Mapping an endometrial cancer tumor suppressor gene at 10q25 and development of a bacterial clone contig for the consensus deletion interval

Empty spiracles homeobox genes EMX1 and EMX2 regulate WNT pathway activation in sarcomagenesis

Background

Sarcomas are a very heterogeneous group of tumors with intrinsic developmental programs derived from the cell of origin. This implies a functional hierarchy inside tumors governed by sarcoma stem cells. Therefore, genetic and/or epigenetic changes profoundly affect the biology of sarcoma tumor stem cells. EMX genes are proposed to be transcription factors that are involved in the sarcomagenesis process, regardless of the neural or mesodermal embryological sarcoma origin. It has been shown that EMX1 or EMX2 overexpression reduces tumorigenic properties, while reducing the levels of these genes enhances these properties. Furthermore, it has been shown that EMX genes decrease the expression of stem cell regulatory genes and the stem cell phenotype. Taken together, these results indicate that the EMX1 and EMX2 genes negatively regulate these tumor-remodeling populations or sarcoma stem cells, acting as tumor suppressors in sarcoma.

Methods

Bioinformatic analysis, quantitative mRNA and protein expression analysis, cell models of sarcoma by ectopic expression of EMX genes. By cell biology methods we measured tumorigenesis and populations enriched on stem cell phenotypes, either in vitro or in vivo.

Results

In this work, we showed that the canonical Wnt pathway is one of the mechanisms that explains the relationships of EMX1/EMX2 and stem cell genes in sarcoma. The Wnt-EMX1/EMX2 relationship was validated in silico with sarcoma patient datasets, in vitro in primary derived sarcoma cell lines, and in vivo. EMX expression was found to negatively regulate the Wnt pathway. In addition, the constitutive activation of the Wnt pathway revers to a more aggressive phenotype with stem cell properties, and stemness gene transcription increased even in the presence of EMX1 and/or EMX2 overexpression, establishing the relationship among the Wnt pathway, stem cell genes and the EMX transcription factors.

Conclusions

Our data showed that Empty Spiracles Homeobox Genes EMX1 and EMX2 represses WNT signalling and activation of WNT pathway bypass EMX-dependent stemness repression and induces sarcomagenesis. These results also suggest the relevance of the Wnt/b-catenin/stemness axis as a therapeutic target in sarcoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02048-9.

Regulation of sarcomagenesis by the empty spiracles homeobox genes EMX1 and EMX2

The EMX (Empty Spiracles Homeobox) genes EMX1 and EMX2 are two homeodomain gene members of the EMX family of transcription factors involved in the regulation of various biological processes, such as cell proliferation, migration, and differentiation, during brain development and neural crest migration. They play a role in the specification of positional identity, the proliferation of neural stem cells, and the differentiation of certain neuronal cell phenotypes. In general, they act as transcription factors in early embryogenesis and neuroembryogenesis from metazoans to higher vertebrates. The EMX1 and EMX2's potential as tumor suppressor genes has been suggested in some cancers. Our work showed that EMX1/EMX2 act as tumor suppressors in sarcomas by repressing the activity of stem cell regulatory genes (OCT4, SOX2, KLF4, MYC, NANOG, NES, and PROM1). EMX protein downregulation, therefore, induced the malignance and stemness of cells both in vitro and in vivo. In murine knockout (KO) models lacking Emx genes, 3MC-induced sarcomas were more aggressive and infiltrative, had a greater capacity for tumor self-renewal, and had higher stem cell gene expression and nestin expression than those in wild-type models. These results showing that EMX genes acted as stemness regulators were reproduced in different subtypes of sarcoma. Therefore, it is possible that the EMX genes could have a generalized behavior regulating proliferation of neural crest-derived progenitors. Together, these results indicate that the EMX1 and EMX2 genes negatively regulate these tumor-altering populations or cancer stem cells, acting as tumor suppressors in sarcoma.

The expression of EMX2 lead to cell cycle arrest in glioblastoma cell line

Background

Glioblastoma (GB) is a highly invasive primary brain tumor that nearly always systematically recurs at the site of resection despite aggressive radio-chemotherapy. Previously, we reported a gene expression signature related to tumor infiltration. Within this signature, the EMX2 gene encodes a homeodomain transcription factor that we found was down regulated in glioblastoma. As EMX2 is reported to play a role in carcinogenesis, we investigated the impact of EMX2 overexpression in glioma-related cell lines.

