Lost in translation: preclinical studies on 3,4-methylenedioxymethamphetamine provide information on mechanisms of action, but do not allow accurate prediction of adverse events in humans

3,4-Methylenedioxymethamphetamine (MDMA) induces both acute adverse effects and long-term neurotoxic loss of brain 5-HT neurones in laboratory animals. However, when choosing doses, most preclinical studies have paid little attention to the pharmacokinetics of the drug in humans or animals. The recreational use of MDMA and current clinical investigations of the drug for therapeutic purposes demand better translational pharmacology to allow accurate risk assessment of its ability to induce adverse events. Recent pharmacokinetic studies on MDMA in animals and humans are reviewed and indicate that the risks following MDMA ingestion should be re-evaluated. Acute behavioural and body temperature changes result from rapid MDMA-induced monoamine release, whereas long-term neurotoxicity is primarily caused by metabolites of the drug. Therefore acute physiological changes in humans are fairly accurately mimicked in animals by appropriate dosing, although allometric dosing calculations have little value. Long-term changes require MDMA to be metabolized in a similar manner in experimental animals and humans. However, the rate of metabolism of MDMA and its major metabolites is slower in humans than rats or monkeys, potentially allowing endogenous neuroprotective mechanisms to function in a species specific manner. Furthermore acute hyperthermia in humans probably limits the chance of recreational users ingesting sufficient MDMA to produce neurotoxicity, unlike in the rat. MDMA also inhibits the major enzyme responsible for its metabolism in humans thereby also assisting in preventing neurotoxicity. These observations question whether MDMA alone produces long-term 5-HT neurotoxicity in human brain, although when taken in combination with other recreational drugs it may induce neurotoxicity.

Deletion of the Scl +19 enhancer increases the blood stem cell compartment without affecting the formation of mature blood lineages

The stem cell leukemia (Scl)/Tal1 gene is essential for normal blood and endothelial development, and is expressed in hematopoietic stem cells (HSCs), progenitors, erythroid, megakaryocytic, and mast cells. The Scl +19 enhancer is active in HSCs and progenitor cells, megakaryocytes, and mast cells, but not mature erythroid cells. Here we demonstrate that in vivo deletion of the Scl +19 enhancer (Scl(Δ19/Δ19)) results in viable mice with normal Scl expression in mature hematopoietic lineages. By contrast, Scl expression is reduced in the stem/progenitor compartment and flow cytometry analysis revealed that the HSC and megakaryocyte-erythroid progenitor populations are enlarged in Scl(Δ19/Δ19) mice. The increase in HSC numbers contributed to enhanced expansion in bone marrow transplantation assays, but did not affect multilineage repopulation or stress responses. These results affirm that the Scl +19 enhancer plays a key role in the development of hematopoietic stem/progenitor cells, but is not necessary for mature hematopoietic lineages. Moreover, active histone marks across the Scl locus were significantly reduced in Scl(Δ19/Δ19) fetal liver cells without major changes in steady-state messenger RNA levels, suggesting post-transcriptional compensation for loss of a regulatory element, a result that might be widely relevant given the frequent observation of mild phenotypes after deletion of regulatory elements.

Janus kinase deregulation in leukemia and lymphoma

Genetic alterations affecting members of the Janus kinase (JAK) family have been discovered in a wide array of cancers and are particularly prominent in hematological malignancies. In this review, we focus on the role of such lesions in both myeloid and lymphoid tumors. Oncogenic JAK molecules can activate a myriad of canonical downstream signaling pathways as well as directly interact with chromatin in noncanonical processes, the interplay of which results in a plethora of diverse biological consequences. Deciphering these complexities is shedding unexpected light on fundamental cellular mechanisms and will also be important for improved diagnosis, identification of new therapeutic targets, and the development of stratified approaches to therapy.

