Silencing Of E-cadherin Research Articles

MGRN1 depletion promotes intercellular adhesion in melanoma by upregulation of E-cadherin and inhibition of CDC42

Mahogunin Ring Finger 1 is an E3-ubiquitin ligase encoded by the color gene MGRN1. Our previous in vitro and in vivo studies demonstrated that Mgrn1 deletion in mouse melanoma cells induced cell differentiation and adhesion, and decreased cell motility and invasion on collagen I, and lung colonization in an in vivo model. Here, we investigated the role of MGRN1 on human melanoma cell morphology, adhesion and expression of genes/proteins involved in an EMT-like transition. We demonstrated that wild-type BRAF human melanoma cells adopted a clustering-like morphology on collagen I, with permanent MGRN1 abrogation resulting in bigger cell clusters. Enhanced intercellular adhesion was mostly mediated by induction of E-cadherin and higher co-localization with β-catenin. Transcriptional upregulation of E-cadherin likely occurred through downregulation of the ZEB1 repressor. Finally, pulldown assays showed reduced activation of CDC42 in the absence of MGRN1, which was reverted after E-cadherin silencing. Overall, these findings highlight a new MGRN1-dependent pathway regulating melanoma cell shape, motility, and invasion potential.

ZEB2/TWIST1/PRMT5/NuRD Multicomplex Contributes to the Epigenetic Regulation of EMT and Metastasis in Colorectal Carcinoma

Simple SummaryThe epithelial-mesenchymal transition (EMT) program plays a central role in the metastasis of patients with colorectal carcinoma (CRC). However, few studies have investigated the dominant regulatory factors and underlying mechanisms during the EMT process in CRC metastasis. Here we have characterized a novel transcriptionally repressive complex, ZEB2/TWIST1/PRMT5/NuRD, which epigenetically silences E-cadherin, leading to the invasion and metastasis of CRC cells. Our work provides a comprehensive understanding of the epigenetic mechanisms by which the key EMT metastasis driver, E-cadherin, is regulated in CRC, thereby suggesting PRMT5 and HDAC2 inhibitors as potentially therapeutic agents in CRC therapy.(1) Background: The EMT plays a crucial role in tumor metastasis, which is the major cause for colorectal carcinoma-related mortality. However, the underlying regulators and mechanisms of EMT in CRC metastasis are still poorly understood; (2) Methods: The transcriptional regulators of EMT in CRC and their functions were examined using RT2212PCR, Western blotting, and luciferase reporter assay. The components of ZEB2/TWIST1 complex and their mutual interactions were identified via affinity purification, mass spectrometry, co-immunoprecipitation, and pull-down experiments. The functional mechanisms of ZEB2/TWIST1/PRMT5/NuRD axis were determined by chromatin immunoprecipitation and luciferase reporter assay. The contribution of ZEB2/TWIST1/PRMT5/NuRD complex in the CRC metastasis was investigated using wound healing, transwell assay, and in vivo xenograft mouse model; (3) Results: We found that ZEB2 and TWIST1 were both significantly upregulated in CRC tissues and EMT of CRC cells. ZEB2 could recruit TWIST1 to the E-cadherin promoter and synergistically repressed its transcription. In addition, ZEB2 physically interacted with TWIST1, PRMT5, and the nucleosome remodeling and deacetylase (NuRD) complex to form a novel repressive multicomplex, leading to epigenetic silencing of E-cadherin in CRC cells. Notably, the combined inhibition of ZEB2 and TWIST1 and epigenetic inhibition markedly reduced CRC metastasis in mice; (4) Conclusions: We revealed for the first time that ZEB2 could recruit TWIST1, PRMT5, and NuRD to form a repressive multicomplex and epigenetically suppresses the transcription of E-cadherin, thereby inducing the EMT process and metastasis in CRC. Our results also confirmed the therapeutic potential of epigenetic inhibitors in CRC.

MIER3 induces epithelial-mesenchymal transition and promotes breast cancer cell aggressiveness via forming a co-repressor complex with HDAC1/HDAC2/Snail

Breast cancer is one of the most frequently diagnosed cancers and the leading cause of cancer death in women. MIER3 (Mesoderm induction early response 1, family member3) is considered as a potential oncogene for breast cancer. However, the role of MIER3 in breast cancer remain largely unknown. The expression of MIER3 was detected and the relationship between its expression and clinicopathological characteristics was also analyzed. The effect of MIER3 on proliferation and migration of breast cancer cells was detected in vitro and in vivo. Western blot, IF, and Co-IP were employed to detect the relationship between MIER3, HDAC1, HDAC2, and Snail. ChIP assay was performed to determine the binding of MIER3/HDAC1/HDAC2/Snail complex to the promoter of E-cadherin. In this study, we found that MIER3 was upregulated in breast cancer tissue and closely associated with poor prognosis of patients. MIER3 could promote the proliferation, migration, and epithelial-mesenchymal transition (EMT) of breast cancer cells. Further studies showed that MIER3 interacted with HDAC1/HDAC2 and Snail to form a repressive complex which could bind to E-cadherin promoter and was related to its deacetylation. Our study concluded that MIER3 was involved in forming a co-repressor complex with HDAC1/HDAC2/Snail to promote EMT by silencing E-cadherin.

