Reduced expression and novel splice variants of ING4 in human gastric adenocarcinoma

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.

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.

Comprehensive Analysis of Alternative Splicing Signature in Gastric Cancer Prognosis Based on The Cancer Genome Atlas (TCGA) and SpliceSeq Databases

BACKGROUND Increasing evidence suggests that the alternative splicing (AS) signature plays a role in the carcinogenesis and prognosis of various cancers. However, the prognostic role of AS in gastric cancer is not clear and needs to be clarified. MATERIAL AND METHODS To identify the differentially expressed AS (DEAS) events, we performed a differential expression analysis between normal and tumor tissue. The DEAS event was further applied to construct a prognostic signature by performing univariate Cox regression analysis and least absolute shrinkage and selection operator (LASSO) analysis. The Kaplan-Meier curve analysis and receiver operating characteristic curve (ROC) analysis were used to evaluate the prognostic value of the AS signature. In addition, the network of the splicing events with splicing factors was constructed using the Cytoscape software. RESULTS A total of 30 005 alternative splicing (AS) events with 372 patients were retrieved from the SpliceSeq database and TCGA database. By performing differential expression analysis, a total of 419 alternative splicing events were screened out, including 56 upregulated and 363 downregulated. We further constructed an AS-related prognostic signature by conducting a series bioinformatics analyses. Moreover, we identified that the AS signature could serve as an independent predictor for the prognosis of GC. We also found that AS signature had a more robust and precise efficacy for prognostic prediction in GC patients. Interestingly, the areas under 3- and 5-year survival curves are similar, both of which are greater than 1-year survival curve, suggesting that the long-term predictive accuracy of our prognostic model built upon AS signature is superior. CONCLUSIONS We performed a comprehensive analysis of overall prognostic-associated AS events concerning GC and constructed a prognostic model to predict the long-term prognostic survival outcomes in GC patients. We also developed a network of splicing events with splicing factors to reveal new potential molecular diagnostic biomarkers and therapeutic targets for GC patients.

ING4 alleviated lipopolysaccharide-induced inflammation by regulating the NF-κB pathway via a direct interaction with SIRT1

Sepsis is a complex inflammatory disorder in which high mortality is associated with an excessive inflammatory response. Inhibitor of growth 4 (ING4), which is a cofactor of histone acetyltransferase and histone deacetylase complexes, could negatively regulate this inflammation. However, the exact molecular signaling pathway regulated by ING4 remains uncertain. As a pivotal histone deacetylase, Sirtuin1 (SIRT1), which is widely accepted to be an anti‐inflammatory molecule, has not been found to be linked to ING4. This study investigated how ING4 is involved in the regulation of inflammation by constructing lipopolysaccharide (LPS)‐induced macrophage and mouse sepsis models. Our results revealed that ING4 expression decreased, whereas the levels of proinflammatory cytokines increased in LPS‐stimulated cultured primary macrophages and RAW 264.7 cells. ING4 transfection was confirmed to alleviate the LPS‐induced upregulation of proinflammatory cytokine expression both in vitro and in vivo. In addition, ING4‐overexpressing mice were hyposensitive to an LPS challenge and displayed reduced organ injury. Furthermore, immunoprecipitation indicated a direct interaction between ING4 and the SIRT1 protein. Moreover, ING4 could block nuclear factor‐kappa B (NF‐κB) P65 nuclear translocation and restrict P65 acetylation at lysine 310 induced by LPS treatment. These results are the first to clarify that the anti‐inflammatory role of ING4 is associated with SIRT1, through which ING4 inhibits NF‐κB signaling activation. Our studies provide a novel signaling axis involving ING4/SIRT1/NF‐κB in LPS‐induced sepsis.

The essential role of tumor suppressor gene ING4 in various human cancers and non-neoplastic disorders

Inhibitor of growth 4 (ING4), a member of the ING family discovered in 2003, has been shown to act as a tumor suppressor and is frequently down-regulated in various human cancers. Numerous published in vivo and in vitro studies have shown that ING4 is responsible for important cancer hallmarks such as pathologic cell cycle arrest, apoptosis, autophagy, contact inhibition, and hypoxic adaptation, and also affects tumor angiogenesis, invasion, and metastasis. These characteristics are typically associated with regulation through chromatin acetylation by binding histone H3 trimethylated at lysine 4 (H3K4me3) and through transcriptional activity of transcription factor P53 and NF-κB. In addition, emerging evidence has indicated that abnormalities in ING4 expression and function play key roles in non-neoplastic disorders. Here, we provide an overview of ING4-modulated chromosome remodeling and transcriptional function, as well as the functional consequences of different genetic variants. We also present the current understanding concerning the role of ING4 in the development of neoplastic and non-neoplastic diseases. These studies offer inspiration for pursuing novel therapeutics for various cancers.