Translational neuropharmacology and the appropriate and effective use of animal models

This issue of the British Journal of Pharmacology is dedicated to reviews of the major animal models used in neuropharmacology to examine drugs for both neurological and psychiatric conditions. Almost all major conditions are reviewed. In general, regulatory authorities require evidence for the efficacy of novel compounds in appropriate animal models. However, the failure of many compounds in clinical trials following clear demonstration of efficacy in animal models has called into question both the value of the models and the discovery process in general. These matters are expertly reviewed in this issue and proposals for better models outlined. In this editorial, we further suggest that more attention be made to incorporate pharmacokinetic knowledge into the studies (quantitative pharmacology). We also suggest that more attention be made to ensure that full methodological details are published and recommend that journals should be more amenable to publishing negative data. Finally, we propose that new approaches must be used in drug discovery so that preclinical studies become more reflective of the clinical situation, and studies using animal models mimic the anticipated design of studies to be performed in humans, as closely as possible.

Mapping and functional characterisation of a CTCF-dependent insulator element at the 3' border of the murine Scl transcriptional domain

The Scl gene encodes a transcription factor essential for haematopoietic development. Scl transcription is regulated by a panel of cis-elements spread over 55 kb with the most distal 3′ element being located downstream of the neighbouring gene Map17, which is co-regulated with Scl in haematopoietic cells. The Scl/Map17 domain is flanked upstream by the ubiquitously expressed Sil gene and downstream by a cluster of Cyp genes active in liver, but the mechanisms responsible for delineating the domain boundaries remain unclear. Here we report identification of a DNaseI hypersensitive site at the 3′ end of the Scl/Map17 domain and 45 kb downstream of the Scl transcription start site. This element is located at the boundary of active and inactive chromatin, does not function as a classical tissue-specific enhancer, binds CTCF and is both necessary and sufficient for insulator function in haematopoietic cells in vitro. Moreover, in a transgenic reporter assay, tissue-specific expression of the Scl promoter in brain was increased by incorporation of 350 bp flanking fragments from the +45 element. Our data suggests that the +45 region functions as a boundary element that separates the Scl/Map17 and Cyp transcriptional domains, and raise the possibility that this element may be useful for improving tissue-specific expression of transgenic constructs.

P4-09-11: Kinesin Family Member 2C (KIF2C) Is a New Surrogate Prognostic Marker in Breast Cancer (BC)

Introduction

Gene expression microarrays, artificial neural network (ANN), tissue microarray and immunohistochemistry (IHC) techniques allow for the analysis of huge numbers of gene transcripts and their corresponding proteins and have been widely applied in predicting clinical outcome.

Methods

1- In this study, we analysed 48,000 gene transcripts of 171 unselected series of BC using ANN and pathways analysis to identify genes that can be used to predict clinical outcome of BC.

2- The clinic-pathological outcome of candidate genes were validated by using IHC in 4 independent primary BC data sets: a) a series of 379 consecutive high risk BC (NPI>3.4) who treated with surgery (S)+ radiotherapy (RT) and did not received neither endocrine (ET) nor chemo-therapies (CT), b) A series of 1650 consecutive cases of BC who treated with S + RT and received adjuvant CMF and/or ET according to Nottingham prognostic index (NPI), menopausal and ER status, c) 250 locally advanced BC treated with anthracycline-based combination with or without Taxane followed by S + RT and d) 145 BC overexpressing HER-2 treated with S + RT followed by sequential adjuvant anthracycline combination CT + trastuzumab.

Results

Gene expression analysis

ANN analysis revealed that KIF2C gene was the highest ranked gene that predicted clinical outcome and accurately differentiated between low and high grade BC based on a 10-fold external cross-validation analysis with an average classification accuracy of >98%. High KIF2C gene expression level was associated with shortest BC specific survival (BCSS), disease free (DFS) and distal metastasis free survivals (DM-FS); p<0.0001. In univariate analysis, high level of KIF2C gene expression was associated with large tumour size, higher lymph node stage, negative ER, positive p53 expression and HER2 overexpression. However in multivariate analysis, KIF2C gene expression level was only statistically associated with histological grade (p<00001) and mitosis (p<0.0001). Pathways analysis revealed that KIF2C is likely to play a significant role in cytokinesis, cell division and cell cycle regulations.

