The ING gene family in the regulation of cell growth and tumorigenesis

The Killer's Web: Interconnection between Inflammation, Epigenetics and Nutrition in Cancer

Inflammation is a key contributor to both the initiation and progression of tumors, and it can be triggered by genetic instability within tumors, as well as by lifestyle and dietary factors. The inflammatory response plays a critical role in the genetic and epigenetic reprogramming of tumor cells, as well as in the cells that comprise the tumor microenvironment. Cells in the microenvironment acquire a phenotype that promotes immune evasion, progression, and metastasis. We will review the mechanisms and pathways involved in the interaction between tumors, inflammation, and nutrition, the limitations of current therapies, and discuss potential future therapeutic approaches.

Cyclic peptides target the aromatic cage of a PHD-finger reader domain to modulate epigenetic protein function

Plant homeodomain fingers (PHD-fingers) are a family of reader domains that can recruit epigenetic proteins to specific histone modification sites. Many PHD-fingers recognise methylated lysines on histone tails and play crucial roles in transcriptional regulation, with their dysregulation linked to various human diseases. Despite their biological importance, chemical inhibitors for targeting PHD-fingers are very limited. Here we report a potent and selective de novo cyclic peptide inhibitor (OC9) targeting the Nε-trimethyllysine-binding PHD-fingers of the KDM7 histone demethylases, developed using mRNA display. OC9 disrupts PHD-finger interaction with histone H3K4me3 by engaging the Nε-methyllysine-binding aromatic cage through a valine, revealing a new non-lysine recognition motif for the PHD-fingers that does not require cation-π interaction. PHD-finger inhibition by OC9 impacted JmjC-domain mediated demethylase activity at H3K9me2, leading to inhibition of KDM7B (PHF8) but stimulation of KDM7A (KIAA1718), representing a new approach for selective allosteric modulation of demethylase activity. Chemoproteomic analysis showed selective engagement of OC9 with KDM7s in T cell lymphoblastic lymphoma SUP T1 cells. Our results highlight the utility of mRNA-display derived cyclic peptides for targeting challenging epigenetic reader proteins to probe their biology, and the broader potential of this approach for targeting protein-protein interactions.

The chromatin reader protein ING5 is required for normal hematopoietic cell numbers in the fetal liver

ING5 is a component of KAT6A and KAT7 histone lysine acetylation protein complexes. ING5 contains a PHD domain that binds to histone H3 lysine 4 when it is trimethylated, and so functions as a 'reader' and adaptor protein. KAT6A and KAT7 function are critical for normal hematopoiesis. To examine the function of ING5 in hematopoiesis, we generated a null allele of Ing5. Mice lacking ING5 during development had decreased foetal liver cellularity, decreased numbers of hematopoietic stem cells and perturbed erythropoiesis compared to wild-type control mice. Ing5^-/- pups had hypoplastic spleens. Competitive transplantation experiments using foetal liver hematopoietic cells showed that there was no defect in long-term repopulating capacity of stem cells lacking ING5, suggesting that the defects during the foetal stage were not cell intrinsic. Together, these results suggest that ING5 function is dispensable for normal hematopoiesis but may be required for timely foetal hematopoiesis in a cell-extrinsic manner.

In silico analysis prediction of HepTH1-5 as a potential therapeutic agent by targeting tumour suppressor protein networks

Many studies reported that the activation of tumour suppressor protein, p53 induced the human hepcidin expression. However, its expression decreased when p53 was silenced in human hepatoma cells. Contrary to Tilapia hepcidin TH1-5, HepTH1-5 was previously reported to trigger the p53 activation through the molecular docking approach. The INhibitor of Growth (ING) family members are also shown to directly interact with p53 and promote cell cycle arrest, senescence, apoptosis and participate in DNA replication and DNA damage responses to suppress the tumour initiation and progression. However, the interrelation between INGs and HepTH1-5 remains unknown. Therefore, this study aims to identify the mechanism and their protein interactions using in silico approaches. The finding revealed that HepTH1-5 and its ligands had interacted mostly on hotspot residues of ING proteins which involved in histone modifications via acetylation, phosphorylation, and methylation. This proves that HepTH1-5 might implicate in an apoptosis signalling pathway and preserve the protein structure and function of INGs by reducing the perturbation of histone binding upon oxidative stress response. This study would provide theoretical guidance for the design and experimental studies to decipher the role of HepTH1-5 as a potential therapeutic agent for cancer therapy. Communicated by Ramaswamy H. Sarma.

Prognostic significance of ING3 expression in patients with cancer: A systematic review and meta-analysis

Background

It has been reported that ING3 inhibits the progression of various cancers. However, some studies have shown that it promotes the development of prostate cancer. The purpose of this study was to investigate whether ING3 expression is associated with the prognosis of patients with cancer.

Materials and methods

PubMed, Cochrane Database, Embase, Medline, ScienceDirect, Scopus and Web of Science were searched until September 2022. The hazard ratio (HR)/odds ratio (OR) and 95% confidence interval (95% CI) were calculated using Stata 17 software. We used the Newcastle-Ottawa Scale (NOS) to assess the risk of bias.

Result

Seven studies involving 2371 patients with five types of cancer were included. The results showed that high expression of ING3 was negatively associated with a more advanced TNM stage (III-IV vs. I-II) (OR=0.61, 95% CI: 0.43-0.86), lymph node metastasis (OR=0.67, 95% CI: 0.49-0.90) and disease-free survival (HR=0.63, 95% CI: 0.37-0.88). However, ING3 expression was not associated with overall survival (HR=0.77, 95% CI: 0.41-1.12), tumor size (OR=0.67, 95% CI: 0.33-1.37), tumor differentiation (OR=0.86, 95% CI: 0.36-2.09) and gender (OR=1.14, 95% CI: 0.78-1.66).

Conclusion

This study showed that the expression of ING3 was associated with better prognosis, suggesting that ING3 may be a potential biomarker for cancer prognosis.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier (CRD42022306354).

Molecular mechanisms of inhibitor of growth (ING) family members in health and malignancy

ING genes belong to family of tumor suppressor genes with regulatory functions on cell proliferation, apoptosis, and cellular senescence. These include a family of proteins with 5 members (ING1-5), which are downregulated in human malignancies and/or affected by pathogenic mutations. ING proteins are highly evolutionarily conserved proteins containing several domains through which bind to chromatin structures by exerting their effects as readers of histone modification marks, and also binding to proteins like p53 involved in biological processes such as cell cycle regulation. Further, they are known as subunits of histone acetylation as well as deacetylation complexes and so exert their regulatory roles through epigenetic mechanisms. Playing role in restriction of proliferative but also invasive potentials of normal cells, INGs are particularly involved in cancer development and progression. However, additional studies and experimental confirmation are required for these models. This paper highlights the potential impact that INGs may have on the development of human cancer and explores what new information has recently arise on the functions of ING genes.

Inhibitor of Growth Factors Regulate Cellular Senescence

Simple Summary

Five members of the Inhibitor of Growth (ING) family share a highly conserved plant homeodomian with affinity to the specific histone modification H3K4me3. Since some ING family members are preferentially associated with histone acetyltransferaseactivity while other members with histone deacetlyse activity, the ING family membres are epigenetic regulators. Interestingly, ING members can regulate the induction cellular senescence in both primray untransformed human cells as well as human cancer cells. We discuss here the up-to-date knowledge about their regulatory activity within the cellular senescent program.

