Examining the use of alternative light sources in medico-legal assessments of blunt-force trauma: a systematic review.

The ability to analyze blunt-force trauma is crucial for deciphering valuable clues concerning mechanisms of injury and as evidence for medico-legal investigations. The use of alternate light sources (ALS) has been studied over the past decade, and is proposed to outperform conventional white light (CWL) during bruise assessments. In response to the growing interest of the technology worldwide, a systematic review of the literature was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) to address the ability of ALS to detect and visualize bruising. From an initial 4055 records identified, ten studies met the eligibly criteria and were selected for this review. Evaluation also included a novel framework, referred to as SPICOT, to further systematically assess both scientific evidence and risk of bias in forensic literature. Analysis reveals that narrowband wavelengths within in the infrared or ultraviolet spectral ranges do not significantly outperform CWL in visualizing or detecting bruising. However, wavelengths within the visible spectrum, particularly 415 nm combined with longpass or bandpass yellow filters, are more effective. However, the majority of selected studies only address the sensitivity of ALS, and therefore, results may only be considered valid when the location of a bruise is known. Further investigation is required to understand the specificity of ALS, in particular how the use of topical cosmetic products, previous wounds/scar-tissue, tattoos, moles and freckles may affect detection. The ethical concern regarding the interpretation of enhanced visualized trauma should also be considered in prospect discussions prior to implementing ALS into routine practice. Nevertheless, this review finds that narrowband ALS within the visible spectrum demonstrates potential for improved injury documentation, outperforming CWL in the detection and visualization of bruising.

Postmortem CT analysis of paranasal sinuses using an experimental model of drowning.

Fluid-filled paranasal sinuses are suggested to be a valuable tool to distinguish between drowning and non-drowning postmortem, yet the mechanisms governing fluid entry remains unknown. We investigate if fluid-filled paranasal sinuses are caused by a passive influx from submersion or an active aspiration mechanism during drowning. The ovine nasal cavity and maxillary sinuses are remarkably similar anatomically to humans, and have been used for endoscopic surgical training in recent decades. We submerged 15 decapitated ovine heads from agricultural waste at a depth of 2 m in flowing water for 1, 8, and 24 h and 7 days. Paranasal sinuses were CT imaged and compared pre- and post-submersion to non-submerged controls. Furthermore, we examined the paranasal sinuses of a single homicide case of a non-drowned submerged subject. Results demonstrate that fluid passively enters the maxillary sinus postmortem in the non-drowned ovine heads following 1 h of submersion. Fluid volume was independent of submersion time and influenced by time out of water as well as handling, since volume was reduced between consecutive CT scans. In contrast to our hypothesis, the filling of the paranasal sinuses is due to passive influx of fluid from submersion rather than an active aspiration during drowning. The observation that paranasal sinuses were fluid-filled in a single medico-legal case of postmortem submersion supports the finding of passive influx. Consequently, careful interpretation of fluid-filled paranasal sinuses is required when bodies are found in water, as the finding cannot distinguish between postmortem submersion and drowning.

A probability model for estimating age in young individuals relative to key legal thresholds: 15, 18 or 21-year.

Age estimations are relevant for pre-trial detention, sentencing in criminal cases and as part of the evaluation in asylum processes to protect the rights and privileges of minors. No current method can determine an exact chronological age due to individual variations in biological development. This study seeks to develop a validated statistical model for estimating an age relative to key legal thresholds (15, 18, and 21 years) based on a skeletal (CT-clavicle, radiography-hand/wrist or MR-knee) and tooth (radiography-third molar) developmental stages. The whole model is based on 34 scientific studies, divided into examinations of the hand/wrist (15 studies), clavicle (5 studies), distal femur (4 studies), and third molars (10 studies). In total, data from approximately 27,000 individuals have been incorporated and the model has subsequently been validated with data from 5,000 individuals. The core framework of the model is built upon transition analysis and is further developed by a combination of a type of parametric bootstrapping and Bayesian theory. Validation of the model includes testing the models on independent datasets of individuals with known ages and shows a high precision with separate populations aligning closely with the model's predictions. The practical use of the complex statistical model requires a user-friendly tool to provide probabilities together with the margin of error. The assessment based on the model forms the medical component for the overall evaluation of an individual's age.

The histone H4 lysine 16 acetyltransferase hMOF regulates the outcome of autophagy.

