Amplification and overexpression of the IGF2 regulator PLAG1 in hepatoblastoma

Pleomorphic adenoma gene1 in reproduction and implication for embryonic survival in cattle: a review

The pleomorphic adenoma gene1 (PLAG1) encodes a DNA-binding, C2H2 zinc-finger protein which acts as a transcription factor that regulates the expression of diverse genes across different organs and tissues; hence, the name pleomorphic. Rearrangements of the PLAG1 gene, and/or overexpression, are associated with benign tumors and cancers in a variety of tissues. This is best described for pleomorphic adenoma of the salivary glands in humans. The most notable expression of PLAG1 occurs during embryonic and fetal development, with lesser expression after birth. Evidence has accumulated of a role for PLAG1 protein in normal early embryonic development and placentation in mammals. PLAG1 protein influences the expression of the ike growth factor 2 (IGF2) gene and production of IGF2 protein. IGF2 is an important mitogen in ovarian follicles/oocytes, embryos, and fetuses. The PLAG1-IGF2 axis, therefore, provides one pathway whereby PLAG1 protein can influence embryonic survival and pregnancy. PLAG1 also influences over 1,000 other genes in embryos including those associated with ribosomal assembly and proteins. Brahman (Bos indicus) heifers homozygous for the PLAG1 variant, rs109815800 (G > T), show greater fertility than contemporary heifers with either one, or no copy, of the variant. Greater fertility in heifers homozygous for rs109815800 could be the result of early puberty and/or greater embryonic survival. The present review first looks at the broader roles of the PLAG1 gene and PLAG1 protein and then focuses on the emerging role of PLAG1/PLAG1 in embryonic development and pregnancy. A deeper understanding of factors which influence embryonic development is required for the next transformational increase in embryonic survival and successful pregnancy for both in vivo and in vitro derived embryos in cattle.

Ectopic PLAG1 induces muscular dystrophy in the mouse

Even though various genetic mutations have been identified in muscular dystrophies (MD), there is still a need to understand the biology of MD in the absence of known mutations. Here we reported a new mouse model of MD driven by ectopic expression of PLAG1. This gene encodes a developmentally regulated transcription factor known to be expressed in developing skeletal muscle, and implicated as an oncogene in certain cancers including rhabdomyosarcoma (RMS), an aggressive soft tissue sarcoma composed of myoblast-like cells. By breeding loxP-STOP-loxP-PLAG1 (LSL-PLAG1) mice into the MCK-Cre line, we achieved ectopic PLAG1 expression in cardiac and skeletal muscle. The Cre/PLAG1 mice died before 6 weeks of age with evidence of cardiomyopathy significantly limiting left ventricle fractional shortening. Histology of skeletal muscle revealed dystrophic features, including myofiber necrosis, fiber size variation, frequent centralized nuclei, fatty infiltration, and fibrosis, all of which mimic human MD pathology. QRT-PCR and Western blot revealed modestly decreased Dmd mRNA and dystrophin protein in the dystrophic muscle, and immunofluorescence staining showed decreased dystrophin along the cell membrane. Repression of Dmd by ectopic PLAG1 was confirmed in dystrophic skeletal muscle and various cell culture models. In vitro studies showed that excess IGF2 expression, a transcriptional target of PLAG1, phenocopied PLAG1-mediated down-regulation of dystrophin. In summary, we developed a new mouse model of a lethal MD due to ectopic expression of PLAG1 in heart and skeletal muscle. Our data support the potential contribution of excess IGF2 in this model. Further studying these mice may provide new insights into the pathogenesis of MD and perhaps lead to new treatment strategies.

Human IGF2 Gene Epigenetic and Transcriptional Regulation: At the Core of Developmental Growth and Tumorigenic Behavior

Regulation of the human IGF2 gene displays multiple layers of control, which secures a genetically and epigenetically predetermined gene expression pattern throughout embryonal growth and postnatal life. These predominantly nuclear regulatory mechanisms converge on the function of the IGF2-H19 gene cluster on Chromosome 11 and ultimately affect IGF2 gene expression. Deregulation of such control checkpoints leads to the enhancement of IGF2 gene transcription and/or transcript stabilization, ultimately leading to IGF-II peptide overproduction. This type of anomaly is responsible for the effects observed in terms of both abnormal fetal growth and increased cell proliferation, typically observed in pediatric overgrowth syndromes and cancer. We performed a review of relevant experimental work on the mechanisms affecting the human IGF2 gene at the epigenetic, transcriptional and transcript regulatory levels. The result of our work, indeed, provides a wider and diversified scenario for IGF2 gene activation than previously envisioned by shedding new light on its extended regulation. Overall, we focused on the functional integration between the epigenetic and genetic machinery driving its overexpression in overgrowth syndromes and malignancy, independently of the underlying presence of loss of imprinting (LOI). The molecular landscape provided at last strengthens the role of IGF2 in cancer initiation, progression and malignant phenotype maintenance. Finally, this review suggests potential actionable targets for IGF2 gene- and regulatory protein target-degradation therapies.

Exploring and Identifying Candidate Genes and Genomic Regions Related to Economically Important Traits in Hanwoo Cattle

The purpose of the current review was to explore and summarize different studies concerning the detection and characterization of candidate genes and genomic regions associated with economically important traits in Hanwoo beef cattle. Hanwoo cattle, the indigenous premium beef cattle of Korea, were introduced for their marbled fat, tenderness, characteristic flavor, and juiciness. To date, there has been a strong emphasis on the genetic improvement of meat quality and yields, such as backfat thickness (BFT), marbling score (MS), carcass weight (CW), eye muscle area (EMA), and yearling weight (YW), as major selection criteria in Hanwoo breeding programs. Hence, an understanding of the genetics controlling these traits along with precise knowledge of the biological mechanisms underlying the traits would increase the ability of the industry to improve cattle to better meet consumer demands. With the development of high-throughput genotyping, genomewide association studies (GWAS) have allowed the detection of chromosomal regions and candidate genes linked to phenotypes of interest. This is an effective and useful tool for accelerating the efficiency of animal breeding and selection. The GWAS results obtained from the literature review showed that most positional genes associated with carcass and growth traits in Hanwoo are located on chromosomes 6 and 14, among which LCORL, NCAPG, PPARGC1A, ABCG2, FAM110B, FABP4, DGAT1, PLAG1, and TOX are well known. In conclusion, this review study attempted to provide comprehensive information on the identified candidate genes associated with the studied traits and genes enriched in the functional terms and pathways that could serve as a valuable resource for future research in Hanwoo breeding programs.

PLAG1 Immunohistochemical Staining Is a Surrogate Marker for PLAG1 Fusions in Lipoblastomas

BACKGROUND

The hallmark of lipoblastoma is a PLAG1 fusion. PLAG1 protein overexpression has been reported in sporadic PLAG1-rearranged lipoblastomas.

METHODS

We evaluated the utility of PLAG1 immunohistochemical staining (IHC) in 34 pediatric lipomatous tumors, correlating the results with histology and conventional cytogenetics, FISH and/or next generation sequencing (NGS) results.

RESULTS

The study included 24 lipoblastomas, divided into 2 groups designated as "Lipoblastoma 1" with both lipoblastoma histology and PLAG1 rearrangement (n = 16) and "Lipoblastoma 2" with lipoblastoma histology but without PLAG1 cytogenetic rearrangement (n = 8), and 10 lipomas with neither lipoblastoma histology nor a PLAG1 rearrangement. Using the presence of a fusion as the "gold standard" for diagnosing lipoblastoma (Lipoblastoma 1), the sensitivity of PLAG1 IHC was 94%. Using histologic features alone (Lipoblastoma 1 + 2), the sensitivity was 96%. Specificity, as defined by the ability to distinguish lipoma from lipoblastoma, was 100%, as there were no false positives in the lipoma group.

CONCLUSIONS

Cytogenetics/molecular testing is expensive and may not be ideal for detecting PLAG1 fusions because PLAG1 fusions are often cytogenetically cryptic and NGS panels may not include all partner genes. PLAG1 IHC is an inexpensive surrogate marker of PLAG1 fusions and may be useful in distinguishing lipoblastomas from lipomas.