Methods

For that purpose, we constructed tetracycline-inducible EMX2 expression lines. Transfected cell phenotypes (proliferation, cell death and cell cycle) were assessed in time-course experiments.

Results

Restoration of EMX2 expression in U87 glioblastoma cells significantly inhibited cell proliferation. This inhibition was reversible after EMX2 removal from cells. EMX2-induced proliferative inhibition was very likely due to cell cycle arrest in G1/S transition and was not accompanied by signs of cell death.

Conclusion

Our results suggest that EMX2 may constitute a putative therapeutic target for GB treatment.

Further studies are required to decipher the gene networks and transduction signals involved in EMX2’s effect on cell proliferation.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5094-y) contains supplementary material, which is available to authorized users.

The Role of Chromosomal Instability in Cancer and Therapeutic Responses

Cancer is one of the leading causes of death, and despite increased research in recent years, control of advanced-stage disease and optimal therapeutic responses remain elusive. Recent technological improvements have increased our understanding of human cancer as a heterogeneous disease. For instance, four hallmarks of cancer have recently been included, which in addition to being involved in cancer development, could be involved in therapeutic responses and resistance. One of these hallmarks is chromosome instability (CIN), a source of genetic variation in either altered chromosome number or structure. CIN has become a hot topic in recent years, not only for its implications in cancer diagnostics and prognostics, but also for its role in therapeutic responses. Chromosomal alterations are mainly used to determine genetic heterogeneity in tumors, but CIN could also reveal treatment efficacy, as many therapies are based on increasing CIN, which causes aberrant cells to undergo apoptosis. However, it should be noted that contradictory findings on the implications of CIN for the therapeutic response have been reported, with some studies associating high CIN with a better therapeutic response and others associating it with therapeutic resistance. Considering these observations, it is necessary to increase our understanding of the role CIN plays not only in tumor development, but also in therapeutic responses. This review focuses on recent studies that suggest possible mechanisms and consequences of CIN in different disease types, with a primary focus on cancer outcomes and therapeutic responses.

Long non-coding RNA CASC2 in human cancer

Long non-coding RNAs cover large part of the non-coding information of the human DNA, which represents more than 90% of the whole genome. They constitute a wide and complex group of molecules with more than 200 nucleotides, which generally lack an open reading frame, and are involved in various ways in the pathophysiology of cancer. Their roles in the regulation of gene expression, imprinting, transcription, and post-translational processing have been described in several types of cancer. CASC2 was discovered in 2004 in patients with endometrial carcinoma as a potential tumor suppressor. Since then, additional studies in other types of neoplasia have been carried out, and both mechanisms and interactions of CASC2 in cancer have been better elucidated. In this review, we summarize the current knowledge on the role of CASC2 in the genesis, progression, and clinical management of human cancer.

Tissue selective estrogen complexes (TSECs) differentially modulate markers of proliferation and differentiation in endometrial cells

Selective estrogen receptor modulators (SERMs) have tissue-specific estrogen receptor (ER) modulating properties. Combining an SERM with one or more estrogens to form a tissue selective estrogen complex (TSEC) can provide an improved blend of tissue-specific ER agonist and antagonist effects. While both estrogens and SERMs affect the uterine endometrium, not all TSECs reverse the endometrial effects of estrogens preventing endometrial proliferation and hyperplasia. Their action in uterine cells is not completely understood. HOXA 10, leukemia inhibitory factor (LIF), progesterone receptor (PR), and EMX2 are genes known to regulate endometrial proliferation and differentiation. The expression of these genes was used to assess endometrial effects of SERMs and TSECs. We evaluated the effects of raloxifene (RAL), tamoxifen (TAM), lasofoxifene (LAS), bazedoxifene acetate (BZA), and progesterone (P) alone and in combination with estradiol (E2) in Ishikawa cells. Increased HOXA10, LIF, PR, and EMX2 messenger RNA (mRNA) expression was noted in E2-treated cells compared with vehicle-treated controls. All TSECs maintained E2-induced PR expression and all except TAM prevented estrogen-induced LIF expression. The TSEC containing BZA uniquely decreased HOXA10 expression and increased EMX2 expression. The TSECs alter endometrial cell proliferation by selective modulation of estrogen responsive genes, maintaining the antiproliferative effects mediated by PR and inhibiting LIF. The differential effect of TSECs on endometrial gene expression suggests a mechanism by which they manifest differential effects on endometrial safety against the risk of estrogen-induced endometrial hyperplasia.