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.

N-methyl-N-nitro-N-nitrosoguanidine-mediated ING4 downregulation contributed to the angiogenesis of transformed human gastric epithelial cells

AIMS

Angiogenesis is associated with the progression and mortality of gastric cancer. Epidemiological evidences indicate that long-term N-nitroso compounds (NOCs) exposure predominantly contributes to the mortality of gastric cancer. Therefore, further reduced mortality of gastric cancer demands to explore the exact mechanisms of NOCs induced angiogenesis. As a tumor suppressor gene, inhibitor of growth protein 4 (ING4) plays an important role in pathological angiogenesis. In this study, we will investigate ING4 expression level in human gastric epithelial cells after the long-term low dose exposure of N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and the pathological impact of MNNG-reduced ING4 on angiogenesis of transformed cells.

MAIN METHODS

The soft agar colony formation assay, Western blotting, immunofluorescence and wound healing assay were used to evaluate the characteristics of transformed cells. HUVEC growth and tube formation assays were performed to test the angiogenic abilities. EMSA, luciferase reporter gene assay, real-time PCR and Western blotting were used to explore the exact mechanism.

KEY FINDINGS

By establishing transformed human gastric epithelial cells via chronic low dose treatment, a gradually ING4 downregulation was observed in the later-stage of MNNG-induced cell transformation. Moreover, we demonstrated that MNNG exposure-reduced ING4 expression significantly resulted into aggravating angiogenesis through increasing the phosphorylation level of NF-κB p65 and subsequently DAN binding activity and regulating the expressions of NF-κB p65 downstream pro-angiogenic genes, MMP-2 and MMP-9.

SIGNIFICANCE

Our findings provided a significant mechanistic insight into angiogenesis of MNNG-transformed human gastric epithelial cell and supported the concept that ING4 may be a relevant therapeutic target for gastric cancer.

ING4 expressing oncolytic vaccinia virus promotes anti-tumor efficiency and synergizes with gemcitabine in pancreatic cancer

With no effective treatments available for most pancreatic cancer patients, pancreatic cancer continues to be one of the most difficult malignancies to treat. Oncolytic virus mediated-gene therapy has exhibited ubiquitous antitumor potential. In this study, we constructed a novel oncolytic vaccinia virus harboring the inhibitor of growth family member 4 gene (VV-ING4) to investigate its therapeutic efficacy alone or in combination with gemcitabine against pancreatic cancer cells in vitro and in vivo. ING4 expression was determined via quantitative real-time polymerase chain reaction (qPCR) and western blot. The cytotoxicity of VV-ING4 was measured using a cell proliferation assay. Both flow cytometry and western blot were applied to analyze the cell cycle and apoptosis. Furthermore, the combination inhibitory effect of VV-ING4 and gemcitabine was assessed using Chou-Talalay analysis in vitro and a BLAB/c mice model in vivo. We found that VV-ING4 significantly increases ING4 expression, displayed greater cytotoxic efficiency, and induced pancreatic cancer cell apoptosis and G2/M phase arrest. Additionally, the combination of VV-ING4 and gemcitabine synergistically effect in vitro and in vivo. Taken together, our data implicate VV-ING4 as a conceivable pancreatic cancer therapeutic candidate alone or in combination with gemcitabine.