Abstract

The Inhibitor of Growth (ING) proteins are a group of tumor suppressors with five conserved genes. A common motif of ING factors is the conserved plant homeodomain (PHD), with which they bind to chromatin as readers of the histone mark trimethylated histone H3 (H3K4me3). These genes often produce several protein products through alternative splicing events. Interestingly, ING1 and ING2 participate in the establishment of the repressive mSIN3a-HDAC complexes, whereas ING3, ING4, and ING5 are associated with the activating HAT protein complexes. In addition to the modulation of chromatin’s structure, they regulate cell cycle transition, cellular senescence, repair of DNA damage, apoptosis, and angiogenic pathways. They also have fundamental effects on regulating cellular senescence in cancer cells. In the current review, we explain their role in cellular senescence based on the evidence obtained from cell line and animal studies, particularly in the context of cancer.

CG7379 and ING1 suppress cancer cell invasion by maintaining cell-cell junction integrity

Approximately 90% of cancer-related deaths can be attributed to a tumour's ability to spread. We have identified CG7379, the fly orthologue of human ING1, as a potent invasion suppressor. ING1 is a type II tumour suppressor with well-established roles in the transcriptional regulation of genes that control cell proliferation, response to DNA damage, oncogene-induced senescence and apoptosis. Recent work suggests a possible role for ING1 in cancer cell invasion and metastasis, but the molecular mechanism underlying this observation is lacking. Our results show that reduced expression of CG7379 promotes invasion in vivo in Drosophila, reduces the junctional localization of several adherens and septate junction components, and severely disrupts cell-cell junction architecture. Similarly, ING1 knockdown significantly enhances invasion in vitro and disrupts E-cadherin distribution at cell-cell junctions. A transcriptome analysis reveals that loss of ING1 affects the expression of several junctional and cytoskeletal modulators, confirming ING1 as an invasion suppressor and a key regulator of cell-cell junction integrity.

A Novel Splice Variant of the Inhibitor of Growth 3 Lacks the Plant Homeodomain and Regulates Epithelial-Mesenchymal Transition in Prostate Cancer Cells

Inhibitor of growth 3 (ING3) is one of five members of the ING tumour suppressor family, characterized by a highly conserved plant homeodomain (PHD) as a reader of the histone mark H3K4me3. ING3 was reported to act as a tumour suppressor in many different cancer types to regulate apoptosis. On the other hand, ING3 levels positively correlate with poor survival prognosis of prostate cancer (PCa) patients. In PCa cells, ING3 acts rather as an androgen receptor (AR) co-activator and harbours oncogenic properties in PCa. Here, we show the identification of a novel ING3 splice variant in both the human PCa cell line LNCaP and in human PCa patient specimen. The novel ING3 splice variant lacks exon 11, ING3∆ex11, which results in deletion of the PHD, providing a unique opportunity to analyse functionally the PHD of ING3 by a natural splice variant. Functionally, overexpression of ING3Δex11 induced morphological changes of LNCaP-derived 3D spheroids with generation of lumen and pore-like structures within spheroids. Since these structures are an indicator of epithelial-mesenchymal transition (EMT), key regulatory factors and markers for EMT were analysed. The data suggest that in contrast to ING3, ING3Δex11 specifically modulates the expression of key EMT-regulating upstream transcription factors and induces the expression of EMT markers, indicating that the PHD of ING3 inhibits EMT. In line with this, ING3 knockdown also induced the expression of EMT markers, confirming the impact of ING3 on EMT regulation. Further, ING3 knockdown induced cellular senescence via a pathway leading to cell cycle arrest, indicating an oncogenic role for ING3 in PCa. Thus, the data suggest that the ING3Δex11 splice variant lacking functional PHD exhibits oncogenic characteristics through triggering EMT in PCa cells.

Knockdown screening of chromatin binding and regulatory proteins in zebrafish identified Suz12b as a regulator of tfpia and an antithrombotic drug target

Tissue factor pathway inhibitor (TFPI) is an anticoagulant protein that inhibits factor VIIa and Xa in the coagulation cascade. It has been shown that forkhead box P3 protein is a TFPI transcriptional repressor. However, there are no studies on chromatin remodeling that control TFPI expression. We hypothesized that the genome-wide knockdowns of the chromatin binding and regulatory proteins (CBRPs) in zebrafish could identify novel tfpia gene regulators. As an initial step, we selected 69 CBRP genes from the list of zebrafish thrombocyte-expressed genes. We then performed a 3-gene piggyback knockdown screen of these 69 genes, followed by quantification of tfpia mRNA levels. The results revealed that knockdown of brd7, ing2, ing3, ing4, and suz12b increased tfpia mRNA levels. The simultaneous knockdown of these 5 genes also increased tfpia mRNA levels. We also performed individual gene and simultaneous 5-gene knockdowns on the 5 genes in zebrafish larvae. We found that after laser injury, it took a longer time for the formation of the thrombus to occlude the caudal vessel compared to the control larvae. We then treated the larvae and adults with a chemical UNC6852 known to proteolytically degrade polycomb repressor complex 2, where SUZ12 is a member, and observed prolongation of time to occlude (TTO) the caudal vein after laser injury and increased tfpia mRNA levels in larvae and adults, respectively. In summary, our results have identified novel epigenetic regulators for tfpia and exploited this information to discover a drug that enhances tfpia mRNA levels and prolongation of TTO. This discovery provides the basis for testing whether UNC6852 could be used as an antithrombotic drug. This approach could be used to study the regulation of other plasma proteins, including coagulant and anticoagulant factors.

Roles of the tumor suppressor inhibitor of growth family member 4 (ING4) in cancer

Inhibitor of growth family member 4 (ING4) is best known as a tumor suppressor that is frequently downregulated, deleted, or mutated in many cancers. ING4 regulates a broad array of tumor-related processes including proliferation, apoptosis, migration, autophagy, invasion, angiogenesis, DNA repair and chromatin remodeling. ING4 alters local chromatin structure by functioning as an epigenetic reader of H3K4 trimethylation histone marks (H3K4Me3) and regulating gene transcription through directing histone acetyltransferase (HAT) and histone deacetylase (HDAC) protein complexes. ING4 may serve as a useful prognostic biomarker for many cancer types and help guide treatment decisions. This review provides an overview of ING4's central functions in gene expression and summarizes current literature on the role of ING4 in cancer and its possible use in therapy.

SCFJFK is functionally linked to obesity and metabolic syndrome

Dysregulation of lipid metabolism could lead to the development of metabolic disorders. We report here that the F-box protein JFK promotes excessive lipid accumulation in adipose tissue and contributes to the development of metabolic syndrome. JFK transgenic mice develop spontaneous obesity, accompanied by dyslipidemia, hyperglycemia, and insulin resistance, phenotypes that are further exacerbated under high-fat diets. In contrast, Jfk knockout mice are lean and resistant to diet-induced metabolic malfunctions. Liver-specific reconstitution of JFK expression in Jfk knockout mice leads to hepatic lipid accumulation resembling human hepatic steatosis and nonalcoholic fatty liver disease. We show that JFK interacts with and destabilizes ING5 through assembly of the SCF complex. Integrative transcriptomic and genomic analysis reveals that the SCF^JFK -ING5 axis interferes with AMPK activity and fatty acid β-oxidation, leading to the suppression of hepatic lipid catabolism. Significantly, JFK is upregulated and AMPKα1 is down-regulated in liver tissues from NAFLD patients. These results reveal that SCF^JFK is a bona fide E3 ligase for ING5 and link the SCF^JFK -ING5 axis to the development of obesity and metabolic syndrome.

