Role In Molecular Pathogenesis Research Articles

Sodium current abnormalities and deregulation of Wnt/β-catenin signaling in iPSC-derived cardiomyocytes generated from patient with arrhythmogenic cardiomyopathy harboring compound genetic variants in plakophilin 2 gene

BackgroundMutations in desmosomal genes linked to arrhythmogenic cardiomyopathy are commonly associated with Wnt/β-catenin signaling abnormalities and reduction of the sodium current density. Inhibitors of GSK3B were reported to restore sodium current and improve heart function in various arrhythmogenic cardiomyopathy models, but mechanisms underlying this effect remain unclear. We hypothesized that there is a crosstalk between desmosomal proteins, signaling pathways, and cardiac sodium channels. Methods and resultsTo reveal molecular mechanisms of arrhythmogenic cardiomyopathy, we established human iPSC-based model of this pathology. iPSC-derived cardiomyocytes from patient carrying two genetic variants in PKP2 gene demonstrated that PKP2 haploinsufficiency due to frameshift variant, in combination with the missense variant expressed from the second allele, was associated with decreased Wnt/β-catenin activity and reduced sodium current. Different approaches were tested to restore impaired cardiomyocytes functions, including wild type PKP2 transduction, GSK3B inhibition and Wnt/β-catenin signaling modulation. Inhibition of GSK3B led to the restoration of both Wnt/β-catenin signaling activity and sodium current density in patient-specific cardiomyocytes while GSK3B activation led to the reduction of sodium current density. Moreover, we found that upon inhibition GSK3B sodium current was restored through Wnt/β-catenin-independent mechanism. ConclusionWe propose that alterations in GSK3B-Wnt/β-catenin signaling pathways lead to regulation of sodium current implying its role in molecular pathogenesis of arrhythmogenic cardiomyopathy.

Aberrant integrin αv and α5 expression in prostate adenocarcinomas and bone-metastases is consistent with a bone-colonizing phenotype.

BackgroundCollaborative signaling between fibronectin-binding αv and α5 integrins has been implicated in the lethal dissemination of prostate cancer in the bone-metastatic niche, the major source of morbidity and mortality in the disease.MethodsWe assessed the frequency and pattern of expression of these integrins in primary high-grade adenocarcinomas and bone metastases compared to the physiological gland. Formalin-fixed paraffin-embedded (FFPE) radical prostatectomy (RP) samples (n=25) containing ≥ Gleason grade 4 cancer and decalcified surgical or diagnostic bone metastatic samples from 10 patients were stained for integrin αv (ITGAV) and integrin α5 (ITGA5) expression. Antibody optimization and antigen-retrieval was performed beforehand.ResultsITGAV was exclusively expressed in the basal layer of physiological prostate glands whereas αv expression was invariably recapitulated in the malignant gland and bone metastases (100%) in multiple distinct patterns: epithelial membranous, basilar/luminal membranous, punctate cytoplasmic, intense foci as single cells or clusters, and rim stromal layers. The luminal/basilar layer of ITGAV expression was striking in cribriform carcinomas, suggestive of a role in molecular pathogenesis. ITGA5 infrequently highlighted the basal layer of the physiological gland, was absent in primary adenocarcinoma, but was expressed with ITGAV exclusively in bone metastases (71%).ConclusionsWe conclude that ITGAV expression is aberrantly expressed in high frequency in high-grade prostatic adenocarcinomas in patterns suggestive of recapitulated basal cell functions, consistent with a stem-regulatory role that has been proposed. Co-expression and enrichment of αv and α5 in osseous metastases supports their proposed collaborative role in colonization of the bone microenvironment and as candidate targets for therapy.

