaging requests (149 of 294). An AIR score of 5 or more (intermediate and high risk) had high sensitivity for all severities of appendicitis (90 per cent) and also for advanced appendicitis (98 per cent). An AIR score of 9 or more (high risk) was very specific (97 per cent) for appendicitis, and the majority of patients with appendicitis in the high-risk group (21 of 30, 70 per cent) had perforation or gangrene. Ultrasound imaging could not exclude appendicitis in low-risk patients (negative likelihood ratio (LR) 1·0) but could rule-in the diagnosis in intermediate-risk patients (positive LR 10·2). CT could exclude appendicitis in low-risk patients (negative LR 0·0) and rule-in appendicitis in the intermediate group (positive LR 10·9).

CONCLUSION

Risk stratification of patients with suspected appendicitis by the AIR score could guide decision-making to reduce admissions, optimize utility of diagnostic imaging and prevent negative explorations.

The early management of the burned patient in the Naval service

Burns represent a perpetual threat in military combat and are a pervasive threat in the land, maritime and air arenas. Therefore, it is imperative that military clinicians are well versed in managing burns in order to ensure optimal survival and recovery. This article aims to explore the epidemiology, pathophysiology, assessment and early management of the burned patient with a focus on the austere maritime environment and current military guidance.

Synergistic Anti-Tumor Activity of EZH2 Inhibitors and Glucocorticoid Receptor Agonists in Models of Germinal Center Non-Hodgkin Lymphomas

Patients with non-Hodgkin lymphoma (NHL) are treated today with a cocktail of drugs referred to as CHOP (Cyclophosphamide, Hydroxyldaunorubicin, Oncovin, and Prednisone). Subsets of patients with NHL of germinal center origin bear oncogenic mutations in the EZH2 histone methyltransferase. Clinical testing of the EZH2 inhibitor EPZ-6438 has recently begun in patients. We report here that combining EPZ-6438 with CHOP in preclinical cell culture and mouse models results in dramatic synergy for cell killing in EZH2 mutant germinal center NHL cells. Surprisingly, we observe that much of this synergy is due to Prednisolone - a glucocorticoid receptor agonist (GRag) component of CHOP. Dramatic synergy was observed when EPZ-6438 is combined with Prednisolone alone, and a similar effect was observed with Dexamethasone, another GRag. Remarkably, the anti-proliferative effect of the EPZ-6438+GRag combination extends beyond EZH2 mutant-bearing cells to more generally impact germinal center NHL. These preclinical data reveal an unanticipated biological intersection between GR-mediated gene regulation and EZH2-mediated chromatin remodeling. The data also suggest the possibility of a significant and practical benefit of combining EZH2 inhibitors and GRag that warrants further investigation in a clinical setting.

Reaction coupling between wild-type and disease-associated mutant EZH2

EZH2 and EZH1 are protein methyltransferases (PMTs) responsible for histone H3, lysine 27 (H3K27) methylation. Trimethylation of H3K27 (H3K27me3) is a hallmark of many cancers, including non-Hodgkin lymphoma (NHL). Heterozygous EZH2 point mutations at Tyr641, Ala677, and Ala687 have been observed in NHL. The Tyr641 mutations enhance activity on H3K27me2 but have weak or no activity on unmethylated H3K27, whereas the Ala677 and Ala687 mutations use substrates of all methylation states effectively. It has been proposed that enzymatic coupling of the wild-type and mutant enzymes leads to the oncogenic H3K27me3 mark in mutant-bearing NHL. We show that coupling with the wild-type enzyme is needed to achieve H3K27me3 for several mutants, but that others are capable of achieving H3K27me3 on their own. All forms of PRC2 (wild-type and mutants) display kinetic signatures that are consistent with a distributive mechanism of catalysis.

DOT1L inhibitor EPZ-5676 displays synergistic antiproliferative activity in combination with standard of care drugs and hypomethylating agents in MLL-rearranged leukemia cells