Lentiviral vector with a radiation-inducible promoter, carrying the ING4 gene, mediates radiosensitization controlled by radiotherapy in cervical cancer cells

The presence of hypoxia in solid tumors is considered one of the major factors that contribute to radiation resistance. The aim of the present study was to establish a therapeutic system, which can be controlled by radiation itself, to enhance radiosensitivity. For this purpose, a lentiviral gene therapy vector containing the human inhibitor of growth 4 (ING4) and its upstream promoter, human early growth response factor-1 (EGR1), which possesses the radiation-inducible characteristics to activate the transcription of its downstream genes, was constructed. Downstream fluorescence proteins were investigated to ensure that the EGR1 promoter was induced by irradiation. Furthermore, ING4 open reading frame (ORF) expression was detected by western blotting. The cell cycle was analyzed by fluorescence-activated cell sorting analysis 48 h after the cells were exposed to X-rays ranging between 0 and 8 Gy. In cells stably and transiently transfected with reporter plasmids, the EGR1-driver gene was sensitive to ionizing irradiation. Furthermore, irradiation-induced ING4 gene expression was observed. The enhanced ING4 expression increased the number of cells in the G₂/M phase and decreased the proportion of cells in the G₁/S phase. Therefore, ING4 expression inhibited cell proliferation and was associated with less colonies being formed. Furthermore, ING4 suppressed hypoxia-inducible factor 1α expression under hypoxic conditions and promoted cell apoptosis. Overall, these results revealed that combining the EGR1 promoter and ING4 ORF using a lentivirus system may be a promising therapeutic strategy with which to enhance radiosensitivity controlled by radiation. However, further studies using in vivo models are required to confirm these findings.

Downregulation of nuclear ING3 expression and translocalization to cytoplasm promotes tumorigenesis and progression in head and neck squamous cell carcinoma (HNSCC)

ING3 (inhibitor of growth gene 3) is a member of the ING gene family, and is considered as a candidate tumor suppressor gene. In order to explore the roles of ING3 in tumorigenesis and cancer progression of head and neck squamous cell carcinoma (HNSCC), ING3 expression was assessed in 173 cases of HNSCC by immunohistochemistry. The expression of ING3 was also compared to clinicopathological variables, and the expression of several tumorigenic markers. Nuclear expression of ING3 in HNSCC was significantly lower than that in dysplasia and normal epithelium, and was negatively correlated with a poor-differentiated status, T staging and TNM staging. In contrast, cytoplasmic expression of ING3 was significantly increased in HNSCC, and was statistically associated with lymph node metastasis and 14-3-3η expression. In addition, nuclear expression of ING3 was positively correlated with the expression of p300, p21 and acetylated p53. In conclusion, decreases in nuclear ING3 may play important roles in tumorigenesis, progression and tumor differentiation in HNSCC. Increases in cytoplasmic ING3 may be due to 14-3-3η binding and may also be involved in malignant progression. Nuclear ING3 may modulate the transactivation of target genes, promoting apoptosis through interactions with p300 and p21. Moreover, ING3 may interact with p300 to upregulate the level of acetylation of p53, and promote p53-mediated cell cycle arrest, senescence and/or apoptosis. Therefore, ING3 may be a potential tumor suppressor and a possible therapeutic target in HNSCC.

Loss of Ing3 Expression Results in Growth Retardation and Embryonic Death

The ING3 candidate tumour suppressor belongs to a family of histone modifying proteins involved in regulating cell proliferation, senescence, apoptosis, chromatin remodeling, and DNA repair. It is a stoichiometric member of the minimal NuA4 histone acetyl transferase (HAT) complex consisting of EAF6, EPC1, ING3, and TIP60. This complex is responsible for the transcription of an essential cascade of genes involved in embryonic development and in tumour suppression. ING3 has been linked to head and neck and hepatocellular cancers, although its status as a tumour suppressor has not been well established. Recent studies suggest a pro-metastasis role in prostate cancer progression. Here, we describe a transgenic mouse strain with insertional mutation of an UbC-mCherry expression cassette into the endogenous Ing3 locus, resulting in the disruption of ING3 protein expression. Homozygous mutants are embryonically lethal, display growth retardation, and severe developmental disorders. At embryonic day (E) 10.5, the last time point viable homozygous embryos were found, they were approximately half the size of heterozygous mice that develop normally. µCT analysis revealed a developmental defect in neural tube closure, resulting in the failure of formation of closed primary brain vesicles in homozygous mid-gestation embryos. This is consistent with high ING3 expression levels in the embryonic brains of heterozygous and wild type mice and its lack in homozygous mutant embryos that show a lack of ectodermal differentiation. Our data provide direct evidence that ING3 is an essential factor for normal embryonic development and that it plays a fundamental role in prenatal brain formation.

Inhibitor of Growth 4 (ING4) is a positive regulator of rRNA synthesis

Ribosome biogenesis is essential for maintaining basic cellular activities although its mechanism is not fully understood. Inhibitor of growth 4 (ING4) is a member of ING family while its cellular functions remain controversial. Here, we identified several nucleolar proteins as novel ING4 interacting proteins. ING4 localized in the nucleus with strong accumulation in the nucleolus through its plant homeodomain, which is known to interact with histone trimethylated H3K4, commonly present in the promoter of active genes. ING4 deficient cells exhibited slower proliferation and the alteration in nucleolar structure with reduced rRNA transcription, which was rescued by exogenous expression of GFP-ING4 to the similar levels of wild type cells. In the ING4 deficient cells, histone H3K9 acetylation and the key rRNA transcription factor UBF at the promoter of rDNA were reduced, both of which were also recovered by exogenous GFP-ING4 expression. Thus, ING4 could positively regulate rRNA transcription through modulation of histone modifications at the rDNA promoter.

Epigenetic Regulation of p21cip1/waf1 in Human Cancer

p21^cip1/waf1 is a central regulator of cell cycle control and survival. While mutations are rare, it is commonly dysregulated in several human cancers due to epigenetic mechanisms influencing its transcriptional control. These mechanisms include promoter hypermethylation as well as additional pathways such as histone acetylation or methylation. The epigenetic regulators include writers, such as DNA methyltransferases (DNMTs); histone acetyltransferases (HATs) and histone lysine methyltransferases; erasers, such as histone deacetylases (HDACs); histone lysine demethylases [e.g., the Lysine Demethylase (KDM) family]; DNA hydroxylases; readers, such as the methyl-CpG-binding proteins (MBPs); and bromodomain-containing proteins, including the bromo- and extraterminal domain (BET) family. We further discuss the roles that long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) play in the epigenetic control of p21^cip1/waf1 expression and its function in human cancers.

Non-viral nucleic acid delivery to the central nervous system and brain tumors

Gene therapy is a rapidly emerging remedial route for many serious incurable diseases, such as central nervous system (CNS) diseases. Currently, nucleic acid medicines, including DNAs encoding therapeutic or destructive proteins, small interfering RNAs or microRNAs, have been successfully delivered to the CNS with gene delivery vectors using various routes of administration and have subsequently exhibited remarkable therapeutic efficiency. Among these vectors, non-viral vectors are favorable for delivering genes into the CNS as a result of their many special characteristics, such as low toxicity and pre-existing immunogenicity, high gene loading efficiency and easy surface modification. In this review, we highlight the main types of therapeutic genes that have been applied in the therapy of CNS diseases and then outline non-viral gene delivery vectors.