Immunohistochemistry

75% of BC showed overexpression of KIF2C protein. KIF2C protein overexpression was associated with unfavourable clinic-pathological features including high grade, high mitotic index, basal like phenotype, triple negative phenotype, HER2 overexpression, TOP2A overexpression, p53 mutation, and loss of BRCA1 (adjusted p<0.0001).

In univariate analysis, KIF2C protein overexpression was associated with patient's BCSS in both ER+/high risk patients (NPI > 3.4) who did not received ET (HR: 3.3, 95% CI: 1.2−9.3, p=0.02) and ER-/high risk patients who did not received CT (HR: 3.2, 95% CI: 1.1−8.8, p=0.025).

In 1650 BC series, multivariate Cox regression model including validated prognostic factors, confirmed that KIF2C overexpression is an independent prognostic factor. KIF2C overexpression showed increase in the risk of death (HR: 1.5, 95% CI: 1.1−2.0, p=0.009), recurrence (HR: 1.4, 95% CI: 1.1−1.8, p=0.017) and DM (HR: 1.6, 95% CI: 1.2−2.3, p=0.005).

In conclusion, our findings provide a new insight to a better understanding of mammary carcinogenesis and that KIF2C is a promising molecular prognostic factor and a potential therapeutic target.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-09-11.

P1-06-14: Topoisomerase II alpha (Top2a) Protein Expression Is a Predictor for Response to Anthracycline-Based Chemotherapy (ATC-CT): Is It Due to Gene Amplification, HER2−Coamplification or a Summation of Pathways Leading to This Highly Proliferative Phenotype?

Background: The evaluation of Top2a protein may be clinically more useful than gene alterations as a predictive marker for ATC-CT. In this study we assessed the association between gene copy number, gene and protein expressions of both TOP2A and HER2, and their effect on clinicopathological outcomes and management of breast cancer (BC).

Methods: 1- To study the response to anthracycline based chemotherapy (ATC-CT): The associations between clinical outcomes and both gene copy number changes (using in-situ hybridization; CISH) and protein expression (using immunohistochemistry) were studied in the neoadjuvant and adjuvant settings: a) 250 locally advanced primary BC treated with Neoadjuvant ATC-CT with or without Taxane followed by surgery (S) + radiotherapy (RT); pathological complete response (pCR) was used as the primary end point (PEP), b) 245 BC in which all patients were treated with S + RT followed by Adjuvant ATC-CT; progression free survival (PFS) was used as PEP ii) 145 primary BC overexpressing HER-2 treated with S+ RT followed by sequential adjuvant ATC-CT+ trastuzumab; PFS was used as PEP. 2- To study the clinic-pathological association of TOP2A alterations, we evaluated TOP2A alterations detected by CISH and IHC in unselected series of 1650 consecutive cases of primary BC who treated with S + RT and received adjuvant CMF and/or endocrine therapies according to Nottingham prognostic index and ER status. 3- To study in details the molecular alterations of TOP2A/HER2, in 171 unselected series of primary BC, we evaluated a) gene copy number changes using both high resolution oligo array CGH and CISH, b) mRNA expression using Agilent gene expression array and c) protein expression using IHC. We analysed 48,000 gene transcripts using Artificial Neural Networks (ANN) and pathway analysis to identify genes and biological pathways that related to TOP2A gene alterations.

Results: 1) In the ATC-CT neoadjuvant series, the pCR rate was 32/115 (28%) in tumours expressing high levels of Topo2A, compared to 5/74 (7%) in tumours expressing low levels of Topo2A (p<0.0001).

