HDLG5/KIAA0583, encoding a MAGUK-family protein, is a primary progesterone target gene in breast cancer cells

A double-edged sword: DLG5 in diseases

Discs large homolog 5 (DLG5), a key member of the membrane-associated guanylate kinase (MAGUKs) family, is a scaffold molecule for signal transduction complexes and is responsible for assembling receptors and adapters. This scaffold protein stabilizes adhesion and tight bonding complexes in many organs and tissues, and is involved of maintaining epithelial polarity. Although DLG5 plays a role in normal development in mice, it has also been linked to the onset and development of several diseases, particularly Crohn's disease and various malignancies. DLG5 has been shown to impact the progression of cancer through direct or indirect interactions with H-catenin, E-cadherin, Vimentin, p53, P21, Cyclin D1, TGF-β1, AKT, Hippo, and classic G protein signaling pathways. DLG5 and DLG5 variants has been found to have a dual role in human diseases. Although it is overexpressed in pancreatic adenocarcinoma, its expression is reduced in lung, liver, breast, prostate, and bladder cancers. However, two independent studies on glioblastoma (GBM) have shown the opposite effects of DLG5. Our study evaluates the existing literature on the role of DLG5 and DLG5 variants in disease processes, and summarizes the available data on the role of DLG5 in disease based on cell experiments, clinical samples, and animal models, while highlighting its future potential in disease treatment.

Selective Progesterone Receptor Modulators-Mechanisms and Therapeutic Utility

Selective progesterone receptor modulators (SPRMs) are a new class of compounds developed to target the progesterone receptor (PR) with a mix of agonist and antagonist properties. These compounds have been introduced for the treatment of several gynecological conditions based on the critical role of progesterone in reproduction and reproductive tissues. In patients with uterine fibroids, mifepristone and ulipristal acetate have consistently demonstrated efficacy, and vilaprisan is currently under investigation, while studies of asoprisnil and telapristone were halted for safety concerns. Mifepristone demonstrated utility for the management of endometriosis, while data are limited regarding the efficacy of asoprisnil, ulipristal acetate, telapristone, and vilaprisan for this condition. Currently, none of the SPRMs have shown therapeutic success in treating endometrial cancer. Multiple SPRMs have been assessed for efficacy in treating PR-positive recurrent breast cancer, with in vivo studies suggesting a benefit of mifepristone, and multiple in vitro models suggesting the efficacy of ulipristal acetate and telapristone. Mifepristone, ulipristal acetate, vilaprisan, and asoprisnil effectively treated heavy menstrual bleeding (HBM) in patients with uterine fibroids, but limited data exist regarding the efficacy of SPRMs for HMB outside this context. A notable class effect of SPRMs are benign, PR modulator-associated endometrial changes (PAECs) due to the actions of the compounds on the endometrium. Both mifepristone and ulipristal acetate are effective for emergency contraception, and mifepristone was approved by the US Food and Drug Administration (FDA) in 2012 for the treatment of Cushing's syndrome due to its additional antiglucocorticoid effect. Based on current evidence, SPRMs show considerable promise for treatment of several gynecologic conditions.

DLG5 suppresses breast cancer stem cell-like characteristics to restore tamoxifen sensitivity by inhibiting TAZ expression

Tamoxifen (TAM) is a primary drug for treatment of estrogen receptor positive breast cancer. However, TAM resistance remains a serious threat to breast cancer patients and may be attributed to increased stemness of breast cancer. Here, we show that discs large homolog 5 (DLG5) expression is down‐regulated in TAM‐resistant breast cancer and cells. DLG5 silencing decreased the sensitivity to TAM and increased the frequency and stemness of CD44⁺/CD24⁻ breast cancer stem cells (BCSCs) and TAZ, a transducer of the Hippo pathway, expression in MCF7 cells while DLG5 overexpression had opposite effects. TAZ silencing restored the sensitivity to TAM and reduced the frequency and stemness in TAM‐resistant breast cancer cells. Taken together, our data indicate that down‐regulated DLG5 expression increases the stemness of breast cancer cells by enhancing TAZ expression, contributing to TAM resistance in breast cancer.

