Abstract P4-04-02: Bromodomain and extra-terminal proteins regulate the epithelial-mesenchymal transition in breast cancer

BACKGROUND. The epithelial-mesenchymal transition (EMT) is a developmental program that cancer cells often activate to acquire a highly plastic phenotype that promotes invasion, metastasis, but also chemoresistance and cancer stem cell generation. As readers of epigenetic marks, bromodomain and extra-terminal (BET) proteins BRD2, BRD3 and BRD4 participate in the regulation of multiple transcriptional programs implicated in cancer progression. We sought to unravel the roles of BET proteins in EMT in breast cancer.

METHODS. Cell line models of the different subtypes of breast cancer were used in this study (luminal A: MCF-7, T47D, basal-like: MDA-MB-231, SUM149PT). BET expression was modulated by using RNA interference or plasmid-mediated overexpression. Small molecule JQ1 was used to inhibit BET proteins. The expression of 84 key EMT genes was monitored by PCR using a Qiagen kit. We also monitored EMT by measuring the expression of epithelial and mesenchymal markers by immunoblot and immunofluorescence staining.

RESULTS. Despite their homology, we report that BET proteins differentially regulate EMT. Based on an EMT PCR array, we identified a BRD2-specific transcriptional profile that promotes EMT, whereas BRD3 and BRD4 signatures repress this program. These individual signatures are unidentifiable upon pan-BET inhibition using JQ1, reinforcing the necessity to target each BET member separately to better understand their functions. Upon BRD2 depletion, basal-like breast cancer cells, which present a mesenchymal phenotype, exhibit a reduced expression of mesenchymal markers (N-cadherin, vimentin) and re-express epithelial markers (E-cadherin, cytokeratins). Moreover, a large panel of EMT master transcription factors is downregulated in BRD2-depleted cells, including the Snail and ZEB families or Twist. Interestingly, we found that BRD3 or BRD4 depletion leads to the opposite phenotype: an increase of mesenchymal marker expression and repression of the epithelial markers. In luminal A breast cancer cells which present an epithelial phenotype, BRD2 overexpression leads to the expression of mesenchymal markers. Similar results were obtained by depleting BRD3 or BRD4 in these cells, confirming the differential roles of BET proteins in EMT regulation.

CONCLUSION. Taken together, our results establish that BRD2 positively regulates EMT, whereas BRD3 and BRD4 repress this program. BET proteins possess separate and opposite biological functions, reinforcing the relevance of an individual targeting instead of a pan-BET inhibition using JQ1. We hypothesize that BET proteins modulate EMT through the regulation of its master transcription factors. We propose that the balance of BET proteins present at the promoters of the EMT genes is a novel mechanism of regulation of this program in breast cancer cells.BACKGROUND. The epithelial-mesenchymal transition (EMT) is a developmental program that cancer cells often activate to acquire a highly plastic phenotype that promotes invasion, metastasis, but also chemoresistance and cancer stem cell generation. As readers of epigenetic marks, bromodomain and extra-terminal (BET) proteins BRD2, BRD3 and BRD4 participate in the regulation of multiple transcriptional programs implicated in cancer progression. We sought to unravel the roles of BET proteins in EMT in breast cancer.

METHODS. Cell line models of the different subtypes of breast cancer were used in this study (luminal A: MCF-7, T47D, basal-like: MDA-MB-231, SUM149PT). BET expression was modulated by using RNA interference or plasmid-mediated overexpression. Small molecule JQ1 was used to inhibit BET proteins. The expression of 84 key EMT genes was monitored by PCR using a Qiagen kit. We also monitored EMT by measuring the expression of epithelial and mesenchymal markers by immunoblot and immunofluorescence staining.

RESULTS. Despite their homology, we report that BET proteins differentially regulate EMT. Based on an EMT PCR array, we identified a BRD2-specific transcriptional profile that promotes EMT, whereas BRD3 and BRD4 signatures repress this program. These individual signatures are unidentifiable upon pan-BET inhibition using JQ1, reinforcing the necessity to target each BET member separately to better understand their functions. Upon BRD2 depletion, basal-like breast cancer cells, which present a mesenchymal phenotype, exhibit a reduced expression of mesenchymal markers (N-cadherin, vimentin) and re-express epithelial markers (E-cadherin, cytokeratins). Moreover, a large panel of EMT master transcription factors is downregulated in BRD2-depleted cells, including the Snail and ZEB families or Twist. Interestingly, we found that BRD3 or BRD4 depletion leads to the opposite phenotype: an increase of mesenchymal marker expression and repression of the epithelial markers. In luminal A breast cancer cells which present an epithelial phenotype, BRD2 overexpression leads to the expression of mesenchymal markers. Similar results were obtained by depleting BRD3 or BRD4 in these cells, confirming the differential roles of BET proteins in EMT regulation.