SKY analysis revealed recurrent numerical and structural chromosome changes in BDII rat endometrial carcinomas

Background

Genomic alterations are common features of cancer cells, and some of these changes are proven to be neoplastic-specific. Such alterations may serve as valuable tools for diagnosis and classification of tumors, prediction of clinical outcome, disease monitoring, and choice of therapy as well as for providing clues to the location of crucial cancer-related genes.

Endometrial carcinoma (EC) is the most frequently diagnosed malignancy of the female genital tract, ranking fourth among all invasive tumors affecting women. Cytogenetic studies of human ECs have not produced very conclusive data, since many of these studies are based on karyotyping of limited number of cases and no really specific karyotypic changes have yet been identified. As the majority of the genes are conserved among mammals, the use of inbred animal model systems may serve as a tool for identification of underlying genes and pathways involved in tumorigenesis in humans. In the present work we used spectral karyotyping (SKY) to identify cancer-related aberrations in a well-characterized experimental model for spontaneous endometrial carcinoma in the BDII rat tumor model.

Results

Analysis of 21 experimental ECs revealed specific nonrandom numerical and structural chromosomal changes. The most recurrent numerical alterations were gains in rat chromosome 4 (RNO4) and losses in RNO15. The most commonly structural changes were mainly in form of chromosomal translocations and were detected in RNO3, RNO6, RNO10, RNO11, RNO12, and RNO20. Unbalanced chromosomal translocations involving RNO3p was the most commonly observed structural changes in this material followed by RNO11p and RNO10 translocations.

Conclusion

The non-random nature of these events, as documented by their high frequencies of incidence, is suggesting for dynamic selection of these changes during experimental EC tumorigenesis and therefore for their potential contribution into development of this malignancy. Comparative molecular analysis of the identified genetic changes in this tumor model with those reported in the human ECs may provide new insights into underlying genetic changes involved in EC development and tumorigenesis.

Hedgehog signaling update

In vertebrate hedgehog signaling, hedgehog ligands are processed to become bilipidated and then multimerize, which allows them to leave the signaling cell via Dispatched 1 and become transported via glypicans and megalin to the responding cells. Hedgehog then interacts with a complex of Patched 1 and Cdo/Boc, which activates endocytic Smoothened to the cilium. Patched 1 regulates the activity of Smoothened (1) via Vitamin D3, which inhibits Smoothened in the absence of hedgehog ligand or (2) via oxysterols, which activate Smoothened in the presence of hedgehog ligand. Hedgehog ligands also interact with Hip1, Patched 2, and Gas1, which regulate the range as well as the level of hedgehog signaling. In vertebrates, Smoothened is shortened at its C-terminal end and lacks most of the phosphorylation sites of importance in Drosophila. Cos2, also of importance in Drosophila, plays no role in mammalian transduction, nor do its homologs Kif7 and Kif27. The cilium may provide a function analogous to that of Cos2 by linking Smoothened to the modulation of Gli transcription factors. Disorders associated with the hedgehog signaling network follow, including nevoid basal cell carcinoma syndrome, holoprosencephaly, Smith-Lemli-Opitz syndrome, Greig cephalopolysyndactyly syndrome, Pallister-Hall syndrome, Carpenter syndrome, and Rubinstein-Taybi syndrome.

