HER2 Status Assessment in Endometrial Serous Carcinoma: Comparative Analysis of Two Proposed Testing and Interpretation Algorithms.

HER2 status is now routinely assessed in endometrial serous carcinoma (ESC) due to the reported predictive value of HER2 protein overexpression and/or gene amplification. Herein the authors compare 2 proposed testing and interpretation guidelines for HER2 in ESC. Forty-three consecutive cases of ESC that had been dually tested by both HER2 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) were interpreted using 2 sets of guidelines. Guideline set 1 (GS1) is the 2018 American Society of Clinical Oncology/College of American Pathologists guidelines for breast cancer. Guideline set 2 (GS2) is a recent proposal that is a slight modification of the enrollment criteria for the clinical trial (NCT01367002) that demonstrated a survival benefit for anti-HER2 therapy in ESC. By IHC, GS1 and GS2, respectively classified 39.5% (17/43) and 28% (12/43) of ESC as HER2-negative, 37.2% (16/43) and 53.4% (23/43) as HER2 equivocal, and 23.2% (10/43) and 18.6% (8/43) as HER2-positive ( P > 0.05 for all). IHC and FISH were highly concordant at the extremes using either set of guidelines, as no cases were found to be IHC3+/FISH-negative or IHC 0-1+/FISH-positive. GS1 and GS2 were comparable regarding the proportion of IHC equivocal cases that were HER2 amplified by FISH (19% vs 23% respectively; [ P = 0.71]). GS1 and GS2 displayed 98% (42/43) concordance regarding the final (IHC and/or FISH-based) classification of tumors as being HER2-positive or negative, and the same 13 cases were ultimately classified as HER2 amplified using either GS1 or GS2. One "discordant" case was classified as HER2-positive using GS2 but HER2-negative using GS1 (HER2 IHC score 2+ using both guidelines, HER2:CEP17 signal ratio of 3, HER2 signal number of 3.4). Six (14%) of the 43 cases (FISH Groups: 2, 3, and 4) would require IHC results to interpret the FISH findings using GS1. Because GS1 requires that the HER2 IHC staining be observed within a homogeneous and contiguous invasive cell population, and this is not a requirement in GS2, GS2 may be better suited for ESC given its frequently heterogeneous staining pattern. Additional studies may be required on the optimal interpretation of problematic dual-probe FISH scenarios in GS2 and the necessity for IHC correlation in such scenarios. Using either set of guidelines, our findings support a reflex testing strategy of restricting FISH testing to cases that are IHC equivocal.

Systemic AAV9.LAMP2B injection reverses metabolic and physiologic multiorgan dysfunction in a murine model of Danon disease.

Danon disease (DD) is a rare X-linked autophagic vacuolar myopathy associated with multiorgan dysfunction, including the heart, skeletal muscle, and liver. There are no specific treatments, and most male patients die from advanced heart failure during the second or third decade of life. DD is caused by mutations in the lysosomal-associated membrane protein 2 (LAMP2) gene, a key mediator of autophagy. LAMP2 has three isoforms: LAMP2A, LAMP2B, and LAMP2C. LAMP2B is the predominant isoform expressed in cardiomyocytes. This study evaluates the efficacy of human LAMP2B gene transfer using a recombinant adeno-associated virus 9 carrying human LAMP2B (AAV9.LAMP2B) in a Lamp2 knockout (KO) mouse, a DD model. AAV9.LAMP2B was intravenously injected into 2- and 6-month-old Lamp2 KO male mice to assess efficacy in adolescent and adult phenotypes. Lamp2 KO mice receiving AAV9.LAMP2B demonstrated dose-dependent restoration of human LAMP2B protein in the heart, liver, and skeletal muscle tissue. Impaired autophagic flux, evidenced by increased LC3-II, was abrogated by LAMP2B gene transfer in all tissues in both cohorts. Cardiac function was also improved, and transaminases were reduced in AAV9.LAMP2B-treated KO mice, indicating favorable effects on the heart and liver. Survival was also higher in the older cohort receiving high vector doses. No anti-LAMP2 antibodies were detected in mice that received AAV9.LAMP2B. In summary, LAMP2B gene transfer improves metabolic and physiologic function in a DD murine model, suggesting that a similar therapeutic approach may be effective for treating patients with this highly morbid disease.

Association of Human iPSC Gene Signatures and X Chromosome Dosage with Two Distinct Cardiac Differentiation Trajectories.