Autophagy is an evolutionarily conserved catabolic process involved in several physiological and pathological processes. Although primarily cytoprotective, autophagy can also contribute to cell death; it is thus important to understand what distinguishes the life or death decision in autophagic cells. Here we report that induction of autophagy is coupled to reduction of histone H4 lysine 16 acetylation (H4K16ac) through downregulation of the histone acetyltransferase hMOF (also called KAT8 or MYST1), and demonstrate that this histone modification regulates the outcome of autophagy. At a genome-wide level, we find that H4K16 deacetylation is associated predominantly with the downregulation of autophagy-related genes. Antagonizing H4K16ac downregulation upon autophagy induction results in the promotion of cell death. Our findings establish that alteration in a specific histone post-translational modification during autophagy affects the transcriptional regulation of autophagy-related genes and initiates a regulatory feedback loop, which serves as a key determinant of survival versus death responses upon autophagy induction.

Mesenchymal Stromal Cell Secretion of Programmed Death-1 Ligands Regulates T Cell Mediated Immunosuppression.

Mesenchymal stromal cells (MSCs) exert broad immunosuppressive potential, modulating the activity of cells of innate and adaptive immune systems. As MSCs become accepted as a therapeutic option for the treatment of immunological disorders such as Graft versus Host Disease, our need to understand the intricate details by which they exert their effects is crucial. Programmed death-1 (PD-1) is an important regulator in T cell activation and homeostatic control. It has been reported that this pathway may be important in contact-dependent mediated immunomodulation by MSCs. The aim of this study was to establish whether MSCs, in addition to their cell-surface expression, are able to secrete PD-1 ligands (PD-L1 and PD-L2) and their potential importance in modulating contact-independent mechanisms of MSC immunosuppression. Here we report that MSCs express and secrete PD-L1 and PD-L2 and that this is regulated by exposure to interferon γ and tumor necrosis factor α. MSCs, via their secretion of PD-1 ligands, suppress the activation of CD4+ T cells, downregulate interleukin-2 secretion and induce irreversible hyporesponsiveness and cell death. Suppressed T cells demonstrated a reduction in AKT phosphorylation at T308 and a subsequent increase in FOXO3 expression that could be reversed with blockade of PD-L1. In conclusion, we demonstrate for the first time, that MSCs are able to secrete PD-1 ligands, with this being the first known report of a biological role for PD-L2 in MSCs. These soluble factors play an important role in modulating immunosuppressive effects of MSCs directly on T cell behavior and induction of peripheral tolerance. Stem Cells 2017;35:766-776.

Do cryopreserved mesenchymal stromal cells display impaired immunomodulatory and therapeutic properties?

We have recently reported that therapeutic mesenchymal stromal cells (MSCs) have low engraftment and trigger the instant blood mediated inflammatory reaction (IBMIR) after systemic delivery to patients, resulting in compromised cell function. In order to optimize the product, we compared the immunomodulatory, blood regulatory, and therapeutic properties of freeze-thawed and freshly harvested cells. We found that freeze-thawed MSCs, as opposed to cells harvested from continuous cultures, have impaired immunomodulatory and blood regulatory properties. Freeze-thawed MSCs demonstrated reduced responsiveness to proinflammatory stimuli, an impaired production of anti-inflammatory mediators, increased triggering of the IBMIR, and a strong activation of the complement cascade compared to fresh cells. This resulted in twice the efficiency in lysis of thawed MSCs after 1 hour of serum exposure. We found a 50% and 80% reduction in viable cells with freshly detached as opposed to thawed in vitro cells, indicating a small benefit for fresh cells. In evaluation of clinical response, we report a trend that fresh cells, and cells of low passage, demonstrate improved clinical outcome. Patients treated with freshly harvested cells in low passage had a 100% response rate, twice the response rate of 50% observed in a comparable group of patients treated with freeze-thawed cells at higher passage. We conclude that cryobanked MSCs have reduced immunomodulatory and blood regulatory properties directly after thawing, resulting in faster complement-mediated elimination after blood exposure. These changes seem to be paired by differences in therapeutic efficacy in treatment of immune ailments after hematopoietic stem cell transplantation.