FTO and PLAG1 Genes Expression and FTO Methylation Predict Changes in Circulating Levels of Adipokines and Gastrointestinal Peptides in Children

Adipokines and gastrointestinal tract hormones are important metabolic parameters, and both epigenetic factors and differential gene expression patterns may be associated with the alterations in their concentrations in children. The function of the FTO gene (FTO alpha-ketoglutarate dependent dioxygenase) in the regulation of the global metabolic rate is well described, whereas the influence of protooncogene PLAG1 (PLAG1 zinc finger) is still not fully understood. A cross-sectional study on a group of 26 children with various BMI values (15.3–41.7; median 28) was carried out. The aim was to evaluate the dependencies between the level of methylation and expression of aforementioned genes with the concentration of selected gastrointestinal tract hormones and adipokines in children. Expression and methylation were measured in peripheral blood mononuclear DNA by a microarray technique and a restriction enzyme method, respectively. All peptide concentrations were determined using the enzyme immunoassay method. The expression level of both FTO and PLAG1 genes was statistically significantly related to the concentration of adipokines: negatively for apelin and leptin receptor, and positively for leptin. Furthermore, both FTO methylation and expression negatively correlated with the concentration of resistin and visfatin. Cholecystokinin was negatively correlated, whereas fibroblast growth factor 21 positively correlated with methylation and expression of the FTO gene, while FTO and PLAG1 expression was negatively associated with the level of cholecystokinin and glucagon-like peptide-1. The PLAG1 gene expression predicts an increase in leptin and decrease in ghrelin levels. Our results indicate that the FTO gene correlates with the concentration of hormones produced by the adipose tissue and gastrointestinal tract, and PLAG1 gene may be involved in adiposity pathogenesis. However, the exact molecular mechanisms still need to be clarified.

Silver Russell syndrome in a preterm girl with 8q12.1 deletion encompassing PLAG1

Silver Russell syndrome (SRS) is a congenital disorder characterized by intrauterine growth retardation (IUGR), feeding difficulties and postnatal growth retardation. In a small number of cases, PLAG1 variants have been described (OMIM #618907). PLAG1 haploinsufficiency decreases Insulin-like growth factor 2 expression and produces a Silver Russell syndrome-like phenotype. Here, we describe the phenotype and molecular features of a 26 months girl with clinical features of SRS, and a de novo 2.1 Mb deletion encompassing PLAG1 is reported in association with clinical features suggestive of SRS.

PLAG1-rearrangment in a uterine leiomyosarcoma with myxoid stroma and heterologous differentiation

A variety of molecular alterations have been reported in uterine leiomyosarcomas, but most are considered nondiagnostic. There are, however, rare exceptions including PLAG1 rearrangement which has recently been identified in a subset of myxoid leiomyosarcomas. A 41-year-old woman presented with symptoms of a fibroid. She underwent a myomectomy which revealed a high-grade uterine sarcoma with areas of myxoid stroma and heterologous elements. The tumor expressed desmin, smooth muscle actin, H-caldesmon, and estrogen and progesterone receptors. RNA sequencing revealed a novel TRIM13-PLAG1 fusion gene which was subsequently independently confirmed by fluorescence in situ hybridization. On further evaluation the patient was found to have multiple pulmonary metastases and died due to disease progression shortly after diagnosis. This report describes a novel fusion partner of PLAG1 in a uterine leiomyosarcoma with myxoid leiomyosarcoma and heterologous elements, thereby broadening the spectrum of morphologic and genetic findings within this rare group of neoplasms.

Methylation and Expression of FTO and PLAG1 Genes in Childhood Obesity: Insight into Anthropometric Parameters and Glucose-Lipid Metabolism

The occurrence of childhood obesity is influenced by both genetic and epigenetic factors. FTO (FTO alpha-ketoglutarate dependent dioxygenase) is a gene of well-established connection with adiposity, while a protooncogene PLAG1 (PLAG1 zinc finger) has been only recently linked to this condition. We performed a cross-sectional study on a cohort of 16 obese (aged 6.6-17.7) and 10 healthy (aged 11.4-16.9) children. The aim was to evaluate the relationship between methylation and expression of the aforementioned genes and the presence of obesity as well as alterations in anthropometric measurements (including waist circumference (WC), body fat (BF_kg) and body fat percent (BF_%)), metabolic parameters (lipid profile, blood glucose and insulin levels, presence of insulin resistance) and blood pressure. Expression and methylation were measured in peripheral blood mononuclear cells using a microarray technique and a method based on restriction enzymes, respectively. Multiple regression models were constructed to adjust for the possible influence of age and sex on the investigated associations. We showed significantly increased expression of the FTO gene in obese children and in patients with documented insulin resistance. Higher FTO expression was also associated with an increase in WC, BF_kg, and BF_% as well as higher fasting concentration of free fatty acids (FFA). FTO methylation correlated positively with WC and BF_kg. Increase in PLAG1 expression was associated with higher BF%. Our results indicate that the FTO gene is likely to play an important role in the development of childhood adiposity together with coexisting impairment of glucose-lipid metabolism.

Pediatric fibromyxoid soft tissue tumor with PLAG1 fusion: A novel entity?

The classification of undifferentiated soft tissue tumors continues to evolve with the expanded application of molecular analysis in clinical practice. We report three cases of a unique soft tissue tumor in young children (5 months to 2 years old) displaying a purely fibromyxoid histology, with positive staining for desmin and CD34. In two cases, RNA sequencing detected a YWHAZ-PLAG1 gene fusion, while in the third case, a previously unreported EEF1A1-PLAG1 fusion was identified. PLAG1 fusions have been reported in several pathologic entities including pleomorphic adenoma, myoepithelial tumors of skin and soft tissue, and lipoblastoma, the latter occurring preferentially in young children. In these tumors, expression of a full length PLAG1 protein comes under the control of the constitutively active promoter of the partner gene in the fusion, and the current cases conform to that model. Overexpression of PLAG1 was confirmed by diffusely positive immunostaining for PLAG1 in all three cases. Our findings raise the possibility of a novel fibromyxoid neoplasm in childhood associated with these rare PLAG1 fusion variants. The only other report of a PLAG1-YWHAZ fusion occurred in a pediatric tumor diagnosed as a "fibroblastic lipoblastoma." This finding raises the possibility of a relationship with our three cases, even though our cases lacked any fat component. Further studies with regard to a shared pathogenesis are required.

PLAGL2-EGFR-HIF-1/2α Signaling Loop Promotes HCC Progression and Erlotinib Insensitivity

BACKGROUND AND AIMS

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide, hence a major public health threat. Pleomorphic adenoma gene like-2 (PLAGL2) has been reported to play a role in tumorigenesis. However, its precise function in HCC remains poorly understood.

APPROACH AND RESULTS

In this study, we demonstrated that PLAGL2 was up-regulated in HCC compared with that of adjacent nontumorous tissues and also correlated with overall survival times. We further showed that PLAGL2 promoted HCC cell proliferation, migration, and invasion both in vitro and in vivo. PLAGL2 expression was positively correlated with epidermal growth factor receptor (EGFR) expression. Mechanistically, this study demonstrated that PLAGL2 functions as a transcriptional regulator of EGFR and promotes HCC cell proliferation, migration, and invasion through the EGFR-AKT pathway. Moreover, hypoxia was found to significantly induce high expression of PLAGL2, which promoted hypoxia inducible factor 1/2 alpha subunit (HIF1/2A) expression through EGFR. Therefore, this study demonstrated that a PLAGL2-EGFR-HIF1/2A signaling loop promotes HCC progression. More importantly, PLAGL2 expression reduced hepatoma cells' response to the anti-EGFR drug erlotinib. PLAGL2 knockdown enhanced the response to erlotinib.

CONCLUSIONS

This study reveals the pivotal role of PLAGL2 in HCC cell proliferation, metastasis, and erlotinib insensitivity. This suggests that PLAGL2 can be a potential therapeutic target of HCC.