Prognostic Significance of Reduced BCAS4 expression in Bone Marrow Cells of Patients with Myelodysplastic Syndromes

Deletion of long arm of chromosome 20 (del(20q)) is commonly observed in myelodysplastic syndromes (MDS). Reduced expression of genes located within the common deleted region (CDR) of del(20q) due to haploinsufficiency may play a role in molecular pathogenesis of MDS. In the previous study, we examined expression of genes located within the CDR which we determined using array-CGH, in bone marrow mononuclear cells in MDS patients with or without del(20q), indicating that BCAS4 expression was significantly reduced in bone marrow cells in MDS patients with or without del(20q). The BCAS4 gene, which was identified as a fusion transcript expressed in MCF7 cells, encodes 23kD protein. Although function of BCAS4 protein remains unclear, it could be a member of "cappuccino" family, which belong to lysosome-related organelles. Abnormality of genes encoding lysosome-related organelles cause variety of congenital disorders, including the Hermansky-Pudlak syndromes, which is characterized by oculocutaneous albinism and bleeding tendency due to platelet dysfunction as a result of lysosome abnormalities. In the present study we investigated clinical implication of BCAS4 expression level in MDS patients. Mononuclear cells separated from bone marrow samples taken at the time of MDS diagnosis were used for analysis. Written informed consent was obtained from patients before study. To analyze BCAS4 expression, quantitative RT-PCR was performed using cDNA from mononuclear cells as template by the TaqMan probe method (Applied Biosystems) with co-amplification of the endogenous control gene, human GAPDH (Applied Biosystems). Samples from 103 MDS patients, 64 males and 39 females with median age of 67 years (range: 20-91 years), with (n=14) or without (n=89) del(20q), were examined in the present study. Patients were classified as RCUD (n=12), RCMD (n=55), RARS (n=9), RAEB-1 (n=10), and RAEB-2 (n=13), according to WHO 2008 classification, and in RAEB-T (n=4) according to FAB classification. They also were categorized in four IPSS risk groups, low risk (n=30), intermediate-1 risk (n=46), intermediate-2 risk (n=18), and high risk (n=9). There was no significant difference in relative BCAS4 expression level between patients with del(20q) and those without del(20q), and among WHO subtypes. Higher IPSS risk groups (INT-2 and High) showed trend in association with reduced BCAS4 expression compared with lower IPSS risk groups (Low and INT-1) (P=0.104). We analyzed impact of BCAS4 expression on overall survival (OS). Based on BCAS4 expression level, 103 patients were divided into four groups, highest (Q1), intermediate (Q2, Q3), and lowest (Q4) quartiles. The Kaplan-Meier analysis demonstrated that Q4 showed significantly worse OS compared with remaining quartiles (Q1-Q3) (log-rank test, P=0.0031). The estimated 2-year OS rates in Q1-3 group and Q4 group were 75.1% and 48.9%, respectively. According to the COX proportional hazards model, univariate analysis showed lower BCAS4 expression (Q4 vs Q1-Q3) was associated with worse OS (hazard ratio 3.43, 95%CI 1.89-6.11, P=0.0001) as well as older age (65 years or older vs less than 65 years), and higher IPSS risk groups (INT-2 and High vs Low and INT-1). Multivariate analysis indicated that lower BCAS4 expression showed trend for association with worse OS (hazard ratio 1.90, 95%CI 0.96-3.64, P=0.0651) by analyzing with two variables (older age and higher IPSS groups). Next, we investigated whether OS is predicted by combination of three variables, BCAS4 expression level, IPSS risk groups, and age at diagnosis. We defined lower BCAS4 expression (Q4), higher IPSS (INT-2 and High), and older age (65 years or older), as risk factors. The Kaplan-Meier analysis showed that survival curves were well separated according to number of risk factors (0, 1, and 2 or more) (P<0.0001). The estimated 1-year, 2-year, and 5-year survival rates were 100%, 100%, and 86.5% in patients without risk factor, 75%, 70.2%, and 51.7% in patients with one risk factor, and 54%, 34.3%, and 11.4% in patients with two or more risk factors. The present study demonstrated that reduced BCAS4 expression is associated with inferior clinical outcome, indicating that BCAS4 expression level could be a useful prognostic marker in MDS, especially by combination with IPSS risk and patients age at diagnosis. Disclosures Tanaka: Bristol-Myers Squibb: Research Funding.

Recent trends in predictive biomarkers for determining malignant potential of oral potentially malignant disorders.