CONCLUSION. Taken together, our results establish that BRD2 positively regulates EMT, whereas BRD3 and BRD4 repress this program. BET proteins possess separate and opposite biological functions, reinforcing the relevance of an individual targeting instead of a pan-BET inhibition using JQ1. We hypothesize that BET proteins modulate EMT through the regulation of its master transcription factors. We propose that the balance of BET proteins present at the promoters of the EMT genes is a novel mechanism of regulation of this program in breast cancer cells.

Citation Format: Andrieu G, Tran AH, Denis GV. Bromodomain and extra-terminal proteins regulate the epithelial-mesenchymal transition in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-04-02.

Neuronal correlates of attention and its disengagement in the superior colliculus of rat

Orienting attention to a new target requires prior disengagement of attention from the current focus. Previous studies indicate that the superior colliculus (SC) plays an important role in attention. However, recordings of responses of SC neurons during attentional disengagement have not yet been reported. Here, we analyzed rat SC neuronal activity during performance of an attention-shift task with and without disengagement. In this task, conditioned stimuli (CSs; right and/or left light-flash or sound) were sequentially presented. To obtain an intracranial self-stimulation reward, rats were required to lick a spout when an infrequent conditioned stimulus appeared (reward trials). In the disengagement reward trials, configural stimuli consisting of an infrequent stimulus and frequent stimulus in the former trials were presented; in the non-disengagement reward trials, only an infrequent stimulus was presented. Of the 186 SC neurons responding to the CSs, 41 showed stronger responses to the CSs in the disengagement reward trials than in the non-disengagement reward trials (disengagement-related neurons). Furthermore, lick latencies in the disengagement reward trials were negatively correlated with response magnitudes to the CSs in half of the disengagement-related neurons. These disengagement-related neurons were located mainly in the deep layers of the SC. Another 70 SC neurons responded to the CSs in both disengagement and non-disengagement reward trials, suggesting that these neurons were involved in attention engagement. Our results suggest complementary mechanisms of attentional shift based on two subpopulations of neurons in the SC.

2,3,7,8-Tetrachlorodibenzo-p-dioxin in breast milk increases autistic traits of 3-year-old children in Vietnam

Dioxin levels in the breast milk of mothers residing near a contaminated former airbase in Vietnam remain much higher than in unsprayed areas, suggesting high perinatal dioxin exposure for their infants. The present study investigated the association of perinatal dioxin exposure with autistic traits in 153 3-year-old children living in a contaminated area in Vietnam. The children were followed up from birth using the neurodevelopmental battery Bayley-III. The high-2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposed groups (⩾3.5 pg per g fat) showed significantly higher Autism Spectrum Rating Scale (ASRS) scores for both boys and girls than the mild-TCDD exposed groups, without differences in neurodevelopmental scores. In contrast, the high total dioxin-exposed group, indicated by polychlorinated dibenzo-p-dioxins/furans (PCDDs/Fs)--the toxic equivalents (TEQ) levels⩾17.9 pg-TEQ per g fat, had significantly lower neurodevelopmental scores than the mild-exposed group in boys, but there was no difference in the ASRS scores. The present study demonstrates a specific impact of perinatal TCDD on autistic traits in childhood, which is different from the neurotoxicity of total dioxins (PCDDs/Fs).

