Expression of DCC and netrin-1 in normal human endometrium and its implication in endometrial carcinogenesis

Expression of netrin-1 in uterine serous carcinoma and its association with prognosis

BACKGROUND/OBJECTIVES

At present, there are few biomarkers used to predict the prognosis of uterine serous carcinoma (USC). Netrin-1 may be a promising biomarker candidate. We investigated netrin-1 expression in USC tissues and healthy endometrial tissues to determine its relevance to disease prognosis.

MATERIALS AND METHODS

Netrin-1 expression was examined in the tissues of 48 patients with USC and 30 patients with healthy benign endometrial tissues via immunohistochemistry.

RESULTS

None of the healthy tissues were stained with netrin-1. In tumor tissues, the overall positivity rate of netrin-1 was 75%, detected as high expression in 17 patients (35%) and low in 19 (40%). Patients who had tumors with no netrin-1 expression (n = 12) had a median overall survival (OS) of 60.0 months (95% confidence interval [CI], 47-98), whereas patients who had tumors with low to strong netrin-1 expression (n = 33) had a lower median OS of 50 months, but the difference was not statistically significant (95% CI, 58-108; P = 0.531). Disease-free survival (DFS) was not statistically significant between the groups (95% CI, 67.7-115.9; P = 0.566). Patients with a tumor diameter ≥2 cm had higher netrin-1 expression than those with a tumor diameter of 2 cm (P = 0.027). We did not find any difference in overall and DFS when age, tumor stage, histology, tumor diameter, p53 status, lymphovascular space invasion, myometrial invasion, and lymph node metastasis were compared according to netrin-1 expression (P > 0.05).

CONCLUSION

Netrin-1 was expressed in USC but not in healthy tissues. Its expression was not associated with OS or DFS.

Transcriptomics analysis of the bovine endometrium during the perioestrus period

During the oestrous cycle, the bovine endometrium undergoes morphological and functional changes, which are regulated by alterations in the levels of oestrogen and progesterone and consequent changes in gene expression. To clarify these changes before and after oestrus, RNA-seq was used to profile the transcriptome of oestrus-synchronized beef heifers. Endometrial samples were collected from 29 animals, which were slaughtered in six groups beginning 12 h after the withdrawal of intravaginal progesterone releasing devices until seven days post-oestrus onset (luteal phase). The groups represented proestrus, early oestrus, metoestrus and early dioestrus (luteal phase). Changes in gene expression were estimated relative to gene expression at oestrus. Ingenuity Pathway Analysis (IPA) was used to identify canonical pathways and functional processes of biological importance. A total of 5,845 differentially expressed genes (DEGs) were identified. The lowest number of DEGs was observed at the 12 h post-oestrus time point, whereas the greatest number was observed at Day 7 post-oestrus onset (luteal phase). A total of 2,748 DEGs at this time point did not overlap with any other time points. Prior to oestrus, Neurological disease and Organismal injury and abnormalities appeared among the top IPA diseases and functions categories, with upregulation of genes involved in neurogenesis. Lipid metabolism was upregulated before oestrus and downregulated at 48h post-oestrus, at which point an upregulation of immune-related pathways was observed. In contrast, in the luteal phase the Lipid metabolism and Small molecule biochemistry pathways were upregulated.

Endometrial Expression of Steroidogenic Factor 1 Promotes Cystic Glandular Morphogenesis

Epigenetic silencing of steroidogenic factor 1 (SF1) is lost in endometriosis, potentially contributing to de novo local steroidogenesis favoring inflammation and growth of ectopic endometrial tissue. In this study, we examine the impact of SF1 expression in the eutopic uterus by a novel mouse model that conditionally expresses SF1 in endometrium. In vivo SF1 expression promoted the development of enlarged endometrial glands and attenuated estrogen and progesterone responsiveness. Endometriosis induction by autotransplantation of uterine tissue to the mesenteric membrane resulted in the increase in size of ectopic lesions from SF1-expressing mice. By integrating the SF1-dependent transcriptome with the whole genome binding profile of SF1, we identified uterine-specific SF1-regulated genes involved in Wingless and Progesterone receptor-Hedgehog-Chicken ovalbumin upstream promoter transcription factor II signaling for gland development and epithelium-stroma interaction, respectively. The present results indicate that SF1 directly contributes to the abnormal uterine gland morphogenesis, an inhibition of steroid hormone signaling and activation of an immune response, in addition to previously postulated estrogen production.

Role of DNA methylation and epigenetic silencing of HAND2 in endometrial cancer development

BACKGROUND

Endometrial cancer incidence is continuing to rise in the wake of the current ageing and obesity epidemics. Much of the risk for endometrial cancer development is influenced by the environment and lifestyle. Accumulating evidence suggests that the epigenome serves as the interface between the genome and the environment and that hypermethylation of stem cell polycomb group target genes is an epigenetic hallmark of cancer. The objective of this study was to determine the functional role of epigenetic factors in endometrial cancer development.

