Cancer-type regulation of MIG-6 expression by inhibitors of methylation and histone deacetylation

DNA methyltransferase inhibitors combination therapy for the treatment of solid tumor: mechanism and clinical application

DNA methylation, an epigenetic modification, regulates gene transcription and maintains genome stability. DNA methyltransferase (DNMT) inhibitors can activate silenced genes at low doses and cause cytotoxicity at high doses. The ability of DNMT inhibitors to reverse epimutations is the basis of their use in novel strategies for cancer therapy. In this review, we examined the literature on DNA methyltransferase inhibitors. We summarized the mechanisms underlying combination therapy using DNMT inhibitors and clinical trials based on combining hypomethylation agents with other chemotherapeutic drugs. We also discussed the efficacy of such compounds as antitumor agents, the need to optimize treatment schedules and the regimens for maximal biologic effectiveness. Notably, the combination of DNMT inhibitors and chemotherapy and/or immune checkpoint inhibitors may provide helpful insights into the development of efficient therapeutic approaches.

Gene 33/Mig6/ERRFI1, an Adapter Protein with Complex Functions in Cell Biology and Human Diseases

Gene 33 (also named Mig6, RALT, and ERRFI1) is an adapter/scaffold protein with a calculated molecular weight of about 50 kD. It contains multiple domains known to mediate protein–protein interaction, suggesting that it has the potential to interact with many cellular partners and have multiple cellular functions. The research over the last two decades has confirmed that it indeed regulates multiple cell signaling pathways and is involved in many pathophysiological processes. Gene 33 has long been viewed as an exclusively cytosolic protein. However, recent evidence suggests that it also has nuclear and chromatin-associated functions. These new findings highlight a significantly broader functional spectrum of this protein. In this review, we will discuss the function and regulation of Gene 33, as well as its association with human pathophysiological conditions in light of the recent research progress on this protein.

Differential Glucocorticoid-Dependent Regulation and Function of the ERRFI1 Gene in Triple-Negative Breast Cancer

Glucocorticoids (GCs; eg, hydrocortisone [CORT]) are routinely used as chemotherapeutic, anti-emetic, and palliative agents in breast cancer (BCa) therapy. The effects of GC signaling on BCa progression, however, remain a contentious topic as GC treatment seems to be beneficial for receptor-positive subtypes but elicits unfavorable responses in triple-negative BCa (TNBC). The mechanistic basis for these conflicting effects of GC in BCa is poorly understood. In this study, we sought to decipher the molecular mechanisms that govern the GC-dependent induction of the tumor suppressor ERRFI1 gene, an inhibitor of epidermal growth factor receptor (EGFR) signaling, and characterize the role of the GC-ERRFI1 regulatory axis in TNBC. Treatment of TNBC cell lines with a protein synthesis inhibitor or GC receptor (GR) antagonist followed by gene expression analysis suggests that ERRFI1 is a direct GR target. Using in silico analysis coupled with enhancer-reporter assays, we identified a putative ERRFI1 enhancer that supports CORT-dependent transactivation. In orthogonal assays for cell proliferation, survival, migration, and apoptosis, CORT mostly facilitated an oncogenic phenotype regardless of malignancy status. Lentiviral knockdown and overexpression of ERRFI1 showed that the CORT-enhanced oncogenic phenotype is restricted by ERRFI1 in the normal breast epithelial model MCF10A and to a lesser degree in the metastatic TNBC line MDA-MB-468. Conversely, ERRFI1 conferred pro-tumorigenic effects in the highly metastatic TNBC model MDA-MB-231. Taken together, our findings suggest that the progressive loss of the GC-dependent regulation and anti-tumorigenic function of ERRFI1 influences BCa progression and may contribute to the unfavorable effects of GC therapy in TNBC.