Proteomic analysis of the OGT interactome: novel links to epithelial-mesenchymal transition and metastasis of cervical cancer

The role of O-GlcNAc transferase (OGT) in gene regulation and tumor invasion is poorly understood. Here, we have identified several previously undiscovered OGT-interacting proteins, including the PRMT5/WDR77 complex, the PRC2 complex, the ten-eleven translocation (TET) family, the CRL4B complex and the nucleosome remodeling and deacetylase (NuRD) complex. Genome-wide analysis of target genes responsive to OGT resulted in identification of a cohort of genes including SNAI1 and ING4 that are critically involved in cell epithelial–mesenchymal transition and invasion/metastasis. We have demonstrated that OGT promotes carcinogenesis and metastasis of cervical cancer cells. OGT’s expression is significantly upregulated in cervical cancer, and low OGT level is correlated with improved prognosis. Our study has thus revealed a mechanistic link between OGT and tumor progression, providing potential prognostic indicators and targets for cancer therapy.

Overexpression of miR-101-2 in donor cells improves the early development of Holstein cow somatic cell nuclear transfer embryos

Accumulating studies have suggested that microRNA play a part in regulating multiple cellular processes, such as cell proliferation, apoptosis, the cell cycle, and embryo development. This study explored the effects of miR-101-2 on donor cell physiological status and the development of Holstein cow somatic cell nuclear transfer (SCNT) embryos in vitro. Holstein cow bovine fetal fibroblasts (BFF) overexpressing miR-101-2 were used as donor cells to perform SCNT; then, cleavage rate, blastocyst rate, inner cell mass-to-trophectoderm ratio, and the expression of some development- and apoptosis-related genes in different groups were analyzed. The miR-101-2 suppressed the expression of inhibitor of growth protein 3 (ING3) at mRNA and protein levels, expedited cell proliferation, and decreased apoptosis in BFF, suggesting that ING3, a target gene of miR-101-2, is a potential player in this process. Moreover, by utilizing donor cells overexpressing miR-101-2, the development of bovine SCNT embryos in vitro was significantly enhanced; the apoptotic rate in SCNT blastocysts was reduced, and the inner cell mass-to-trophectoderm ratio and SOX2, POU5F1, and BCL2L1 expression significantly increased, whereas BAX and ING3 expression decreased. Collectively, these findings suggest that miR-101-2 promotes BFF proliferation and vitality, reduces their apoptosis, and improves the early development of SCNT embryos.

Regulat-INGs in tumors and diseases: Focus on ncRNAs

ING family genes (Inhibitor of Growth) are tumor suppressor genes that play a vital role in cell homeostasis. It has been shown that their expression is lost or diminished in many cancers and other diseases. The main mechanisms by which they are regulated in oncogenesis have not yet been fully elucidated. The involvement of non-coding RNAs (ncRNAs) and in particular microRNAs (miRNAs) in post-transcriptional gene regulation is well established. miRNAs are short sequences (18-25 nucleotides) that can bind to the 3 'UTR sequence of the targeted messenger RNA (mRNA), leading to its degradation or translational repression. Interactions between the ING family and miRNAs have been described in some cancers but also in other diseases. The involvement of miRNAs in ING family regulation opens up new fields of investigation, particularly for targeted therapies. In this review, we will summarize the regulatory mechanisms at the RNA and protein level of the ING family and focus on the interactions with ncRNAs.

The Diverse Roles of microRNAs at the Host⁻Virus Interface

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression at the post-transcriptional level. Through this activity, they are implicated in almost every cellular process investigated to date. Hence, it is not surprising that miRNAs play diverse roles in regulation of viral infections and antiviral responses. Diverse families of DNA and RNA viruses have been shown to take advantage of cellular miRNAs or produce virally encoded miRNAs that alter host or viral gene expression. MiRNA-mediated changes in gene expression have been demonstrated to modulate viral replication, antiviral immune responses, viral latency, and pathogenesis. Interestingly, viruses mediate both canonical and non-canonical interactions with miRNAs to downregulate specific targets or to promote viral genome stability, translation, and/or RNA accumulation. In this review, we focus on recent findings elucidating several key mechanisms employed by diverse virus families, with a focus on miRNAs at the host–virus interface during herpesvirus, polyomavirus, retroviruses, pestivirus, and hepacivirus infections.

Up-regulated MiR-27-3p promotes the G1-S phase transition by targeting inhibitor of growth family member 5 in osteosarcoma

OBJECTIVE

MicroRNAs (miRNAs) play an essential role in regulating malignant progression of tumour cells by inhibiting translation or stability of messenger RNA. However, the expression pattern and regulatory mechanism of miR-27-3p in osteosarcoma remains unclear.

METHODS

We examined the expression of miR-27-3p in 5 osteosarcoma cell lines compared with that in 2 normal osteocyte cell lines. Osteosarcoma cells U-2OS and MG-63 were transduced to up-regulate or down-regulate the expression of miR-27-3p. The 3-(4, 5-Dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide, or MTT, assay, colony formation assays, BrdUrd labelling, immunofluorescence, anchorage-independent growth ability assay and flow cytometry analysis were used to test the effect of miR-27-3p. Luciferase assays were added to verify the direct relationship between miR-27-3p and the predicted target gene inhibitor of growth family member 5 (ING5).

RESULTS

The expression of miR-27-3p was significantly increased in examined osteosarcoma cell lines compared with that in normal osteocyte cell lines. Up-regulation of miR-27-3p significantly accelerated osteosarcoma cell growth via promoting G1-S transition. In addition, the opposite result was observed in miR-27-3p-down-regulated cells. Up-regulation of ING5 significantly attenuated the miR-27-3p-induced proliferation in osteosarcoma cells.

CONCLUSIONS

These data suggested that miR-27-3p could promote the G1-S phase transition that leads to proliferation by down-regulating the expression of ING5 in osteosarcoma.

Environmental history impacts gene expression during diapause development in the alfalfa leafcutting bee, Megachile rotundata

Our understanding of the mechanisms controlling insect diapause has increased dramatically with the introduction of global gene expression techniques, such as RNA-seq. However, little attention has been given to how ecologically relevant field conditions may affect gene expression during diapause development because previous studies have focused on laboratory reared and maintained insects. To determine whether gene expression differs between laboratory and field conditions, prepupae of the alfalfa leafcutting bee, Megachile rotundata, entering diapause early or late in the growing season were collected. These two groups were further subdivided in early autumn into laboratory and field maintained groups, resulting in four experimental treatments of diapausing prepupae: early and late field, and early and late laboratory. RNA-seq and differential expression analyses were performed on bees from the four treatment groups in November, January, March and May. The number of treatment-specific differentially expressed genes (97 to 1249) outnumbered the number of differentially regulated genes common to all four treatments (14 to 229), indicating that exposure to laboratory or field conditions had a major impact on gene expression during diapause development. Principle component analysis and hierarchical cluster analysis yielded similar grouping of treatments, confirming that the treatments form distinct clusters. Our results support the conclusion that gene expression during the course of diapause development is not a simple ordered sequence, but rather a highly plastic response determined primarily by the environmental history of the individual insect.