Distinct Ring1b complexes defined by DEAD-box helicases and EMT transcription factors synergistically enhance E-cadherin silencing in breast cancer

Ring1b is a core subunit of polycomb repressive complex 1 (PRC1) and is essential in several high-risk cancers. However, the epigenetic mechanism of Ring1b underlying breast cancer malignancy is poorly understood. In this study, we showed increased expression of Ring1b promoted metastasis by weakening cell–cell adhesions of breast cancer cells. We confirmed that Ring1b could downregulate E-cadherin and contributed to an epigenetic rewiring via PRC1-dependent function by forming distinct complexes with DEAD-box RNA helicases (DDXs) or epithelial-mesenchymal transition transcription factors (EMT TFs) on site-specific loci of E-cadherin promoter. DDXs-Ring1b complexes moderately inhibited E-cadherin, which resulted in an early hybrid EMT state of epithelial cells, and EMT TFs-Ring1b complexes cooperated with DDXs-Ring1b complexes to further repress E-cadherin in mesenchymal-like cancer cells. Clinically, high expression of Ring1b with DDXs or EMT TFs predicted low levels of E-cadherin, metastatic behavior, and poor prognosis. These findings provide an epigenetic regulation mechanism of Ring1b complexes in E-cadherin expression. Ring1b complexes may be potential therapeutic targets and biomarkers for diagnosis and prognosis in invasion breast cancer.

Hsa‐miR‐199b‐3p Prevents the Epithelial‐Mesenchymal Transition and Dysfunction of the Renal Tubule by Regulating E‐cadherin through Targeting KDM6A in Diabetic Nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. The association between epithelial-mesenchymal transition (EMT) and fibrosis is quite ascertained, but its link to eventual tubule dysfunction is missing. Here, we show that human microRNA- (hsa-miR-) 199b-3p protects renal tubules from diabetic-induced injury by repressing KDM6A, a histone lysine demethylase regulating E-cadherin expression. Lower E-cadherin expression is related to a higher level of KDM6A, while E-cadherin is promoted upon treatment with the KDM6A inhibitor GSK-J4 in both high glucose- (HG-) induced HK2 cells and the kidneys from streptozotocin- (STZ-) induced type 1 diabetic mice. However, overexpression or RNA silencing of E-cadherin fails to alter KDM6A expression. We also show that the upregulation of KDM6A is associated with the increased methylation level of the E-cadherin promoter. Then, the target prediction results and a dual-luciferase assay show that hsa-miR-199b-3p is a new miRNA that targets KDM6A. Overexpression of hsa-miR-199b-3p increases E-cadherin expression and prevents EMT through repressing KDM6A expression in HG-induced HK2 cells. In contrast, inhibitor-induced hsa-miR-199b-3p knockdown has opposite effects, as it decreases E-cadherin level and worsens EMT, accompanied by increased levels of KDM6A. Besides, Mir199b-knockout mice without mmu-miR-119b-3p expression exhibit more renal tubule dysfunction and more serious kidney tissue damage upon treatment with STZ. These results demonstrate that hsa-miR-199b-3p improves E-cadherin expression and prevents the progression of DN through targeting KDM6A. miR-199b-3p could be a future biomarker or target for the diagnosis or treatment of DN.

Abstract 3821: Fusobacterium Nucleatum and HPV16 cooperate to reprogram the human primary oral keratinocyte to enhanced stemness state, a newly identified pre-malignant cell state