Loss of DLG5 promotes breast cancer malignancy by inhibiting the Hippo signaling pathway

Discs Large Homolog 5 (DLG5) plays an important role in the maintenance of epithelial cell polarity. Recent research showed that DLG5 is decreased in Yes-associated protein (YAP)-overexpressing cells. However, the exact relationship between DLG5 and YAP is not clear. In this study, we showed that loss of DLG5 promoted breast cancer cell proliferation by inhibiting the Hippo signaling pathway and increasing nuclear YAP expression. Furthermore, depletion of DLG5 induced epithelial-mesenchymal transition (EMT) and disrupted epithelial cell polarity, which was associated with altered expression of Scribble, ZO1, E-cadherin and N-cadherin and their mislocalization. Interestingly, we first reported that loss of DLG5 inhibited the interaction of Mst1 and Lats1 with Scribble, which was crucial for YAP activation and the transcription of TEA domain (TEAD) family members. In summary, loss of DLG5 expression promoted breast cancer malignancy by inactivating the Hippo signaling pathway and increasing nuclear YAP.

Bifurcating action of Smoothened in Hedgehog signaling is mediated by Dlg5

Binding of the Hedgehog (Hh) protein signal to its receptor, Patched, induces accumulation of the seven-pass transmembrane protein Smoothened (Smo) within the primary cilium and of the zinc finger transcription factor Gli2 at the ciliary tip, resulting ultimately in Gli-mediated changes in nuclear gene expression. However, the mechanism by which pathway activation is communicated from Smo to Gli2 is not known. In an effort to elucidate this mechanism, we identified Dlg5 (Discs large, homolog 5) in a biochemical screen for proteins that preferentially interact with activated Smo. We found that disruption of Smo-Dlg5 interactions or depletion of endogenous Dlg5 leads to diminished Hh pathway response without a significant impact on Smo ciliary accumulation. We also found that Dlg5 is localized at the basal body, where it associates with another pathway component, Kif7. We show that Dlg5 is required for Hh-induced enrichment of Kif7 and Gli2 at the tip of the cilium but is dispensable for Gpr161 exit from the cilium and the consequent suppression of Gli3 processing into its repressor form. Our findings suggest a bifurcation of Smo activity in Hh response, with a Dlg5-independent arm for suppression of Gli repressor formation and a second arm involving Smo interaction with Dlg5 for Gli activation.

DLG5 in cell polarity maintenance and cancer development

Failure in establishment and maintenance of epithelial cell polarity contributes to tumorigenesis. Loss of expression and function of cell polarity proteins is directly related to epithelial cell polarity maintenance. The polarity protein discs large homolog 5 (DLG5) belongs to a family of molecular scaffolding proteins called Membrane Associated Guanylate Kinases (MAGUKs). As the other family members, DLG5 contains the multi-PDZ, SH3 and GUK domains. DLG5 has evolved in the same manner as DLG1 and ZO1, two well-studied MAGUKs proteins. Just like DLG1 and ZO1, DLG5 plays a role in cell migration, cell adhesion, precursor cell division, cell proliferation, epithelial cell polarity maintenance, and transmission of extracellular signals to the membrane and cytoskeleton. Since the roles of DLG5 in inflammatory bowel disease (IBD) and Crohn's disease (CD) have been reviewed, here, our review focuses on the roles of DLG5 in epithelial cell polarity maintenance and cancer development.

Polarity protein alterations in carcinoma: a focus on emerging roles for polarity regulators

In this review we discuss both gene expression and protein localization changes of polarity proteins in carcinoma. We highlight the importance of protein mislocalization and its possible role in cancer. We also discuss the emerging role of polarity proteins as regulators of proliferation, apoptosis, tissue polarity, epithelial-mesenchymal transition, in addition to their known role in cell junction biogenesis.

Early-onset Crohn disease is associated with male sex and a polymorphism in the IL-6 promoter

AIMS

Pediatric onset of Crohn disease (CD) is characterized by male sex predominance while adult-onset disease demonstrates female sex predominance. It has been postulated that this phenomenon may be genetically determined or due to an effect of estrogen on age of onset. Interleukin (IL)-6 modulates the TH17 pathway, and the IL-6 promoter is modulated by estrogen, possibly linking genetically determined inflammation and the presence of estrogen. The aim of our study was to investigate whether differences in IL-6 promoter genotype could explain male sex in earlier disease onset.

PATIENTS AND METHODS

We genotyped 333 patients with CD and 100 controls, 162 pediatric-onset patients (age of onset 18 years and younger) for the IL-6-174 polymorphic site. Genotype, sex, and age of onset were compared.