In multivariate analysis, Top2A overexpression was an independent predictor for pCR (HR 5.1, CI 95%; 1.4−18.4, p<0.001). 2) TOP2A overexpression was strongly associated with mitotic index, histological grade, KIF2C, loss of p53 function and the absence of both BRCA1 and ATM inactivation (p<0.0001). 3) ANN and pathway analysis revealed that TOP2A-strongly correlated genes are involved in: mitotic cell cycle regulation especially M phase and cell division (AURKB, KIF2C, BRIC5, ASPM, CCNA2, BUB1, FBXO5, PTTG1, CDCA5, CDCA3 CDCA8), Kinesin and microtubules regulator genes (KIF2C, KIF11, KIF14, KIF20A, KIF23, and KIFC1), and metastases (BRIC5, BUB1B, CCNA2, CCNE, PRRG1, PRM2, STMN1). Conclusions: Top2A protein expression is an independent predictor for pCR after ATC-CT treatment. The high response rate of top2A protein overexpression supports the theory that Top2a protein is a direct target of ATC-CT in these highly proliferative tumour cells. Furthermore, evaluation of Top2A protein may lead to a clinically useful test.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-06-14.

Tumour-infiltrating macrophages and clinical outcome in breast cancer

BACKGROUND

Macrophages constitute a major component of the leucocytic infiltrate of tumours. Human studies show an association between tumour-associated macrophages and tumours with poor prognostic features. In breast cancer, the presence of macrophages has been correlated with increased angiogenesis and poor prognosis but little information is available about the independent prognostic role of macrophages infiltrating breast carcinomas.

AIMS AND METHODS

This study used immunohistochemistry and tissue microarrays to assess the density and localisation of CD68 macrophages infiltrating 1322 breast tumours and to identify any relationship with clinicopathological factors and patient outcome.

RESULTS

Tumour-infiltrating macrophages were present in the majority of tumours with a predominantly diffuse pattern. The density of distant stromal macrophages (infiltrating stroma away from the carcinoma, median count 14 cells) was higher than intratumoural (median zero cells) and adjacent stromal macrophages (median three cells). Higher total macrophage number was associated with higher tumour grade (r(s)=0.39, p<0.001), ER and PgR negativity, HER-2 positivity and basal phenotype (p<0.001). In univariate survival analysis, higher numbers of CD68 macrophages were significantly associated with worse breast cancer-specific survival (p<0.001) and shorter disease-free interval (p=0.004). However in multivariate model analysis, the CD68 macrophage count was not an independent prognostic marker.

CONCLUSIONS

Macrophages are heterogeneous with different subsets having different functions. The present study suggests that overall macrophage numbers are not related to prognosis in breast cancer. However, further studies are needed to investigate the potential role of different subsets of macrophages.

Somatic SF3B1 mutation in myelodysplasia with ring sideroblasts

BACKGROUND

Myelodysplastic syndromes are a diverse and common group of chronic hematologic cancers. The identification of new genetic lesions could facilitate new diagnostic and therapeutic strategies.

METHODS

We used massively parallel sequencing technology to identify somatically acquired point mutations across all protein-coding exons in the genome in 9 patients with low-grade myelodysplasia. Targeted resequencing of the gene encoding RNA splicing factor 3B, subunit 1 (SF3B1), was also performed in a cohort of 2087 patients with myeloid or other cancers.

RESULTS

We identified 64 point mutations in the 9 patients. Recurrent somatically acquired mutations were identified in SF3B1. Follow-up revealed SF3B1 mutations in 72 of 354 patients (20%) with myelodysplastic syndromes, with particularly high frequency among patients whose disease was characterized by ring sideroblasts (53 of 82 [65%]). The gene was also mutated in 1 to 5% of patients with a variety of other tumor types. The observed mutations were less deleterious than was expected on the basis of chance, suggesting that the mutated protein retains structural integrity with altered function. SF3B1 mutations were associated with down-regulation of key gene networks, including core mitochondrial pathways. Clinically, patients with SF3B1 mutations had fewer cytopenias and longer event-free survival than patients without SF3B1 mutations.

CONCLUSIONS

Mutations in SF3B1 implicate abnormalities of messenger RNA splicing in the pathogenesis of myelodysplastic syndromes. (Funded by the Wellcome Trust and others.).