Abstract The mechanism of HPV16 induced malignant transformation of oral epithelial cells is not yet clear. We speculated that HPV16 may induce stem cell altruism that reprogram specific subfraction of the keratinocyte population to enhanced stemness state, a previously reported pre-malignant phenotype in human ES cells by our lab (1). Indeed, using HPV16 E6 transduction method, we demonstrated that CD271+ primary human keratinocytes undergo enhanced stemness switch i.e. low p53 activity, and high expression of HIF-2a, Nanog, sox2 and oct4. Importantly, these cells indicated resistance to calcium and serum induced differentiation, and clonogenic activities and failed to undergo malignant transformation (2). Considering that HPV16 induced carcinogenesis may involve additional steps to transformation, next, we treated CD271+ cells from HPV16 E6 transduced cells with 4-NQO oral carcinogen. We found that 4-NQO tx induced the MYC-HIF-2a stemness pathway (3), which we recently characterized in cancer stem cells (4). However, MYC activity was transient and therefore, the cells did not exhibit reprograming of enhanced stemness to tumor stemness state, the later being identified in cancer stem cells (5). Thus, it seems that additional oncogenes, in addition to MYC may be involved in the reprograming of enhanced stemness to tumor stemness state. Here we evaluate the ability of oral bacteria F. nucleatum (F.N.) to accelerate malignant process and facilitate the enhanced stemness to acquire tumor stemness state. Previously, we showed that F.N. can induce HIF-2a stemness pathway in oral cancer cell line (6), which prompted us to use this model for this present work. Considering that F.N. surface protein Fap2 can modulate E cadherins, we speculated that F.N. might induce E. cadherin-EGFR axis to promote ras oncogene activity in collaboration with HPV16. Methods: The HPV16 E6 transduced (by using the retroviral LXSN 16E6 system) primary oral keratinocytes were grown for two weeks as previously described (2-3). In these cells. F.N. was added in 1:10 MOI for 12 hours under anerobic condition (5), and then washed and cultured in vitro for 2 weeks. The CD271+ cells were then immunomagnetically sorted and subjected to evaluation for MYC/HIF2 stemness pathway. Because, ABCG2+ cells are endowed with this stemness pathway (1,5), we next sorted the CD271+/ABCG2+ cells. Results: We found that addition of F.N. led to upregulation of MYC/HIF-2a stemness pathway in the CD271+/ABCG2+ cells. These cells showed rapid proliferation for 2-3 weeks, and resistance to calcium and serum induced terminal differentiation and activated the EGFR/HRas axis. Interestingly, F.N. lysate is sufficient to induce EGFR expression and the activation of MYC/stemness pathway in these E6 transduced cells. Notably silencing of E-cadherin by siRNA led to loss of F.N mediated induction of MYC and Ras, and spontaneous apoptosis of the cells. Conclusions: These data indicate that oral bacteria like F.N. can cause enhanced stemness switch, a pre-malignant state by activating the EGFR/Ras pathway that activate MYC/stemness pathway. 1. Das B,etal. Stem Cells. 2012 2. AACR Abstract nr 4297 3. AACR Abstract nr 4073 4. Das B et al. Cancer Res. 2019 5. AACR Abstract nr 3064. Citation Format: Ibrahim Akeel, Bidisha Pal, Partha Jyoti Saikia, Lekhika Pathak, Sandhya Sorra, Bikul Das. Fusobacterium Nucleatum and HPV16 cooperate to reprogram the human primary oral keratinocyte to enhanced stemness state, a newly identified pre-malignant cell state [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3821.

Long Noncoding RNA MRPL23-AS1 Promotes Adenoid Cystic Carcinoma Lung Metastasis.

Lung metastasis is a major factor affecting long-term survival in patients with adenoid cystic carcinoma. Here, we showed that the long noncoding RNA (lncRNA) MRPL23 antisense RNA 1 (MRPL23-AS1) was highly expressed and correlated with lung metastasis and overall survival in patients with salivary adenoid cystic carcinoma (SACC). MRPL23-AS1 positively regulated epithelial-mesenchymal transition by forming an RNA-protein complex with enhancer of zeste homolog 2 (EZH2). MRPL23-AS1 increased the binding of EZH2 and H3K27me3 on the E-cadherin promoter region. Moreover, MRPL23-AS1 levels were higher in exosomes isolated from the blood plasma of patients with SACC, and exosomal MRPL23-AS1 affected pulmonary microvascular endothelial cells in an "exosomecrine" manner. MRPL23-AS1-enriched exosomes increased microvascular permeability and facilitated the metastasis of SACC in vivo. Collectively, these findings highlight a molecular mechanism of lung metastasis in SACC. MRPL23-AS1 may represent a biomarker and target for clinical intervention to control this intractable disease. SIGNIFICANCE: This study identifies a novel metastasis-promoting lncRNA MRPL23-AS1, which mediates the transcriptional silencing of E-cadherin through forming an RNA-protein complex with EZH2.