Hdac2 regulates the cardiac hypertrophic response by modulating Gsk3 beta activity

In the adult heart, a variety of stresses induce re-expression of a fetal gene program in association with myocyte hypertrophy and heart failure. Here we show that histone deacetylase-2 (Hdac2) regulates expression of many fetal cardiac isoforms. Hdac2 deficiency or chemical histone deacetylase (HDAC) inhibition prevented the re-expression of fetal genes and attenuated cardiac hypertrophy in hearts exposed to hypertrophic stimuli. Resistance to hypertrophy was associated with increased expression of the gene encoding inositol polyphosphate-5-phosphatase f (Inpp5f) resulting in constitutive activation of glycogen synthase kinase 3beta (Gsk3beta) via inactivation of thymoma viral proto-oncogene (Akt) and 3-phosphoinositide-dependent protein kinase-1 (Pdk1). In contrast, Hdac2 transgenic mice had augmented hypertrophy associated with inactivated Gsk3beta. Chemical inhibition of activated Gsk3beta allowed Hdac2-deficient adults to become sensitive to hypertrophic stimulation. These results suggest that Hdac2 is an important molecular target of HDAC inhibitors in the heart and that Hdac2 and Gsk3beta are components of a regulatory pathway providing an attractive therapeutic target for the treatment of cardiac hypertrophy and heart failure.

Genomewide linkage study in 1,176 affected sister pair families identifies a significant susceptibility locus for endometriosis on chromosome 10q26

Endometriosis is a common gynecological disease that affects up to 10% of women in their reproductive years. It causes pelvic pain, severe dysmenorrhea, and subfertility. The disease is defined as the presence of tissue resembling endometrium in sites outside the uterus. Its cause remains uncertain despite >50 years of hypothesis-driven research, and thus the therapeutic options are limited. Disease predisposition is inherited as a complex genetic trait, which provides an alternative route to understanding the disease. We seek to identify susceptibility loci, using a positional-cloning approach that starts with linkage analysis to identify genomic regions likely to harbor these genes. We conducted a linkage study of 1,176 families (931 from an Australian group and 245 from a U.K. group), each with at least two members--mainly affected sister pairs--with surgically diagnosed disease. We have identified a region of significant linkage on chromosome 10q26 (maximum LOD score [MLS] of 3.09; genomewide P = .047) and another region of suggestive linkage on chromosome 20p13 (MLS = 2.09). Minor peaks (with MLS > 1.0) were found on chromosomes 2, 6, 7, 8, 12, 14, 15, and 17. This is the first report of linkage to a major locus for endometriosis. The findings will facilitate discovery of novel positional genetic variants that influence the risk of developing this debilitating disease. Greater understanding of the aberrant cellular and molecular mechanisms involved in the etiology and pathophysiology of endometriosis should lead to better diagnostic methods and targeted treatments.

Identification of a novel candidate gene,CASC2, in a region of common allelic loss at chromosome 10q26 in human endometrial cancer

Allelic deletions, which are suggestive for the presence of tumor suppressor genes, represent a common event in endometrial cancer (EC). Previous loss-of-heterozygosity studies for human chromosome 10q identified a candidate deletion interval at 10q25-q26, which we further narrowed to a 160-kb region at 10q26, bounded by markers D10S1236 and WIAF3299. Using a positional candidate approach, we identified three alternative transcripts of a novel human gene, CASC2 (cancer susceptibility candidate 2; formely C10orf5). One of such transcripts, CASC2a, encodes a short protein of 102 amino acids with no similarity to any other known gene product. Three (7%) CASC2a mutations were identified in tumor DNA from 44 EC patients. While c.-156G>T and c.22C>T (p.Pro8Ser) are sequence variants with unknown functional significance, c.84delA is a mutation with a truncation effect on the predicted protein (p. Asn28fsX50). Expression studies by real-time RT-PCR on several normal and tumor cells revealed that CASC2a mRNA is downregulated in cancer, suggesting that it may act as a potential tumor suppressor gene. The very low mutation rate seems to also indicate that inactivation of CASC2a might probably be due to mechanisms different from genetic alterations.

Systematic genome-wide approach to positional candidate cloning for identification of novel human disease genes

BACKGROUND

Recent large-scale genome projects afford a unique opportunity to identify many novel disease genes and thereby better understand the genetic basis of human disease. Functional Annotation of Mouse (FANTOM) 2, the largest mouse transcriptome project yet, provides a wealth of data on novel genes, splice variants and non-coding RNA, and provides a unique opportunity to identify novel human disease genes.

AIMS

To demonstrate the power of combining the FANTOM 2 cDNA dataset with a positional candidate approach and bioinformatics analysis to identify genes underlying human genetic disease.