Neuronal responses to face-like and facial stimuli in the monkey superior colliculus

The superficial layers of the superior colliculus (sSC) appear to function as a subcortical visual pathway that bypasses the striate cortex for the rapid processing of coarse facial information. We investigated the responses of neurons in the monkey sSC during a delayed non-matching-to-sample (DNMS) task in which monkeys were required to discriminate among five categories of visual stimuli [photos of faces with different gaze directions, line drawings of faces, face-like patterns (three dark blobs on a bright oval), eye-like patterns, and simple geometric patterns]. Of the 605 sSC neurons recorded, 216 neurons responded to the visual stimuli. Among the stimuli, face-like patterns elicited responses with the shortest latencies. Low-pass filtering of the images did not influence the responses. However, scrambling of the images increased the responses in the late phase, and this was consistent with a feedback influence from upstream areas. A multidimensional scaling (MDS) analysis of the population data indicated that the sSC neurons could separately encode face-like patterns during the first 25-ms period after stimulus onset, and stimulus categorization developed in the next three 25-ms periods. The amount of stimulus information conveyed by the sSC neurons and the number of stimulus-differentiating neurons were consistently higher during the 2nd to 4th 25-ms periods than during the first 25-ms period. These results suggested that population activity of the sSC neurons preferentially filtered face-like patterns with short latencies to allow for the rapid processing of coarse facial information and developed categorization of the stimuli in later phases through feedback from upstream areas.

sLORETA current source density analysis of evoked potentials for spatial updating in a virtual navigation task

Previous studies have reported that multiple brain regions are activated during spatial navigation. However, it is unclear whether these activated brain regions are specifically associated with spatial updating or whether some regions are recruited for parallel cognitive processes. The present study aimed to localize current sources of event related potentials (ERPs) associated with spatial updating specifically. In the control phase of the experiment, electroencephalograms (EEGs) were recorded while subjects sequentially traced 10 blue checkpoints on the streets of a virtual town, which were sequentially connected by a green line, by manipulating a joystick. In the test phase of the experiment, the checkpoints and green line were not indicated. Instead, a tone was presented when the subjects entered the reference points where they were then required to trace the 10 invisible spatial reference points corresponding to the checkpoints. The vertex-positive ERPs with latencies of approximately 340 ms from the moment when the subjects entered the unmarked reference points were significantly larger in the test than in the control phases. Current source density analysis of the ERPs by standardized low-resolution brain electromagnetic tomography (sLORETA) indicated activation of brain regions in the test phase that are associated with place and landmark recognition (entorhinal cortex/hippocampus, parahippocampal and retrosplenial cortices, fusiform, and lingual gyri), detecting self-motion (posterior cingulate and posterior insular cortices), motor planning (superior frontal gyrus, including the medial frontal cortex), and regions that process spatial attention (inferior parietal lobule). The present results provide the first identification of the current sources of ERPs associated with spatial updating, and suggest that multiple systems are active in parallel during spatial updating.

Abstract 568: Identification of Novel Pre-translational Regulatory Mechanisms for NF-?B Activation

NF-κB controlled transcriptional regulation plays a central role in inflammatory and immune responses. Currently understanding about NF-κB activation mechanism emphasizes IκB-tethered complex inactivation in the cytoplasm. In the case of NF-κB activation, IκB phosphorylation leads to its degradation followed by NF-κB relocating to the nuclear and transactivation of NF-κB targeted genes. Pre-translational mechanism mediated NF-κB activation remains poorly understood. In this study, we studied NF-κB pre-translational regulation by performed a series of data-base mining using experimental data-based NCBI Unigene EST profile database, Gene Expression Omnibus (GEO) database, Transcription Element Search System (TESS) database, AceView database, Epigenomics databases, and TargetScan software. We reported the following findings: 1) NF-κB family/signaling genes are differentially expressed in 20 human and 19 mouse tissues; 2) Heart and vessels are the inflammation privilege tissues and less easy to be inflamed because lacking of NF-κB signaling key molecular expression; 3) NF-κB activation is readily induced by cardiovascular disease risk factors oxidized-LDL and pro-inflammatory cytokines in endothelial cells; 4) Transcription factors C/EBPs and NF-κB have higher binding site frequencies in the promoters of Pro-inflammatory cytokine-induced NF-κB genes; 5) Most NF-κB signaling genes have multiple alternative promoters and alternatively spliced isoforms; 6) NF-κB family genes have DNA methylation characteristics and may be subjected to epigenetic regulation; 7) 27 out of 38 NF-κB signaling gene can be regulated by microRNAs, with the binding qualities to mRNA targets being equivalent to what have been approved experimentally. Our findings provide important insight in the mechanism of NF-κB activation, which may contribute to cardiovascular disease, inflammatory diseases and immunological disorders.