Insights Into the Somatic Mutation Burden of Hepatoblastomas From Brazilian Patients

Hepatoblastoma is a very rare embryonal liver cancer supposed to arise from the impairment of hepatocyte differentiation during embryogenesis. In this study, we investigated by exome sequencing the burden of somatic mutations in a cohort of 10 hepatoblastomas, including a congenital case. Our data disclosed a low mutational background and pointed out to a novel set of candidate genes for hepatoblastoma biology, which were shown to impact gene expression levels. Only three recurrently mutated genes were detected: CTNNB1 and two novel candidates, CX3CL1 and CEP164. A relevant finding was the identification of a recurrent mutation (A235G) in two hepatoblastomas at the CX3CL1 gene; evaluation of RNA and protein expression revealed upregulation of CX3CL1 in tumors. The analysis was replicated in two independents cohorts, substantiating that an activation of the CX3CL1/CX3CR1 pathway occurs in hepatoblastomas. In inflammatory regions of hepatoblastomas, CX3CL1/CX3CR1 were not detected in the infiltrated lymphocytes, in which they should be expressed in normal conditions, whereas necrotic regions exhibited negative labeling in tumor cells, but strongly positive infiltrated lymphocytes. Altogether, these data suggested that CX3CL1/CX3CR1 upregulation may be a common feature of hepatoblastomas, potentially related to chemotherapy response and progression. In addition, three mutational signatures were identified in hepatoblastomas, two of them with predominance of either the COSMIC signatures 1 and 6, found in all cancer types, or the COSMIC signature 29, mostly related to tobacco chewing habit; a third novel mutational signature presented an unspecific pattern with an increase of C>A mutations. Overall, we present here novel candidate genes for hepatoblastoma, with evidence that CX3CL1/CX3CR1 chemokine signaling pathway is likely involved with progression, besides reporting specific mutational signatures.

Circular RNA Circ100084 functions as sponge of miR‑23a‑5p to regulate IGF2 expression in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has become a major cause of cancer-related mortality worldwide. Circular RNAs (circRNAs) are non-coding RNAs that serve important roles in multiple cancers. However, the role of circRNAs in HCC remains largely unknown. In the present study, a circRNA microarray dataset of HCC samples, GSE97332, was downloaded from the gene expression omnibus database. Following data preprocessing, differentially expressed circRNAs between HCC tissues and normal tissues were determined using GEO2R. The circRNA-miRNA interactions were predicted by the miRanda database. The miRTarbase database was used to search for target genes of the miRNAs. A circRNA-miRNA-mRNA network was constructed using Cytoscape based on the obtained circRNA, miRNA and mRNA. In this network, the upregulated circRNA hsa_circRNA_100084 was found to be involved in a competing endogenous relationship of hsa_circRNA_100084-hsa-miR-23a-5p- insulin-like growth factor 2 (IGF2). The differential expression of hsa_circRNA_100084, hsa-miR-23a-5p and IGF2 in HCC tissues and liver cancer cells was validated by reverse transcription-quantitative PCR. Additionally, the interactions between hsa-miR-23a-5p with hsa_circRNA_100084 and IGF2 were validated by dual-luciferase reporter assays. Knocking down hsa_circRNA_100084 inhibited the proliferation, migration and invasion of liver cancer cells, while the simultaneous overexpression of IGF2 reversed the effects of hsa_circRNA_100084 knockdown. The results show that hsa_circRNA_100084 could promote the expression of IGF2 by acting as a sponge of hsa-miR-23a-5p in liver cancer cells.

Bayesian Modeling Identifies PLAG1 as a Key Regulator of Proliferation and Survival in Rhabdomyosarcoma Cells

We recently developed a novel computational algorithm that incorporates Bayesian methodology to identify rhabdomyosarcoma disease genes whose expression level correlates with copy-number variations, and we identified PLAG1 as a candidate oncogenic driver. Although PLAG1 has been shown to contribute to other type of cancers, its role in rhabdomyosarcoma has not been elucidated. We observed that PLAG1 mRNA is highly expressed in rhabdomyosarcoma and is associated with PLAG1 gene copy-number gain. Knockdown of PLAG1 dramatically decreased cell accumulation and induced apoptosis in rhabdomyosarcoma cells, whereas its ectopic expression increased cell accumulation in vitro and as a xenograft and promoted G₁ to S-phase cell-cycle progression. We found that PLAG1 regulates IGF2 expression and influences AKT and MAPK pathways in rhabdomyosarcoma, and IGF2 partially rescues cell death triggered by PLAG1 knockdown. The expression level of PLAG1 correlated with the IC₅₀ of rhabdomyosarcoma cells to BMS754807, an IGF receptor inhibitor. IMPLICATIONS: Our data demonstrate that PLAG1 contributes to proliferation and survival of rhabdomyosarcoma cells at least partially by inducing IGF2, and this new understanding may have the potential for clinical translation.

Expression and differential regulation of human TERRA at several chromosome ends

The telomeric long noncoding RNA TERRA has been implicated in regulating telomere maintenance by telomerase and homologous recombination, and in influencing telomeric protein composition during the cell cycle and the telomeric DNA damage response. TERRA transcription starts at subtelomeric regions resembling the CpG islands of eukaryotic genes extending toward chromosome ends. TERRA contains chromosome-specific subtelomeric sequences at its 5' end and long tracts of UUAGGG-repeats toward the 3' end. Conflicting studies have been published as to whether TERRA is expressed from one or several chromosome ends. Here, we quantify TERRA species by RT-qPCR in normal and several cancerous human cell lines. By using chromosome-specific subtelomeric DNA primers, we demonstrate that TERRA is expressed from a large number of telomeres. Deficiency in DNA methyltransferases leads to TERRA up-regulation only at the subset of chromosome ends that contain CpG-island sequences, revealing differential regulation of TERRA promoters by DNA methylation. However, independently of the differences in TERRA expression, short telomeres were uniformly present in a DNA methyltransferase deficient cell line, indicating that telomere length was not dictated by TERRA expression in cis Bioinformatic analyses indicated the presence of a large number of putative transcription factors binding sites at TERRA promoters, and we identified a subset of them that repress TERRA expression. Altogether, our study confirms that TERRA corresponds to a large gene family transcribed from multiple chromosome ends where we identified two types of TERRA promoters, only one of which is regulated by DNA methylation.

A SNP in PLAG1 is associated with body height trait in Chinese cattle

Stature is an important quantitative trait for cattle performance, which influences herd productivity. Previous studies have reported that an SNP (AC_000171.1:g.25015640G>T, rs109815800) in Pleomorphic adenoma gene 1 (PLAG1) on chromosome 14 (CHR14) is associated with bovine stature. To validate whether rs109815800 is associated with the body height of Chinese cattle, we carried out an association analysis using 558 adult cattle samples from seven populations. Then, 1038 samples from 38 Chinese cattle breeds were used to show the geographical distribution of this variant in China. The results showed that the Q allele (G allele) increased the height of cattle. Furthermore, the frequencies of Q allele in Chinese native breeds tend to decrease from northern China to southern China, and the frequency of Q allele in two Chinese beef cattle breeds is much higher than that in another 36 Chinese local cattle breeds. Our data suggest that the prevalence of the Q allele is correlated with latitude in China.

Three Novel Aberrations Involving PLAG1 Leading to Lipoblastoma in Three Different Patients: High Amplification, Partial Deletion, and a Unique Complex Rearrangement

Lipoblastoma is a rare benign neoplasm with overlapping histology with other lipomatous tumors. Genetic aberrations including translocations of 8q and splitting of the PLAG1 probe leading to "promoter swapping" and gains of chromosome 8 or PLAG1 foci have been described in lipoblastoma. Here, we report 3 lipoblastomas revealing novel genetic aberrations involving PLAG1: a high level of PLAG1 amplification up to 50 copies in a 4-year-old girl with recurrence of a right flank mass, a partial deletion of PLAG1 with the flanking junction breakpoints involving the 3'PLAG1 and 5'HAS2 genes in a 17-month-old boy with a retroperitoneal mass, and an insertion of 2q31 into 8q11.2 and translocation of 8q to 2q with the latter translocated onto 12q leading to separation of the PLAG1 FISH probe in a 5-year-old girl with a left back mass. Our novel cytogenetic findings further expand the mechanisms of PLAG1 transcriptional upregulation in lipoblastoma pathogenesis.