Autologous Peripheral Blood Mononuclear Cells as Treatment in Refractory Acute Respiratory Distress Syndrome.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is a devastating disorder. Despite enormous efforts in clinical research, effective treatment options are lacking, and mortality rates remain unacceptably high. OBJECTIVES: A male patient with severe ARDS showed no clinical improvement with conventional therapies. Hence, an emergent experimental intervention was performed. METHODS: We performed intratracheal administration of autologous peripheral blood-derived mononuclear cells (PBMCs) and erythropoietin (EPO). RESULTS: We found that after 2 days of initial PBMC/EPO application, lung function improved and extracorporeal membrane oxygenation (ECMO) support was reduced. Bronchoscopy and serum inflammatory markers revealed reduced inflammation. Additionally, serum concentration of miR-449a, b, c and miR-34a, a transient upregulation of E-cadherin and associated chromatin marks in PBMCs indicated airway epithelial differentiation. Extracellular vesicles from PBMCs demonstrated anti-inflammatory capacity in a TNF-α-mediated nuclear factor-x03BA;B in vitro assay. Despite improving respiratory function, the patient died of multisystem organ failure on day 38 of ECMO treatment. CONCLUSIONS: This case report provides initial encouraging evidence to use locally instilled PBMC/EPO for treatment of severe refractory ARDS. The observed clinical improvement may partially be due to the anti-inflammatory effects of PBMC/EPO to promote tissue regeneration. Further studies are needed for more in-depth understanding of the underlying mechanisms of in vivo regeneration.

Like a rolling histone: epigenetic regulation of neural stem cells and brain development by factors controlling histone acetylation and methylation.

BACKGROUND: The development of the nervous system is a highly organized process involving the precise and coordinated timing of many complex events. These events require proper expression of genes promoting survival, differentiation, and maturation, but also repression of alternative cell fates and restriction of cell-type-specific gene expression. SCOPE OF THE REVIEW: As the enzymes mediating post-translational histone acetylation and methylation are regulating higher order chromatin structure and controlling gene transcription, knowledge of the roles for these enzymes becomes crucial for understanding neural development and disease. The widespread expression and general biological roles for chromatin-modifying factors have hampered the studies of such enzymes in neural development, but in recent years, in vivo and in vitro studies have started to shed light on the various processes these enzymes regulate. In this review we summarize the implications of chromatin-modifying enzymes in neural development, with particular emphasis on enzymes regulating histone acetylation and methylation. MAJOR CONCLUSIONS: Enzymes controlling histone acetylation and methylation are involved in the whole process of neural development, from controlling proliferation and undifferentiated, "poised", state of stem cells to promoting and inhibiting neurogenic and gliogenic pathways and neuronal survival as well as neurite outgrowth. GENERAL SIGNIFICANCE: Aberrant enzymatic activities of histone acetyl transferases, deacetylases, and demethylases have been chemically and genetically associated with neural developmental disorders and cancer. Future studies may aim at linking the genetic and developmental studies to more in-depth biochemical characterization to provide a clearer picture of how to improve the diagnosis, prognosis, and treatment of such disorders. This article is part of a Special Issue entitled Biochemistry of Stem Cells.

Diagnosing fatal drownings: A review of the postmortem findings.

The lack of drowning-specific pathological findings postmortem complicates medico-legal investigations when bodies are recovered in water. This review provides an in-depth analysis of macroscopic and microscopic findings, as well as biochemical and molecular approaches typically used to diagnose drownings. To ensure that only studies fulfilling established scientific criteria were selected to form conclusions in this review, existing literature was systematically assessed using SPICOT for evaluation of scientific evidence and risk of bias. Analysis of selected studies indicates that several pathophysiological findings following suspected drowning lack scientific evidence, while others are supported by the literature. However, the shortage of suitable controls in drowning research, specifically addressing non-drowned immersed bodies significantly limits investigations on postmortem drowning pathology, and further research is warranted.

A probability model for assessing age relative to the 18-year old threshold based on magnetic resonance imaging of the knee combined with radiography of third molars in the lower jaw.