Association between the expression of inhibitor of growth family member 4 and the progression of clear cell renal carcinoma

Inhibitor of growth family member 4 (ING4) is a candidate tumor suppressor that serves important roles in tumor growth and angiogenesis. In the present study ING4 expression was assessed in clear cell renal carcinoma (CCRC) tissues and its association with the progression of CCRC was determined. The expression of ING4 in 125 patients with CCRC was analyzed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blot analysis and immunohistochemical methods. A total of 40 adjacent normal renal tissues were used as control samples. The results identified that ING4 expression was positive in 100% of normal renal tissues, but in only 82.3% CCRC samples. RT-qPCR and western blotting results demonstrated that expression levels of ING4 mRNA and protein were significantly decreased in CCRC compared with in normal tissues (P<0.0001). ING4 expression was not associated with sex, age or tumor volume (P>0.05), but was associated with the nuclear grade of renal cancer (P<0.0001), the clinical stage of CCRC (P<0.0001) and lymphatic metastasis (P<0.0001). The results of the present study indicated that dysregulation of ING4 expression may be involved in the initiation and progression of CCRC.

Adenovirus-mediated co-expression of ING4 and PTEN cooperatively enhances their antitumor activity in human hepatocellular carcinoma cells

Both inhibitor of growth 4 (ING4) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) are well known as tumor suppressors that are closely related to tumor occurrence and progression. It was reported that ING4 and PTEN showed synergistic antitumor activities in nasopharyngeal carcinoma cells. The two tumor suppressors demonstrated synergistic effect on growth inhibition and apoptosis activation. In this study, we investigated their therapeutic potential in hepatocellular carcinoma (HCC) cells. Recombinant adenoviruses co-expressing ING4 and PTEN (Ad-ING4-PTEN) were constructed, and the antitumor effect on SMMC-7721 and HepG2 HCC cells was evaluated. Ad-ING4-PTEN cooperatively inhibited cell growth, stimulated apoptosis, and suppressed invasion in both HCC cells, and regulated cell cycle in SMMC-7721. Further studies showed that the combination of ING4 and PTEN by Ad-ING4-PTEN cooperatively enhanced the alteration of the expression of cell cycle-related proteins (p53, p21, and cyclin D1) and apoptotic factors (Bad, Bcl-2, Bcl-XL, and Bax), which are involved in the regulation of cell cycle and the activation of apoptotic pathways, leading to the synergistic antitumor effect. These results indicate that the combination of ING4 and PTEN may provide an effective therapeutic strategy for HCC.

Reduced expression and prognostic implication of inhibitor of growth 4 in human osteosarcoma

Osteosarcoma is the most prevalent type of primary malignant bone tumor. Inhibitor of growth 4 (ING4) has been demonstrated to function as a tumor suppressor through multiple pathways, and is its expression is understood to be suppressed or reduced in various malignancies. The present study aimed to investigate the expression of ING4 and to determine its prognostic value in osteosarcoma tissue. Formalin-fixed, paraffin-embedded tissue microarrays were analyzed, and contained 41 osteosarcoma specimens and 11 normal bone tissue specimens with duplicate cores. ING4 expression was evaluated by immunohistochemical staining. The association between ING4 expression in the osteosarcoma and normal bone tissues was analyzed, in addition to the association between ING4 expression and Enneking classification of the osteosarcoma tissues. A significant statistical difference was observed in the ING4 immunohistochemical staining score between the osteosarcoma and normal bone tissues (P<0.001). Furthermore, a significant negative correlation was detected between the ING4 immunohistochemical staining scores and the Enneking classification results of the 41 osteosarcoma tissues (P=0.002). Low expression of ING4 was observed in the osteosarcoma specimens, and this reduced expression of ING4 was negatively correlated with Enneking classification. Thus, the results of the present study indicate that ING4 may serve as a promising prognostic marker in osteosarcoma.

Recombinant ING4 suppresses the migration of SW579 thyroid cancer cells via epithelial to mesenchymal transition

Thyroid cancer is a common endocrine malignancy that has rapidly increased in global incidence. Inhibitor of growth 4 (ING4) has been identified in various types of carcinoma; however, to the best of our knowledge, no previous studies have investigated the effects of ING4 on thyroid cancer. In the present study, SW579 thyroid cancer cells were treated with recombinant ING4 protein, and the results confirmed that recombinant ING4 protein was able to reduce the rate of proliferation, increase the rate of apoptosis and inhibit the mobility of SW579 cells. These results were obtained using a colony formation, fluoroscein isothiocyanate/propidium iodide double staining and Transwell assays, respectively. Furthermore, in the western blot analysis assays, ING4 was demonstrated to inhibit the Wnt/β catenin signaling pathway and epithelial to mesenchymal transition (EMT). Therefore, the present study demonstrated the antitumor activities of recombinant ING4 and identified ING4 could inhibit EMT in thyroid cancer cell. However, additional studies are required to confirm these results in other cell types.