Constitutive activation of JAK2 in mammary epithelium elevates Stat5 signalling, promotes alveologenesis and resistance to cell death, and contributes to tumourigenesis

Signalling through the janus kinase (JAK)/signal transducer and activator of transcription (Stat) pathway is required at different stages of mammary gland development, and this pathway is frequently hyper-activated in cancer, including tumours of the breast. Stats 3, 5 and 6 have important roles in the differentiation and survival of mammary alveolar cells, but somewhat paradoxically, both Stat3 and 5 can have oncogenic activity in the mammary gland. Constitutive activation of JAK2 could be anticipated to result in hyper-activation of Stats 1, 3, 5 and 6 with concomitant cell transformation, although the outcome is difficult to envisage, particularly since Stats 3 and 5 play opposing roles in normal mammary gland development. Here, we show that expression of a constitutively active JAK2 mutant, JAK2 V617F, leads to hyper-activation of Stat5 in mammary epithelial cells (MECs), and transgenic mice expressing JAK2 V617F specifically in the mammary gland exhibit accelerated alveologenesis during pregnancy and delayed post-lactational regression. Overexpressing JAK2 V617F in MECs in vitro results in elevated proliferation and resistance to cell death. Furthermore, constitutively active JAK2 enhances anchorage-independent cell growth in the presence of a co-operating oncogene and accelerates tumourigenesis in a xenograft model. Taken together, our results provide insights into signalling downstream of constitutively active JAK2 and could be important for understanding the molecular mechanisms of breast tumourigenesis.

Mouse models of myeloproliferative neoplasms: JAK of all grades

In 2005, several groups identified a single gain-of-function point mutation in the JAK2 kinase that was present in the majority of patients with myeloproliferative neoplasms (MPNs). Since this discovery, much effort has been dedicated to understanding the molecular consequences of the JAK2V617F mutation in the haematopoietic system. Three waves of mouse models have been produced recently (bone marrow transplantation, transgenic and targeted knock-in), which have facilitated the understanding of the molecular pathogenesis of JAK2V617F-positive MPNs, providing potential platforms for designing and validating novel therapies in humans. This Commentary briefly summarises the first two types of mouse models and then focuses on the more recently generated knock-in models.

Long-term clinical outcome of oestrogen receptor-positive operable primary breast cancer in older women: a large series from a single centre

INTRODUCTION

A Cochrane review of seven randomised trials (N=1571) comparing surgery and primary endocrine therapy (PET) (oestrogen receptor (ER) unselected) shows no difference in overall survival (OS). We report outcome of a large series with ER-positive (ER+) early invasive primary breast cancer.

METHODS

Between 1973 and 2009, 1065 older (≥ 70 years) women (median age 78 years (70-99)) had either surgery (N=449) or PET (N=616) as initial treatment.

RESULTS

At 49-month median follow-up (longest 230 months), the 5-year breast cancer-specific survival (BCSS) and OS were 90 and 62%, respectively. Majority (74.2%) died from causes other than breast cancer. The rates (per annum) of local/regional recurrence (<1%) (following surgery), contralateral tumour (<1%) and metastases (<3%) were low. For patients on PET, 97.9% achieved clinical benefit (CB) at 6 months, with median time to progression of 49 months (longest 132 months) and significantly longer BCSS when compared with those who progressed (P<0.001). All patients with strongly ER+ (H-score >250) tumours achieved CB and had better BCSS (P<0.01). Patients with tumours having an H-score >250 were found to have equivalent BCSS regardless of treatment (surgery or PET; P=0.175), whereas for those with H-score ≤ 250, surgery produced better outcome (P<0.001).

CONCLUSION

Older women with ER+ breast cancer appear to have excellent long-term outcome regardless of initial treatment. Majority also die from non-breast cancer causes. Although surgery remains the treatment of choice, patients with ER-rich (H-score >250) tumours tend to do equally well when treated by PET. This should be taken into account when therapies are considered.