Despite of the tremendous advancements in the field of cancer prevention, detection and treatment, the overall prognosis of oral squamous cell carcinoma (OSCC) still remains poor. This can be partly imparted to the lack of early detection of oral potentially malignant disorders (OPMDs), especially those at a higher risk of progression into OSCC. Over years, various specific and non-specific markers have been introduced that could predict the malignant transformation of OPMDs; however detail information on these OPMD markers in a concise manner is lacking. Moreover, their use on daily clinical basis still remains questionable. With continuous research in the field of cytology and genomics, several contemporary biomarkers have been discovered that are not yet foregrounded and proved to be more promising than those used conventionally. Here, in the present paper, we overview several recently concluded predictive biomarkers with special emphasis on their role in molecular pathogenesis of OSCC transformation. These markers can be used for risk assessment of malignant transformation in patients with OPMDs as well as for prophylactic conciliation and fair management of the high-risk OPMD patient group.

Parallel reaction pathways and noncovalent intermediates in thymidylate synthase revealed by experimental and computational tools

Thymidylate synthase was one of the most studied enzymes due to its critical role in molecular pathogenesis of cancer. Nevertheless, many atomistic details of its chemical mechanism remain unknown or debated, thereby imposing limits on design of novel mechanism-based anticancer therapeutics. Here, we report unprecedented isolation and characterization of a previously proposed intact noncovalent bisubstrate intermediate formed in the reaction catalyzed by thymidylate synthase. Free-energy surfaces of the bisubstrate intermediates interconversions computed with quantum mechanics/molecular mechanics (QM/MM) methods and experimental assessment of the corresponding kinetics indicate that the species is the most abundant productive intermediate along the reaction coordinate, whereas accumulation of the covalent bisubstrate species largely occurs in a parallel nonproductive pathway. Our findings not only substantiate relevance of the previously proposed noncovalent intermediate but also support potential implications of the overstabilized covalent intermediate in drug design targeting DNA biosynthesis.

Reduced PLCG1 expression Is Associated with Inferior Survival in Myelodysplastic Syndromes

The PLCG1 gene encodes phospholipase C g isoform, which is involved in diverse physiological and pathological cellular processes through catalyzing the hydrolysis of phosphatidylinositol 4,5-bisphosphate to produce the second messenger molecules inositol 1,4,5-trisphosphate and diacylglycerole. Until now, roles of phospholipase C g 1 in hematopoiesis have been shown in animal models. Plcg1 deficient mouse lacks erythropoiesis and die in early embryonic stage. In zebrafish model, it was demonstrated that phospholipase C g 1 is required in granulocyte maturation. Physiological and/or pathological role of phospholipase C g 1 in human hematopoiesis has not been elucidated. In human, the PLCG1 gene is located on long arm of chromosome 20. Deletion of long arm of chromosome 20 (del(20q)) is commonly observed in myelodysplastic syndromes (MDS). Previously, we determined the common deleted region (CDR) of del(20q) in MDS, and the PLCG1 gene is located within the CDR. Reduced expression of genes located in the CDR due to haploinsufficiency may play role in molecular pathogenesis of MDS. Therefore, we analyzed PLCG1 expression in bone marrow mononuclear cells in MDS patients with or without del(20q), and investigated its clinical significance in the present study.Mononuclear cells separated from bone marrow samples taken at the time of diagnosis with written informed consent from patients were used. To analyze PLCG1 expression, quantitative RT-PCR was performed. Total RNA was extracted from mononuclear cells and subjected to cDNA synthesis. Real-time RT-PCR was carried out using cDNA as template by the TaqMan probe method (Applied Biosystems) with co-amplification of the endogenous control gene, human GAPDH (Applied Biosystems) were performed. The human PLCG1 primer-probe set was from Applied Biosystems. A total of 109 MDS patients, 65 males and 44 females with median age of 69 years (range: 22-91 years), with (n=20) or without (n=89) del(20q), were included in the present study. They were classified as RCUD (n=11), RCMD (n=55), RARS (n=11), RAEB-1 (n=16), and RAEB-2 (n=16) according to WHO classification. They were categorized in four IPSS risk groups, low risk (n=21), intermediate-1 risk (n=52), intermediate-2 risk (n=20), and high risk (n=6).Relative PLCG1 expression level was significantly reduced in MDS patients with del(20q) compared to control subjects (n=20) (P=0.011). Median values of relative PLCG1 expression level in MDS patients with del(20q) and control subjects were 0.94 and 1.96. In addition, relative expression level of PLCG1 in whole MDS cohort significantly lower than that in control subjects (P=0.046). Expression patterns of PLCG1 among, were not different. Median values of relative PLCG1 expression level in five WHO-subtypes, RCUD, RCMD, RARS, RAEB-1, and RAEB-2 were 1.50, 1.55, 1.29, 1.13, and 1.12, respectively, but no statistically difference was observed. WHO-subtypes with high blast counts (RAEB-1 and RAEB-2) showed trend in association with reduced PLCG1 expression compared with those with low blast counts (RCUD, RCMD, and RARS) (median value: 1.01 vs. 1.54, P =0.11). To investigate prognostic implication of PLCG1 expression in MDS, we analyzed impact of PLCG1 expression on overall survival (OS). Based on PLCG1 expression level, 109 patients were divided into four groups, high (Q1), intermediate (Q2, Q3), and low (Q4) quartiles. Kaplan-Meier analysis demonstrated that the lowest quartile (Q4) showed significantly worse survival compared with remaining quartiles (Q1-Q3) (P =0.0015). The estimated 5-year OS rates in Q1-3 group and Q4 group were 63.2% and 29.7%, respectively. Percentage of patients with WHO-subtypes with high blast count (RAEB-1 and RAEB-2) was significantly higher in Q4 than other quartiles (46.9% vs 22.1%, P =0.019 by Fisher's exact test).The present study demonstrated that reduced PLCG1 expression is associated with inferior clinical outcome, indicating that PLCG1 expression could be a useful prognostic marker in MDS. Association between reduced PLCG1 expression and WHO-subtypes with high blasts counts, suggesting that PLCG1 dysfunction play a role in disease progression. DisclosuresNo relevant conflicts of interest to declare.