Long noncoding RNA ANRIL promotes the malignant progression of cholangiocarcinoma by epigenetically repressing ERRFI1 expression

Long noncoding RNAs (lncRNAs) have recently been verified to have significant regulatory functions in many types of human cancers. The lncRNA ANRIL is transcribed from the INK4b-ARF-INK4a gene cluster in the opposite direction. Whether ANRIL can act as an oncogenic molecule in cholangiocarcinoma (CCA) remains unknown. Our data show that ANRIL knockdown greatly inhibited CCA cell proliferation and migration in vitro and in vivo. According to the results of RNA sequencing analysis, ANRIL knockdown dramatically altered target genes associated with the cell cycle, cell proliferation, and apoptosis. By binding to a component of the epigenetic modification complex enhancer of zeste homolog 2 (EZH2), ANRIL could maintain lysine residue 27 of histone 3 (H3K27me3) levels in the promoter of ERBB receptor feedback inhibitor 1 (ERRFI1), which is a tumor suppressor gene in CCA. In this way, ERRFI1 expression was suppressed in CCA cells. These data verified the key role of the epigenetic regulation of ANRIL in CCA oncogenesis and indicate its potential as a target for CCA intervention.

Effects of 5-Aza-2'-deoxycytidine (decitabine) on gene expression

5-Aza-2'-deoxycytidine (AzaD), also known as Decitabine, is a deoxycytidine analog that is typically used to activate methylated and silenced genes by promoter demethylation. However, a survey of the scientific literature indicates that promoter demethylation may not be the only (or, indeed, the major) mechanism by which AzaD affects gene expression. Regulation of gene expression by AzaD can occur in several ways, including some that are independent of DNA demethylation. Results from several studies indicate that the effect of AzaD on gene expression is highly context-dependent and can differ for the same gene under different environmental settings. This may, in part, be due to the nature of the silencing mechanism(s) involved - DNA methylation, repressive histone modifications, or a combination of both. The varied effects of AzaD on such context-dependent regulation of gene expression may underlie some of the diverse responses exhibited by patients undergoing AzaD therapy. In this review, we describe the salient properties of AzaD with particular emphasis on its diverse effects on gene expression, aspects that have barely been discussed in most reviews of this interesting drug.

Mig-6 deficiency cooperates with oncogenic Kras to promote mouse lung tumorigenesis

OBJECTIVES

Lung cancer is the leading cause of cancer related deaths worldwide and mutation activating KRAS is one of the most frequent mutations found in lung adenocarcinoma. Identifying regulators of KRAS may aid in the development of therapies to treat this disease. The mitogen-induced gene 6, MIG-6, is a small adaptor protein modulating signaling in cells to regulate the growth and differentiation in multiple tissues. Here, we investigated the role of Mig-6 in regulating adenocarcinoma progression in the lungs of genetically engineered mice with activation of Kras.

MATERIALS AND METHODS

Using the CCSPCre mouse to specifically activate expression of the oncogenic KrasG12D in Club cells, we investigated the expression of Mig-6 in CCSPCreKrasG12D-induced lung tumors. To determine the role of Mig-6 in KrasG12D-induced lung tumorigenesis, Mig-6 was conditionally ablated in the Club cells by breeding Mig6f/f mice to CCSPCreKrasG12D mice, yielding CCSPCreMig-6d/dKrasG12D mice (Mig-6d/dKrasG12D).

RESULTS

We found that Mig-6 expression is decreased in CCSPCreKrasG12D-induced lung tumors. Ablation of Mig-6 in the KrasG12D background led to enhanced tumorigenesis and reduced life expectancy. During tumor progression, there was increased airway hyperplasia, a heightened inflammatory response, reduced apoptosis in KrasG12D mouse lungs, and an increase of total and phosphorylated ERBB4 protein levels. Mechanistically, Mig-6 deficiency attenuates the cell apoptosis of lung tumor expressing KRASG12D partially through activating the ErbB4 pathway.

CONCLUSIONS

In summary, Mig-6 deficiency promotes the development of KrasG12D-induced lung adenoma through reducing the cell apoptosis in KrasG12D mouse lungs partially by activating the ErbB4 pathway.