RESULTS

Males with IL-6-174GG genotype (the wild-type allele) had an increased risk for a younger age of onset compared to males with IL-6-174GC or CC genotype (G --> C genotype), hazard ratio (HR) 1.49, P = 0.02, 95% confidence interval (CI) 1.07-2.09. Females with GG genotype were not found to have an increased risk for a younger age of onset compared with females with G --> C genotype, HR 1.01, P = 0.96, 95% CI 0.72-1.41.

CONCLUSIONS

Males with IL-6-174GG genotype are prone to develop CD at a younger age than males with the IL-6-174G --> C genotype. Our study suggests that age of onset may be modified by the IL-6-174GG genotype and this modification is sex dependent. This may be due to increased transcription of IL-6, an effect that may be repressed by estrogen in females.

Coordinate up-regulation of TMEM97 and cholesterol biosynthesis genes in normal ovarian surface epithelial cells treated with progesterone: implications for pathogenesis of ovarian cancer

Background

Ovarian cancer (OvCa) most often derives from ovarian surface epithelial (OSE) cells. Several lines of evidence strongly suggest that increased exposure to progesterone (P4) protects women against developing OvCa. However, the underlying mechanisms of this protection are incompletely understood.

Methods

To determine downstream gene targets of P4, we established short term in vitro cultures of non-neoplastic OSE cells from six subjects, exposed the cells to P4 (10^-6 M) for five days and performed transcriptional profiling with oligonucleotide microarrays containing over 22,000 transcripts.

Results

We identified concordant but modest gene expression changes in cholesterol/lipid homeostasis genes in three of six samples (responders), whereas the other three samples (non-responders) showed no expressional response to P4. The most up-regulated gene was TMEM97 which encodes a transmembrane protein of unknown function (MAC30). Analyses of outlier transcripts, whose expression levels changed most significantly upon P4 exposure, uncovered coordinate up-regulation of 14 cholesterol biosynthesis enzymes, insulin-induced gene 1, low density lipoprotein receptor, ABCG1, endothelial lipase, stearoyl- CoA and fatty acid desaturases, long-chain fatty-acyl elongase, and down-regulation of steroidogenic acute regulatory protein and ABCC6. Highly correlated tissue-specific expression patterns of TMEM97 and the cholesterol biosynthesis genes were confirmed by analysis of the GNF Atlas 2 universal gene expression database. Real-time quantitative RT-PCR analyses revealed 2.4-fold suppression of the TMEM97 gene expression in short-term cultures of OvCa relative to the normal OSE cells.

Conclusion

These findings suggest that a co-regulated transcript network of cholesterol/lipid homeostasis genes and TMEM97 are downstream targets of P4 in normal OSE cells and that TMEM97 plays a role in cholesterol and lipid metabolism. The P4-induced alterations in cholesterol and lipid metabolism in OSE cells might play a role in conferring protection against OvCa.

DLG5 R30Q variant is a female-specific protective factor in pediatric onset Crohn's disease

OBJECTIVE

A significant association between the DLG5 variant (R30Q) and inflammatory bowel disease (IBD) has been confirmed in several independent adult IBD cohorts. There is growing evidence that gender significantly influences R30Q susceptibility in Crohn's disease (CD). Pediatric onset CD features a significantly lower incidence for female children compared with male children. We, therefore, studied the influence of gender on R30Q susceptibility in an exclusively pediatric onset IBD cohort.

DESIGN

A total of 281 CD (181 trios) and 479 population-based controls were genotyped for DLG5 R30Q using Taqman assay. Association was tested by case-control and transmission disequilibrium testing analysis. Multivariate logistic regression was performed to investigate gene-gene and gene-gender interactions, as well as genotype-phenotype correlations.

RESULTS

Overall allele frequency for R30Q was 8.5% in CD and 10.3% in controls. Logistic regression showed R30Q had no association with CD (OR 0.81, 95% CI 0.55-1.20, P= 0.3) when the cohort was analyzed as a whole. Stratified by gender, a significant negative association was detected for R30Q in female children (OR 0.39, 95% CI 0.2-0.77, P= 0.006), but not in male children. Gender was found to be an effect modifier of the association between R30Q and CD as the odds ratios in female children and male children differed significantly. The gender-specific association of R30Q and CD was independent of additional CD risk factors such as CARD15 and IBD5.

CONCLUSIONS

DLG5 has a gender-specific role in the susceptibility of pediatric CD. Specifically, the significant negative association found between DLG5 R30Q and CD in female children suggests DLG5 may have a protective effect in CD susceptibility for female children.