CD99 correlates with low cyclin D1, high topoisomerase 2 status and triple negative molecular phenotype but is prognostically irrelevant in breast carcinoma.

CD99 is a protein initially described in the Ewing sarcoma family of tumors, but growing evidence has shown its expression in other tumors of mesenchymal, hematopoietic and even epithelial origin. Some articles report CD99 in metaplastic carcinoma of the breast, a subtype of breast carcinoma (BC) with pronounced epithelial to mesenchymal (EMT) phenotype. Our aim was to analyse the potential relationship between CD99 and selected EMT (vimentin, E-cadherin, Twist) and proliferation markers (Ki-67, c-myc, cyclin D1, topoisomerase 2), molecular subtypes of BC, as well as overall survival (OS) and progression-free survival (PFS). In a group of 122 cases CD99 membrane expression was seen in 14 (11.5%) cases: strong in 11 (9%) and moderate in 3 (2.5%). Expression of CD99 correlated with low cyclin D1 index, high level of topoisomerase 2 expression and lack of progesterone receptor (PR) but not with EMT characteristics. Additionally, strong expression of CD99 correlated with triple negative molecular BC phenotype. CD99 was prognostically irrelevant for OS and PFS. CD99 correlates with selected proliferative markers and low ER/PR receptor status but not with patients' outcome in BC. Further studies are required to explain precisely its role in molecular pathogenesis of BC.

Deregulation of brain insulin signaling in Alzheimer's disease.

Contrary to the previous belief that insulin does not act in the brain, studies in the last three decades have demonstrated important roles of insulin and insulin signal transduction in various functions of the central nervous system. Deregulated brain insulin signaling and its role in molecular pathogenesis have recently been reported in Alzheimer's disease (AD). In this article, we review the roles of brain insulin signaling in memory and cognition, the metabolism of amyloid β precursor protein, and tau phosphorylation. We further discuss deficiencies of brain insulin signaling and glucose metabolism, their roles in the development of AD, and recent studies that target the brain insulin signaling pathway for the treatment of AD. It is clear now that deregulation of brain insulin signaling plays an important role in the development of sporadic AD. The brain insulin signaling pathway also offers a promising therapeutic target for treating AD and probably other neurodegenerative disorders.

