Search

Mutations of the PTEN gene do not cause all uterine sarcomas, according to a study that only found a PTEN mutation in two out of 36 tissue samples from women with uterine sarcoma. This type of uterine cancer is rare, making up 5% of all uterine cancers.

It is well established that there is a dynamic relationship between the expanding tumor and the host surrounding tissue. Cancer-associated fibroblasts (CAFs), the most common cellular population found in the tumor microenvironment, supporting tumor growth and dissemination. Here, we set out to determine the factors that may be involved in dramatic alteration of gene expression pattern in CAFs, focusing on microRNA and transcriptional regulators. We established matched pairs of human CAFs isolated from endometrial cancer and normal endometrial fibroblasts.  MicroRNA and mRNA analyses identified differential expression of 11 microRNAs, with miR-31 being the most downregulated microRNA in CAFs (p=0.007). We examined several putative miR-31 target genes identified by microarray analysis and demonstrated that miR-31 directly targets the homeobox gene SATB2, which is responsible for chromatin remodeling and regulation of gene expression, and was significantly elevated in CAFs. The functional relevance of miR-31 and SATB2 were tested in in vitromodels of endometrial cancer.  Overexpression of miR-31 significantly impaired the ability of CAFs to stimulate tumor cell migration and invasion, without affecting tumor cell proliferation. Genetic manipulation of SATB2 levels in normal fibroblasts or CAFs showed that, reciprocally to miR-31, SATB2 increased tumor cell migration and invasion, while knock-down of endogenous SATB2 in CAFs reversed this phenotype. Introduction of SATB2 into normal fibroblasts stimulated expression of a number of genes involved in cell invasion, migration and scattering. These findings provide new insights into tumor-stroma interaction and document that miR

Epigenetic mechanisms that result in aberrant gene expression are a prominent feature of many cancer types. One main epigenetic mechanism for gene silencing involves promoter hypermethylation. Type I and type II endometrial cancers exhibit differing clinical, histologic, and molecular genetic characteristics. We hypothesize that these differences also extend to epigenetic phenomena. Promoter methylation analysis of 11 genes in a panel of endometrial cancers supports this hypothesis. These initial data indicate that promoter hypermethylation events occur frequently in type 1 cancer and were not detected in type II cancers using this panel of loci. These data tend to support the hypothesis that type I and type II endometrial cancers will exhibit distinct patterns of gene silencing based on promoter hypermethylation events.

ABSTRACTAn in vitro transformation system of carcinogen-treated Syrian hamster embryo (SHE) cell cultures represents multistep genetic and nongenetic changes that develop during the neoplastic progression of normal cells to tumor cells in vivo. During this neoplastic progression, SHE cells demonstrate an altered response to epidermal growth factor (EGF). In the present report, we examined the role of the adapter protein Gab1 (Grb2-associated binder-1) in the neoplastic progression of SHE cells. We used two asbestos-transformed SHE cell clones in different neoplastic stages: a 10W+8 clone, which is immortal and retains the ability to suppress the tumorigenicity of tumor cells in cell-cell hybrid experiments, and a 10W−1 clone, which has lost this tumor suppressor ability. 10W+8 cells expressed full-length 100-kDa Gab1 and associated 5.2-kb mRNA. Upon repeated cell passaging, 10W−1 cells showed increasing expression of a novel 87-kDa form of Gab1 as well as 4.6-kb mRNA with diminishing expression of the original 100-kDa Gab1. cDNA encoding the 87-kDa Gab1 predicts a form of Gab1 lacking the amino-terminal 103 amino acids (Gab1Δ1-103), which corresponds to loss of most of the pleckstrin homology (PH) domain. Gab1Δ1-103retains the ability to be phosphorylated in an EGF-dependent manner and to associate with the EGF receptor and SHP-2 upon EGF stimulation. The endogenous expression of Gab1Δ1-103in 10W−1 cells appeared closely related to EGF-dependent colony formation in soft agar. Moreover, transfection and expression of Gab1Δ1-103, but not Gab1, in 10W+8 cells enhanced their EGF-dependent colony formation in soft agar. These results demonstrate that Gab1 is a target of carcinogen-induced transformation of SHE cells and that the expression of a Gab1 variant lacking most of the PH domain plays a specific role in the neoplastic progression of SHE cells.