Alpha- and beta-adrenergic receptor (AR) protein expression is associated with poor clinical outcome in breast cancer: an immunohistochemical study

Breast cancer mortality is frequently associated with metastatic disease. Metastasis models have shown adrenoceptor (AR) stimulation induces cell migration which is inhibited by adrenoceptor antagonist drugs. We investigated adrenoceptor protein expression in clinical breast tumours and its association with disease progression and prognosis. Immunohistochemistry on tissue microarrays was used to characterise α1b, α2c and β(2)2 adrenoceptor protein expression in operable breast tumours. Associations with tumour-relevant biological markers and clinical outcome were statistically assessed. Strong α1b expression occurred in large high grade (P < 0.0001), HER2+ (P < 0.0001) or basal-like (CK5/6, P = 0.0005; CK14, P = 0.0001; EGFR, P = 0.003) cancers, showing increased proliferation (Mib1, P = 0.002), decreased apoptosis (Bcl2, P < 0.0001) and poor NPI membership (P = 0.001). α1b expression correlated with poor cancer-specific survival (LR = 7.628, P = 0.022) and tumour recurrence (LR = 6.128, P = 0.047). Strong α2c was over-expressed in high grade (P = 0.007), HER3+ (P = 0.002) and HER4+ (P < 0.0001) cancers with borderline increase in EGFR, p53 and MIB1 proteins, and inverse association with hormonal (PgR, P = 0.002) phenotype. In contrast, strong β(2) expression occurred in small-size, luminal-like (ER+, P < 0.001) tumours of low grade (P < 0.001) and lymph node stage (P = 0.027) that showed poor prognosis when hormonal treatment was withheld. Adrenoceptors were not found to be independent predictors of clinical outcome. Alpha1b and α2c AR is over-expressed in basal-like breast tumours of poor prognosis. Strong β(2) adrenoceptor expression is seen in patients with a luminal (ER+) tumour phenotype and good prognosis, due to benefits derived from hormonal therapy. These findings suggest a possible role for targeted therapy using adrenoceptor antagonists.

Massive genomic rearrangement acquired in a single catastrophic event during cancer development

Cancer is driven by somatically acquired point mutations and chromosomal rearrangements, conventionally thought to accumulate gradually over time. Using next-generation sequencing, we characterize a phenomenon, which we term chromothripsis, whereby tens to hundreds of genomic rearrangements occur in a one-off cellular crisis. Rearrangements involving one or a few chromosomes crisscross back and forth across involved regions, generating frequent oscillations between two copy number states. These genomic hallmarks are highly improbable if rearrangements accumulate over time and instead imply that nearly all occur during a single cellular catastrophe. The stamp of chromothripsis can be seen in at least 2%–3% of all cancers, across many subtypes, and is present in ∼25% of bone cancers. We find that one, or indeed more than one, cancer-causing lesion can emerge out of the genomic crisis. This phenomenon has important implications for the origins of genomic remodeling and temporal emergence of cancer.

PaperClip

Abstract S3-7: Kinome Screening for Regulators of Estrogen Receptor Identifies a Novel Kinase as a New Therapeutic Target in Breast Cancer

Background: Estrogen Receptor (ER) positive breast cancer is usually treated with hormone reduction or anti-estrogens. Still, only half the ER+ breast tumors respond to tamoxifen. Mutations in ER are rarely found; instead other mechanisms have been associated with resistance, namely phosphorylation of ERα. Since phosphorylation has been shown to be important for the stimulation of its transcriptional activity, focusing on the role of kinases and the influence of site specific phosphorylation in modulating activity may reveal fundamental insights and derive new druggable targets for exploitation in the clinic.

Materials and Methods: A systematic high-throughput RNAi screening using a large Human Kinase siRNA Library was carried out to identify novel kinases able to phosphorylate and/or modulate ERα activity; quantitative real-time RT-PCR analysis of pS2, PR and GREB1, three well characterized ERα-regulated genes, was performed after silencing each kinase individually. We then examined the effects of each newly identified kinase on various ERα features/functions including: i) ERα stability (Western blot), ii) ERα sub-cellular localization (confocal microscopy) and iii) ERα interactions with major components of the transcriptional machinery (co-immunoprecipitation). In addition, we examined the effects of these kinases on i) cell-cycle progression (FACS), ii) proliferation rate (MTT) and, iii) apoptosis levels (Annexin V, Caspase assays). We assessed clinical significance of our observations, by analyzing the expression of the novel kinases in BC tissue microarrays (TMAs, n=614) by immunohistochemistry.