RESULTS

By mapping all FANTOM 2 cDNA to the human genome, we were able to identify mouse clones that co-localised on the human genome with mapped but uncloned human disease loci. By this method we identified mouse and corresponding human genes mapping within the loci of 100 different human genetic diseases (mapped interval of <5 cM). Of particular interest was the elucidation through FANTOM 2 novel mouse gene data of candidate human genes for the following: (i) developmental -disorders: neural tube defect, Meckel syndrome, Wolf--Hirschhorn syndrome and keratosis follicularis spinulosa decalvans cum ophiasi; (ii) neurological disorders: benign familial infantile convulsions 3, early-onset cerebellar ataxia with retained tendon reflexes, infantile-onset spinocerebellar ataxia and vacuolar neuro-myopathy and (iii) cancer-related syndromes: tylosis with oesophageal cancer and low-grade B-cell chronic lymphatic leukaemia.

CONCLUSIONS

The FANTOM 2 data will dramatically accelerate efforts to identify genes underlying human disease. It will also facilitate the creation of transgenic mouse models to help elucidate the function of potential human disease genes.

Antisense transcripts at the EMX2 locus in human and mouse

The homeodomain transcription factor EMX2 is critical for central nervous system and urogenital development. In addition, EMX2 maps to a region of allelic deletion corresponding to a putative endometrial tumor suppressor at 10q26. We now report another polyadenylated transcript that is transcribed on the strand opposite to EMX2 and overlaps with the EMX2 transcript. This transcript was designated EMX2OS (OS, opposite strand), and an orthologous transcript present at the murine Emx2 locus was designated Emx2os. Alternative splicing to generate transcripts with varying 5' sequences was detected in the human but not the mouse. Neither ortholog contains a significant open reading frame, nor is primary sequence conserved between the two species. The sense and antisense transcripts display coordinate expression in that EMX2 and EMX2OS are abundant in normal postmenopausal endometrium, reduced in premenopausal endometrium, and absent or reduced in a majority of primary endometrial tumors. EMX2, EMX2OS, Emx2, and Emx2os are abundant in the uterine endometrium, with sense and antisense transcripts exhibiting identical expression patterns. Conservation of functional human and murine EMX2 antisense genes, of overlap between the sense and the antisense transcripts, and of identical cellular expression patterns suggests a biological function for EMX2OS, presumably to regulate EMX2.

Chromosomal abnormalities and microsatellite instability in sporadic endometrial cancer

Defective DNA mismatch repair and nonfunctional mechanisms controlling the proper progression of the cell cycle have been proposed as being responsible for the genomic instability and accumulation of karyotypic alterations in endometrial cancer (EC). To assess whether numerical chromosomal anomalies (aneuploidy) and microsatellite instability (MSI) might be representative of distinctive tumour behaviour, paraffin-embedded tissue samples from 86 patients with sporadic EC were evaluated by both fluorescence in situ hybridisation (FISH) and microsatellite analysis, using free nuclei and genomic DNAs (respectively). Approximately one-third of the tumours analysed (24/74; 32%) exhibited MSI, whereas 38/86 (44%) of the EC samples displayed aneuploidy. The majority of the unstable cases (15/24; 63%) were from advanced-stage patients. Conversely, 23 (61%) out of the 38 tumours with aneuploidy were from early-stage patients. No apparent correlation was found between MSI and aneuploidy, whereas the immunohistochemical (IHC) analysis revealed that inactivation of the MLH1 mismatch repair gene may be involved in the majority of the MSI+ sporadic ECs. No genetic or cytogenetic alteration analysed here seems to add any significant predictive value to the stage of disease.

Microsatellite instability and mutation analysis of candidate genes in unselected sardinian patients with endometrial carcinoma

BACKGROUND

Microsatellite instability (MSI) is due mostly to a defective DNA mismatch repair (MMR). Inactivation of the two principal MMR genes, hMLH1 and hMSH2, and the PTEN tumor suppressor gene seems to be involved in endometrial tumorigenesis. In this study, Sardinian patients with endometrial carcinoma (EC) were analyzed to assess the prevalence of both the mutator phenotype (as defined by the presence of MSI and abnormal MMR gene expression at the somatic level) and the hMLH1, hMSH2, and PTEN germline mutations among patients with MSI positive EC.