METHODS AND FINDINGS

Epigenome-wide methylation analysis of >27,000 CpG sites in endometrial cancer tissue samples (n = 64) and control samples (n = 23) revealed that HAND2 (a gene encoding a transcription factor expressed in the endometrial stroma) is one of the most commonly hypermethylated and silenced genes in endometrial cancer. A novel integrative epigenome-transcriptome-interactome analysis further revealed that HAND2 is the hub of the most highly ranked differential methylation hotspot in endometrial cancer. These findings were validated using candidate gene methylation analysis in multiple clinical sample sets of tissue samples from a total of 272 additional women. Increased HAND2 methylation was a feature of premalignant endometrial lesions and was seen to parallel a decrease in RNA and protein levels. Furthermore, women with high endometrial HAND2 methylation in their premalignant lesions were less likely to respond to progesterone treatment. HAND2 methylation analysis of endometrial secretions collected using high vaginal swabs taken from women with postmenopausal bleeding specifically identified those patients with early stage endometrial cancer with both high sensitivity and high specificity (receiver operating characteristics area under the curve = 0.91 for stage 1A and 0.97 for higher than stage 1A). Finally, mice harbouring a Hand2 knock-out specifically in their endometrium were shown to develop precancerous endometrial lesions with increasing age, and these lesions also demonstrated a lack of PTEN expression.

CONCLUSIONS

HAND2 methylation is a common and crucial molecular alteration in endometrial cancer that could potentially be employed as a biomarker for early detection of endometrial cancer and as a predictor of treatment response. The true clinical utility of HAND2 DNA methylation, however, requires further validation in prospective studies. Please see later in the article for the Editors' Summary.

The brain within the tumor: new roles for axon guidance molecules in cancers

Slits, semaphorins and netrins are three families of proteins that can attract or repel growing axons and migrating neurons in the developing nervous system of vertebrates and invertebrates. Recent studies have shown that they are widely expressed outside the nervous system and that they may play important roles in cancers. Several of the genes encoding these proteins are localized on chromosomal region associated with frequent loss-of-heterozygosity in tumors and cancer cell lines and there is also significant hypermethylation of their promoter suggesting that they may act as tumor suppressors. In addition, proteins in all these families and their receptors appear to control the vascularization of the tumors. Last, many axon guidance molecules also regulate cell migration and apoptosis in normal and tumorigenic tissues. Overall, this suggests that molecules that could mimick or block the activity of axon guidance molecules may be used as therapeutic agents for the treatment of malignancy.

Role of netrin-1 and netrin-1 dependence receptors in colorectal cancers

Although cancer is a multifaceted disease, all cancer types share identical molecular and cellular mechanisms. These mechanisms involve a collection of alterations critical to the normal physiological functioning of cells, such as alterations of growth factor signalling pathways, angiogenesis, cell adhesion signals, DNA replication and apoptotic cell death. Many genes involved in the processes enumerated above are functionally inactive in tumour cells, designating them as putative ‘tumour suppressor genes’. Back in the early 1990s, Vogelstein and colleagues suggested that a gene called DCC (for Deleted in Colorectal Cancer) could be a tumour suppressor gene because it was found to be deleted in more than 70% of colorectal cancers, as well as in many other cancers. During the last 15 years, controversial data have failed to firmly establish whether DCC is indeed a tumour suppressor gene. However, the recent observations that DCC triggers cell death and is a receptor for netrin-1, a molecule recently implicated in colorectal tumorigenesis, have prompted a renewal of interest in the role of DCC in tumorigenesis and suggest that the netrin-1/receptor pairs act as novel negative regulators of tumour development.

Sharing of unrelated receptors and ligands by cognate partners: possible implications for ovarian and endometrial physiology

The majority of the recognized extracellular signalling molecules are known to participate in paracrine and autocrine functions. The classical model of signalling involves a ligand and its cognate receptor. A unique number of ligands activate two phylogenetically unrelated receptors; some receptors are activated by more than one unrelated polypeptide ligand, and some unrelated receptors share common co-receptors. Such a situation introduces a new dimension of complexity into the processes governed by these signalling mechanisms. These unique 'three-way partnerships' often involve signalling molecules that have key roles in the reproductive system. This review presents the known cases of three-way partnerships and examines their possible significance to the reproductive processes in the ovary and endometrium. Most notably present in the ovary are Wnt, Frizzled, Dickkopf (Dkk), low density lipoprotein receptor-related protein (LRP)5, RYK and Kremen system, and semaphorin, plexin, vascular endothelial growth factor and neuropilin system. In the endometrium one finds potential three-way partnerships in Wnt, Frizzled and RYK system, and ATP, P2X7, P2Y2 system. Three-way partnerships may explain previously enigmatic cases of biphasic effects of a ligand, or may reveal that a ligand thought to be pleiotrophic through the activation of one receptor is actually affecting two unrelated signalling receptors in the same tissue. The potential significance to new pharmacological developments is evident.