OBJECTIVE: This study aims to generate a statistical model based on magnetic resonance imaging of the knee and radiography of third molars in the lower jaw, for assessing age relative to the 18-year old threshold. METHODS: In total, 58 studies correlating knee or tooth development to age were assessed, 5 studies for knee and 7 studies for tooth were included in the statistical model. The relation between the development of the anatomical site, based on a binary system, and age were estimated using logistic regression. Separate meta-populations for knee and tooth were generated from the individual based data for men and women. A weighted estimate of probabilities was made by combining the probability densities for knee and tooth. Margin of errors for males and females in different age groups and knee and tooth maturity were calculated within the larger framework of transition analysis using a logit model as a base. Evidentiary values for combinations of knee and tooth maturity were evaluated with likelihood ratios. RESULTS: For males, the sensitivity for the method was calculated to 0.78 (probability of correctly classifying adults), the specificity 0.90 (probability of correctly classifying minors), the negative predictive value 0.80 (proportion identified minors are minors) and the positive predictive value 0.89 (proportion identified adults are adults) indicating a model better at identifying minors than adults. The point at which half the female population has reached closed knee lies before the 18-year threshold, adding the knee as an indicator lowers specificity and increases sensitivity. The sensitivity when using tooth as an indicator for females is 0.24 and specificity 0.97, signifying few minors misclassified as adults but also a low probability of identifying adults. The negative predictive value for women when using tooth as the sole indicator is 0.56 and positive predictive value 0.88. Probabilities were calculated for males and females assuming a uniform age distribution between 15 and 21years. The calculated margin of error of minors classified as adults in a population between 15 and 21 years with the model was 11% for males and 12% for females. Further, the evidentiary value as well as margin of error vary for different combinations of knee and tooth maturity. CONCLUSION: The statistical model based on the combination of MRI knee and radiography of mandibular third molars is a valid method to assess age relative to the 18-year old threshold when applied on males and of limited value in females.

Notch induces cyclin-D1-dependent proliferation during a specific temporal window of neural differentiation in ES cells.

The Notch signaling pathway controls cell fate choices at multiple steps during cell lineage progression. To produce the cell fate choice appropriate for a particular stage in the cell lineage, Notch signaling needs to interpret the cell context information for each stage and convert it into the appropriate cell fate instruction. The molecular basis for this temporal context-dependent Notch signaling output is poorly understood, and to study this, we have engineered a mouse embryonic stem (ES) cell line, in which short pulses of activated Notch can be produced at different stages of in vitro neural differentiation. Activation of Notch signaling for 6h specifically at day 3 during neural induction in the ES cells led to significantly enhanced cell proliferation, accompanied by Notch-mediated activation of cyclin D1 expression. A reduction of cyclin-D1-expressing cells in the developing CNS of Notch signaling-deficient mouse embryos was also observed. Expression of a dominant negative form of cyclin D1 in the ES cells abrogated the Notch-induced proliferative response, and, conversely, a constitutively active form of cyclin D1 mimicked the effect of Notch on cell proliferation. In conclusion, the data define a novel temporal context-dependent function of Notch and a critical role for cyclin D1 in the Notch-induced proliferation in ES cells.

Fatal anaphylactic shock: A review of postmortem biomarkers and diagnostics.

Diagnosing anaphylactic shock postmortem is challenging since differential diagnoses exist and the forensic pathologist often faces subtle findings and lacks relevant information which prevents reaching an opinion of certainty. This review provides an overview of the literature covering research and existing recommendations on the postmortem diagnosis of anaphylactic shock. In order to harmonize the approach and provide guidance for diagnosing deaths from anaphylactic shock in the six forensic centers in Sweden, a guidance protocol aligned with the notion of a holistic view in the approach was devised. Areas in need of further studies include both immunohistological and biochemical investigations to stratify quantitative approaches based on condition and anaphylactic trigger and to lay the ground for and possibly establish alternative matrices.

Treatment of chronic GvHD with mesenchymal stromal cells induces durable responses: A phase II study.

Steroid-refractory chronic graft-vs-host disease (cGvHD) contributes to morbidity after allogeneic hematopoietic stem cell transplantation. Here, we report on 11 patients with severe, refractory cGvHD treated with repeated infusions of allogeneic bone marrow-derived mesenchymal stromal cells (MSC) over a 6- to 12-month period. Six patients responded to MSC treatment following National Institutes of Health response criteria, accompanied by improvement in GvHD-related symptoms and quality of life. This response was durable, with systemic immunosuppressive therapy withdrawn from two responders, and a further two free from steroids and tapering calcineurin inhibitors. All responders displayed a distinct immune phenotype characterized by higher levels of naïve T cells and B cells before treatment compared with the nonresponders, and a significantly higher fraction of CD31+ naïve CD4+ T cells. MSC treatment was associated with significant increases in naïve T cells, B cells, and Tregs 7 days after each infusion. Skin biopsies showed resolution of epidermal pathology. CXCL9 and CXCL10 showed differential responses in responder and nonresponder patients. Our data support the use of MSC infusions as treatment for steroid-refractory cGvHD with durable responses. We propose CXCL9 and CXCL10 as early biomarkers for responsiveness to MSC treatment. Our results highlight the importance of the MSC recipient immune phenotype in promoting treatment response. This trial was registered at www.ClinicalTrials.gov as #NCT01522716.