<p>Regulations of miR-183-5p and Snail-Mediated Shikonin-Reduced Epithelial-Mesenchymal Transition in Cervical Cancer Cells</p>

BackgroundShikonin, the main ingredient of Lithospermum erythrorhizon, has been reported to have antitumor effects via multiple targets and signaling pathways. However, the detailed mechanism underlying the effects in cervical cancer still remained unknown.MethodsMTT, wound-healing, transwell assays and flow cytometry experiments were used to measure cell growth, migration, invasion, and cell cycle analysis. Western blot was used to examine protein levels of Snail, Vimentin and E-cadherin. The expression level of miR-183-5p was measured via qRT-PCR. The E-cadherin promoter activity was detected via Secrete-PairTM Dual Luminescence Assay Kit. The transient transfection experiments were used for silencing of E-cadherin and overexpression of Snail genes. Tumor xenograft and bioluminescent imaging experiments were carried out to confirm the in vitro findings.ResultsWe showed that shikonin inhibited cell viability, migration and invasion, and induced cell cycle arrest in a dose-dependent manner in cervical cancer Hela and C33a cells. Mechanistically, we found that shikonin increased miR-183-5p expression and inhibited expression of transcription factor Snail protein. The mimics of miR-183-5p reduced, while the inhibitors of miR-183-5p reversed shikonin-inhibited Snail protein expression. In addition, shikonin decreased Vimentin, increased E-cadherin protein expressions and E-cadherin promoter activity, the latter was reversed in cells transfected with exogenous Snail overexpression vectors. Moreover, silencing of E-cadherin significantly abolished shikonin-inhibited cervical cancer cell growth. Similar findings were also observed in vivo using one xenograft mouse model.ConclusionOur results show that shikonin inhibits EMT through inhibition of Snail and stimulation of miR-183-5p expressions, which resulted in induction of E-cadherin expression. Thus, blockade of EMT could be a novel mechanism underlying the anti-cervical cancer effects of shikonin.

CD9 regulates keratinocyte differentiation and motility by recruiting E-cadherin to the plasma membrane and activating the PI3K/Akt pathway

During keratinocyte stratification and wound healing, keratinocytes undergo a switch between differentiation and motility. However, limited knowledge exists on the mechanisms of the switch. We have previously demonstrated that the expression of CD9 was changed in different wound stages and involved in the regulation of keratinocyte migration. In this study, we showed that CD9 expression was increased in both human and mouse keratinocytes undergoing differentiation. CD9 overexpression in keratinocytes stimulated terminal differentiation and reduced cell motility. CD9 silencing inhibited calcium-induced keratinocyte differentiation and increased cell motility. Furthermore, CD9 overexpression recruited E-cadherin to the plasma membrane and subsequently activated PI3K/Akt signaling, while CD9 knockdown inhibited the recruitment of E-cadherin to the plasma membrane and PI3K/Akt activation. Importantly, silencing E-cadherin expression or inhibiting PI3K/Akt signaling reversed CD9 overexpression-induced differentiation and -reduced motility. These results demonstrate that CD9 acts as an important node that regulates keratinocyte differentiation and motility. The recruitment of E-cadherin to the plasma membrane and activation of the PI3K/Akt signaling pathway mediated by CD9 play an important role in these processes.

Electric Field Based Dressing Disrupts Mixed-Species Bacterial Biofilm Infection and Restores Functional Wound Healing

This study was designed to employ electroceutical principles, as an alternative to pharmacological intervention, to manage wound biofilm infection. Mechanism of action of a United States Food and Drug Administration-cleared wireless electroceutical dressing (WED) was tested in an established porcine chronic wound polymicrobial biofilm infection model involving inoculation with Pseudomonas aeruginosa PAO1 and Acinetobacter baumannii 19606. Bacterial biofilms represent a major wound complication. Resistance of biofilm toward pharmacologic interventions calls for alternative therapeutic strategies. Weak electric field has anti-biofilm properties. We have previously reported the development of WED involving patterned deposition of Ag and Zn on fabric. When moistened, WED generates a weak electric field without any external power supply and can be used as any other disposable dressing. WED dressing was applied within 2 hours of wound infection to test its ability to prevent biofilm formation. Alternatively, WED was applied after 7 days of infection to study disruption of established biofilm. Wounds were treated with placebo dressing or WED twice a week for 56 days. Scanning electron microscopy demonstrated that WED prevented and disrupted wound biofilm aggregates. WED accelerated functional wound closure by restoring skin barrier function. WED blunted biofilm-induced expression of (1) P. aeruginosa quorum sensing mvfR (pqsR), rhlR and lasR genes, and (2) miR-9 and silencing of E-cadherin. E-cadherin is critically required for skin barrier function. Furthermore, WED rescued against biofilm-induced persistent inflammation by circumventing nuclear factor kappa B activation and its downstream cytokine responses. This is the first pre-clinical porcine mechanistic study to recognize the potential of electroceuticals as an effective platform technology to combat wound biofilm infection.