GWAS for Meat and Carcass Traits Using Imputed Sequence Level Genotypes in Pooled F2-Designs in Pigs

In order to gain insight into the genetic architecture of economically important traits in pigs and to derive suitable genetic markers to improve these traits in breeding programs, many studies have been conducted to map quantitative trait loci. Shortcomings of these studies were low mapping resolution, large confidence intervals for quantitative trait loci-positions and large linkage disequilibrium blocks. Here, we overcome these shortcomings by pooling four large F2 designs to produce smaller linkage disequilibrium blocks and by resequencing the founder generation at high coverage and the F1 generation at low coverage for subsequent imputation of the F2 generation to whole genome sequencing marker density. This lead to the discovery of more than 32 million variants, 8 million of which have not been previously reported. The pooling of the four F2 designs enabled us to perform a joint genome-wide association study, which lead to the identification of numerous significantly associated variant clusters on chromosomes 1, 2, 4, 7, 17 and 18 for the growth and carcass traits average daily gain, back fat thickness, meat fat ratio, and carcass length. We could not only confirm previously reported, but also discovered new quantitative trait loci. As a result, several new candidate genes are discussed, among them BMP2 (bone morphogenetic protein 2), which we recently discovered in a related study. Variant effect prediction revealed that 15 high impact variants for the traits back fat thickness, meat fat ratio and carcass length were among the statistically significantly associated variants.

IGF2/IGF1R Signaling as a Therapeutic Target in MYB-Positive Adenoid Cystic Carcinomas and Other Fusion Gene-Driven Tumors

Chromosome rearrangements resulting in pathogenetically important gene fusions are a common feature of many cancers. They are often potent oncogenic drivers and have key functions in central cellular processes and pathways and encode transcription factors, transcriptional co-regulators, growth factor receptors, tyrosine kinases, and chromatin modifiers. In addition to being useful diagnostic biomarkers, they are also targets for development of new molecularly targeted therapies. Studies in recent decades have shown that several oncogenic gene fusions interact with the insulin-like growth factor (IGF) signaling pathway. For example, the MYB-NFIB fusion in adenoid cystic carcinoma is regulated by IGF1R through an autocrine loop, and IGF1R is a downstream target of the EWSR1-WT1 and PAX3-FKHR fusions in desmoplastic small round cell tumors and alveolar rhabdomyosarcoma, respectively. Here, we will discuss the mechanisms behind the interactions between oncogenic gene fusions and the IGF signaling pathway. We will also discuss the role of therapeutic inhibition of IGF1R in fusion gene driven malignancies.

The PLAG1 mRNA expression analysis among genetic variants and relevance to growth traits in Chinese cattle

Pleomorphic adenoma gene 1 (PLAG1) encodes a developmentally regulated zinc finger protein, locating in growth-related QTNs. The mRNA expression of this gene was investigated in different tissues and from two different developmental periods, whilst to explore the functions of PLAG1 in growth traits of cattle. The results showed that PLAG1 was expressed in all examined tissues. However, PLAG1 expression levels in all examined tissues were significantly different between the 5-month fetus and 36-month adult cattle. Our juvenile results indicated PLAG1 is primarily expressed in embryonic tissues of Chinese cattle. Furthermore, two variations were identified. Association analysis revealed that the two variations were associated with growth traits (p < 0.05 or p < 0.01). These new findings provide a comprehensive overview of the critical roles of PLAG1 in growth traits modulation and can be highlighted as candidate molecular markers in cattle breeding.

Dysregulated long non‑coding RNAs in pleomorphic adenoma tissues of pleomorphic adenoma gene 1 transgenic mice

Long non-coding RNAs (lncRNAs) have been proven to serve vital roles in various human diseases. However, their involvement in the development of pleomorphic adenoma (PA) in the salivary gland has yet to be examined. In the present study, microarray analysis of the lncRNA and mRNA expression profiles in pleomorphic adenoma gene 1 (PLAG1) transgenic mice was performed. Next, bioinformatics tools were used to predict the differentially expressed genes associated with PA, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and lncRNA-mRNA co-expression network analyses. Comparison of the transgenic and control mice demonstrated that a total of 9,110 lncRNAs and 7,750 mRNAs were significantly differentially expressed (fold change >2; P<0.05). Subsequently, six lncRNAs were randomly selected for further analysis, and five of these were validated as differentially expressed in PA by quantitative polymerase chain reaction, supporting the methodology employed in the current study. The GO and KEGG enrichment analysis of the differentially expressed mRNAs revealed that these mRNAs were closely associated with a number of processes involved in the development of PA. Furthermore, the lncRNA-mRNA co-expression network indicated that certain lncRNAs may serve vital roles in the pathogenesis of PA by interacting with a number of core genes. Taken together, these results indicated that lncRNAs and mRNAs were differentially expressed in PA tissues obtained from PLAG1 transgenic mice as compared with those from control mice. These differentially expressed lncRNAs may act as novel biomarkers and therapeutic targets for PA.

The Role of MicroRNAs in Hepatoblastoma Tumors

Hepatoblastoma is the most common hepatic malignancy during childhood. However, little is still known about the molecular mechanisms that govern the development of this disease. This review is focused on the recent advances regarding the study of microRNAs in hepatoblastoma and their substantial contribution to improv our knowledge of the pathogenesis of this disease. We show here that miRNAs represent valuable tools to identify signaling pathways involved in hepatoblastoma progression as well as useful biomarkers and novel molecular targets to develop alternative therapeutic strategies in this disease.

CircHMGCS1 Promotes Hepatoblastoma Cell Proliferation by Regulating the IGF Signaling Pathway and Glutaminolysis

Circular RNAs (circRNAs), a novel class of endogenous RNAs, have been recently shown to participate in cellular development and several pathophysiological processes. The identification of dysregulated circRNAs and their function in cancer have attracted considerable attention. Nevertheless, the expression profile and role of circRNAs in human hepatoblastoma (HB) remain to be studied. In this report, we analyzed the expression prolife of circRNAs in HB tissues and identified circHMGCS1 (3-hydroxy-3-methylglutaryl-CoA synthase 1; hsa_circ_0072391) as a remarkably upregulated circRNA. Methods: The expression prolife of circRNAs in HB tissues were investigated through circRNA sequencing analyses. ISH and qRT-PCR assays were performed to measure the expression level of circHMGCS1. The effect of knocking down circHMGCS1 in HB cells in vitro and in vivo were evaluated by colony formation assay, flow cytometry, xenograft tumors assay and untargeted metabolomics assay. MRE analysis and dual luciferase assay were performed to explore the underlying molecular mechanisms. Results: HB patients with high circHMGCS1 expression have shorted overall survival. Knockdown of circHMGCS1 inhibits HB cells proliferation and induces apoptosis. CircHMGCS1 regulates IGF2 and IGF1R expression via sponging miR-503-5p, and affects the downstream PI3K-Akt signaling pathway to regulate HB cell proliferation and glutaminolysis. Conclusions: The circHMGCS1/miR-503-5p/IGF-PI3K-Akt axis regulates the proliferation, apoptosis and glutaminolysis of HB cells, implying that circHMGCS1 is a promising therapeutic target and prognostic marker for HB patients.