A Novel Mutation K673R In STAT1 Impaired the STAT1 Signal Transduction In a dominant– Negative Manner Identified In a Japanese Boy with MSMD

Abstract Abstract 1734 Mendelian susceptibility to mycobacterial disease (MSMD) is a rare congenital disorder characterized by susceptibility to infection by poorly virulent intracellular pathogens such as BCG, non-tuberculosis mycobacterium and Salmonellae. MSMD is associated with genetic defects in the IL-12/IFN-γ pathway, and six responsible genes, IFNGR1, IFNGR2, IL12B, IL12RB1, STAT1, and NEMO have been identified so far. Singnal transducer and activation of transcription 1 (STAT1) is a DNA-binding factor which regulates specific gene transcription. IFN-γ stimulation results in phosphorylation of STAT1 at Tyr701 (Y701) to induce the homodimerization, so called a gamma-activated factor (GAF), through the conformational change and the nuclear import. The GAF binds to the gamma-activated sequence (GAS) to induce the transcriptional activities. Patients with STAT1 deficiency were known in both recessive and dominant forms and three mutations in STAT1, L706S, E320Q and Q463H, have previously been reported from three family with an autosomal-dominant form of STAT1 partial deficiency. L706S mutation in the tail segment domain of STAT1 is shown to impair the phosphorylation at Tyr701. Although the phosphorylation is normal in other two mutations, the E320Q or Q463H mutant, in which the DNA-binding ability was abolished. Here we identified a novel heterozygous STAT1 mutation, 2018A>G (K673R), in a Japanese patient with MSMD. This was thought to be first report whose mutation was identified in the SH2 domain of autosomal-dominant form of STAT1. He had a past history of BCGitis after vacctination and multifocal osteomyelitis at the age of 5. Bone biopsy revealed granulomatous change without detecting Mycobacterium. The same mutation was also identified in his father and older sister. Although his sister had a history of BCGitis, his father had no clinical manifestations. A peripheral blood mononuclear cells from the patient could not sufficiently produce TNF-α in response to IFN-γ. EB-transformed B cells from the patient showed that induction of STAT1 phosphorylation by IFN-γ was partially impaired. We generated Flag-tagged STAT1 expression constructs of wild-type (WT) and three mutants including our mutant and analyzed molecular functions along with STAT1 signaling. K673R STAT1 showed partial impairment in the phosphorylation in response to both IFN-α and IFN-γ. Further, the electrophoretic mobility shift assay revealed that the K673R mutant abolished the DNA-binding ability. The nuclear translocation was normally detected. Curiously, dose-dependent negative effect on WT STAT1 was observed in K673R mutant by the reporter assay. K673R mutant interacted with WT to abrogate the DNA-binding activity, thus, exerted a dominant-negative effect on the transcription activity of WT STAT1. Based on these results, a novel heterozygous mutation, K673R, in SH2 domain of the STAT1 gene impaired the STAT1 signal transduction in a dominant-negative manner. K673R mutation in STAT1 may play an important role in molecular pathogenesis of MSMD. Disclosures: No relevant conflicts of interest to declare.

Insulin‐like growth factor binding protein‐4 gene silencing in lung adenocarcinomas

Gene silencing by promoter hypermethylation plays an important role in molecular pathogenesis. We previously reported that insulin-like growth factor (IGF) binding protein-4 (IGFBP-4), which inhibits IGF-dependent growth, is expressed via early growth response-1 (EGR-1) and is often silenced in cultivated lung cancer cells. The purpose of the present study was to clarify clinicopathological factors associated with IGFBP-4 gene silencing in lung adenocarcinomas. Seventy-six surgically resected adenocarcinomas (20 well-, 35 moderately-, and 21 poorly-differentiated) were subjected to methylation-specific polymerase chain reaction (PCR) analysis for EGR-1-binding sites located in the IGFBP-4 promoter and immunohistochemistry for IGFBP-4, EGR-1, and Ki-67. Thirty-two adenocarcinomas (42%) revealed IGFBP-4 promoter hypermethylation, and the severity inversely correlated with the level of IGFBP-4 expression (P < 0.0001) and tumor differentiation (well versus poor, P = 0.0278; well/moderate versus poor, P = 0.0395). Furthermore, there was a negative correlation between Ki-67 labeling index and IGFBP-4 expression (P = 0.0361). These findings suggest that the expression of IGFBP-4 in adenocarcinoma cells in vivo is downregulated by epigenetic silencing in association with tumor differentiation, resulting in disruption of the mechanism of IGFBP-4-mediated growth inhibition.

An integrated study of aberrant gene copy number and gene expression in GIST and LMS.