Formononetin attenuated allergic diseases through inhibition of epithelial-derived cytokines by regulating E-cadherin

Radix Astragali, has long been used to alleviate allergic diseases (ADs). Formononetin is one of the major active components in Radix Astragali, but its mechanism on ADs is not definitively known. The fluorescein isothiocyanate isomer-induced atopic contact dermatitis mouse model and poly I:C or lipopolysaccharide-treated HaCaT cells were used to examine thymic stromal lymphopoietin (TSLP)/interleukin (IL)-33 production and expression of E-cadherin. After administration of formononetin, TSLP/IL-33 levels decreased both in vitro and in vivo, while E-cadherin was increased in vivo and restored in vitro. Furthermore, small interference RNA silencing of E-cadherin resulted in elevated levels of TSLP, whereas the inhibitory effect of formononetin on TSLP was no longer observed. In addition, TSLP resulted in no detectable changes in delocalization or protein expression of E-cadherin in HaCaT cells. These results indicated that formononetin showed a protective effect in ADs, which was correlated with decreasing TSLP/IL-33 production via regulation of E-cadherin.

Decreased expression of MUC1 induces apoptosis and inhibits migration in pancreatic cancer PANC-1 cells via regulation of Slug pathway.

MUC1, a membrane tethered mucin glycoprotein, is overexpressed in > 60% of human pancreatic cancers (PCs), and is associated with poor prognosis and enhanced metastasis. Here, we report the effect of silencing MUC1 expression on the growth, migration and invasive ability of pancreatic cancer cells, and explored its mechanisms. We observed that siRNA mediated suppression of the MUC1 expression significantly reduced invasive and migrative capability and induced apoptosis of the pancreatic cancer PANC-1 cells. We found that Slug was inhibited in the MUC1 siRNA transfected PANC-1 cells (MUC1 siRNA/PANC-1 cells). Expression of PUMA and E-cadherin was increased in the MUC1 siRNA/PANC-1 cells. PANC-1 cells overexpressing full long Slug gene (when transfected with Slug cDNA plasmid) significantly inhibited PUMA and E-cadherin expression in the MUC1 siRNA/PANC-1 cells. Silencing PUMA expression inhibited apoptosis in the MUC1 siRNA transfected PANC-1 cells (MUC1 siRNA/PANC-1 cells). Silencing E-cadherin expression restored the invasion and migration ability in the MUC1 siRNA/PANC-1 cells. We therefore concluded that silencing MUC1 expression inhibited migration and invasion, and induced apoptosis of PANC-1 cells via downregulation of Slug and upregulation of Slug dependent PUMA and E-cadherin expression. MUC1 could serve as a potential therapeutic target in pancreatic cancer.

Abstract 1748: Organ-specific epigenetic reprogramming of leukemia cells: Clues to chemoresistance

Abstract We previously reported our observation that tumors composed of leukemic cells found in breast mimic solid breast cancers in gross and histologic appearance (single-filing of cells and distinctive keloid-like fibrosis), invasiveness, metastatic pathway, and high mortality. They are resistant to anti-leukemia drugs; only 4% treated without excision lived 4 years but survivals over 20 yrs resulted when tumor and its microenvironment were excised. The incidence of occult leukemic tumors, still unknown as scans are not yet routine, was estimated near 20% in 1970s autopsy studies. We hypothesized there may be similarly altered genes in leukemic and epithelial breast tumors directing clinical behavior and resistance that could provide targets for curative treatment. We performed RNA sequencing on 11 FFPE breast tumors from annotated AML cases, all IHC-negative for hormones and E-cadherin, compared to normal breast samples. Differential expression analysis identified 3647 genes that were significantly downregulated (adjusted p < 0.05 and log2 fold change < -2). Among the 100 genes downregulated 8-10 fold in leukemic breast, FOXA1, CA12, CXCL14, SFRP1, SFRP4, DCN, LUM, PHLDA1, NTN4, GABRP, TAGLN, AZGP1, and ARRDC3 have been associated with poor prognosis in breast cancer, mainly triple-negative (TNBC)/basal types. Compared to TNBC cases in the TCGA database, 851 genes were similarly deregulated; significantly enriched KEGG pathways include neuroactive ligand-receptor interaction, focal adhesion, ECM-receptor interaction, and regulation of lipolysis in adipocytes. A role for altered stroma is suggested as many of the similarly downregulated genes were reported in dissected breast cancer stroma and silenced SFRP1 and CXCL14 were found in keloid fibroblasts. Silencing of SFRP1 and E-cadherin in AML marrows was reported in 30-50% and each was correlated with poor survival. Reversal of SFRP1 silencing has been achieved by epigenetic-modifying drugs in cancers and keloid fibroblasts. We validated loss of SFRP1 and RGS6 in leukemic breasts by RT-PCR. Loss of RGS6 in breast and other cancers promotes doxorubicin resistance and DNMT1 upregulation leading to silencing of tumor suppressor genes. These data open a new view of resistance of AML cells to marrow-directed drugs through interaction with aberrant microenvironment. Solid tumors of epithelial and leukemic cells may share unrecognized treatable targets. Adding drugs directed at tumor, including available epigenetic-modifying agents, to marrow-effective protocols, may finally decrease the persistently high rate of AML treatment failure. Citation Format: Isabel Cunningham, Diane Hamele-Bena, Audrey Papp, Yan Guo, Antony B. Holmes, Yu Shyr, Rory A. Fisher. Organ-specific epigenetic reprogramming of leukemia cells: Clues to chemoresistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1748. doi:10.1158/1538-7445.AM2017-1748