Objective: To determine whether microsatellite instability in endometrioid endometrial cancer is associated with favorable survival.

Objective.ThePTENtumor suppressor gene on chromosome 10q23 undergoes inactivating mutations in several types of malignancies including glioblastomas and prostate and endometrial carcinomas. The aim of this study was to determine if mutation of thePTENtumor suppressor gene is a feature of sporadic or BRCA1-associated ovarian carcinomas.Methods.Genomic deoxyribonucleic acid was extracted from 11 ovarian cancer cell lines and 50 frozen ovarian cancers, including 4 cases that developed in women with germline mutations in the BRCA1 breast/ovarian cancer susceptibility gene. The polymerase chain reaction was used to amplify each of the nine exons and intronic splice sites of thePTENgene. These products were then screened for mutations using single strand conformation polymorphism analysis. Variant bands were further evaluated using automated DNA sequencing.Results.A previously unreported silent polymorphism at codon 240 (TAT to TAC) in exon 7 was noted in one of the primary ovarian carcinomas. Mutations in thePTENgene were not found in any of the 50 primary ovarian cancers or 11 immortalized ovarian cancer cell lines.Conclusion.Alteration of thePTENtumor suppressor gene does not appear to be a feature of sporadic or BRCA1-associated ovarian cancers.

Many human tumours have length alterations in repetitive sequence elements1. Although this microsatellite instability has been attributed to mutations in four DNA mismatch repair genes in hereditary nonpolyposis colorectal cancer (HNPCC) kindreds2,3, many sporadic tumours exhibit instability but no detectable mutations in these genes4–6. It is therefore of interest to identify other genes that contribute to this instability. In yeast, mutations in several genes, including RTH and MSH3, cause microsatellite instability7–11. Thus, we screened 16 endometrial carcinomas with microsatellite instability for alterations in FEN1 (the human homolog of RTH) and in MSH3 (refs 12–14). Although we found no FEN1 mutations, a frameshift mutation in MSH3 was observed in an endometrial carcinoma and in an endometrial carcinoma cell line. Extracts of the cell line were deficient in repair of DNA substrates containing mismatches or extra nucleotides. Introducing chromosome 5, encoding the MSH3 gene, into the mutant cell line increased the stability of some but not all microsatellites. Extracts of these cells repaired certain substrates containing extra nucleotides, but were deficient in repair of those containing mismatches or other extra nucleotides. A subsequent search revealed a second gene mutation in HHUA cells, a missense mutation in the MSH6 gene. Together the data suggest that the MSH3 gene encodes a product that functions in repair of some but not all pre-mutational intermediates, its mutation in tumours can result in genomic instability and, as in yeast, MSH3 and MSH6 are partially redundant for mismatch repair.

To determine whether mutation in the DNA of the estrogen-receptor gene occurs in endometrial cancer.

Human cells contain several homologs of the bacterial mutLgene required for mismatch repair, including a gene on chromosome 7 designated hPMS2. We have identified an endometrial carcinoma cell line, HEC-1-A, that has a C → T mutation in hPMS2that generates a nonsense codon and yields a protein truncated at the C terminus. No wild-type gene or gene product was detected. The missing amino acids in hPMS2 are highly conserved among PMShomologs, suggesting that they may be critical for function. In support of this, extracts of HEC-1-A cells are defective in repairing a variety of mismatched substrates. Moreover, di-, tri-, and tetranucleotide repeated sequences are highly unstable in single cell clones of HEC-1-A cells, and HEC-1-A cells are resistant to killing by N-methyl-Nʹ-nitro-N-nitrosoguanidine. The results provide strong experimental support for the involvement of the hPMS2 gene product in mismatch repair in human cells and support the concept that a defective hPMS2gene may lead to predisposition to certain forms of cancer.