Role of inhibitor of growth 4 in the suppression of human melanoma cells through the Fas/FasL-mediated apoptosis pathway

Melanoma, the most aggressive form of skin cancer, is notoriously resistant to all current available therapies. Inhibitor of growth 4 (ING4), a novel member of the ING family of proteins, has previously been shown to play a critical role in the development of multiple tumors by regulating apoptosis, proliferation, cell cycle progress, migration and invasion. However, the functional role of ING4 in human melanoma remains unclear. To fully understand its potential role in human melanoma, in the present study, lentivirus (LV)‑ING4 and LV‑ING4‑short hairpin RNA were constructed and transfected into human melanoma A375 cells. First, the effect of overexpressing or downregulating ING4 on the apoptosis of the transfected melanoma cells and cluster of differentiation (CD)3+ T cells was investigated. In the present study, we found that the late apoptotic cells, and not the early apoptotic cells, were more in LV-ING4 group compared with LV-control, and both the early and late apoptosis of CD3+ T cells was significantly observed in A375 cells transfected with LV-ING4 compared with LV-control. Importantly, it was determined whether the overexpression of ING4 significantly induce apoptotic cell death via Fas/FasL (Fas death receptor/FasL) pathway activation and downregulation of poly(ADP‑ribose) polymerase, caspase‑3 and caspase‑8 in the melanoma cells and CD3+ T cells. These results demonstrated that overexpression of ING4 can induce the apoptosis of melanoma cells and CD3+ T cells through signaling pathways such as the Fas/FasL pathway, and that ING4 gene therapy for melanoma treatment is a novel approach.

The PHD-containing protein EARLY BOLTING IN SHORT DAYS regulates seed dormancy in Arabidopsis

The Arabidopsis protein EARLY BOLTING IN SHORT DAYS (EBS), a plant-specific transcriptional regulator, is involved in the control of flowering time by repressing the floral integrator FT. The EBS protein binds the H3K4me3 histone mark and interacts with histone deacetylases to modulate gene expression. Here, we show that EBS also participates in the regulation of seed dormancy. ebs mutations cause a reduction in seed dormancy, and the concurrent loss of function of the EBS homologue SHORT LIFE (SHL) enhances this dormancy alteration. Transcriptomic analyses in ebs mutant seeds uncovered the misregulation of several regulators of seed dormancy including the MADS box gene AGAMOUS-LIKE67 (AGL67). AGL67 interacts genetically with EBS in seed dormancy regulation, indicating that both loci act in the same pathway. Interestingly, EBS functions independently of the master regulator gene of dormancy DELAY OF GERMINATION 1 (DOG1) and other genes encoding chromatin remodelling factors involved in the control of seed dormancy. Altogether, these data show that EBS is a central repressor of germination during seed dormancy and that SHL acts redundantly with EBS in the control of this developmental process. Our observations suggest that a tightly regulated crosstalk among histone modifications is necessary for a proper control of seed dormancy.

ING5 suppresses breast cancer progression and is regulated by miR-24

Background

The inhibitor of growth (ING) gene family of tumor suppressors is involved in multiple cellular functions such as cell cycle regulation, apoptosis, and chromatin remodeling. ING5 is a new member of the ING family whose function and regulation remain largely unknown.

Methods

Quantitative real-time PCR and western blot were used to examine the expression levels of ING5 in breast cancer tissues. The miRNAs that potentially targeted ING5 were determined by bioinformatics analysis and luciferase reporter assay. Cell viability assay, transwell invasion and apoptosis assay were used to characterize the changes induced by overexpressing or knocking down miR-24 or ING5. Hematoxylin and eosin (H&E) staining and immunohistochemical staining for ING5 and Ki-67 were used for xenograft assays in BALB/c nude mice.

Results

We showed that the ING5 protein rather than the mRNA, was significantly downregulated in breast cancer tissues. We also investigated the potential function of ING5 in breast tumorigenesis and found that ING5 suppressed the proliferation and invasion of breast cancer cells and promoted their apoptosis. Furthermore, we explored the molecular mechanisms accounting for the dysregulation of ING5 in breast cancer cells and identified an oncomiR, miR-24, as a direct upstream regulator of ING5. We revealed that miR-24 had the opposite effects to those of ING5 on breast cancer cells and could accelerate xenografted tumor growth in vivo.

Conclusion

Our findings uncover the tumor-suppressive role of ING5 and the regulatory pathway of ING5 in breast cancer and may provide insights into the molecular mechanisms of breast carcinogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0658-z) contains supplementary material, which is available to authorized users.

Roles of microRNA-330 and Its Target Gene ING4 in the Development of Aggressive Phenotype in Hepatocellular Carcinoma Cells

BACKGROUND

Aberrant expression of microRNAs contributes to tumor growth and progression.

AIMS

This study was designed to explore the prognostic and biological significance of miR-330 in hepatocellular carcinoma (HCC).

METHODS

The expression of miR-330 and its associations with tumor parameters and overall survival were analyzed in HCC patients. The biological functions of miR-330 in HCC cell growth, invasion, and tumorigenesis were investigated. Bioinformatic analysis and luciferase reporter assays were performed to search for potential targets of miR-330.

RESULTS

The miR-330 level was significantly higher in HCCs than in adjacent normal tissues (P = 0.0085). High expression of miR-330 was significantly associated with more aggressive phenotypes and shorter overall survival in HCC. Loss- and gain-of-function studies indicated the favorable effect of miR-330 on tumor cell growth, invasion, and tumorigenesis. Inhibitor of growth 4 (ING4) was identified to be a direct target of miR-330. Overexpression of miR-330 reduced the expression of ING4 in HCC cells. Importantly, restoration of ING4 almost completely reversed the promotion of HCC cell proliferation and invasion by miR-330.

CONCLUSIONS

Altogether, this study demonstrates that upregulation of miR-330 is associated with poor prognosis and contributes to more aggressive phenotypes of HCC. The oncogenic role of miR-330 in HCC is linked to downregulation of ING4.

Miz1, a Novel Target of ING4, Can Drive Prostate Luminal Epithelial Cell Differentiation

BACKGROUND

How prostate epithelial cells differentiate and how dysregulation of this process contributes to prostate tumorigenesis remain unclear. We recently identified a Myc target and chromatin reader protein, ING4, as a necessary component of human prostate luminal epithelial cell differentiation, which is often lost in primary prostate tumors. Furthermore, loss of ING4 in the context of oncogenic mutations is required for prostate tumorigenesis. Identifying the gene targets of ING4 can provide insight into how its loss disrupts differentiation and leads to prostate cancer.

METHODS

Using a combination of RNA-Seq, a best candidate approach, and chromatin immunoprecipitation (ChIP), we identified Miz1 as a new ING4 target. ING4 or Miz1 overexpression, shRNA knock-down, and a Myc-binding mutant were used in a human in vitro differentiation assay to assess the role of Miz1 in luminal cell differentiation.

RESULTS

ING4 directly binds the Miz1 promoter and is required to induce Miz1 mRNA and protein expression during luminal cell differentiation. Miz1 mRNA was not induced in shING4 expressing cells or tumorigenic cells in which ING4 is not expressed. Miz1 dependency on ING4 was unique to differentiating luminal cells; Miz1 mRNA expression was not induced in basal cells. Although Miz1 is a direct target of ING4, and its overexpression can drive luminal cell differentiation, Miz1 was not required for differentiation.

CONCLUSIONS

Miz1 is a newly identified ING4-induced target gene which can drive prostate luminal epithelial cell differentiation although it is not absolutely required. Prostate 77:49-59, 2017. © 2016 Wiley Periodicals, Inc.

miR-423-5p contributes to a malignant phenotype and temozolomide chemoresistance in glioblastomas

BACKGROUND

Gliomas are based on a genetic abnormality and present with a dismal prognosis. MicroRNAs (miRNAs) are considered to be important mediators of gene expression in glioma tissues.