Reduced ING4 Expression Is Associated with the Malignancy of Human Bladder

Introduction: Inhibitor of growth 4 (ING4) is a tumor suppressor. However the role of ING4 in human bladder malignancy is unknown. In this study, ING4 expression in human bladder cancer and its potential effects were studied. Materials and Methods: ING4 expression in 47 human bladder cancer tissues and paired adjacent normal tissues was detected by Western blotting, quantitative reverse transcription-polymerase chain reaction, and immunohistochemistry. The migration and cell cycle progression of SV-HUC-1 and T24 cells with aberrant ING4 expression were examined. Results: ING4 protein and mRNA were significantly decreased in bladder cancer tissues. ING4 protein level was significantly lower in the group of patients over 50 years of age. ING4 knockdown caused more rapid cell migration and increased the population of SV-HUC-1 and T24 cells in the G2-M phase. Conclusion: Our data suggest a close connection between aberrant ING4 expression and the carcinogenesis of human bladder cells. ING4 may be a potential target for bladder cancer chemotherapy.

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.

Keep-ING balance: tumor suppression by epigenetic regulation

Cancer cells accumulate genetic and epigenetic changes that alter gene expression to drive tumorigenesis. Epigenetic silencing of tumor suppressor, cell cycle, differentiation and DNA repair genes contributes to neoplastic transformation. The ING (inhibitor of growth) proteins (ING1-ING5) have emerged as a versatile family of growth regulators, phospholipid effectors, histone mark sensors and core components of HDAC1/2 - and several HAT chromatin-modifying complexes. This review will describe the characteristic pathways by which ING family proteins differentially affect the Hallmarks of Cancer and highlight the various epigenetic mechanisms by which they regulate gene expression. Finally, we will discuss their potentials as biomarkers and therapeutic targets in epigenetic treatment strategies.

Tumor suppressor ING4 overexpression contributes to proliferation and invasion inhibition in gastric carcinoma by suppressing the NF-κB signaling pathway

There is growing evidence that inhibitor of growth 4 (ING4) plays a pivotal role in development and progression of multiple different tumors; however, its precise function in gastric carcinoma remains to be elucidated. In the present study, we investigated ING4 level in gastric carcinoma tissues and cells, and preliminarily elucidated the role of ING4 in the proliferation and invasion of gastric carcinoma. The results demonstrated that expressions of ING4 mRNA and protein in gastric carcinoma tissues and cells were significantly lower than those in normal tissues and cells (P < 0.05). ING4 level in gastric carcinoma cells stably expressing ING4 was markedly higher than those in untreated group and empty vector pcDNA3.1 group (P < 0.05). Elevated ING4 level resulted in the inhibition of proliferation and invasion in three of gastric carcinoma cell lines MKN-28, SGC-7901 and MKN-45. Most notably, increased ING4 level evidently evoked the down-regulation of p65, p-IκBα, MMP-9 and uPA proteins and the up-regulation of IκBα protein. Our results presented herein suggest that ING4 level elevation mediated proliferation and invasion inhibition may be tightly associated with the suppression of NF-κB signaling pathway.

MicroRNA-650 was a prognostic factor in human lung adenocarcinoma and confers the docetaxel chemoresistance of lung adenocarcinoma cells via regulating Bcl-2/Bax expression