A promoter-proximal transcript targeted by genetic polymorphism controls E-cadherin silencing in human cancers

Long noncoding RNAs are emerging players in the epigenetic machinery with key roles in development and diseases. Here we uncover a complex network comprising a promoter-associated noncoding RNA (paRNA), microRNA and epigenetic regulators that controls transcription of the tumour suppressor E-cadherin in epithelial cancers. E-cadherin silencing relies on the formation of a complex between the paRNA and microRNA-guided Argonaute 1 that, together, recruit SUV39H1 and induce repressive chromatin modifications in the gene promoter. A single nucleotide polymorphism (rs16260) linked to increased cancer risk alters the secondary structure of the paRNA, with the risk allele facilitating the assembly of the microRNA-guided Argonaute 1 complex and gene silencing. Collectively, these data demonstrate the role of a paRNA in E-cadherin regulation and the impact of a noncoding genetic variant on its function. Deregulation of paRNA-based epigenetic networks may contribute to cancer and other diseases making them promising targets for drug discovery.

Abstract 1146: Enhancer of zeste homolog 2 (EZH2) inhibition in metastatic melanoma promotes tumor regression in vivo

Abstract Melanoma is a deadly variety of skin cancer, which is responsible for three-fourths of skin cancer-related deaths, but constitutes less than 5% of all skin cancer cases. It has been estimated that in 2015, about 73,870 new cases of melanoma will be diagnosed in United States alone, of which 9,940 are expected to die. According to the ACS, melanoma is also the fastest growing cancer, which makes it essential to investigate the pathogenesis involved in the advanced stage of melanoma, and design effective therapeutics for its treatment. Drugs targeting epigenetic modifiers like EZH2 are becoming increasingly popular because of the fact that most epigenetic modifications and their effects can be reversed using these drugs. There has been no study till date investigating the role of EZH2 in melanoma. Our laboratory is investigating the role of EZH2 in the pathogenesis involved in the advanced stage of melanoma, to enable the design of effective therapeutic strategies for the treatment of melanoma. Here we investigate the relationship between EZH2 and tumor suppressors E-cadherin and RUNX3 in melanoma using matched melanoma cell lines (WM115 and WM266-4), formalin-fixed-paraffin-embedded (FFPE) patient tissue samples and in vivo xenograft model. The studies performed in cell lines and FFPE tissue samples suggested EZH2-mediated silencing of E-cadherin and RUNX3 by promoting H3K27-trimethylation of the E-CADHERIN and RUNX3 promoters in WM266-4 cells (metastatic; high EZH2; low E-cadherin) relative to WM115 cells (primary; low EZH2; high E-cadherin). Furthermore, we observed that EZH2 inhibition restores E-cadherin and RUNX3 expression in metastatic melanoma cells by reducing EZH2 and H3K27me3 occupancy at E-CADHERIN and RUNX3 promoters respectively. In addition, we found that inhibition of EZH2 besides inducing apoptosis and inhibiting cellular proliferation, also adversely affected invasion of metastatic melanoma. E-cadherin depletion had an opposite effect, suggesting that EZH2 mediated E-cadherin silencing promotes invasion in metastatic melanoma. In vivo, treatment of WM266-4 xenografts with EZH2 inhibitor resulted in significant reduction of tumor growth. In combination with Dabrafenib, this effect was highly synergistic. Analysis of harvested tumors indicated increased E-cadherin and RUNX3 levels in EZH2 inhibited group compared to vehicle, due to reduced H3K27me3 enrichment by EZH2 at E-cadherin and RUNX3 promoters, validating our in vitro finding. Tumor regression by combination therapy was also accompanied by significant increased pro-apoptotic proteins like Bak, Bax and decreased anti-apoptotic proteins Bcl-xL and Bcl-2. Hence, our findings suggest strong potential of EZH2 inhibitors as promising melanoma drugs either by itself (monotherapy), or in conjunction with other chemotherapeutics (combination therapy). Citation Format: Deepanwita Sengupta, Nathan Avaritt, Sara C. Shalin, Alan J. Tackett. Enhancer of zeste homolog 2 (EZH2) inhibition in metastatic melanoma promotes tumor regression in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1146.