METHODS

Real-time PCR was used to analyze the expression of microRNA-423-5p (miR-423-5p) in human glioma samples and normal brain tissue. Apoptosis, cell cycle, proliferation, immunostaining, transwell, in vitro 2D and 3D migration, and chemosensitivity assays were performed to assess the phenotypic changes in glioma cells overexpressing miRNA-423-5p. Western blotting was used to determine the expression of inhibitor of growth 4 (ING-4)in glioma tissues, and a luciferase reporter assay was conducted to confirm whether ING-4 is a direct target of miR-423-5p. Western blotting was used to identify the potential signaling pathways that are affected in glioma cell growth by miR-423-5p. Xenograft tumors were examined in vivo for the carcinogenic effects of miR-423-5p in glioma tissues.

RESULTS

We first reported that miR-423-5p expression was increased in gliomas and was a potential tumor promoter via targeting ING-4. The overexpression of miR-423-5p resulted in upregulation of important signaling molecules such as p-AKT and p-ERK1/2. In clinical samples, miR-423-5p was dysregulated, and a corresponding alteration in ING-4 expression was observed (P = .0207). Furthermore, the overexpression of miR-423-5p strengthened glioma cell proliferation, angiogenesis, and invasion. Finally, miR-423-5p overexpression also strengthened GBM neurosphere formation and rendered glioma cells resistant to temozolomide (TMZ).

CONCLUSION

This study establishes that miR-423-5p functions as an oncogene in glioma tissues by suppressing ING-4 and suggests that it has therapeutic potential for glioma.

Targeting Hsp70: A possible therapy for cancer

In all organisms, heat-shock proteins (HSPs) provide an ancient defense system. These proteins act as molecular chaperones by assisting proper folding and refolding of misfolded proteins and aid in the elimination of old and damaged cells. HSPs include Hsp100, Hsp90, Hsp70, Hsp40, and small HSPs. Through its substrate-binding domains, Hsp70 interacts with wide spectrum of molecules, ranging from unfolded to natively folded and aggregated proteins, and provides cytoprotective role against various cellular stresses. Under pathophysiological conditions, the high expression of Hsp70 allows cells to survive with lethal injuries. Increased Hsp70, by interacting at several points on apoptotic signaling pathways, leads to inhibition of apoptosis. Elevated expression of Hsp70 in cancer cells may be responsible for tumorigenesis and for tumor progression by providing resistance to chemotherapy. In contrast, inhibition or knockdown of Hsp70 reduces the size of tumors and can cause their complete regression. Moreover, extracellular Hsp70 acts as an immunogen that participates in cross presentation of MHC-I molecules. The goals of this review are to examine the roles of Hsp70 in cancer and to present strategies targeting Hsp70 in the development of cancer therapeutics.

DNA Methylation and Chromatin Remodeling: The Blueprint of Cancer Epigenetics

Epigenetics deals with the interactions between genes and the immediate cellular environment. These interactions go a long way in shaping up each and every person's individuality. Further, reversibility of epigenetic interactions may offer a dynamic control over the expression of various critical genes. Thus, tweaking the epigenetic machinery may help cause or cure diseases, especially cancer. Therefore, cancer epigenetics, especially at a molecular level, needs to be scrutinised closely, as it could potentially serve as the future pharmaceutical goldmine against neoplastic diseases. However, in view of its rapidly enlarging scope of application, it has become difficult to keep abreast of scientific information coming out of various epigenetic studies directed against cancer. Using this review, we have attempted to shed light on two of the most important mechanisms implicated in cancer, that is, DNA (deoxyribonucleic acid) methylation and histone modifications, and their place in cancer pathogenesis. Further, we have attempted to take stock of the new epigenetic drugs that have emerged onto the market as well as those in the pipeline that offer hope in mankind's fight against cancer.

The miR-193a-3p-regulated ING5 gene activates the DNA damage response pathway and inhibits multi-chemoresistance in bladder cancer

As the major barrier to curative cancer chemotherapy, chemoresistance presents a formidable challenge to both cancer researchers and clinicians. We have previously shown that the bladder cancer (BCa) cell line 5637 is significantly more sensitive to the cytoxicity of five chemotherapeutic agents than H-bc cells. Using an RNA-seq-based omic analysis and validation at both the mRNA and protein levels, we found that the inhibitor of growth 5 (ING5) gene was upregulated in 5637 cells compared with H-bc cells, indicating that it has an inhibitory role in BCa chemoresistance. siRNA-mediated inhibition of ING5 increased the chemoresistance and inhibited the DNA damage response pathway in 5637 cells. Conversely, forced expression of EGFP-ING5 decreased the chemoresistance of and activated the DNA damage response pathway in H-bc cells. We also showed that ING5 gene expression is inhibited by miR-193a-3p and is instrumental in miR-193a-3p's role in activating BCa chemoresistance. Our results demonstrate both the role and mechanism of inhibition of BCa chemoresistance by ING5.

SCF(JFK) is a bona fide E3 ligase for ING4 and a potent promoter of the angiogenesis and metastasis of breast cancer

The tumor suppressor ING4 (inhibitor of growth protein 4) is involved in various cellular processes by virtue of its epigenetic regulatory capability and through its positive regulation of p53 and negative regulation of NFκB. Yan et al. find that the F-box protein JFK targets ING4 for ubiquitination and degradation through assembly of an Skp1-Cul1-F-box (SCF) complex. JFK-mediated ING4 destabilization leads to the hyperactivation of the canonical NFκB pathway and promotes angiogenesis and metastasis of breast cancer.

Loss of function/dysregulation of inhibitor of growth 4 (ING4) and hyperactivation of NF-κB are frequent events in many types of human malignancies. However, the molecular mechanisms underlying these remarkable aberrations are not understood. Here, we report that ING4 is physically associated with JFK. We demonstrated that JFK targets ING4 for ubiquitination and degradation through assembly of an Skp1–Cul1–F-box (SCF) complex. We showed that JFK-mediated ING4 destabilization leads to the hyperactivation of the canonical NF-κB pathway and promotes angiogenesis and metastasis of breast cancer. Significantly, the expression of JFK is markedly up-regulated in breast cancer, and the level of JFK is negatively correlated with that of ING4 and positively correlated with an aggressive clinical behavior of breast carcinomas. Our study identified SCF^JFK as a bona fide E3 ligase for ING4 and unraveled the JFK–ING4–NF-κB axis as an important player in the development and progression of breast cancer, supporting the pursuit of JFK as a potential target for breast cancer intervention.

ING5 is phosphorylated by CDK2 and controls cell proliferation independently of p53

Inhibitor of growth (ING) proteins have multiple functions in the control of cell proliferation, mainly by regulating processes associated with chromatin regulation and gene expression. ING5 has been described to regulate aspects of gene transcription and replication. Moreover deregulation of ING5 is observed in different tumors, potentially functioning as a tumor suppressor. Gene transcription in late G1 and in S phase and replication is regulated by cyclin-dependent kinase 2 (CDK2) in complex with cyclin E or cyclin A. CDK2 complexes phosphorylate and regulate several substrate proteins relevant for overcoming the restriction point and promoting S phase. We have identified ING5 as a novel CDK2 substrate. ING5 is phosphorylated at a single site, threonine 152, by cyclin E/CDK2 and cyclin A/CDK2 in vitro. This site is also phosphorylated in cells in a cell cycle dependent manner, consistent with it being a CDK2 substrate. Furthermore overexpression of cyclin E/CDK2 stimulates while the CDK2 inhibitor p27^KIP1 represses phosphorylation at threonine 152. This site is located in a bipartite nuclear localization sequence but its phosphorylation was not sufficient to deregulate the subcellular localization of ING5. Although ING5 interacts with the tumor suppressor p53, we could not establish p53-dependent regulation of cell proliferation by ING5 and by phospho-site mutants. Instead we observed that the knockdown of ING5 resulted in a strong reduction of proliferation in different tumor cell lines, irrespective of the p53 status. This inhibition of proliferation was at least in part due to the induction of apoptosis. In summary we identified a phosphorylation site at threonine 152 of ING5 that is cell cycle regulated and we observed that ING5 is necessary for tumor cell proliferation, without any apparent dependency on the tumor suppressor p53.