Increasing evidence shows that dysregulation of microRNAs (miRNAs) is involved in malignant transformation. We investigated the clinical significance of miR-650 and its involvement in chemoresistance to docetaxel. Our results showed that the relative expression level of miR-650 was significantly higher in LAD tissues than in corresponding nontumor tissues and high level of miR-650 expression was found to be significantly associated with high incidence of lymph node metastasis, advanced clinical stage and poor prognosis of LAD patients. Univariate and multivariate analyses indicated that high miR-650 expression was an independent prognostic factor for survival. Also, we found that the level of miR-650 in LAD tissues was correlated with the response of patients to docetaxel-based chemotherapy. Silencing of miR-650 could increase the in vitro sensitivity of docetaxel-resistant LAD cells to docetaxel, while upregulation of miR-650 decreased the sensitivity of parental LAD cells to docetaxel both in vitro and in vivo. Additionally, silencing of miR-650 could enhance the caspase-3-dependent apoptosis, which might be correlated with the decreased ratio of Bcl-2/Bax. Further researches suggested that inhibitor of growth 4 (ING4) was a direct target of miR-650. Downregulated or upregulated ING4 expression could partially rescue the effects of miR-650 inhibitor or mimics in docetaxel-resistant or parental LAD cells. Furthermore, we found that ING4 was upregulated in docetaxel-responding LAD tissues, and its expression was inversely correlated with miR-650. Thus, miR-650 is a novel prognostic marker in LAD and its expression is a potential indicator of chemosensitivity to docetaxel-based chemotherapy regimen.

RegulatING chromatin regulators: post-translational modification of the ING family of epigenetic regulators

The five human ING genes encode at least 15 splicing isoforms, most of which affect cell growth, differentiation and apoptosis through their ability to alter gene expression by epigenetic mechanisms. Since their discovery in 1996, ING proteins have been classified as type II tumour suppressors on the basis of reports describing their down-regulation and mislocalization in a variety of cancer types. In addition to their regulation by transcriptional mechanisms, understanding the range of PTMs (post-translational modifications) of INGs is important in understanding how ING functions are fine-tuned in the physiological setting and how they add to the repertoire of activities affected by the INGs. In the present paper we review the different PTMs that have been reported to occur on INGs. We discuss the PTMs that modulate ING function under normal conditions and in response to a variety of stresses. We also describe the ING PTMs that have been identified by several unbiased MS-based PTM enrichment techniques and subsequent proteomic analysis. Among the ING PTMs identified to date, a subset has been characterized for their biological significance and have been shown to affect processes including subcellular localization, interaction with enzymatic complexes and ING protein half-life. The present review aims to highlight the emerging role of PTMs in regulating ING function and to suggest additional pathways and functions where PTMs may effect ING function.

Negative regulation of NF-κB by the ING4 tumor suppressor in breast cancer

Nuclear Factor kappa B (NF-κB) is a key mediator of normal immune response but contributes to aggressive cancer cell phenotypes when aberrantly activated. Here we present evidence that the Inhibitor of Growth 4 (ING4) tumor suppressor negatively regulates NF-κB in breast cancer. We surveyed primary breast tumor samples for ING4 protein expression using tissue microarrays and a newly generated antibody. We found that 34% of tumors expressed undetectable to low levels of the ING4 protein (n = 227). Tumors with low ING4 expression were frequently large in size, high grade, and lymph node positive, suggesting that down-regulation of ING4 may contribute to breast cancer progression. In the same tumor set, we found that low ING4 expression correlated with high levels of nuclear phosphorylated p65/RelA (p-p65), an activated form of NF-κB (p = 0.018). Fifty seven percent of ING4-low/p-p65-high tumors were lymph node-positive, indicating a high metastatic tendency of these tumors. Conversely, ectopic expression of ING4 inhibited p65/RelA phosphorylation in T47D and MCF7 breast cancer cells. In addition, ING4 suppressed PMA-induced cell invasion and NF-κB-target gene expression in T47D cells, indicating that ING4 inhibited NF-κB activity in breast cancer cells. Supportive of the ING4 function in the regulation of NF-κB-target gene expression, we found that ING4 expression levels inversely correlated with the expression of NF-κB-target genes in primary breast tumors by analyzing public gene expression datasets. Moreover, low ING4 expression or high expression of the gene signature composed of a subset of ING4-repressed NF-κB-target genes was associated with reduced disease-free survival in breast cancer patients. Taken together, we conclude that ING4 negatively regulates NF-κB in breast cancer. Consequently, down-regulation of ING4 leads to activation of NF-κB, contributing to tumor progression and reduced disease-free patient survival in breast cancer.