Despite the importance of understanding how variability across induced pluripotent stem cell (iPSC) lines due to non-genetic factors (clone and passage) influences their differentiation outcome, large-scale studies capable of addressing this question have not yet been conducted. Here, we differentiated 191 iPSC lines to generate iPSC-derived cardiovascular progenitor cells (iPSC-CVPCs). We observed cellular heterogeneity across the iPSC-CVPC samples due to varying fractions of two cell types: cardiomyocytes (CMs) and epicardium-derived cells (EPDCs). Comparing the transcriptomes of CM-fated and EPDC-fated iPSCs, we discovered that 91 signature genes and X chromosome dosage differences are associated with these two distinct cardiac developmental trajectories. In an independent set of 39 iPSCs differentiated into CMs, we confirmed that sex and transcriptional differences affect cardiac-fate outcome. Our study provides novel insights into how iPSC transcriptional and X chromosome gene dosage differences influence their response to differentiation stimuli and, hence, cardiac cell fate.

Fulminant Versus Acute Nonfulminant Myocarditis in Patients With Left Ventricular Systolic Dysfunction.

BACKGROUND: Fulminant myocarditis (FM) is a form of acute myocarditis characterized by severe left ventricular systolic dysfunction requiring inotropes and/or mechanical circulatory support. A single-center study found that a patient with FM had better outcomes than those with acute nonfulminant myocarditis (NFM) presenting with left ventricular systolic dysfunction, but otherwise hemodynamically stable. This was recently challenged, so disagreement still exists. OBJECTIVES: This study sought to provide additional evidence on the outcome of FM and to ascertain whether patient stratification based on the main histologic subtypes can provide additional prognostic information. METHODS: A total of 220 patients (median age 42 years, 46.3% female) with histologically proven acute myocarditis (onset of symptoms <30 days) all presenting with left ventricular systolic dysfunction were included in a retrospective, international registry comprising 16 tertiary hospitals in the United States, Europe, and Japan. The main endpoint was the occurrence of cardiac death or heart transplantation within 60 days from admission and at long-term follow-up. RESULTS: Patients with FM (n = 165) had significantly higher rates of cardiac death and heart transplantation compared with those with NFM (n = 55), both at 60 days (28.0% vs. 1.8%, p = 0.0001) and at 7-year follow-up (47.7% vs. 10.4%, p < 0.0001). Using Cox multivariate analysis, the histologic subtype emerged as a further variable affecting the outcome in FM patients, with giant cell myocarditis having a significantly worse prognosis compared with eosinophilic and lymphocytic myocarditis. In a subanalysis including only adults with lymphocytic myocarditis, the main endpoints occurred more frequently in FM compared with in NFM both at 60 days (19.5% vs. 0%, p = 0.005) and at 7-year follow up (41.4% vs. 3.1%, p = 0.0004). CONCLUSIONS: This international registry confirms that patients with FM have higher rates of cardiac death and heart transplantation both in the short- and long-term compared with patients with NFM. Furthermore, we provide evidence that the histologic subtype of FM carries independent prognostic value, highlighting the need for timely endomyocardial biopsy in this condition.

Impaired mitophagy facilitates mitochondrial damage in Danon disease.

RATIONALE: Lysosomal associated membrane protein type-2 (LAMP-2) is a highly conserved, ubiquitous protein that is critical for autophagic flux. Loss of function mutations in the LAMP-2 gene cause Danon disease, a rare X-linked disorder characterized by developmental delay, skeletal muscle weakness, and severe cardiomyopathy. We previously found that human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from Danon patients exhibited significant mitochondrial oxidative stress and apoptosis. Understanding how loss of LAMP-2 expression leads to cardiomyocyte dysfunction and heart failure has important implications for the treatment of Danon disease as well as a variety of other cardiac disorders associated with impaired autophagy. OBJECTIVE: Elucidate the pathophysiology of cardiac dysfunction in Danon disease. METHODS AND RESULTS: We created hiPSCs from two patients with Danon disease and differentiated those cells into hiPSC-CMs using well-established protocols. Danon hiPSC-CMs demonstrated an accumulation of damaged mitochondria, disrupted mitophagic flux, depressed mitochondrial respiratory capacity, and abnormal gene expression of key mitochondrial pathways. Restoring the expression of LAMP-2B, the most abundant LAMP-2 isoform in the heart, rescued mitophagic flux as well as mitochondrial health and bioenergetics. To confirm our findings in vivo, we evaluated Lamp-2 knockout (KO) mice. Impaired autophagic flux was noted in the Lamp-2 KO mice compared to WT reporter mice, as well as an increased number of abnormal mitochondria, evidence of incomplete mitophagy, and impaired mitochondrial respiration. Physiologically, Lamp-2 KO mice demonstrated early features of contractile dysfunction without overt heart failure, indicating that the metabolic abnormalities associated with Danon disease precede the development of end-stage disease and are not merely part of the secondary changes associated with heart failure. CONCLUSIONS: Incomplete mitophagic flux and mitochondrial dysfunction are noted in both in vitro and in vivo models of Danon disease, and proceed overt cardiac contractile dysfunction. This suggests that impaired mitochondrial clearance may be central to the pathogenesis of disease and a potential target for therapeutic intervention.