Hepatitis C virus depends on E-cadherin as an entry factor and regulates its expression in epithelial-to-mesenchymal transition

Hepatitis C virus (HCV) enters the host cell through interactions with a cascade of cellular factors. Although significant progress has been made in understanding HCV entry, the precise mechanisms by which HCV exploits the receptor complex and host machinery to enter the cell remain unclear. This intricate process of viral entry likely depends on additional yet-to-be-defined cellular molecules. Recently, by applying integrative functional genomics approaches, we identified and interrogated distinct sets of host dependencies in the complete HCV life cycle. Viral entry assays using HCV pseudoparticles (HCVpps) of various genotypes uncovered multiple previously unappreciated host factors, including E-cadherin, that mediate HCV entry. E-cadherin silencing significantly inhibited HCV infection in Huh7.5.1 cells, HepG2/miR122/CD81 cells, and primary human hepatocytes at a postbinding entry step. Knockdown of E-cadherin, however, had no effect on HCV RNA replication or internal ribosomal entry site (IRES)-mediated translation. In addition, an E-cadherin monoclonal antibody effectively blocked HCV entry and infection in hepatocytes. Mechanistic studies demonstrated that E-cadherin is closely associated with claudin-1 (CLDN1) and occludin (OCLN) on the cell membrane. Depletion of E-cadherin drastically diminished the cell-surface distribution of these two tight junction proteins in various hepatic cell lines, indicating that E-cadherin plays an important regulatory role in CLDN1/OCLN localization on the cell surface. Furthermore, loss of E-cadherin expression in hepatocytes is associated with HCV-induced epithelial-to-mesenchymal transition (EMT), providing an important link between HCV infection and liver cancer. Our data indicate that a dynamic interplay among E-cadherin, tight junctions, and EMT exists and mediates an important function in HCV entry.

DNA methylation-induced E-cadherin silencing is correlated with the clinicopathological features of melanoma.

E-cadherin, a calcium-dependent cell-cell adhesion molecule, has an important role in epithelial cell function, maintenance of tissue architecture and cancer suppression. Loss of E-cadherin promotes tumor metastatic dissemination and predicts poor prognosis. The present study investigated the clinicopathological significance of E-cadherin expression in cutaneous, mucosal and uveal melanoma related to epigenetic mechanisms that may contribute to E-cadherin silencing. E-cadherin expression was reduced in 55/130 cutaneous (42.3%), 49/82 mucosal (59.7%) and 36/64 uveal (56.2%) melanoma samples as compared to normal skin controls and was inversely associated with promoter methylation. Of the 10 different CpG sites studied (nt 863, 865, 873, 879, 887, 892, 901, 918, 920 and 940), two sites (nt 892 and 940) were 90-100% methylated in all the melanoma specimens examined and the other ones were partially methylated (range, 53-86%). In contrast, the methylation rate of the E-cadherin gene was low in normal tissues (range, 5-24%). In all the three types of melanoma studied, a significant correlation was found between reduced levels of E-cadherin and reduced survival, high mitotic index and metastasis, accounting for the predilection of lymph nodal localization. In cutaneous and mucosal melanoma, low E-cadherin expression was positively correlated also with head/neck localization and ulceration. A high frequency of reduced E-cadherin levels occurred in choroid melanomas. In vitro experiments showed that E-cadherin transcription was restored following 5-aza-2'-deoxycytidine (5-aza-dC) treatment or DNMT1 silencing and was negatively correlated with the invasive potential of melanoma cells. The significant relationship between E-cadherin silencing and several poor prognostic factors indicates that this adhesion molecule may play an important role in melanomagenesis. Therefore, the inverse association of E-cadherin expression with promoter methylation raises the intriguing possibility that reactivation of E-cadherin expression through promoter demethylation may represent a potential therapeutic strategy for the treatment of melanoma.