Identification of novel pretranslational regulatory mechanisms for NF-κB activation

NF-κB-controlled transcriptional regulation plays a central role in inflammatory and immune responses. Currently, understanding about NF-κB activation mechanism emphasizes IκB-tethered complex inactivation in the cytoplasm. In the case of NF-κB activation, IκB phosphorylation leads to its degradation, followed by NF-κB relocation to the nucleus and trans-activation of NF-κB-targeted genes. Pretranslational mechanism mediated NF-κB activation remains poorly understood. In this study, we investigated NF-κB pretranslational regulation by performing a series of database mining analyses and using six large national experimental databases (National Center of Biotechnology Information UniGene expressed sequence tag profile database, Gene Expression Omnibus database, Transcription Element Search System database, AceView database, and Epigenomics database) and TargetScan software. We reported the following findings: 1) NF-κB-signaling genes are differentially expressed in human and mouse tissues; 2) heart and vessels are the inflammation-privileged tissues and less easy to be inflamed because lacking in key NF-κB-signaling molecular expression; 3) NF-κB-signaling genes are induced by cardiovascular disease risk factors oxidized phospholipids and proinflammatory cytokines in endothelial cells; 4) transcription factors CCAAT/enhancer-binding proteins and NF-κB have higher binding site frequencies in the promoters of proinflammatory cytokine-induced NF-κB genes; 5) most NF-κB-signaling genes have multiple alternative promoters and alternatively spliced isoforms; 6) NF-κB family genes can be regulated by DNA methylation; and 7) 27 of 38 NF-κB-signaling genes can be regulated by microRNAs. Our findings provide important insight into the mechanism of NF-κB activation, which may contribute to cardiovascular disease, inflammatory diseases, and immunological disorders.

Influence of Maternal Exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin on Socioemotional Behaviors in Offspring Rats

Effects of dioxins on cognitive functions were reported in previous studies conducted in humans and animals. In the present study, we investigated the influence of dioxin exposure during pregnancy on social interaction and on the activity of offspring, which are related to neurodevelopmental disturbances. In addition, we analyzed neurochemical alterations of the limbic system of rat brains to suggest one mechanism of dioxin effects on brain function. We believe that this manuscript is suitable for publication in "Environmental Health Insights" because it provides an interesting topic for a wide global audience. To clarify the relationships between maternal dioxin exposure and socioemotional functions of rat offspring, dams were given TCDD (1.0 μg/kg) on gestational day 15. Social interactions and forced swimming time were compared between TCDD-exposed and control offspring in each gender. Frequency and duration of locomotion were higher, and durations per one behavior of proximity and social contact were significantly lower in the exposed males, while only the duration of proximity was lower in the exposed females. Forced swimming time on the first day was significantly longer in the exposed males. In the limbic system of the rat brain, the levels and/or activity of CaMKIIα were decreased in males and were increased in females in the exposed offspring. These results suggest that prenatal TCDD exposure induces hyperactivity and socioemotional deficits, particularly in the male offspring due to alterations in CaMKIIα activity in the limbic system of the brain.

Ex vivo organotypic corneal model of acute epithelial herpes simplex virus type I infection

Herpes keratitis is one of the most severe pathologies associated with the herpes simplex virus-type 1 (HSV-1). Herpes keratitis is currently the leading cause of both cornea-derived and infection-associated blindness in the developed world. Typical presentation of herpes keratitis includes infection of the corneal epithelium and sometimes the deeper corneal stroma and endothelium, leading to such permanent corneal pathologies as scarring, thinning, and opacity. Corneal HSV-1 infection is traditionally studied in two types of experimental models. The in vitro model, in which cultured monolayers of corneal epithelial cells are infected in a Petri dish, offers simplicity, high level of replicability, fast experiments, and relatively low costs. On the other hand, the in vivo model, in which animals such as rabbits or mice are inoculated directly in the cornea, offers a highly sophisticated physiological system, but has higher costs, longer experiments, necessary animal care, and a greater degree of variability. In this video article, we provide a detailed demonstration of a new ex vivo model of corneal epithelial HSV-1 infection, which combines the strengths of both the in vitro and the in vivo models. The ex vivo model utilizes intact corneas organotypically maintained in culture and infected with HSV-1. The use of the ex vivo model allows for highly physiologically-based conclusions, yet it is rather inexpensive and requires time commitment comparable to that of the in vitro model.