Panobinostat Enhances Growth Suppressive Effects of Progestin on Endometrial Carcinoma by Increasing Progesterone Receptor and Mitogen-Inducible Gene-6

Although progestin has been used to treat endometrial hyperplasia and endometrial carcinoma (EC), its therapeutic efficacy is limited. In order to improve this, the underlining mechanisms of the effects of progestin need to be elucidated in more detail. In the present study, we examined the involvement of mitogen-inducible gene-6 (MIG6), a negative regulator of the EGF receptor, in the progestin-mediated growth suppression of endometrial epithelia. The immunohistochemical expression of MIG6 was elevated in the early to mid-secretory phases of normal endometrium and also with endometrial hyperplasia after medroxyprogesterone acetate (MPA) therapy. The addition of progesterone (P4) to progesterone receptor (PR)-positive EC cells reduced the viability and induced MIG6 messenger RNA (mRNA) and protein expression. The silencing of MIG6 using siRNA eliminated the P4-mediated reduction of EC cell viability, indicating that MIG6 is an essential downstream component of PR-mediated growth suppression. In order to enhance PR-driven signals, we examined the effects of histone deacetylase (HDAC) inhibitors because histone acetylation has been shown to increase the expression of PR. The addition of three HDAC inhibitors (panobinostat, LBH589; trichostatin A, TSA; suberoylanilide hydroxamic acid, SAHA) decreased the viability of EC cells and up-regulated the expression of PR and MIG6, and these effects were the strongest with LBH589. The addition of LBH589 and MPA synergistically decreased the viability and increased apoptosis in EC cells. These results indicate that LBH589 has potential as an enhancer of progestin therapy via the up-regulation of PR and MIG6.

Trefoil factor family peptides – friends or foes?

Trefoil factor family (TFF) peptides are a group of molecules bearing a characteristic three-loop trefoil domain. They are mainly secreted in mucous epithelia together with mucins but are also synthesized in the nervous system. For many years, TFF peptides were only known for their wound healing and protective function, e.g. in epithelial protection and restitution. However, experimental evidence has emerged supporting a pivotal role of TFF peptides in oncogenic transformation, tumorigenesis and metastasis. Deregulated expression of TFF peptides at the gene and protein level is obviously implicated in numerous cancers, and opposing functions as oncogenes and tumor suppressors have been described. With regard to the regulation of TFF expression, epigenetic mechanisms as well as the involvement of various miRNAs are new, promising aspects in the field of cancer research. This review will summarize current knowledge about the expression and regulation of TFF peptides and the involvement of TFF peptides in tumor biology and cancerogenesis.

Regulation of the ErbB network by the MIG6 feedback loop in physiology, tumor suppression and responses to oncogene-targeted therapeutics

The ErbB signaling network instructs the execution of key cellular programs, such as cell survival, proliferation and motility, through the generation of robust signals of defined strength and duration. In contrast, unabated ErbB signaling disrupts tissue homeostasis and leads to cell transformation. Cells oppose the threat inherent in excessive ErbB activity through several mechanisms of negative feedback regulation. Inducible feedback inhibitors (IFIs) are expressed in the context of transcriptional responses triggered by ErbB signaling, thus being uniquely suited to regulate ErbB activity during the execution of complex cellular programs. This review focuses on MIG6, an IFI that restrains ErbB signaling by mediating ErbB kinase suppression and receptor down-regulation. We will review key issues in MIG6 function, regulation and tumor suppressor activity. Subsequently, the role for MIG6 loss in the pathogenesis of tumors driven by ErbB oncogenes as well as in the generation of cellular addiction to ErbB signaling will be discussed. We will conclude by analyzing feedback inhibition by MIG6 in the context of therapies directed against ErbB and non-ErbB oncogenes.

Histone Modifications, Modifiers and Readers in Melanoma Resistance to Targeted and Immune Therapy

The treatment of melanoma has been revolutionized by new therapies targeting MAPK signaling or the immune system. Unfortunately these therapies are hindered by either primary resistance or the development of acquired resistance. Resistance mechanisms involving somatic mutations in genes associated with resistance have been identified in some cases of melanoma, however, the cause of resistance remains largely unexplained in other cases. The importance of epigenetic factors targeting histones and histone modifiers in driving the behavior of melanoma is only starting to be unraveled and provides significant opportunity to combat the problems of therapy resistance. There is also an increasing ability to target these epigenetic changes with new drugs that inhibit these modifications to either prevent or overcome resistance to both MAPK inhibitors and immunotherapy. This review focuses on changes in histones, histone reader proteins and histone positioning, which can mediate resistance to new therapeutics and that can be targeted for future therapies.