iPSCORE: A Resource of 222 iPSC Lines Enabling Functional Characterization of Genetic Variation across a Variety of Cell Types.

Large-scale collections of induced pluripotent stem cells (iPSCs) could serve as powerful model systems for examining how genetic variation affects biology and disease. Here we describe the iPSCORE resource: a collection of systematically derived and characterized iPSC lines from 222 ethnically diverse individuals that allows for both familial and association-based genetic studies. iPSCORE lines are pluripotent with high genomic integrity (no or low numbers of somatic copy-number variants) as determined using high-throughput RNA-sequencing and genotyping arrays, respectively. Using iPSCs from a family of individuals, we show that iPSC-derived cardiomyocytes demonstrate gene expression patterns that cluster by genetic background, and can be used to examine variants associated with physiological and disease phenotypes. The iPSCORE collection contains representative individuals for risk and non-risk alleles for 95% of SNPs associated with human phenotypes through genome-wide association studies. Our study demonstrates the utility of iPSCORE for examining how genetic variants influence molecular and physiological traits in iPSCs and derived cell lines.

Human-Induced Pluripotent Stem Cell-Based Modeling of Cardiac Storage Disorders.

PURPOSE OF REVIEW: The aim of this study is to review the published human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) models of cardiac storage disorders and to evaluate the limitations and future applications of this technology. RECENT FINDINGS: Several cardiac storage disorders (CSDs) have been modeled using patient-specific hiPSC-CMs, including Anderson-Fabry disease, Danon disease, and Pompe disease. These models have shown that patient-specific hiPSC-CMs faithfully recapitulate key phenotypic features of CSDs and respond predictably to pharmacologic manipulation. hiPSC-CMs generated from patients with CSDs are representative models of the patient disease state and can be used as an in vitro system for the study of human cardiomyocytes. While these models suffer from several limitations, they are likely to play an important role in future mechanistic studies of cardiac storage disorders and the development of targeted therapeutics for these diseases.

Brief Report: Oxidative Stress Mediates Cardiomyocyte Apoptosis in a Human Model of Danon Disease and Heart Failure.

Danon disease is a familial cardiomyopathy associated with impaired autophagy due to mutations in the gene encoding lysosomal-associated membrane protein type 2 (LAMP-2). Emerging evidence has highlighted the importance of autophagy in regulating cardiomyocyte bioenergetics, function, and survival. However, the mechanisms responsible for cellular dysfunction and death in cardiomyocytes with impaired autophagic flux remain unclear. To investigate the molecular mechanisms responsible for Danon disease, we created induced pluripotent stem cells (iPSCs) from two patients with different LAMP-2 mutations. Danon iPSC-derived cardiomyocytes (iPSC-CMs) exhibited impaired autophagic flux and key features of heart failure such as increased cell size, increased expression of natriuretic peptides, and abnormal calcium handling compared to control iPSC-CMs. Additionally, Danon iPSC-CMs demonstrated excessive amounts of mitochondrial oxidative stress and apoptosis. Using the sulfhydryl antioxidant N-acetylcysteine to scavenge free radicals resulted in a significant reduction in apoptotic cell death in Danon iPSC-CMs. In summary, we have modeled Danon disease using human iPSC-CMs from patients with mutations in LAMP-2, allowing us to gain mechanistic insight into the pathogenesis of this disease. We demonstrate that LAMP-2 deficiency leads to an impairment in autophagic flux, which results in excessive oxidative stress, and subsequent cardiomyocyte apoptosis. Scavenging excessive free radicals with antioxidants may be beneficial for patients with Danon disease. In vivo studies will be necessary to validate this new treatment strategy.

Genetic isolation of stem cell-derived pacemaker-nodal cardiac myocytes.