EPZ-5676 [(2R,3R,4S,5R)-2-(6-amino-9H-purin-9-yl)-5-((((1r,3S)-3-(2-(5-(tert-butyl)-1H-benzo[d]imidazol-2-yl)ethyl)cyclobutyl)(isopropyl)amino)methyl)tetrahydrofuran-3,4-diol], a small-molecule inhibitor of the protein methyltransferase DOT1L, is currently under clinical investigation for acute leukemias bearing MLL-rearrangements (MLL-r). In this study, we evaluated EPZ-5676 in combination with standard of care (SOC) agents for acute leukemias as well as other chromatin-modifying drugs in cellular assays with three human acute leukemia cell lines: MOLM-13 (MLL-AF9), MV4-11 (MLL-AF4), and SKM-1 (non-MLL-r). Studies were performed to evaluate the antiproliferative effects of EPZ-5676 combinations in a cotreatment model in which the second agent was added simultaneously with EPZ-5676 at the beginning of the assay, or in a pretreatment model in which cells were incubated for several days in the presence of EPZ-5676 prior to the addition of the second agent. EPZ-5676 was found to act synergistically with the acute myeloid leukemia (AML) SOC agents cytarabine or daunorubicin in MOLM-13 and MV4-11 MLL-r cell lines. EPZ-5676 is selective for MLL-r cell lines as demonstrated by its lack of effect either alone or in combination in the nonrearranged SKM-1 cell line. In MLL-r cells, the combination benefit was observed even when EPZ-5676 was washed out prior to the addition of the chemotherapeutic agents, suggesting that EPZ-5676 sets up a durable, altered chromatin state that enhances the chemotherapeutic effects. Our evaluation of EPZ-5676 in conjunction with other chromatin-modifying drugs also revealed a consistent combination benefit, including synergy with DNA hypomethylating agents. These results indicate that EPZ-5676 is highly efficacious as a single agent and synergistically acts with other chemotherapeutics, including AML SOC drugs and DNA hypomethylating agents in MLL-r cells.

Selective inhibition of EZH2 by EPZ-6438 leads to potent antitumor activity in EZH2-mutant non-Hodgkin lymphoma

Mutations within the catalytic domain of the histone methyltransferase EZH2 have been identified in subsets of patients with non-Hodgkin lymphoma (NHL). These genetic alterations are hypothesized to confer an oncogenic dependency on EZH2 enzymatic activity in these cancers. We have previously reported the discovery of EPZ005678 and EPZ-6438, potent and selective S-adenosyl-methionine-competitive small molecule inhibitors of EZH2. Although both compounds are similar with respect to their mechanism of action and selectivity, EPZ-6438 possesses superior potency and drug-like properties, including good oral bioavailability in animals. Here, we characterize the activity of EPZ-6438 in preclinical models of NHL. EPZ-6438 selectively inhibits intracellular lysine 27 of histone H3 (H3K27) methylation in a concentration- and time-dependent manner in both EZH2 wild-type and mutant lymphoma cells. Inhibition of H3K27 trimethylation (H3K27Me3) leads to selective cell killing of human lymphoma cell lines bearing EZH2 catalytic domain point mutations. Treatment of EZH2-mutant NHL xenograft-bearing mice with EPZ-6438 causes dose-dependent tumor growth inhibition, including complete and sustained tumor regressions with correlative diminution of H3K27Me3 levels in tumors and selected normal tissues. Mice dosed orally with EPZ-6438 for 28 days remained tumor free for up to 63 days after stopping compound treatment in two EZH2-mutant xenograft models. These data confirm the dependency of EZH2-mutant NHL on EZH2 activity and portend the utility of EPZ-6438 as a potential treatment for these genetically defined cancers.

Experts reviews of the multidisciplinary consensus conference colon and rectal cancer 2012: science, opinions and experiences from the experts of surgery

The first multidisciplinary consensus conference on colon and rectal cancer was held in December 2012, achieving a majority of consensus for diagnostic and treatment decisions using the Delphi Method. This article will give a critical appraisal of the topics discussed during the meeting and in the consensus document by well-known leaders in surgery that were involved in this multidisciplinary consensus process. Scientific evidence, experience and opinions are collected to support multidisciplinary teams (MDT) with arguments for medical decision-making in diagnosis, staging and treatment strategies for patients with colon or rectal cancer. Surgery is the cornerstone of curative treatment for colon and rectal cancer. Standardizing treatment is an effective instrument to improve outcome of multidisciplinary cancer care for patients with colon and rectal cancer. In this article, a review of the following focuses; Perioperative care, age and colorectal surgery, obstructive colorectal cancer, stenting, surgical anatomical considerations, total mesorectal excision (TME) surgery and training, surgical considerations for locally advanced rectal cancer (LARC) and local recurrent rectal cancer (LRRC), surgery in stage IV colorectal cancer, definitions of quality of surgery, transanal endoscopic microsurgery (TEM), laparoscopic colon and rectal surgery, preoperative radiotherapy and chemoradiotherapy, and how about functional outcome after surgery?