Plag1 and Plagl2 have overlapping and distinct functions in telencephalic development

The Plag gene family has three members; Plagl1/Zac1, which is a tumor suppressor gene, and Plag1 and Plagl2, which are proto-oncogenes. All three genes are known to be expressed in embryonic neural progenitors, and Zac1 regulates proliferation, neuronal differentiation and migration in the developing neocortex. Here we examined the functions of Plag1 and Plagl2 in neocortical development. We first attempted, and were unable to generate, E12.5 Plag1;Plagl2 double mutants, indicating that at least one Plag1 or Plagl2 gene copy is required for embryonic survival. We therefore focused on single mutants, revealing a telencephalic patterning defect in E12.5 Plagl2 mutants and a proliferation/differentiation defect in Plag1 mutant neocortices. Specifically, the ventral pallium, a dorsal telencephalic territory, expands into the ventral telencephalon in Plagl2 mutants. In contrast, Plag1 mutants develop normal regional territories, but neocortical progenitors proliferate less and instead produce more neurons. Finally, in gain-of-function studies, both Plag1 and Plagl2 reduce neurogenesis and increase BrdU-uptake, indicative of enhanced proliferation, but while Plagl2 effects on proliferation are more immediate, Plag1 effects are delayed. Taken together, we found that the Plag proto-oncogenes genes are essential regulators of neocortical development and although Plag1 and Plagl2 functions are similar, they do not entirely overlap. This article has an associated First Person interview with the first author of the paper.

PLAG1, SOX10, and Myb Expression in Benign and Malignant Salivary Gland Neoplasms

Background

Recent findings in molecular pathology suggest that genetic translocation and/or overexpression of oncoproteins is important in salivary gland tumorigenesis and diagnosis. We investigated PLAG1, SOX10, and Myb protein expression in various salivary gland neoplasm tissues.

Methods

A total of 113 cases of surgically resected salivary gland neoplasms at the National Cancer Center from January 2007 to March 2017 were identified. Immunohistochemical staining of PLAG1, SOX10, and Myb in tissue samples was performed using tissue microarrays.

Results

Among the 113 cases, 82 (72.6%) were benign and 31 (27.4%) were malignant. PLAG1 showed nuclear staining and normal parotid gland was not stained. Among 48 cases of pleomorphic adenoma, 29 (60.4%) were positive for PLAG1. All other benign and malignant salivary gland neoplasms were PLAG1-negative. SOX10 showed nuclear staining. In normal salivary gland tissues SOX10 was expressed in cells of acinus and intercalated ducts. In benign tumors, SOX10 expression was observed in all pleomorphic adenoma (48/48), and basal cell adenoma (3/3), but not in other benign tumors. SOX10 positivity was observed in nine of 31 (29.0%) malignant tumors. Myb showed nuclear staining but was not detected in normal parotid glands. Four of 31 (12.9%) malignant tumors showed Myb positivity: three adenoid cystic carcinomas (AdCC) and one myoepithelial carcinoma with focal AdCC-like histology.

Conclusions

PLAG1 expression is specific to pleomorphic adenoma. SOX10 expression is helpful to rule out excretory duct origin tumor, but its diagnostic value is relatively low. Myb is useful for diagnosing AdCC when histology is unclear in the surgical specimen.

Mutations in microRNA processing genes in Wilms tumors derepress the IGF2 regulator PLAG1

Many childhood Wilms tumors are driven by mutations in the microRNA biogenesis machinery, but the mechanism by which these mutations drive tumorigenesis is unknown. Here we show that the transcription factor pleomorphic adenoma gene 1 (PLAG1) is a microRNA target gene that is overexpressed in Wilms tumors with mutations in microRNA processing genes. Wilms tumors can also overexpress PLAG1 through copy number alterations, and PLAG1 expression correlates with prognosis in Wilms tumors. PLAG1 overexpression accelerates growth of Wilms tumor cells in vitro and induces neoplastic growth in the developing mouse kidney in vivo. In both settings, PLAG1 transactivates insulin-like growth factor 2 (IGF2), a key Wilms tumor oncogene, and drives mammalian target of rapamycin complex 1 (mTORC1) signaling. These data link microRNA impairment to the PLAG1-IGF2 pathway, providing new insight into the manner in which common Wilms tumor mutations drive disease pathogenesis.

PLAG1 immunohistochemistry is a sensitive marker for pleomorphic adenoma: a comparative study with PLAG1 genetic abnormalities

AIMS

Pleomorphic adenoma gene 1 (PLAG1) gene rearrangement is the most common genetic abnormality in pleomorphic adenoma (PA), resulting in overexpression of PLAG1 protein. PA and carcinoma ex pleomorphic adenoma (CA ex-PA) can mimic various benign and malignant salivary gland tumours. The aims of this study are to evaluate the sensitivity and specificity of PLAG1 immunohistochemistry (IHC) in the differential diagnosis of PA and CA ex-PA and to compare the PLAG1 immunohistochemical results to PLAG1 gene abnormalities as detected by fluorescence in-situ hybridisation (FISH).

METHODS AND RESULTS

PLAG1 immunostaining was performed on 83 salivary gland tumours, including 23 PA, 15 CA ex-PA and 45 other salivary gland tumours. In addition, PLAG1 FISH was performed in 44 cases for the presence of gene rearrangements/amplifications. The results showed high sensitivity of PLAG1 IHC in 96% of PA; however, discordant results between PLAG1 FISH abnormalities and IHC were noted in 15 of 44 cases (34%). Seven PA, four de-novo myoepithelial carcinomas and one basal cell adenocarcinoma had negative FISH results, but were positive for IHC; while three salivary duct carcinomas (SDC) ex-PA were positive for FISH but negative for IHC. PLAG1 IHC can differentiate CA ex-PA from de-novo SDC (P = 0.02), but not from de-novo myoepithelial carcinoma. PLAG1 IHC is a sensitive marker for PA. This could be due to PLAG1 gene abnormalities beyond FISH resolution.

CONCLUSIONS

A negative PLAG1 IHC might be helpful in excluding a PA diagnosis. Interestingly, in the context of CA ex-PA, FISH is more sensitive than IHC in detecting PLAG1 abnormalities.

Genetic disruption of the oncogenic HMGA2-PLAG1-IGF2 pathway causes fetal growth restriction

Purpose

Fetal growth is a complex process involving maternal, placental and fetal factors. The etiology of fetal growth retardation remains unknown in many cases. The aim of this study is to identify novel human mutations and genes related to Silver–Russell syndrome (SRS), a syndromic form of fetal growth retardation, usually caused by epigenetic downregulation of the potent fetal growth factor IGF2.

Methods

Whole-exome sequencing was carried out on members of an SRS familial case. The candidate gene from the familial case and two other genes were screened by targeted high-throughput sequencing in a large cohort of suspected SRS patients. Functional experiments were then used to link these genes into a regulatory pathway.

Results

We report the first mutations of the PLAG1 gene in humans, as well as new mutations in HMGA2 and IGF2 in six sporadic and/or familial cases of SRS. We demonstrate that HMGA2 regulates IGF2 expression through PLAG1 and in a PLAG1-independent manner.

Conclusion

Genetic defects of the HMGA2–PLAG1–IGF2 pathway can lead to fetal and postnatal growth restriction, highlighting the role of this oncogenic pathway in the fine regulation of physiological fetal/postnatal growth. This work defines new genetic causes of SRS, important for genetic counseling.

Circulating high mobility group AT-hook 2 and pleomorphic adenoma gene 1 in blood of patients with oral squamous cell carcinoma

BACKGROUND

High mobility group AT-hook 2 (HMGA2) and pleomorphic adenoma gene 1(PLAG1) have been demonstrated to be elevated in many malignant tumors. However, the aim of this study was to evaluate HMGA2 and PLAG1 levels in blood as a non-invasive biomarker for oral squamous cell carcinoma (OSCC) diagnosis.

METHODS

qRT-PCR was performed to measure circulating HMGA2 and PLAG1 levels in OSCC patients (n=43) and matched cancer-free blood control group (n=21). Clinical data of all patients were recorded.