Results: We have categorized the newly identified kinases in two groups depending on their effects on ERα transcriptional activity (30% up-regulation - 70% down-regulation). Among them, we discovered a novel receptor tyrosine kinase (RTK) whose role and/or involvement in ERα regulation has not been described thus far. We demonstrated that silencing of this kinase resulted in a great down-regulation (&gt;70-80%) of all 3 ERα-regulated genes tested (pS2, GREB1, PGR). In addition, upon kinase-silencing, we observed a large decrease in ERα protein levels, suggesting an involvement of this kinase in ERαα stability. Moreover, silencing of this kinase resulted in a &gt;50% decrease of breast cancer cells viability (P&lt;0.001). Analysis of the BC TMAs, the kinase of interest was expressed in weak (27%), moderate (35%) and high levels (38%). High expression correlated significantly with high tumor grade (P&lt;0.001) and predicted for worse BC specific overall survival (p=0.03).

Discussion: As RTKs are considered the primary mediators of the signalling network that transmit extracellular signals into the cell, they represent the first ‘line’ of drug target development in cancer treatment. We propose that our newly identified kinase could be a successful and life-saving drug target for the progression of various types of cancer.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr S3-7.

LIF-independent JAK signalling to chromatin in embryonic stem cells uncovered from an adult stem cell disease

Activating mutations in the tyrosine kinase JAK2 cause myeloproliferative neoplasms, clonal blood stem cell disorders with a propensity for leukaemic transformation. LIF signalling through JAK-STAT enables ES cell self-renewal. Here we show that mouse ES cells carrying the human JAK2V617F mutation could self-renew in chemically defined conditions without cytokines or small molecule inhibitors independently of JAK signalling through STAT3 or PI3K pathways. Phosphorylation of histone H3Y41 by JAK2 was recently shown to interfere with HP1α binding. Chromatin bound HP1α was lower in JAK2V617F ES cells but increased following JAK2 inhibition, coincident with a global reduction in H3Y41ph. JAK2 inhibition reduced Nanog, with a reduction in H3Y41ph and concomitant increase in HP1α at the Nanog promoter. Furthermore, Nanog was required for factor-independence of JAK2V617F ES cells. Taken together, these results uncover a previously unrecognised role for direct signalling to chromatin by JAK2 as an important mediator of ES cell self-renewal.

Distinct clinical phenotypes associated with JAK2V617F reflect differential STAT1 signaling

The JAK2V617F mutation is associated with distinct myeloproliferative neoplasms, including polycythemia vera (PV) and essential thrombocythemia (ET), but it remains unclear how it generates disparate disorders. By comparing clonally-derived mutant and wild-type cells from individual patients, we demonstrate that the transcriptional consequences of JAK2V617F are subtle, and that JAK2V617F-heterozygous erythroid cells from ET and PV patients exhibit differential interferon signaling and STAT1 phosphorylation. Increased STAT1 activity in normal CD34-positive progenitors produces an ET-like phenotype, whereas downregulation of STAT1 activity in JAK2V617F-heterozygous ET progenitors produces a PV-like phenotype. Our results illustrate the power of clonal analysis, indicate that the consequences of JAK2V617F reflect a balance between STAT5 and STAT1 activation and are relevant for other neoplasms associated with signaling pathway mutations.

The role of monoamines in the changes in body temperature induced by 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) and its derivatives