METHODS

Paraffin embedded tissue samples from 116 consecutive patients with EC were screened for MSI by polymerase chain reaction-based microsatellite analysis. Immunohistochemistry (IHC) with anti-hMLH1 and anti-hMSH2 antibodies was performed on MSI positive tumor tissue sections. Germline DNA was used for mutational screening by denaturing high-performance liquid chromatography analysis and automated sequencing.

RESULTS

Thirty-nine patients with EC (34%) exhibited MSI; among them, 25 tumor samples (64%) showed negative immunostaining for hMLH1/hMSH2 proteins (referred to as IHC negative). No disease-causing mutation within the coding sequences of the hMLH1/hMSH2 and PTEN genes was found in patients with EC who had the mutator phenotype (MSI positive and IHC negative), except for a newly described hMLH1 missense mutation, Ile655Val, that was observed in 1 of 27 patients (4%). Although MSI was more common among patients with advanced-stage EC and increased as the tumor grade increased, no significant correlation with disease free survival or overall survival was observed among the two groups (MSI positive or MSI negative) of patients with EC.

CONCLUSIONS

In patients with MSI positive EC, epigenetic inactivations rather than genetic mutations of the MMR genes seem to be involved in endometrial tumorigenesis. No prognostic value was demonstrated for MSI in patients with EC.

Refined mapping of allele loss at chromosome 10q23-26 in prostate cancer

BACKGROUND

Allele loss of at least two segments in 10q, one mapping to the PTEN gene and one more distal were described in prostate cancer, with loss more frequent in advanced prostate cancer.

METHODS

A 63 cM region from 10q23 to q26 was studied for allele loss (LOH) in 59 prostate cancer samples using a dense map of microsatellite markers.

RESULTS

LOH of at least one marker in 10q was observed in 13/59 tumors. LOH increased with grade and stage. Detailed deletion mapping identified three regions of allele loss. The first region mapped to the site of the PTEN gene, the second is defined by loss of one marker, D10S1692, in one tumor, and the third is defined between markers D10S1757 and D10S587, including DMBT, with a subregion of approximately 1.2 Mb mapping between markers D10S209 and D10S1679, lost in one tumor.

CONCLUSIONS

LOH at the PTEN gene is frequent but mutations in the remaining allele were not detected by SSCP-screening. There may be more than two tumor suppressor (TS) genes mapping more distal of PTEN. The site for these putative TS genes can now be mapped with a dense set of precisely localized markers in a larger series of advanced tumors.

Characterization of the homeodomain gene EMX2: sequence conservation, expression analysis, and a search for mutations in endometrial cancers

Previous loss-of-heterozygosity studies in endometrial carcinoma mapped a putative tumor suppressor gene to 10q25.3-26.1. An analysis of genomic sequences for the deletion interval showed several expressed sequence tags and the homeodomain gene EMX2, a homologue of Drosophila melanogaster empty spiracles. Expression studies showed that EMX2 transcripts are abundant in the adult uterus and that message levels seem to be inversely correlated with endometrial proliferation. EMX2 RNA was more abundant in quiescent postmenopausal endometrium than in premenopausal endometrium. We found decreased EMX2 expression in a subset of primary endometrial tumors, and four of six endometrial cancer cell lines investigated failed to express EMX2. The predicted protein showed extensive amino acid conservation with EMX2 sequences from several vertebrates. There was also considerable evolutionary conservation in the 3' untranslated region. To examine the potential function of EMX2 in endometrial tumorigenesis, we investigated 20 primary tumors and 6 endometrial cancer cell lines for mutations. Two primary tumors had mutations. Inactivation or reduced expression of EMX2 in cancers, coupled with increased expression in the quiescent endometrium, indicate that this homeodomain gene is involved in maintenance of the differentiated state.

Microsatellite analysis at 10q25-q26 in Sardinian patients with sporadic endometrial carcinoma: identification of specification patterns of genetic alteration

BACKGROUND

Loss of heterozygosity (LOH) at chromosome 10q25-q26 has been reported previously in endometrial carcinoma (EC), suggesting the presence of tumor suppressor gene(s). Nevertheless, frequency of genome-wide microsatellite instability (MSI) has been demonstrated higher in EC than in other common malignancy, mostly due to defective DNA mismatch repair. The authors further evaluated the role of the chromosome 10q25-q26 in endometrial tumorigenesis as well as the clinical significance of any observed genetic alteration in sporadic EC.