Contribution of hippocampal place cell activity to learning and formation of goal-directed navigation in rats

Although extensive behavioral studies have demonstrated that hippocampal lesions impair navigation toward specific places, the role of hippocampal neuronal activity in the development of efficient navigation during place learning remains unknown. The aim of the present study was to investigate how hippocampal neuronal activity changes as rats learn to navigate efficiently to acquire rewards in an open field. Rats were pre-trained in a random reward task where intracranial self-stimulation rewards were provided at random locations. Then, the rats were trained in a novel place task where they were rewarded at two specific locations as they repeatedly shuttled between them. Hippocampal neuronal activity was recorded during the course of learning of the place task. The rats learned reward sites within several sessions, and gradually developed efficient navigation strategies throughout the learning sessions. Some hippocampal neurons gradually changed spatial firing as the learning proceeded, and discharged robustly near the reward sites when efficient navigation was established. Over the learning sessions, the neuronal activity was highly correlated to formation of efficient shuttling trajectories between the reward sites. At the end of the experiment, spatial firing patterns of the hippocampal neurons were re-examined in the random reward task. The specific spatial firing patterns of the neurons were preserved if the rats navigated, as if they expected to find rewards at the previously valid locations. However, those specific spatial firing patterns were not observed in rats pursuing random trajectories. These results suggest that hippocampal neurons have a crucial role in formation of an efficient navigation.

Localization of cell division protein FtsK to the Escherichia coli septum and identification of a potential N-terminal targeting domain

Escherichia coli cell division protein FtsK is a homolog of Bacillus subtilis SpoIIIE and appears to act late in the septation process. To determine whether FtsK localizes to the septum, we fused three N-terminal segments of FtsK to green fluorescent protein (GFP) and expressed them in E. coli cells. All three segments were sufficient to target GFP to the septum, suggesting that as little as the first 15% of the protein is a septum-targeting domain. Localized fluorescence was detectable only in cells containing a visible midcell constriction, suggesting that FtsK targeting normally occurs only at a late stage of septation. The largest two FtsK-GFP fusions were able at least partially to complement the ftsK44 mutation in trans, suggesting that the N- and C-terminal domains are functionally separable. However, overproduction of FtsK-GFP resulted in a late-septation phenotype similar to that of ftsK44, with fluorescent dots localized at the blocked septa, suggesting that high levels of the N-terminal domain may still localize but also inhibit FtsK activity. Interestingly, under these conditions fluorescence was also sometimes localized as bands at potential division sites, suggesting that FtsK-GFP is capable of targeting very early. In addition, FtsK-GFP localized to potential division sites in cephalexin-induced and ftsI mutant filaments, further supporting the idea that FtsK-GFP can target early, perhaps by recognizing FtsZ directly. This hypothesis was supported by the failure of FtsK-GFP to localize in ftsZ mutant filaments. In ftsK44 mutant filaments, FtsA and FtsZ were usually localized to potential division sites between the blocked septa. When the ftsK44 mutation was incorporated into the FtsK-GFP fusions, localization to midcell ranged between very weak and undetectable, suggesting that the FtsK44 mutant protein is defective in targeting the septum.

Interleukin-1 production in tumor cells of human melanoma surgical specimens

To determine whether IL-1 alpha and/or IL-1 beta protein is expressed by human melanoma tumor in vivo, we first analyzed nine human melanoma cell lines and optimized the in situ detection of these proteins. Three of the melanoma cell lines stained positively for both IL-1 alpha and IL-1 beta using immunohistochemistry (IHC). THe specificity of IHC was confirmed by the ability of purified recombinant IL-1 alpha and IL-1 beta protein to abolish the staining after being adsorbed by their respective antibodies before use in IHC. The three positively staining cell lines were also the only lines to demonstrate IL-1 production by western blot analysis as well as IL-1 secretion by ELISA. Next we examined 29 surgically obtained melanoma tumor specimens (6 primary and 23 metastases) that had been formalin fixed and paraffin embedded. Using the same anti-IL-1 antibodies, 5 of 23 metastatic tumors stained positively. None of the 6 primary lesions stained for either IL-1 alpha or IL-1 beta. Comparison of staining pattern performed on serially sectioned tissue using preimmune serum and antibodies against S-100 protein, melanoma-associated antigen (HMB-45), and CD68 (kappa P1), which recognizes monocyte-macrophage cell lineage, demonstrates for the first time that IL-1 protein is produced by human melanoma tumor cells in vivo. These findings provide the basis for examination of what may be a previously unrecognized biologically distinct subset of patients.