Dysfunction of the cardiac pacemaker tissues due to genetic defects, acquired diseases, or aging results in arrhythmias. When arrhythmias occur, artificial pacemaker implants are used for treatment. However, the numerous limitations of electronic implants have prompted studies of biological pacemakers that can integrate into the myocardium providing a permanent cure. Embryonic stem (ES) cells cultured as three-dimensional (3D) spheroid aggregates termed embryoid bodies possess the ability to generate all cardiac myocyte subtypes. Here, we report the use of a SHOX2 promoter and a Cx30.2 enhancer to genetically identify and isolate ES cell-derived sinoatrial node (SAN) and atrioventricular node (AVN) cells, respectively. The ES cell-derived Shox2 and Cx30.2 cardiac myocytes exhibit a spider cell morphology and high intracellular calcium loading characteristic of pacemaker-nodal myocytes. These cells express abundant levels of pacemaker genes such as endogenous HCN4, Cx45, Cx30.2, Tbx2, and Tbx3. These cells were passaged, frozen, and thawed multiple times while maintaining their pacemaker-nodal phenotype. When cultured as 3D aggregates in an attempt to create a critical mass that simulates in vivo architecture, these cell lines exhibited an increase in the expression level of key regulators of cardiovascular development, such as GATA4 and GATA6 transcription factors. In addition, the aggregate culture system resulted in an increase in the expression level of several ion channels that play a major role in the spontaneous diastolic depolarization characteristic of pacemaker cells. We have isolated pure populations of SAN and AVN cells that will be useful tools for generating biological pacemakers.

Shox2 regulates the pacemaker gene program in embryoid bodies.

The pacemaker tissues of the heart are a complex set of specialized cells that initiate the rhythmic heartbeat. The sinoatrial node (SAN) serves as the primary pacemaker, whereas the atrioventricular node can serve as a subsidiary pacemaker in cases of SAN failure or block. The elucidation of genetic networks regulating the development of these tissues is crucial for understanding the mechanisms underlying arrhythmias and for the design of targeted therapies. Here we report temporal and spatial self-organized formation of the pacemaker and contracting tissues in three-dimensional aggregate cultures of mouse embryonic stem cells termed embryoid bodies (EBs). Using genetic marker expression and electrophysiological analyses we demonstrate that in EBs the pacemaker potential originates from a localized population of cells and propagates into the adjacent contracting region forming a functional syncytium. When Shox2, a major determinant of the SAN genetic pathway, was ablated we observed substantial slowing of spontaneous contraction rates and an altered gene expression pattern including downregulation of HCN4, Cx45, Tbx2, Tbx3, and bone morphogenetic protein 4 (BMP4); and upregulation of Cx40, Cx43, Nkx2.5, and Tbx5. This phenotype could be rescued by adding BMP4 to Shox2 knockout EBs in culture from days 6 to 16 of differentiation. When wild-type EBs were treated with Noggin, a potent BMP4 inhibitor, we observed a phenotype consistent with the Shox2 knockout EB. Altogether, we have generated a reproducible in vitro model that will be an invaluable tool for studying the molecular pathways regulating the development of cardiac pacemaker tissues.

Embryonic stem cell-derived cardiomyocytes harbor a subpopulation of niche-forming Sca-1+ progenitor cells.

The adult mammalian heart is known to contain a population of cardiac progenitor cells. It has not been unambiguously determined, however, whether these cells form as part of the developmental program of the heart or migrate there by way of the circulatory system. This study was done in order to determine the origin of this population of cells. A population of cardiomyocytes was established from mouse embryonic stem (ES) cells using a genetic selection technique. In order to determine whether cardiac progenitor cells exist within this ES cell-derived cardiomyocyte population, the cells were analyzed by fluorescence activated cell sorting (FACS) using an antibody directed against stem cell antigen-1 (Sca-1). We observed that approximately 4% of the cardiomyocyte population was composed of Sca-1(+) cells. When the Sca-1(+) cells were isolated by magnetic cell sorting and differentiated as cellular aggregates, contractions were observed in 100% of the aggregates. Gene expression studies using quantitative RT-PCR showed that these cells expressed terminally differentiated cardiac-specific genes. When three-dimensional cellular aggregates were formed from ES cell-derived cardiomyocytes co-cultured with adult HL-1 cardiomyocytes, the Sca-1(+) cells were found to "sort out" and form niches within the cell aggregates. Our data demonstrate that cardiac progenitor cells in the adult heart originate as part of the developmental program of the heart and that Sca-1(+) progenitor cells can provide an important in vitro model system to study the formation of cellular niches in the heart.