RESULTS

Circulating HMGA2 and PLAG1 in the 43 OSCC patients was significantly higher than in control group (P<.001, P=.038, respectively). Furthermore, HMGA2 expression in OSCC patients with poor-moderate differentiation was increased compared with well-differentiated group. However, no significant differences in PLAG1 expression were detected when differentiation was considered. In addition, the receiver operating characteristic (ROC) curve analysis for circulating HMGA2 revealed an area under the ROC curve of 0.876 (95% confidence interval, 0.793-0.959; P<.001) with 65.1% sensitivity and 100% specificity in discriminating OSCC from controls at a cutoff value of 14.380, demonstrating significant diagnostic value for OSCC.

CONCLUSION

Circulating HMGA2 levels are increased in OSCC patients and may potentially serve as a significant index to evaluate OSCC diagnosis.

Emerging role of PLAG1 as a regulator of growth and reproduction

Pleomorphic adenoma gene 1 (PLAG1) belongs to the PLAG family of zinc finger transcription factors along with PLAG-like 1 and PLAG-like 2. The PLAG1 gene is best known as an oncogene associated with certain types of cancer, most notably pleomorphic adenomas of the salivary gland. While the mechanisms of PLAG1-induced tumorigenesis are reasonably well understood, the role of PLAG1 in normal physiology is less clear. It is known that PLAG1 is involved in cell proliferation by directly regulating a wide array of target genes, including a number of growth factors such as insulin-like growth factor 2. This is likely to be a central mode of action for PLAG1 both in embryonic development and in cancer. The phenotype of Plag1 knockout mice suggests an important role for PLAG1 also in postnatal growth and reproduction, as PLAG1 deficiency causes growth retardation and reduced fertility. A role for PLAG1 in growth and reproduction is further corroborated by genome-wide association studies in humans and domestic animals in which polymorphisms in the PLAG1 genomic region are associated with body growth and reproductive traits. Here we review the current evidence for PLAG1 as a regulator of growth and fertility and discuss possible endocrine mechanisms involved.

Integrated data analysis reveals uterine leiomyoma subtypes with distinct driver pathways and biomarkers

Uterine leiomyomas are common benign smooth muscle tumors that impose a major burden on women's health. Recent sequencing studies have revealed recurrent and mutually exclusive mutations in leiomyomas, suggesting the involvement of molecularly distinct pathways. In this study, we explored transcriptional differences among leiomyomas harboring different genetic drivers, including high mobility group AT-hook 2 (HMGA2) rearrangements, mediator complex subunit 12 (MED12) mutations, biallelic inactivation of fumarate hydratase (FH), and collagen, type IV, alpha 5 and collagen, type IV, alpha 6 (COL4A5-COL4A6) deletions. We also explored the transcriptional consequences of 7q22, 22q, and 1p deletions, aiming to identify possible target genes. We investigated 94 leiomyomas and 60 corresponding myometrial tissues using exon arrays, whole genome sequencing, and SNP arrays. This integrative approach revealed subtype-specific expression changes in key driver pathways, including Wnt/β-catenin, Prolactin, and insulin-like growth factor (IGF)1 signaling. Leiomyomas with HMGA2 aberrations displayed highly significant up-regulation of the proto-oncogene pleomorphic adenoma gene 1 (PLAG1), suggesting that HMGA2 promotes tumorigenesis through PLAG1 activation. This was supported by the identification of genetic PLAG1 alterations resulting in expression signatures as seen in leiomyomas with HMGA2 aberrations. RAD51 paralog B (RAD51B), the preferential translocation partner of HMGA2, was up-regulated in MED12 mutant lesions, suggesting a role for this gene in the genesis of leiomyomas. FH-deficient leiomyomas were uniquely characterized by activation of nuclear factor erythroid 2-related factor 2 (NRF2) target genes, supporting the hypothesis that accumulation of fumarate leads to activation of the oncogenic transcription factor NRF2. This study emphasizes the need for molecular stratification in leiomyoma research and possibly in clinical practice as well. Further research is needed to determine whether the candidate biomarkers presented herein can provide guidance for managing the millions of patients affected by these lesions.

Upregulated genes at 2q24 gains as candidate oncogenes in hepatoblastomas

AIM

Cytogenetic data of hepatoblastomas, a rare embryonal tumor of the liver, mostly consist of descriptions of whole-chromosome aneuploidies and large chromosome alterations. High-resolution cytogenetics may provide clues to hepatoblastoma tumorigenesis and indicate markers with clinical significance.

PATIENTS & METHODS

We used array-CGH (180K) to screen for genomic imbalances in nine hepatoblastomas. Additionally, we investigated the expression pattern of selected genes exhibiting copy number changes.

RESULTS

Analysis showed mainly whole-chromosome or chromosome-arm aneuploidies, but some focal aberrations were also mapped. Expression analysis of 48 genes mapped at one 10 Mb amplification at 2q24 revealed upregulation of DAPL1, ERMN, GALNT5, SCN1A and SCN3A in the set of tumors compared with differentiated livers.

CONCLUSION

These genes appear as candidates for hepatoblastoma tumorigenesis.

Exome sequencing of hepatoblastoma reveals novel mutations and cancer genes in the Wnt pathway and ubiquitin ligase complex

Hepatoblastoma (HB) is the most common primary liver tumor in children. Mutations in the β-catenin gene that lead to constitutive activation of the Wnt pathway have been detected in a large proportion of HB tumors. To identify novel mutations in HB, we performed whole-exome sequencing of six paired HB tumors and their corresponding lymphocytes. This identified 24 somatic nonsynonymous mutations in 21 genes, many of which were novel, including three novel mutations targeting the CTNNB1 (G512V) and CAPRIN2 (R968H/S969C) genes in the Wnt pathway, and genes previously shown to be involved in the ubiquitin ligase complex (SPOP, KLHL22, TRPC4AP, and RNF169). Functionally, both the CTNNB1 (G512V) and CAPRIN2 (R968H/S969C) were observed to be gain-of-functional mutations, and the CAPRIN2 (R968H/S969C) was also shown to activate the Wnt pathway in HB cells. These findings suggested the activation of the Wnt pathway in HB, which was confirmed by immunohistochemical staining of the β-catenin in 42 HB tumors. We further used short hairpin RNA (shRNA)-mediated interference to assess the effect of 21 mutated genes on HB cell survival. The results suggested that one novel oncogene (CAPRIN2) and three tumor suppressors (SPOP, OR5I1, and CDC20B) influence HB cell growth. Moreover, we found that SPOP S119N is a loss-of-function mutation in HB cells. We finally demonstrated that one of the mechanisms by which SPOP inhibits HB cell proliferation is through regulating CDKN2B expression.

CONCLUSION

These results extend the landscape of genetic alterations in HB and highlight the dysregulation of Wnt and ubiquitin pathways in HB tumorigenesis.

Pleomorphic adenoma gene 1 mediates the role of karyopherin alpha 2 and has prognostic significance in hepatocellular carcinoma

Background

Karyopherin alpha 2 (KPNA2) promotes tumor growth in hepatocellular carcinoma (HCC). We aimed to determine the content and clinical significance of mechanism underlying.

Methods

The association of transcriptional factor pleomorphic adenoma gene 1 (PLAG1) with KPNA2 was explored by co-immunoprecipitation. In vitro gain- and loss-of-function models were established to explore the functional interaction. Clinical samples from 314 HCC patients were applied to explore the clinical significance.

Results

We found that PLAG1 could associate with KPNA2 and be promoted into nucleus by KPNA2. The increment of proliferative and metastatic abilities by KPNA2 over-expression can be significantly retarded by PLAG1 inhibition. The co-enrichment of KPNA2 and PLAG1 in nucleus is observed in clinical samples and can distinguish patients with the worst prognosis. The positive PLAG1 expression is an independent risk factor of recurrence free survival (HR: 1.766, 1.315-2.371; P = 0.000) and overall survival (HR: 1.589, 1.138-2.220; P = 0.007). Especially for patients with positive KPNA2 staining (N = 152), the positive PLAG1 expression is the sole risk factor for both recurrence free survival (HR: 1.749, 1.146-2.670; P = 0.010) and overall survival (HR: 1.662, 1.007-2.744; P = 0.047).