Increased chromosomal instability that alters the gene copy numbers throughout the genome is known to have a role in molecular pathogenesis of tumors. The impact of gene dosage effect to the expression levels of genes in GIST and LMS is unknown. In this paper, we used a combination of array comparative genomic hybridization (aCGH) and gene expression data to gain insights into the interplay of structural and functional changes of the genome in GIST and LMSs. We identified specific target genes that change their expression due to the gene dosage effect. Statistical analysis identified four chromosomal regions, 1p, 14q, 15q, and 22q, where both copy number and mRNA expression were significantly different between the tumor types. Multi-dimensional scaling (MDS) analysis showed that the gene expression profiles of these four regions accurately distinguish GIST and LMS. In addition, the gene dosage sensitive genes in these regions are differently involved in several tumor growth promoting pathways, implying that there are different mechanisms underlying the GIST and LMS carcinogenesis. Integration of aCGH and gene expression data has not only provided insights into how DNA copy number variations affect the gene expression patterns in these cancers, but also proves to be a promising method to choose biologically relevant biomarkers.

Transforming capacity of two novel genes JS-1 and JS-2 located in chromosome 5p and their overexpression in human esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) has a high mortality rate and geographic differences in incidence. Previous studies of comparative genomic hybridization (CGH) showed that chromosomal 5p is frequently amplified in cell lines and primary ESCC of Hong Kong Chinese origin. In this report, attempt was made to study two novel genes, named as JS-1 and JS-2, which are located in chromosome 5p15.2 and are 5' upstream to delta catenin for their roles in molecular pathogenesis of ESCC. Eleven cell lines, 27 primary ESCC cases and multiple human tissue cDNA panels (MTC) of digestive system were studied for the expression level of JS-1 and JS-2 by RT-PCR. The full-length cDNA sequences of JS-1 and JS-2 were determined from a non-tumor esophageal epithelial cell line by 3' and 5' rapid amplification of cDNA ends (RACE). The transforming capacity of JS-1 and JS-2 was also investigated by transfecting NIH 3T3 cells with the expression vector pcDNA3.1(-) cloned with the full coding sequences and it was followed by the study of foci formation of the transfected cells under confluence growth and the anchorage-independent growth in soft agar. Forty-five percent (5/11) and 18% (2/11) of the ESCC cell lines showed overexpression of JS-1 and JS-2 respectively, while 55% (15/27) and 14% (3/22) primary ESCC cases showed overexpression of JS-1 and JS-2 respectively. JS-1 overexpression was most common in patients with stage II ESCC (6/27; 22%) whereas JS-2 was only overexpressed in a dysplastic lesion (1/22; 4%) and stage III tumors (2/22; 9%). The expression levels of JS-1 and JS-2 are both low in normal esophageal tissues. Overexpression of JS-1 in NIH 3T3 cells caused foci formation in confluence growth and colony formation in soft agar but not for JS-2. A high grade sarcoma was formed in the athymic nude mice when NIH 3T3 cells overexpressing JS-1 were injected subcutaneously. Our results thus indicate that the frequent overexpression of JS-1 in ESCC and its transforming capacity in normal cells may play a critical role in the molecular pathogenesis of ESCC. The present study also forms the ground work for further identification of novel mechanisms of molecular carcinogenesis in ESCC and other cancers.

Association of the Gln27Glu polymorphism of the beta-2-adrenergic receptor with preterm labor

Objectives: To investigate a potential association between the beta-2-adrenergic receptor (B2AR) polymorphisms occurring at amino acid positions 16 (Arg16Gly) and 27 (Gln27Glu) and preterm labor. Methods: Eighty patients with preterm labor and 76 control subjects were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Results: A significant association was found between Gln27Glu substitution and preterm labor ( P=0.001). The frequency of Gly16 and Glu27 alleles were found to be higher in patients than in control women (0.54 vs. 0.48 and 0.42 vs. 0.26, respectively), and the odds ratio for the occurrence of preterm labor was 2.14 (95% CI, 1.32–3.46; P=0.002) for the Glu 27 allele. An early delivery was noted in 52.5% of patients. Conclusion: The Gln27Glu polymorphism of the B2AR gene may have a role in molecular pathogenesis of preterm labor. Glu27 allele in patients with preterm labor might be a risk factor for deliveries before 37 weeks of gestation.