Maximum Tolerated Dose and Pharmacokinetics of Paclitaxel Micellar in Patients with Recurrent Malignant Solid Tumours: A Dose-Escalation Study.

INTRODUCTION: A water-soluble Cremophor EL-free formulation of paclitaxel, in which retinoic acid derivates solubilize paclitaxel by forming micelles (paclitaxel micellar), was studied for the first time in man to establish the maximum tolerated dose (MTD) and to characterize the pharmacokinetics (PK). METHODS: This was an open-label, one-arm, dose-escalating study in patients with advanced solid malignant tumours, for which no standard therapy was available or had failed. Paclitaxel micellar was given as 1-h intravenous infusion every 21 days for 3 cycles, mainly without premedication. Plasma samples were collected during 24 h at the first cycle and paclitaxel concentrations were assayed by high-performance liquid chromatography. PK was evaluated using a two-compartment model. RESULTS: Thirty-four patients received paclitaxel micellar at doses ranging between 90 and 275 mg/m2. MTD was established as 250 mg/m2. Fatigue and neuropathy were the most frequent dose-limiting toxicities. No hypersensitivity reactions were observed. PK of paclitaxel was evaluated in 25 data sets. Paclitaxel micellar had a rapid initial distribution phase, mean half-life 0.55 h, estimated to be completed 3 h after dosing and a mean terminal half-life of 8.8 h. Mean clearance was 13.4 L/h/m2 with fivefold interindividual variability. The residual areas after 10 h and 24 h were 15.7 ± 8.6% and 5.7 ± 3.9% of the area under the plasma concentration-time curve to infinite time (AUCinf), respectively. CONCLUSION: No new side effects unknown for paclitaxel were observed. Maximum plasma concentration (Cmax) and AUCinf showed a tendency to increase linearly with dose within the 150-275 mg/m2 dose range. The possibility to administer paclitaxel micellar without steroid premedication makes it an attractive candidate for further studies in combination with immunotherapy. TRIAL REGISTRATION: EudraCT no: 2004-001821-54. FUNDING: Oasmia Pharmaceutical AB.

Pharmacokinetics of Total and Unbound Paclitaxel After Administration of Paclitaxel Micellar or Nab-Paclitaxel: An Open, Randomized, Cross-Over, Explorative Study in Breast Cancer Patients.

INTRODUCTION: Paclitaxel micellar is a novel formulation of paclitaxel in which retinoic acid derivates solubilize paclitaxel. The aim of the present study was to compare the unbound and total plasma pharmacokinetics of the new formulation with those of nanoparticle albumin-bound (nab)-paclitaxel and to further assess its safety. METHODS: In this open, randomized, cross-over study, 28 female patients with breast cancer were given paclitaxel micellar and nab-paclitaxel as a 1-h intravenous infusion at a dose of 260 mg/m2. Plasma samples were collected during 10 h, which were projected to cover at least 80% of the area to infinite time, AUCinf. Unbound paclitaxel was measured in ultrafiltrate of plasma. Total paclitaxel in plasma was measured after protein precipitation with acetonitrile. Both assays used ultra-performance liquid chromatography (UPLC) followed by MS/MS for drug quantification. The unbound fraction, fu, was calculated as the ratio between the unbound and the total concentration. RESULTS: No difference in fu of paclitaxel between the two formulations was observed. Statistical comparison of AUC0-10h and Cmax of unbound paclitaxel demonstrated that the two formulations met the criteria for bioequivalence. Regarding total paclitaxel levels, Cmax but not AUC0-10h met the criteria. This study supports a safe administration of paclitaxel micellar. CONCLUSION: The two formulations, paclitaxel micellar and nab-paclitaxel, behaved similarly following infusion. Probably, both formulations dissociate immediately in the blood, whereupon released paclitaxel rapidly distributes into tissue. Judged from the bioequivalence demonstrated for unbound paclitaxel, the two formulations are considered clinically equivalent. TRIAL REGISTRATION: EudraCT no.: 2010-019838-27. FUNDING: Oasmia Pharmaceutical AB.

The Complement System Is Essential for the Phagocytosis of Mesenchymal Stromal Cells by Monocytes.