Conclusions

The nuclear import of PLAG1 by KPNA2 is essential for the role of KPNA2 in HCC cells and is significant to predict poor survival of HCC patients after hepatectomy.

Correlated expression of HMGA2 and PLAG1 in thyroid tumors, uterine leiomyomas and experimental models

In pleomorphic adenomas of the salivary glands (PASG) recurrent chromosomal rearrangements affecting either 8q12 or 12q14∼15 lead to an overexpression of the genes of the genuine transcription factor PLAG1 or the architectural transcription factor HMGA2, respectively. Both genes are also affected by recurrent chromosomal rearrangements in benign adipocytic tumors as e. g. lipomas and lipoblastomas. Herein, we observed a strong correlation between the expression of HMGA2 and PLAG1 in 14 benign and 23 malignant thyroid tumors. To address the question if PLAG1 can be activated by HMGA2, the expression of both genes was quantified in 32 uterine leiomyomas 17 of which exhibited an overexpression of HMGA2. All leiomyomas with HMGA2 overexpression also revealed an activation of PLAG1 in the absence of detectable chromosome 8 abnormalities affecting the PLAG1 locus. To further investigate if the overexpression of PLAG1 is inducible by HMGA2 alone, HMGA2 was transiently overexpressed in MCF-7 cells. An increased PLAG1 expression was observed 24 and 48 h after transfection. Likewise, stimulation of HMGA2 by FGF1 in adipose tissue-derived stem cells led to a simultaneous increase of PLAG1 mRNA. Altogether, these data suggest that HMGA2 is an upstream activator of PLAG1. Accordingly, this may explain the formation of tumors as similar as lipomas and lipoblastomas resulting from an activation of either of both genes by chromosomal rearrangements.

Immunohistochemical features of lacrimal gland epithelial tumors

PURPOSE

To investigate the immunohistochemical features of ocular adnexal pleomorphic adenoma and adenoid cystic carcinoma.

DESIGN

Retrospective clinicopathologic study.

METHODS

Clinical records and microscopic slides of 7 cases of each tumor type were reviewed. Immunohistochemical probes for Ki-67 and p53, and newer nuclear markers MYB for adenoid cystic carcinoma and PLAG1 for pleomorphic adenoma, were employed.

RESULTS

Pleomorphic adenomas were asymptomatic, whereas adenoid cystic carcinomas were painful. No pleomorphic adenomas recurred; 4 adenoid cystic carcinomas recurred, resulting in 3 deaths. Unusual histopathologic variants for which immunohistochemistry proved useful included a myoepithelioma, an atypical pleomorphic adenoma, tubular and solid/basaloid variants of adenoid cystic carcinoma, and a morphologically heterogeneous adenoid cystic carcinoma of a Wolfring gland. For the pleomorphic adenomas, the average Ki-67 proliferation index was 3.8%; p53 was weakly staining, with an average positivity of 18.5%; PLAG1 was strongly positive in all cases; MYB was negative in 5 cases and weakly focally positive in 2 cases. For the adenoid cystic carcinomas, the average Ki-67 proliferation index was 29.1%; p53 stained positively and strongly with an average of 39%; none stained positively for PLAG1; and 6 out of 7 were MYB positive.

CONCLUSIONS

Between pleomorphic adenoma and adenoid cystic carcinoma, there was no overlap in Ki-67 positivity. Positivity for p53 showed overlap in only one lesion of each type. PLAG1 and MYB positivity were highly discriminating between pleomorphic adenoma and adenoid cystic carcinoma. Immunohistochemical analysis should be investigated further for its role in the evaluation of pleomorphic adenoma and adenoid cystic carcinoma.

miR-141 contributes to fetal growth restriction by regulating PLAG1 expression

Background

Fetal growth restriction (FGR) is an important but poorly understood condition of pregnancy, which results in significant fetal, neonatal and long-term morbidity and mortality. Novel research has suggested that altered miRNA expression in the plasma and placenta is associated with adverse pregnancy. We hypothesized that aberrant expression of microRNA-141 (miR-141) in the placenta is associated with FGR. Additionally, expression levels of predicted target genes of miR-141 were also analyzed in placental tissues of FGR and normal controls.

Methodology/Principal Findings

Using quantitative real time PCR, we analyzed the expression level of miR-141 and its target genes in placentas of FGR pregnancies (n = 21) and normal controls (n = 34). Western blot was used to detect the protein expression level of the target genes of miR-141. MiR-141 showed significant up regulation in FGR and significant down regulation of its targets, i.e. E2F transcription factor 3 (E2F3) protein, pleiomorphic adenoma gene 1 (PLAG1) mRNA and protein. Moreover, a positive correlation was found between PLAG1 and insulin-like growth factor 2 (IGF2) expression levels (Spearman r = 0.56, p<0.0001). MiR-141 yields an AUC of 0.83 with 88.5% sensitivity and 71.7% specificity for separating FGR from normal controls. This study indicates that miR-141 may be diagnostically important in FGR.

Conclusions/Significance

Our results indicate that aberrant high expression level of miR-141 might play important roles in the pathogenesis of FGR by suppressing E2F3 and PLAG1. We propose that miR-141 may participate in a miR-141-PLAG1-IGF2 network relating to FGR development. These findings may provide new targets via miR-141 in diagnosis and therapy of FGR in the future.

Genetics and epigenetics of hepatoblastoma

A number of unique genetic features are observed in hepatoblastoma that have provided insights into the origins of hepatoblastoma. Hallmark cytogenetic changes in hepatoblastoma include the acquisition of additional copies of whole chromosomes and a recurring unbalanced translocation involving 1q. Genetic syndromes are associated with approximately 15% of hepatoblastoma and the understanding and recognition of these syndromes will be important in determining future surveillance studies needed to prevent additional cancers in survivors as well as in some case guide the care of family members. This article will review the genetic changes, both germ line and acquired, that are recurring events in hepatoblastoma, with emphasis on how these genetic changes could work together with other developmental factors and influence cancer predisposition, tumor growth, as well as aid in prognosis. Tumor-specific signatures based on transcriptional or epigenetic alterations will be reviewed that might be used in the future to better diagnose and subtype the disease as well as predict prognosis and response to therapy.

Cell type and context-specific function of PLAG1 for IGF2 P3 promoter activity

The fetal transcription factor PLAG1 is found to be overexpressed in cancers, and has been suggested to bind the insulin like growth factor 2 (IGF2) P3 promoter, and to activate the IGF2 gene. The expression of IGF2 has partly been linked to loss of CTCF-dependent chromatin insulator function at the H19 imprinting control region (ICR). We investigated the role of PLAG1 for IGF2 regulation in Hep3B and JEG-3 cell lines. Chromatin immunoprecipitation revealed cell type-specific binding of PLAG1 to the IGF2 P3 promoter, which was substantially insensitive to recombinant PLAG1 overexpression in the endogenous context. We hypothesized that the H19 chromatin insulator may be involved in the cell type-specific PLAG1 response. By using a GFP reporter gene/insulator assay plasmid construct with and without the H19 ICR and/or an SV40 enhancer, we confirm that the effect of the insulator is specifically associated with the activity of the IGF2 P3 promoter in the GFP reporter system, and furthermore, that the reporter insulator is functional in JEG-3 but not in Hep3B cells. FACS analysis was used to assess the function of PLAG1 in low endogenously expressing, but Zn-inducible stable PLAG1 expressing JEG-3 cell clones. Considerable increase in IGF2 expression upon PLAG1 induction with a partial insulator overriding activity was found using the reporter constructs. This is in contrast to the effect of the endogenous IGF2 gene which was insensitive to PLAG1 expression in JEG-3, while modestly induced the already highly expressed IGF2 gene in Hep3B cells. We suggest that the PLAG1 binding to the IGF2 P3 promoter and IGF2 expression is cell type-specific, and that the PLAG1 transcription factor acts as a transcriptional facilitator that partially overrides the insulation by the H19 ICR.