Abstract 26: Suppression of E-cadherin mediates gallotannin-induced apoptosis in Hep G2 hepatocelluar carcinoma cells

Abstract Though gallotannin was known to have anti-oxidant and antitumor activity, the underlying antitumor mechanism of gallotannin still remains unclear. Thus, in the present study, antitumor mechanism of gallotannin was elucidated in hepatocellular carcinoma cells. Gallotannin significantly exerted cytotoxicity against Hep G2 and Chang hepatocellular carcinoma cells with the accumulation of the sub-G1 population and increase of terminal deoxynucleotidyltransferasedUTP nick end labeling (TUNEL) positive cells as an apoptotic feature. Also, gallotannin attenuated the expression of pro-caspase9, pro-caspase3, Bcl2 and integrin β1 and cleaved poly(ADP)-ribose polymerase (PARP) in Hep G2 and Chang cancer cells. Furthermore, gallotannin suppressed cell repair motility by wound healing assay and also inhibited cell adhesion in Hep G2 cells. Of note, gallotannin attenuated the expression of epithelial cadherin (E-cadherin) to form cell-cell adhesion from the early stage, and also beta-catenin at late phase in Hep G2 cells. Consistently, Immunofluorescence assay showed that E-cadherin or β-catenin expression was suppressed in a time dependent manner by gallotannin. Furthermore, silencing of E-cadherin by siRNA transfection method enhanced PAPR cleavage, caspase 3 activation and sub G1 population and attenuated the cell adhesion induced by gallotannin in Hep G2 cells. Overall, our findings demonstrate that the disruption of cell adhesion junction by suppression of E-cadherin mediates gallotannin enhanced apoptosis in Hep G2 liver cancer cells. Citation Format: Hee Young Kwon, Ji Hoon Jung, Hyun Joo Lee, Myoung Seok Jeong, Deok-Beom Jung, Bonglee Kim, Hyemin Lee, Sung-Hoon Kim. Suppression of E-cadherin mediates gallotannin-induced apoptosis in Hep G2 hepatocelluar carcinoma cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 26. doi:10.1158/1538-7445.AM2015-26

E-cadherin and Src associate with extradesmosomal Dsg3 and modulate desmosome assembly and adhesion.

Desmosomes provide strong intercellular cohesion essential for the integrity of cells and tissues exposed to continuous mechanical stress. For desmosome assembly, constitutively synthesized desmosomal cadherins translocate to the cell-cell border, cluster and mature in the presence of Ca(2+) to stable cell contacts. As adherens junctions precede the formation of desmosomes, we investigated in this study the relationship between the classical cadherin E-cadherin and the desmosomal cadherin Desmoglein 3 (Dsg3), the latter of which is indispensable for cell-cell adhesion in keratinocytes. By using autoantibodies from patients with the blistering skin disease pemphigus vulgaris (PV), we showed in loss of function studies that E-cadherin compensates for effects of desmosomal disassembly. Overexpression of E-cadherin reduced the loss of cell cohesion induced by PV autoantibodies and attenuated activation of p38 MAPK. Silencing of E-cadherin abolished the localization of Dsg3 at the membrane and resulted in a shift of Dsg3 from the cytoskeletal to the non-cytoskeletal protein pool which conforms to the notion that E-cadherin regulates desmosome assembly. Mechanistically, we identified a complex consisting of extradesmosomal Dsg3, E-cadherin, β-catenin and Src and that the stability of this complex is regulated by Src. Moreover, Dsg3 and E-cadherin are phosphorylated on tyrosine residues in a Src-dependent manner and Src activity is required for recruiting Dsg3 to the cytoskeletal pool as well as for desmosome maturation towards a Ca(2+)-insensitive state. Our data provide new insights into the role of E-cadherin and the contribution of Src signaling for formation and maintenance of desmosomal junctions.

EZH2 Overexpression in Malignant Melanoma Represses E-cadherin and Promotes Invasion

Decline in the expression of E-cadherin has long been associated with metastasis and ultimately mortality in different types of cancer. However, no such study has yet been performed in melanoma, which is a deadly variety of skin cancer, responsible for 75% of skin cancer-related deaths. Here we investigate the effect of EZH2 on E-cadherin in melanoma. Preliminary studies by our lab have strongly suggested increased levels of EZH2 and increased EZH2-catalyzed histone H3K27 trimethylation (repressive mark) in aggressive stages of melanoma. We used the EZH2 inhibitor GSK126 in our matched cell lines – WM115 and WM266-4, and established that EZH2 inhibition adversely affects invasion by restoring E-cadherin expression. The inverse relationship between EZH2 and E-cadherin expression was further validated by performing large scale immunohistochemistry (IHC) in formalin-fixed-paraffin-embedded (FFPE) patient biopsies as well as human tissue microarrays. The mechanism of EZH2 induced E-cadherin silencing in the m...