A novel tumor suppressor gene in basal cell carcinoma: inhibition of growth factor-2

In loss of heterozygosity (LOH) studies at the chromosome 4q22-35 region, it was shown that the amount of deletion was high in basal cell carcinoma (BCC). It has been proposed that genes located in this chromosomal region could be tumor suppressor genes in BCC. It has been thought that deletions in the ING2 gene located in the same region can play a role in the pathophysiology of BCC and that deletions occurring in this region may influence the level of ING2 expression in BCC. Tumoral and non-tumoral tissues from 75 patients with BCC (45 men and 30 women) were included to the study. Lesions were excised by a surgical margin of 0.5 cm. After excision, RNA was isolated from tumoral and non-tumoral tissue samples. ING2 messenger RNA (mRNA) expression level was determined in tumoral and non-tumoral tissues by the real-time polymerase chain reaction (RT-PCR). It was detected that ING2 mRNA expression level decreased in tumoral tissues when compared to non-tumoral tissues from BCC patients (p = 0.0001). It was found that expression levels of this gene were comparable among patients with primary, recurrent, or multiple BCC. It is thought that ING2 gene expression level could contribute to the development of BCC but not be associated with the stage and the prognosis of the tumor.

Defining the minimal peptide sequence of the ING1b tumour suppressor capable of efficiently inducing apoptosis

The ING1b protein is a type-II tumour suppressor and stoichiometric member of the Sin3 histone deacetylase (HDAC) protein complex in which it acts to target HDAC activity to regulate chromatin structure. Altering ING1 levels by ectopic expression of ING1b in cancer cells promotes apoptosis, whereas altering levels by knockout in normal murine fibroblasts alters sensitivity to doxorubicin-induced apoptosis. We have identified a minimal region of ING1b capable of inducing levels of apoptosis in targeted cells as effectively as full-length ING1b, using transient overexpression of ING1b fragments followed by the Annexin V assay. We observed high levels of apoptosis in 14 of 14 cancer cell lines tested. Infecting triple-negative tumorigenic MDA-MB-468 breast cancer, U2OS or Saos-2 cells at multiplicities of infection (MOIs) ranging from 10 to 20 rapidly triggered apoptosis in ~80% of infected cells within 48 h. This was not due to the effects of virus, as infection at the same MOI with a control adenovirus expressing GFP was not effective in inducing apoptosis. When used at low MOIs, the ING1b fragment showed a cell-killing efficacy that was higher than native, full-length ING1b. Using a doxycycline-regulated inducible p53 expression system demonstrated that apoptosis induced by the ING1b fragment was p53 independent. Given the growing importance of combination therapies, we evaluated whether there was synergism between the ING1b fragment and HDAC inhibitors. Combination treatments with TSA, LBH 589 and SAHA reduced cancer cell survival by 3.9–4.7-fold as compared with single-drug treatment, and resulted in ~90% reduction in cell survival. Normalized isobologram analysis confirmed strong synergism between the ING1b fragment and drugs tested. These findings provide support for using ING1b-derived therapeutics as adjuvant treatments in combination with existing epigenetic therapies.

Delivery of inhibitor of growth 4 (ING4) gene significantly inhibits proliferation and invasion and promotes apoptosis of human osteosarcoma cells

Growing evidence has suggested that inhibitor of growth 4 (ING4), a novel member of ING family proteins, plays a critical role in the development and progression of different tumors via multiple pathways. However, the function of ING4 in human osteosarcoma remains unclear. To understand its potential roles and mechanisms in inhibiting osteosarcoma, we constructed an expression vector pEGFP-ING4 and transfected the human osteosarcoma cells using this vector. We then studied the effects of over-expressed ING4 in the transfected cells on the proliferation, apoptosis and invasion of the osteosarcoma cells. The up-regulation of ING4 in the osteosarcoma cells, arising from the stable pEGFP-ING4 gene transfection, was found to significantly inhibit the cell proliferation by the cell cycle alteration with S phase reduction and G0/G1 phase arrest, induce cell apoptosis via the activation of the mitochondria pathway, and suppress cell invasion through the down-regulation of the matrix metalloproteinase 2 (MMP-2) and MMP-9 expression. In addition, increased ING4 level evoked the blockade of NF-κB signaling pathway and down-regulation of its target proteins. Our work suggests that ING4 can suppress osteosarcoma progression through signaling pathways such as mitochondria pathway and NF-κB signaling pathway and ING4 gene therapy is a promising approach to treating osteosarcoma.

Epigenetics: An emerging player in gastric cancer

Cancers, like other diseases, arise from gene mutations and/or altered gene expression, which eventually cause dysregulation of numerous proteins and noncoding RNAs. Changes in gene expression, i.e., upregulation of oncogenes and/or downregulation of tumor suppressor genes, can be generated not only by genetic and environmental factors but also by epigenetic factors, which are inheritable but nongenetic modifications of cellular chromosome components. Identification of the factors that contribute to individual cancers is a prerequisite to a full understanding of cancer mechanisms and the development of customized cancer therapies. The search for genetic and environmental factors has a long history in cancer research, but epigenetic factors only recently began to be associated with cancer formation, progression, and metastasis. Epigenetic alterations of chromatin include DNA methylation and histone modifications, which can affect gene-expression profiles. Recent studies have revealed diverse mechanisms by which chromatin modifiers, including writers, erasers and readers of the aforementioned modifications, contribute to the formation and progression of cancer. Furthermore, functional RNAs, such as microRNAs and long noncoding RNAs, have also been identified as key players in these processes. This review highlights recent findings concerning the epigenetic alterations associated with cancers, especially gastric cancer.

Transient induction of ING4 by Myc drives prostate epithelial cell differentiation and its disruption drives prostate tumorigenesis

The mechanisms by which Myc overexpression or Pten loss promotes prostate cancer development are poorly understood. We identified the chromatin remodeling protein, ING4, as a crucial switch downstream of Myc and Pten that is required for human prostate epithelial differentiation. Myc-induced transient expression of ING4 is required for the differentiation of basal epithelial cells into luminal cells, while sustained ING4 expression induces apoptosis. ING4 expression is lost in >60% of human primary prostate tumors. ING4 or Pten loss prevents epithelial cell differentiation, which was necessary for tumorigenesis. Pten loss prevents differentiation by blocking ING4 expression, which is rescued by ING4 re-expression. Pten or ING4 loss generates tumor cells that co-express basal and luminal markers, indicating prostate oncogenesis occurs through disruption of an intermediate step in the prostate epithelial differentiation program. Thus, we identified a new epithelial cell differentiation switch involving Myc, Pten, and ING4, which when disrupted leads to prostate tumorigenesis. Myc overexpression and Pten loss are common genetic abnormalities in prostate cancer, whereas loss of the tumor suppressor ING4 has not been reported. This is the first demonstration that transient ING4 expression is absolutely required for epithelial differentiation, its expression is dependent on Myc and Pten, and it is lost in the majority of human prostate cancers. This is the first demonstration that loss of ING4, either directly or indirectly through loss of Pten, promotes Myc-driven oncogenesis by deregulating differentiation. The clinical implication is that Pten/ING4 negative and ING4-only negative tumors may reflect two distinct subtypes of prostate cancer.