Pleomorphic adenoma gene-like 2 regulates expression of the p53 family member, p73, and induces cell cycle block and apoptosis in human promonocytic U937 cells

The proto-oncogene, pleomorphic adenoma gene-like 2 (PLAGL2), is implicated in a variety of cancers including acute myeloid leukemia (AML), malignant glioma, colon cancer, and lung adenocarcinoma. There is additional evidence that PLAGL2 can function as a tumor suppressor by initiating cell cycle arrest and apoptosis. Interestingly, PLAGL2 has also been implicated in human myelodysplastic syndrome, a disease that is characterized by ineffective hematopoiesis and can lead to fatal cytopenias (low blood counts) as a result of increased apoptosis in the marrow, or, in about one-third of cases, can progress to AML. To gain a better understanding of the actions of PLAGL2 in human myeloid cells, we generated a stable PLAGL2-inducible cell line, using human promonocytic U937 cells. PLAGL2 expression inhibited cell proliferation which correlated with an accumulation of cells in G1, apoptotic DNA-laddering, an increase in caspase 3, 8, and 9 activity, and a loss of mitochondrial transmembrane potential. There was significant increase in the p53 homologue, p73, with PLAGL2 expression, and consistent with mechanisms of p73-regulated cell cycle control and apoptosis, there was increased expression of known p73 target genes p21, DR5, TRAIL, and Bax. PLAGL2-induced cell cycle block was abolished in the presence of p73 siRNA. Together, these data support a role for PLAGL2 in cell cycle regulation and apoptosis via activation of p73.

PLAG1 alteration in carcinoma ex pleomorphic adenoma: immunohistochemical and fluorescence in situ hybridization studies of 22 cases

Carcinoma ex pleomorphic adenoma (CA-ex-PA) may arise with nearly any histologic subtype of carcinoma of the salivary gland. In the absence of recognizable residual pleomorphic adenoma (PA) or a prior history of PA, distinction of CA-ex-PA from morphologically similar de novo carcinomas may be difficult. Oncogenic rearrangement of PLAG1 (pleomorphic adenoma gene 1) has been established in PA; however, it has not yet been proven that PLAG1 alteration persists in carcinomas developed from preceding PA. We evaluated 22 histologically diverse CA-ex-PA by immunohistochemistry for PLAG1, and/or by FISH targeting PLAG1. Of these, 17 cases were immunoreactive (1+ to 3+) and 5 were immunonegative/rare positive for PLAG1. For comparison, 39 various salivary gland neoplasms were immunostained for PLAG1, of which all scored negative/rare positive. Twelve of 19 CA-ex-PA analyzed by PLAG1 FISH (63 %) were positive for gene rearrangement, 2 showed only a trisomy/polysomy profile, and 5 had a normal pattern. One FISH-positive tumor showed amplification of PLAG1. One of 3 cases analyzed for HMGA2 FISH was positive for gene rearrangement. In our series, the majority of CA-ex-PA harbored altered PLAG1 or HMGA2 genes detectable by FISH. While PLAG1 immunostain was specific for CA-ex-PA against other carcinomas, its application as a standalone discriminatory test was limited by variable expression. We conclude that most CA-ex-PA, regardless of morphologic subtype, carry altered PLAG1 or HMGA2 genes, and that FISH for PLAG1, along with immunohistochemistry for PLAG1, may help discriminate CA-ex-PA from its de novo carcinoma counterpart.

IGFBP3 impedes aggressive growth of pediatric liver cancer and is epigenetically silenced in vascular invasive and metastatic tumors

Background

Hepatoblastoma (HB) is an embryonal liver neoplasm of early childhood with a poor prognosis for patients with distant metastases and vascular invasion. We and others have previously shown that the overexpression of insulin-like growth factor 2 (IGF2), loss of imprinting at the IGF2/H19 locus, and amplification of pleomorphic adenoma gene 1 (PLAG1) are common features in HB, suggesting a critical role of the IGF axis in hepatoblastomagenesis. In this study, we investigated the role of the insulin-like growth factor binding protein 3 (IGFBP3), a known competitor of the IGF axis, in pediatric liver cancers.

Results

The IGFBP3 gene was highly expressed in normal pediatric livers but was heavily downregulated in four HB cell lines and the majority of HB primary tumors (26/36). Detailed methylation analysis of CpG sites in the IGFBP3 promoter region by bisulfite sequencing revealed a high degree of DNA methylation, which is causatively associated with the suppression of IGFBP3 in HB cell lines. Consequently, the treatment of HB cell lines with 5-aza-2'-deoxycytidine resulted in DNA demethylation and reactivation of the epigenetically silenced IGFBP3 expression. Interestingly, IGFBP3 promoter methylation predominantly occurred in metastatic HB with vascular invasion. Restoring IGFBP3 expression in HB cells resulted in reduced colony formation, migration, and invasion.

Conclusion

This study provides the first direct evidence that the reactivation of IGFBP3 decreases aggressive properties of pediatric liver cancer cells and that IGFBP3 promoter methylation might be used as an indicator for vessel-invasive tumor growth in HB patients.

Disseminated carcinoma ex pleomorphic adenoma in an adolescent confirmed by application of PLAG1 immunohistochemistry and FISH for PLAG1 rearrangement

A 16-year-old previously asymptomatic boy presented with complaints of fatigue, weight loss, and back pain for several months. Imaging studies revealed a large superior mediastinal mass, numerous bilateral pulmonary nodules, and multiple lytic bone lesions. A needle biopsy from a sternal lesion showed a poorly differentiated carcinoma, immunoreactive for cytokeratins and EMA and immunonegative for various organ/tissue-specific markers.His past medical history was significant for excision of aparotid gland tumor 5 years earlier. Histologic review of the salivary gland tumor revealed a pleomorphic adenoma containing a microscopic focus of invasive carcinoma(carcinoma ex pleomorphic adenoma). By immunohistochemistry, both the salivary gland tumor and the disseminated carcinoma expressed PLAG1 with a strong nuclear pattern.Fluorescence in situ hybridization (FISH), using dual-color, break-apart probes for PLAG1, showed rearrangement of the gene in both the salivary gland and the disseminated tumors.FISH demonstrated additional cytogenetic aberrations in the carcinoma, including polysomy for chromosome 8 (in both the primary salivary gland and the metastatic tumors) and PLAG1 amplification (in the metastatic tumor). We conclude that in the proper clinicopathologic setting, application of PLAG1 immunohistochemistry and FISH for PLAG1 gene rearrangement may be valuable in establishing the diagnosis of carcinoma ex pleomorphic adenoma as the source of a cancer of unknown primary site.

A subset of cutaneous and soft tissue mixed tumors are genetically linked to their salivary gland counterpart

Neoplasms morphologically similar to mixed tumors and myoepitheliomas of the salivary glands, under the broad concept of myoepithelial neoplasia, have recently been defined in the skin and soft tissue; however, to date, no data have supported a shared genetic background with their salivary gland counterpart. From a large body of research, it has been well established that rearrangement of pleomorphic adenoma gene 1 (PLAG1) leads to aberrant expression of its protein and is pathogenically relevant in the development of salivary mixed tumors. On the other hand, in soft tissue lesions, compelling evidence suggests that EWSR1 is involved in a significant subset. To examine the hypothesis that there is a genetic link between these histologically similar tumors at different sites, we randomly selected 20 benign myoepitheliomas/mixed tumors of skin and soft tissue (10 cases each). Nineteen cases could be immunostained for PLAG1, of which 11 cases showed distinct nuclear staining with moderate or strong intensity in a significant number of cells. Interphase fluorescence in situ hybridization for PLAG1 was successfully performed in 11 cases (seven in skin and four in soft tissue) and was positive for gene rearrangement in eight cases (five in skin and three in soft tissue). All PLAG1-rearranged tumors, except one, had clear-cut ductal structures and were immunoreactive for PLAG1. In our series, tumors with PLAG1 alteration shared a common morphologic phenotype characterized by prominent tubuloductal differentiation, suggesting that myoepithelial neoplasms with genuine salivary gland-like morphology, so-called soft tissue/cutaneous mixed tumors, are genetically related to their salivary gland counterpart.