The role of specific mismatch repair (MMR) gene products was examined by observing several phenotypic end points in two MMR-deficient human endometrial carcinoma cell lines that were originally isolated from the same tumor. The first cell line, HEC-1-A, contains a nonsense mutation in the hPMS2gene, which results in premature termination and a truncated hPMS2 protein. In addition, HEC-1-A cells carry a splice mutation in thehMSH6gene and lack wild-type hMSH6 protein. The second cell line, HEC-1-B, possesses the same defective hMSH6locus. However, HEC-1-B cells are heterozygous at the hPMS2locus; that is, along with carrying the same nonsense mutation in hPMS2as in HEC-1-A, HEC-1-B cells also contain a wild-type hPMS2gene. Initial recognition of mismatches in DNA requires either the hMSH2/hMSH6 or hMSH2/hMSH3 heterodimer, with hPMS2 functioning downstream of damage recognition. Therefore, cells defective in hPMS2should completely lack MMR (HEC-1-A), whereas cells mutant in hMSH6only (HEC-1-B) can potentially repair damage via the hMSH2/hMSH3 heterodimer. The data presented here in HEC-1-B cells illustrate (i) the reduction of instability at microsatellite sequences, (ii) a significant decrease in frameshift mutation rate at HPRT, and (iii) the in vitrorepair of looped substrates, relative to HEC-1-A cells, illustrating the repair of frameshift intermediates by hMSH2/hMSH3 heterodimer. Furthermore, the role of hMSH2/hMSH3 heterodimer in the repair of base:base mismatches is supported by observing the reduction in base substitution mutation rate at HPRTin HEC-1-B cells (hMSH6-defective but possessing wild-type hPMS2), as compared with HEC-1-A (hMSH6/hPMS2-defective) cells. These data support a critical role for hPMS2 in human MMR, while further defining the role of the hMSH2/hMSH3 heterodimer in maintaining genomic stability in the absence of a wild-type hMSH2/hMSH6 heterodimer.

Expression of the E–cadherin cell adhesion molecule is reduced in several types of human carcinomas, and the protein serves as an invasion suppressor in vitro. To determine if mutations of the E–cadherin gene (on chromosome 16q22) contribute to epithelial tumorigenesis, 135 carcinomas of the endometrium and ovary were examined for alterations in the E–cadherin coding region. Four mutations were identified: one somatic nonsense and one somatic missense mutation, both with retention of the wild–type alleles, and two missense mutations with somatic loss of heterozygosity in the tumour tissue. These data support the classification of E–cadherin as a human tumour suppressor gene.

Despite its importance in reproductive biology and women's health, a detailed molecular-level understanding of the human endometrium is lacking. Indeed, no comprehensive studies have been undertaken to elucidate the important protein expression differences between the endometrial glandular epithelium and surrounding stroma during the proliferative and midsecretory phases of the menstrual cycle. We utilized laser microdissection to harvest epithelial cells and stromal compartments from proliferative and secretory premenopausal endometrial tissue and performed a global, quantitative mass spectrometry-based proteomics analysis. This analysis identified 1224 total proteins from epithelial cells, among which 318 were differentially abundant between the proliferative and secretory phases (q < 0.05), and 1005 proteins from the stromal compartments, 19 of which were differentially abundant between the phases (q < 0.05). Several proteins were chosen for validation by immunohistochemistry in an independent set of uterine tissues, including carboxypeptidase M, tenascin C, neprilysin, and ectonucleotide pyrophosphatase/phosphodiesterase family member 3 (ENPP3). ENPP3, which was elevated in epithelial glandular cells in the secretory phase, was confirmed to be elevated in midsecretory-phase baboon uterine lavage samples and also observed to have an N-linked glycosylated form that was not observed in the proliferative phase. This study provides a detailed view into the global proteomic alterations of the epithelial cells and stromal compartments of the cycling premenopausal endometrium. These proteomic alterations during endometrial remodeling provide a basis for numerous follow-up investigations on the function of these differentially regulated proteins and their role in reproductive biology and endometrial pathologies.

Provides an overview of some of the topics addressed at the conference on Women's Health and the Environment: The Next Century--Advances in Uterine Leiomyoma Research. Developmental biology and histopathology of the uterus; Mechanisms of leiomyoma development; Clinical approaches to uterine leiomyomas.