ErbB2 Pathway Activation upon Smad4 Loss Promotes Lung Tumor Growth and Metastasis

Lung cancer remains the leading cause of cancer death. Genome sequencing of lung tumors from patients with squamous cell carcinoma has identified SMAD4 to be frequently mutated. Here, we use a mouse model to determine the molecular mechanisms by which Smad4 loss leads to lung cancer progression. Mice with ablation of Pten and Smad4 in airway epithelium develop metastatic adenosquamous tumors. Comparative transcriptomic and in vivo cistromic analyses determine that loss of PTEN and SMAD4 results in ELF3 and ErbB2 pathway activation due to decreased expression of ERRFI1, a negative regulator of ERBB2 in mouse and human cells. The combinatorial inhibition of ErbB2 and Akt signaling attenuate tumor progression and cell invasion, respectively. Expression profile analysis of human lung tumors substantiated the importance of the ErbB2/Akt/ELF3 signaling pathway as both a prognostic biomarker and a therapeutic drug target for treating lung cancer.

Liu et al. now show that ablation of Smad4 and Pten in the pulmonary epithelium results in the development of metastatic adenosquamous lung tumors through activation of the ErbB2/ELF3/AKT pathway. ErbB2 activation in mice is due to downregulation of Errfi1 expression, a direct target of SMAD4.

HSPC117 is regulated by epigenetic modification and is involved in the migration of JEG-3 cells

The human hematopoietic stem/progenitor cell 117 (HSPC117) protein is an essential component of protein complexes and has been identified to be involved in many important functions. However, how this gene expression is regulated and whether the HSPC117 gene affects cell migration is still unknown. The aim of this study was to identify whether HSPC117 mRNA expression is regulated by epigenetic modification and whether HSPC117 expression level affects the expression of matrix metalloproteinase 2 (MMP 2), matrix metalloproteinase 14 (MMP 14), and tissue inhibitor of metalloproteinases 2 (TIMP 2), and further affects human placenta choriocarcinoma cell (JEG-3) migration speed. In our epigenetic modification experiment, JEG-3 cells were cultured in medium with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-dC), the histone deacetylase (HDAC) inhibitor trichostatin A (TSA), or both inhibitors. Then, the HSPC117 mRNA and protein expressions were assessed using real-time quantitative PCR (qPCR) and Western blot assay. The results showed that, compared to the control, HSPC117 mRNA expression was increased by TSA or 5-aza-dC. The highest HSPC117 expression level was found after treatment with both 5-aza-dC and TSA. Further, in order to investigate the effect of HSPC117 on MMP 2, MMP 14, and TIMP 2 mRNA expressions, pEGFP-C1-HSPC117 plasmids were transfected into JEG-3 cells to improve the expression of HSPC117 in the JEG-3 cells. Then, the mRNA expression levels of MMP 2, MMP 14, TIMP 2, and the speed of cell migration were assessed using the scratch wound assay. The results showed that over-expression of HSPC117 mRNA reduced MMP 2 and MMP 14 mRNA expression, while TIMP 2 mRNA expression was up-regulated. The scratch wound assay showed that the migration speed of JEG-3 cells was slower than the non-transfected group and the C1-transfected group. All of these results indicate that HSPC117 mRNA expression is regulated by epigenetic modification; over-expression of HSPC117 decreases MMP 2 and MMP 14 transcription, reduces cell migration speed, and increases TIMP 2 transcription.