Downregulated inhibitor of growth 3 (ING3) expression during colorectal carcinogenesis

BACKGROUND & OBJECTIVES

ING3 (inhibitor of growth protein 3) overexpression decreased S-phase cell population and colony-forming efficiency, and induced apoptosis at a p53-mediated manner. The aim of this study was to investigate the clinicopathological and prognostic significance of ING3 expression in colorectal carcinogenesis and subsequent progression.

METHODS

ING3 expression was examined by immunohistochemistry on tissue microarray containing colorectal non-neoplastic mucosa (NNM), adenoma and adenocarcinoma. Colorectal carcinoma tissue and cell lines were studied for ING3 expression by Western blot or RT-PCR.

RESULTS

ING3 mRNA was differentially expressed in Colo201, Colo205, DLD-1, HCT-15, HCT-116, HT-29, KM-12, SW480, SW620 and WiDr cells. Carcinomas showed significantly lower ING3 expression than matched NNM at mRNA level (P< 0.05), but not at protein level. Immunohistochemically, ING3 expression was significantly decreased from NNM, adenoma to adenocarcinoma (P< 0.05). ING3 expression was not correlated with age, sex, tumour size, depth of invasion, lymphatic or venous invasion, lymph node metastasis, tumour- node- metastasis staging or differentiation. Kaplan-Meier analysis indicated that ING3 protein expression was not associated the prognosis of the patients with colorectal carcinoma (P< 0.05).

INTERPRETATION & CONCLUSIONS

Our study showed that downregulated ING3 expression might play an important role in colorectal adenoma-adenocarcinoma sequence. Further studies are required to understand the mechanism.

Truncation of inhibitor of growth family protein 5 effectively induces senescence, but not apoptosis in human tongue squamous cell carcinoma cell line

In these studies, inhibitor of growth protein 5 (ING5) and various fragments of it were overexpressed in the human tongue squamous cell carcinoma cell line, HSC-3. The roles of ING5 in HSC-3 cells were then identified in vitro. Our results indicate that intact ING5 can inhibit proliferation and induce apoptosis in HSC-3 cells. Moreover, two truncated fragments of ING5 (aa 1-184 and aa 107-226) can induce cellular senescence. To analyze the signaling pathway involved, western blotting was performed. In these assays, two truncated fragments of ING5 were found to inhibit the cyclin E and CDK2 expression. These results are consistent with the S phase arrest observed with the overexpression of truncated ING5. However, the mechanisms of ING5-induced cellular senescence remain unclear, and extensive investigations are required in future studies.

Cancer genomics identifies disrupted epigenetic genes

Latest advances in genome technologies have greatly advanced the discovery of epigenetic genes altered in cancer. The initial single candidate gene approaches have been coupled with newly developed epigenomic platforms to hasten the convergence of scientific discoveries and translational applications. Here, we present an overview of the evolution of cancer epigenomics and an updated catalog of disruptions in epigenetic pathways, whose misregulation can culminate in cancer. The creation of these basic mutational catalogs in cell lines and primary tumors will provide us with enough knowledge to move diagnostics and therapy from the laboratory bench to the bedside.

Aberrant expression miR-196a is associated with abnormal apoptosis, invasion, and proliferation of pancreatic cancer cells

OBJECTIVES

MiR-196a levels inversely correlated with survival in pancreatic adenocarcinoma patients. However, the functional contributions of miR-196a to pancreatic cancer remain unclear.

METHODS

Three lentiviral vectors encoding microRNA miR-196a precursor, inhibitor, and scrambled microRNA oligomer were transfected into Panc-1 cells, respectively. Then we explored the regulation of inhibitor of growth 5 (ING5) expression by miR-196a and its impact on apoptosis, invasion, and growth of pancreatic cancer cells. The lentiviral transfected Panc-1 cells were surgically implanted into the pancreas of mice. In vivo tumor growth and ING5 expression were measured.

RESULTS

Down-regulation of ING5 expression was detected in cells transfected with miR-196a precursor (P < 0.01), accompanied by less apoptosis, increased invasion, and proliferation compared with control cells (P < 0.05). Cells transfected with miR-196a inhibitor revealed an opposite trend. Smaller detectable tumors were found in only 60% of mice after implantation of Lenti.miR-196a inhibitor-transfected Panc-1 cells compared with controls (360.7 ± 303.6 mm vs 511.58 ± 365.9 mm in controls; P < 0.01).

CONCLUSION

Our results provide experimental evidence to support aberrant expression of miR-196a is associated with abnormal apoptosis, invasion, and proliferation of pancreatic cancer cells.

ING1 and ING2: multifaceted tumor suppressor genes

Inhibitor of Growth 1 (ING1) was identified and characterized as a "candidate" tumor suppressor gene in 1996. Subsequently, four more genes, also characterized as "candidate" tumor suppressor genes, were identified by homology search: ING2, ING3, ING4, and ING5. The ING proteins are characterized by a high homology in their C-terminal domain, which contains a Nuclear Localization Sequence and a Plant HomeoDomain (PHD), which has a high affinity to Histone 3 tri-methylated on lysine 4 (H3K4Me3). The ING proteins have been involved in the control of cell growth, senescence, apoptosis, chromatin remodeling, and DNA repair. Within the ING family, ING1 and ING2 form a subgroup since they are evolutionarily and functionally close. In yeast, only one gene, Pho23, is related to ING1 and ING2 and possesses also a PHD. Recently, the ING1 and ING2 tumor suppressor status has been fully established since several studies have described the loss of ING1 and ING2 protein expression in human tumors and both ING1 and ING2 knockout mice were reported to have spontaneously developed tumors, B cell lymphomas, and soft tissue sarcomas, respectively. In this review, we will describe for the first time what is known about the ING1 and ING2 genes, proteins, their regulations in both human and mice, and their status in human tumors. Furthermore, we explore the current knowledge about identified functions involving ING1 and ING2 in tumor suppression pathways especially in the control of cell cycle and in genome stability.

ING3 is essential for asymmetric cell division during mouse oocyte maturation

ING3 (inhibitor of growth family, member 3) is a subunit of the nucleosome acetyltransferase of histone 4 (NuA4) complex, which activates gene expression. ING3, which contains a plant homeodomain (PHD) motif that can bind to trimethylated lysine 4 on histone H3 (H3K4me3), is ubiquitously expressed in mammalian tissues and governs transcriptional regulation, cell cycle control, and apoptosis via p53-mediated transcription or the Fas/caspase-8 pathway. Thus, ING3 plays a number of important roles in various somatic cells. However, the role(s) of ING3 in germ cells remains unknown. Here, we show that loss of ING3 function led to the failure of asymmetric cell division and cortical reorganization in the mouse oocyte. Immunostaining showed that in fully grown germinal vesicle (GV) oocytes, ING3 localized predominantly in the GV. After germinal vesicle breakdown (GVBD), ING3 homogeneously localized in the cytoplasm. In oocytes where Ing3 was targeted by siRNA microinjection, we observed symmetric cell division during mouse oocyte maturation. In those oocytes, oocyte polarization was not established due to the failure to form an actin cap or a cortical granule-free domain (CGFD), the lack of which inhibited spindle migration. These features were among the main causes of abnormal symmetric cell division. Interestingly, an analysis of the mRNA expression levels of genes related to asymmetric cell division revealed that only mTOR was downregulated, and, furthermore, that genes downstream of mTOR (e.g., Cdc42, Rac1, and RhoA) were also downregulated in siIng3-injected oocytes. Therefore, ING3 may regulate asymmetric cell division through the mTOR pathway during mouse oocyte maturation.