Down-regulation of RAB6KIFL/KIF20A, a Kinesin Involved with Membrane Trafficking of Discs Large Homologue 5, Can Attenuate Growth of Pancreatic Cancer Cell

To identify novel molecular targets for treatment of pancreatic ductal adenocarcinoma (PDAC), we generated precise gene expression profiles of PDACs on a genome-wide cDNA microarray after populations of tumor cells were purified by laser microdissection. Through functional analysis of genes that were transactivated in PDACs, we identified RAB6KIFL as a candidate for development of drugs to treat PDACs at the molecular level. Knockdown of endogenous RAB6KIFL expression in PDAC cell lines by small interfering RNA drastically attenuated growth of those cells, suggesting an essential role for the gene product in maintaining viability of PDAC cells. RAB6KIFL belongs to the kinesin superfamily of motor proteins, which have critical functions in trafficking of molecules and organelles. Proteomics analyses using a polyclonal anti-RAB6KIFL antibody identified one of the cargoes transported by RAB6KIFL as discs, large homologue 5 (DLG5), a scaffolding protein that may link the vinexin-β-catenin complex at sites of cell-cell contact. Like RAB6KIFL, DLG5 was overexpressed in PDACs, and knockdown of endogenous DLG5 by small interfering RNA significantly suppressed the growth of PDAC cells as well. Decreased levels of endogenous RAB6KIFL in PDAC cells altered the subcellular localization of DLG5 from cytoplasmic membranes to cytoplasm. Our results imply that collaboration of RAB6KIFL and DLG5 is likely to be involved in pancreatic carcinogenesis. These molecules should be promising targets for development of new therapeutic strategies for PDACs.

Genetic variation in DLG5 is associated with inflammatory bowel disease

Crohn disease and ulcerative colitis are two subphenotypes of inflammatory bowel disease (IBD), a complex disorder resulting from gene-environment interaction. We refined our previously defined linkage region for IBD on chromosome 10q23 and used positional cloning to identify genetic variants in DLG5 associated with IBD. DLG5 encodes a scaffolding protein involved in the maintenance of epithelial integrity. We identified two distinct haplotypes with a replicable distortion in transmission (P = 0.000023 and P = 0.004 for association with IBD, P = 0.00012 and P = 0.04 for association with Crohn disease). One of the risk-associated DLG5 haplotypes is distinguished from the common haplotype by a nonsynonymous single-nucleotide polymorphism 113G-->A, resulting in the amino acid substitution R30Q in the DUF622 domain of DLG5. This mutation probably impedes scaffolding of DLG5. We stratified the study sample according to the presence of risk-associated CARD15 variants to study potential gene-gene interaction. We found a significant difference in association of the 113A DLG5 variant with Crohn disease in affected individuals carrying the risk-associated CARD15 alleles versus those carrying non-risk-associated CARD15 alleles. This is suggestive of a complex pattern of gene-gene interaction between DLG5 and CARD15, reflecting the complex nature of polygenic diseases. Further functional studies will evaluate the biological significance of DLG5 variants.

Somatic Mutations and Altered Expression of the Candidate Tumor SuppressorsCSNK1ε,DLG1, andEDD/hHYDin Mammary Ductal Carcinoma

We report somatic mutations in three genes (CSNK1 epsilon, encoding the Ser/Thr kinase casein kinase I epsilon; DLG1, encoding a membrane-associated putative scaffolding protein; and EDD/hHYD, encoding a progestin induced putative ubiquitin-protein ligase) in mammary ductal carcinoma. These genes were suspected of playing a role in cancer because loss-of-function mutations in their Drosophila homologues cause excess tissue growth. Using DNA from 82 laser-microdissected tumor samples, followed by microsatellite analysis, denaturing HPLC and direct sequencing, we found multiple somatic point mutations in all three genes, and these mutations showed significant association with loss of heterozygosity of closely linked polymorphic microsatellite markers. For CSNK1 epsilon and DLG1, most of the mutations affected highly conserved residues, some were found repetitively in different patients, and no synonymous mutations were found, indicating that the observed mutations were selected in tumors and may be functionally significant. Immunohistochemical reactivity of each protein was reduced in poorly differentiated tumors, and there was a positive association between altered protein reactivity, loss of heterozygosity, and somatic mutations. There was a statistically significant association of hDlg staining with p53 and Ki67 reactivity, whereas CSK1 epsilon and EDD/hHYD staining levels were associated with progesterone receptor status. The results provide strong indications for a role of all three genes in mammary ductal carcinoma. They also justify additional studies of the functional significance of the changes, as well as a search for additional changes in these and other genes identified from studies on model systems.