Integrated genomic characterization reveals novel, therapeutically relevant drug targets in FGFR and EGFR pathways in sporadic intrahepatic cholangiocarcinoma

Advanced cholangiocarcinoma continues to harbor a difficult prognosis and therapeutic options have been limited. During the course of a clinical trial of whole genomic sequencing seeking druggable targets, we examined six patients with advanced cholangiocarcinoma. Integrated genome-wide and whole transcriptome sequence analyses were performed on tumors from six patients with advanced, sporadic intrahepatic cholangiocarcinoma (SIC) to identify potential therapeutically actionable events. Among the somatic events captured in our analysis, we uncovered two novel therapeutically relevant genomic contexts that when acted upon, resulted in preliminary evidence of anti-tumor activity. Genome-wide structural analysis of sequence data revealed recurrent translocation events involving the FGFR2 locus in three of six assessed patients. These observations and supporting evidence triggered the use of FGFR inhibitors in these patients. In one example, preliminary anti-tumor activity of pazopanib (in vitro FGFR2 IC₅₀≈350 nM) was noted in a patient with an FGFR2-TACC3 fusion. After progression on pazopanib, the same patient also had stable disease on ponatinib, a pan-FGFR inhibitor (in vitro, FGFR2 IC₅₀≈8 nM). In an independent non-FGFR2 translocation patient, exome and transcriptome analysis revealed an allele specific somatic nonsense mutation (E384X) in ERRFI1, a direct negative regulator of EGFR activation. Rapid and robust disease regression was noted in this ERRFI1 inactivated tumor when treated with erlotinib, an EGFR kinase inhibitor. FGFR2 fusions and ERRFI mutations may represent novel targets in sporadic intrahepatic cholangiocarcinoma and trials should be characterized in larger cohorts of patients with these aberrations.

Cholangiocarcinoma is a cancer that affects the bile ducts. Unfortunately, many patients diagnosed with cholangiocarcinoma have disease that cannot be treated with surgery or has spread to other parts of the body, thus severely limiting treatment options. New advances in drug treatment have enabled treatment of these cancers with “targeted therapy” that exploits an error in the normal functioning of a tumor cell, compared to other cells in the body, thus allowing only tumor cells to be killed by the drug. We sought to identify changes in the genetic material of cholangiocarcinoma patient tumors in order to identify potential errors in cellular functioning by utilizing cutting edge genetic sequencing technology. We identified three patient tumors possessing an FGFR2 gene that was aberrantly fused to another gene. Two of these patients were able to receive targeted therapy for FGFR2 with resulting tumor shrinkage. A fourth tumor contained an error in a gene that controls a very important cellular mechanism in cancer, termed epidermal growth factor pathway (EGFR). This patient received therapy targeting this mechanism and also demonstrated response to treatment. Thus, we have been able to utilize cutting edge technology with targeted drug treatment to personalize medical treatment for cancer in cholangiocarcinoma patients.

MeCP2 modulates the canonical Wnt pathway activation by targeting SFRP4 in rheumatoid arthritis fibroblast-like synoviocytes in rats

Rheumatoid arthritis (RA) is an autoimmune disease characterized by the rheumatoid factor and anti-citrullinated peptide antibody (ACPA) against common autoantigens that are widely expressed within and outside the joints. Many factors participate in the pathogenesis of RA, such as cytokine imbalance, Wnt pathway activation, matrix production, and osteoprotegerin on osteoclasts. Fibroblast-like synoviocytes (FLS) activation has an important role in RA pathogenesis. The methyl-CpG-binding protein (MeCP2) which promoted repressed chromatin structure was selectively detected in synovium of diseased articular in rats. Overexpression of this protein results in an up-regulation of global methylation levels and transcriptional suppression of specific genes. There were increased MeCP2 and decreased secreted frizzled-related protein 4 (SFRP4) in synovium as well as the FLS isolated from the synovium of RA rats. Knockdown of MeCP2 using siRNA technique enhanced SFRP4 expression in both mRNA and protein levels in FLS. These results indicated that epigenetic modification was involved in differential expression of SFRP4. To further explore the underlying molecular mechanisms, we hypothesized that the SFRP4 down-regulation in synovium was caused by DNA methylation. Treatment of FLS with DNA methylation inhibitor 5-Aza-2'-deoxycytidine (5-azadC) blocked the cell proliferation and increased the SFRP4 expression. Increased SFRP4 down-regulated the key gene β-catenin, the downstream effectors gene ccnd1 and fibronectin expression in canonical Wnt pathway at the same time. MeCP2 and DNA methylation may provide molecular mechanisms for canonical Wnt pathway activation in RA. Combination of 5-azadC and MeCP2 may be a promising treatment strategy for individuals with RA in which SFRP4 is inactivated.