METHODS

Paired normal and tumor samples from 94 Sardinian patients with sporadic EC at various stages of disease were screened by polymerase chain reaction (PCR)-based microsatellite analysis. Genomic DNA was isolated from paraffin embedded tissues and amplified by PCR using microsatellite markers spanning approximately 14 cM at 10q25-q26. Microsatellite instability was studied at four loci mapping to different chromosomal locations.

RESULTS

Thirty-two (34%) EC patients were found negative for genetic alterations within the 10q25-q26 region. Among the remaining 62 (66%) EC cases, the authors identified 1) a minimum consensus region of LOH of approximately 1 cM, between D10S610 and D10S542 markers; and 2) a subset of tumors with prevalence of instability at 10q25-q26 (10qMI+), as expression of the presence of a MSI+ phenotype.

CONCLUSIONS

The authors' data establish the existence of significant correlations between disease stages and 10qMI+ (with or without MSI+). However, longer follow-up and additional studies are required to define the clinical significance of these findings as prognostic factors. Moreover, the minimum region of LOH at 10q25-q26 will be further analyzed for identifying the putative tumor suppressor gene involved in EC pathogenesis.

Characterization of the human suppressor of fused, a negative regulator of the zinc-finger transcription factor Gli

Drosophila Suppressor of fused (Su(fu)) encodes a novel 468-amino-acid cytoplasmic protein which, by genetic analysis, functions as a negative regulator of the Hedgehog segment polarity pathway. Here we describe the primary structure, tissue distribution, biochemical and functional analyses of a human Su(fu) (hSu(fu)). Two alternatively spliced isoforms of hSu(fu) were identified, predicting proteins of 433 and 484 amino acids, with a calculated molecular mass of 48 and 54 kDa, respectively. The two proteins differ only by the inclusion or exclusion of a 52-amino-acid extension at the carboxy terminus. Both isoforms were expressed in multiple embryonic and adult tissues, and exhibited a developmental profile consistent with a role in Hedgehog signaling. The hSu(fu) contains a high-scoring PEST-domain, and exhibits an overall 37% sequence identity (63% similarity) with the Drosophila protein and 97% sequence identity with the mouse Su(fu). The hSu(fu) locus mapped to chromosome 10q24-q25, a region which is deleted in glioblastomas, prostate cancer, malignant melanoma and endometrial cancer. HSu(fu) was found to repress activity of the zinc-finger transcription factor Gli, which mediates Hedgehog signaling in vertebrates, and to physically interact with Gli, Gli2 and Gli3 as well as with Slimb, an F-box containing protein which, in the fly, suppresses the Hedgehog response, in part by stimulating the degradation of the fly Gli homologue. Coexpression of Slimb with Su(fu) potentiated the Su(fu)-mediated repression of Gli. Taken together, our data provide biochemical and functional evidence for the hypothesis that Su(fu) is a key negative regulator in the vertebrate Hedgehog signaling pathway. The data further suggest that Su(fu) can act by binding to Gli and inhibiting Gli-mediated transactivation as well as by serving as an adaptor protein, which links Gli to the Slimb-dependent proteasomal degradation pathway.

A 1-Mb bacterial clone contig spanning the endometrial cancer deletion region at 1p32-p33

Our laboratory previously reported a high frequency of loss of heterozygosity (LOH) at 1p32-p33 in endometrial cancers. LOH at 1p32-p33 is a specific feature of one of the most aggressive forms of endometrial carcinoma, uterine papillary serous cancer (UPSC). The minimum region of allelic loss in UPSC is defined by D1S190 and D1S447, an interval corresponding to less than 1 cM. Here we describe the construction and characterization of a sequence-ready clone contig that spans the deletion region. The contig consists of 24 bacterial artificial chromosome clones and 18 P1 artificial chromosome clones and spans approximately 1050 kb. The consensus region of allelic loss between D1S190 and D1S447 represents approximately 792 kb. Eight previously described ESTs have been positioned within the contig.