Mesenchymal stromal cell (MSC) therapy is a promising tool in the treatment of chronic inflammatory diseases. This has been ascribed to the capacity of MSC to release a large variety of immune-modulatory factors. However, all aspects of the mode of therapeutic MSC action in different diseases remain unresolved, mainly because most of the infused MSC are undetectable in the circulation within hours after infusion. The aim of this study was to elucidate the fate of MSC after contact with plasma. We found that upon contact with blood, complement proteins including C3b/iC3b are deposited on MSC. Importantly, we also found that complement bound to MSC enhanced their phagocytosis by classical and intermediate monocytes via a mechanism that involves C3 but not C5. Thus, we describe for the first time a mechanism which might explain, at least partly, why MSC are not found in the blood circulation after infusion. Our results indicate that MSC immune-modulatory effects could be mediated by monocytes that have phagocytosed them.

Co-planar 3,3',4,4',5-pentachlorinated biphenyl and non-co-planar 2,2',4,6,6'-pentachlorinated biphenyl differentially induce recruitment of oestrogen receptor alpha to aryl hydrocarbon receptor target genes.

In the present study we examined the ability of 3,3',4,4',5-pentachlorinated biphenyl [PCB126 (polychlorinated biphenyl 126)], a prototypical AHR (aryl hydrocarbon receptor) agonist, and 2,2',4,6,6'-PCB (PCB104), which does not activate AHR, to induce the recruitment of ERalpha (oestrogen receptor alpha) to CYP1A1 (cytochrome P4501A1 gene) and CYP1B1 promoters in T-47D human breast cancer cells and other cell lines. PCB126 treatment strongly induced CYP1A1 and CYP1B1 mRNA expression that was unaffected by co-treatment with E2 (17beta-oestradiol). PCB104 failed to induce changes in either CYP1A1 or CYP1B1 expression levels. ChIP (chromatin immunoprecipitation) assays show that PCB126, but not PCB104, increased the promoter occupancy by ERalpha to CYP1A1 and CYP1B1 promoters. Co-treatment with PCB126+E2 significantly enhanced the promoter occupancy of ERalpha at CYP1A1, whereas co-treatment with PCB126+4-hydroxytamoxifen or ICI182,780 did not. Competitive binding studies revealed that neither PCB126 nor PCB104 bound to ERalpha. HEK-293 cells (human embryonic kidney-293 cells) stably transfected with ERalpha showed significantly higher PCB126-induced CYP1A1 expression compared with empty vector controls, whereas no increase was observed in cells stably transfected with ERalpha lacking its N-terminal AF1 (activation function-1) domain (ERalphaDeltaAF1). Despite no increase in AHR-mediated gene expression, ChIP assays revealed that ERalphaDeltaAF1 was present at CYP1A1 and CYP1B1 promoters. HC11 mouse mammary cells stably expressing shRNA (small-hairpin RNA) against ERalpha showed an 8-fold reduction in PCB126-dependent Cyp1a1 expression. Our results provide further evidence that AHR agonists induce ERalpha promoter occupancy at AHR target genes through indirect activation of ERalpha, and support a role for ERalpha in AHR transactivation.

Identification of tamoxifen-induced coregulator interaction surfaces within the ligand-binding domain of estrogen receptors.

Tamoxifen is a selective estrogen receptor (ER) modulator that is clinically used as an antagonist to treat estrogen-dependent breast cancers but displays unwanted agonistic effects in other tissues. Previous studies on ERalpha have delineated a role of the N-terminal activation function AF-1 in mediating the agonistic effects of tamoxifen, while the mechanisms for how ERbeta mediates tamoxifen action remain to be elucidated. As peptides can be used to detect distinct receptor conformations and binding surfaces for coactivators and corepressors, we attempted in this study to identify previously unrecognized peptides that interact specifically with ERs in the presence of tamoxifen. We identified two distinct peptides among others that are highly selective for tamoxifen-bound ERalpha or ERbeta. Domain mapping and mutation analysis suggest that these peptides recognize a novel tamoxifen-induced binding surface within the C-terminal ligand-binding domain that is distinct from the agonist-induced AF-2 surface. Peptide expression specifically inhibited transcriptional ER activity in response to tamoxifen, presumably by preventing the binding of endogenous coactivators. Moreover, tamoxifen-responsive and ER subtype-selective coactivators were engineered by replacing the LXXLL motifs in the coactivator TIF2 with either of the two peptides. Finally, our results indicate that related coactivators may act via the novel tamoxifen-induced binding surface, referred to as AF-T, allowing us to propose a revised model of tamoxifen agonism.