Hyperthermia is probably the most widely known acute adverse event that can follow ingestion of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) by recreational users. The effect of MDMA on body temperature is complex because the drug has actions on all three major monoamine neurotransmitters [5-hydroxytryptamine (5-HT), dopamine and noradrenaline], both by amine release and by direct receptor activation. Hyperthermia and hypothermia can be induced in laboratory animals by MDMA, depending on the ambient temperature, and involve both central thermoregulation and peripheral changes in blood flow and thermogenesis. Acute 5-HT release is not directly responsible for hyperthermia, but 5-HT receptors are involved in modulating the hyperthermic response. Impairing 5-HT function with a neurotoxic dose of MDMA or p-chlorophenylalanine alters the subsequent MDMA-induced hyperthermic response. MDMA also releases dopamine, and evidence suggests that this transmitter is involved in both the hyperthermic and hypothermic effects of MDMA in rats. The noradrenergic system is also involved in the hyperthermic response to MDMA. MDMA activates central alpha(2A)-adrenoceptors and peripheral alpha(1)-adrenoceptors to produce cutaneous vasoconstriction to restrict heat loss, and beta(3)-adrenoceptors in brown adipose tissue to increase heat generation. The hyperthermia occurring in recreational users of MDMA can be fatal, but data reviewed here indicate that it is unlikely that any single pharmaceutical agent will be effective in reversing the hyperthermia, so careful body cooling remains the principal clinical approach. Crucially, educating recreational users about the potential dangers of hyperthermia and the control of ambient temperature should remain key approaches to prevent this potentially fatal problem.

Molecular mechanisms associated with leukemic transformation of MPL-mutant myeloproliferative neoplasms

Somatic activating mutations in MPL, the thrombopoietin receptor, occur in the myeloproliferative neoplasms, although virtually nothing is known about their role in evolution to acute myeloid leukemia. In this study, the MPL T487A mutation, identified in de novo acute myeloid leukemia, was not detected in 172 patients with a myeloproliferative neoplasm. In patients with a prior MPL W515L-mutant myeloproliferative neoplasm, leukemic transformation was accompanied by MPL-mutant leukemic blasts, was seen in the absence of prior cytoreductive therapy and often involved loss of wild-type MPL by mitotic recombination. Moreover, clonal analysis of progenitor colonies at the time of leukemic transformation revealed the presence of multiple genetically distinct but phylogenetically-related clones bearing different TP53 mutations, implying a mutator-phenotype and indicating that leukemic transformation may be preceded by the parallel expansion of diverse hematopoietic clones.

BCL2 in breast cancer: a favourable prognostic marker across molecular subtypes and independent of adjuvant therapy received

BACKGROUND

Breast cancer is heterogeneous and the existing prognostic classifiers are limited in accuracy, leading to unnecessary treatment of numerous women. B-cell lymphoma 2 (BCL2), an antiapoptotic protein, has been proposed as a prognostic marker, but this effect is considered to relate to oestrogen receptor (ER) status. This study aimed to test the clinical validity of BCL2 as an independent prognostic marker.

METHODS

Five studies of 11 212 women with early-stage breast cancer were analysed. Individual patient data included tumour size, grade, lymph node status, endocrine therapy, chemotherapy and mortality. BCL2, ER, progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) levels were determined in all tumours. A Cox model incorporating the time-dependent effects of each variable was used to explore the prognostic significance of BCL2.

RESULTS

In univariate analysis, ER, PR and BCL2 positivity was associated with improved survival and HER2 positivity with inferior survival. For ER and PR this effect was time dependent, whereas for BCL2 and HER2 the effect persisted over time. In multivariate analysis, BCL2 positivity retained independent prognostic significance (hazard ratio (HR) 0.76, 95% confidence interval (CI) 0.66-0.88, P<0.001). BCL2 was a powerful prognostic marker in ER- (HR 0.63, 95% CI 0.54-0.74, P<0.001) and ER+ disease (HR 0.56, 95% CI 0.48-0.65, P<0.001), and in HER2- (HR 0.55, 95% CI 0.49-0.61, P<0.001) and HER2+ disease (HR 0.70, 95% CI 0.57-0.85, P<0.001), irrespective of the type of adjuvant therapy received. Addition of BCL2 to the Adjuvant! Online prognostic model, for a subset of cases with a 10-year follow-up, improved the survival prediction (P=0.0039).

CONCLUSIONS

BCL2 is an independent indicator of favourable prognosis for all types of early-stage breast cancer. This study establishes the rationale for introduction of BCL2 immunohistochemistry to improve prognostic stratification. Further work is now needed to ascertain the exact way to apply BCL2 testing for risk stratification and to standardise BCL2 immunohistochemistry for this application.