ING4 is negatively correlated with microvessel density in colon cancer

ING4 is a novel tumor suppressor which is downregulated in a number of cancers. In this study, we investigated the role of ING4 in tumor angiogenesis in colorectal carcinoma (CRC) patients. Semi-quantitative RT-PCR, western blots, and immunohistochemistry were used to determine ING4 mRNA and protein expression in CRC and normal tissue from 60 CRC specimens and 30 colonic adenoma specimens. The correlation between ING4 expression and clinical stage, histological grade as well as lymph node metastasis was evaluated. Immunohistochemistry was performed to explore the correlation between ING4 expression and microvessel density (MVD) in CRC. CRC tissue had significantly lower levels of ING4 mRNA and protein compared to colonic adenoma and normal intestinal tissue. Immunostaining showed ING4 expression in 38 (63.3 %), 30 (100 %), and 60 (100 %) cases of normal colonic mucosa, adenoma, and normal intestinal mucosal tissue, respectively. Lower ING4 levels correlated with higher clinical stage and histological grade. ING4 mRNA and protein levels were significantly lower in CRC patients with lymph node metastasis compared to patients without lymph node metastasis (0.41 ± 0.30 vs. 0.91 ± 0.29 and 0.60 ± 0.21 vs. 0.87 ± 0.27, respectively; p < 0.001). Importantly, ING4 mRNA and protein levels were negatively correlated with MVD in CRC patients (p < 0.001). Our data suggest that ING4 levels are a potential biomarker of CRC progression and that ING4 may inhibit tumor growth by modulating angiogenesis in CRC.

Regulation of p53 by ING family members in suppression of tumor initiation and progression

The INhibitor of Growth (ING) family is an evolutionarily conserved set of proteins, implicated in suppression of initiation and progression of cancers in various tissues. They promote cell cycle arrest, cellular senescence and apoptosis, participate in stress responses, regulate DNA replication and DNA damage responses, and inhibit cancer cell migration, invasion, and angiogenesis of the tumors. At the molecular level, ING proteins are believed to participate in chromatin remodeling and transcriptional regulation of their target genes. However, the best known function of ING proteins is their cooperation with p53 tumor suppressor protein in tumor suppression. All major isoforms of ING family members can promote the transactivition of p53 and the majority of them are shown to directly interact with p53. In addition, ING proteins are thought to interact with and modulate the function of auxiliary members of p53 pathway, such as MDM2, ARF , p300, and p21, indicating their widespread involvement in the regulation and function of this prominent tumor suppressor pathway. It seems that p53 pathway is the main mechanism by which ING proteins exert their functions. Nevertheless, regulation of other pathways which are not relevant to p53, yet important for tumorigenesis such as TGF-β and NF-κB, by ING proteins is also observed. This review summarizes the current understanding of the mutual interactions and cooperation between different members of ING family with p53 pathway and implications of this cooperation in the suppression of cancer initiation and progression.

Upregulation of miR-650 is correlated with down-regulation of ING4 and progression of hepatocellular carcinoma

BACKGROUND

In the last decade, studies in hepatocellular carcinoma (HCC) demonstrate dysregulation of miRNAs expression. For instance, miR-650 has been implicated in gastric and colorectal cancer tumorigenicity; however, the role of miR-650 remains unknown in HCC.

METHODS

In this study, we performed a comprehensive analysis to examine the miR-650 expression level in 248 HCC and 120 paracarcinomatous liver (PCL) tissues. The correlations between miR-650 expression level and the clinicopathological characteristics (HCC tumorigenicity) were evaluated. The role of miR-650 played in HCC was investigated by Q-PCR, western blot, and MTT.

RESULTS

We found that miR-650 expression was significantly increased in HCC patients and significantly associated with the patients' age (P = 0.0019), differentiation capability (P = 0.0108), and also tumor stage (P = 0.0069). Moreover, we compared the expression level of both ING4 and miR-650 in 122 HCC patients by western blot and real-time PCR. Statistical result showed a significant negative correlation between them (r(s)  = -0.2011, P = 0.0264). Transfection and MTT test suggested that miR-650 decreased the expression of ING4 and stimulate liver cells proliferation significantly.

CONCLUSION

These data suggested that miR-650 is correlated with the pathogenesis of HCC and is involved in the HCC tumorigenesis process by inhibiting the expression of ING4.

Expression of tumor suppressor gene ING4 in ovarian carcinoma is correlated with microvessel density

PURPOSE

Angiogenesis, estimated by microvessel density (MVD), has been shown to predict poor progression-free survival in women with advanced epithelial ovarian cancer. Inhibitor of growth (ING) family proteins inhibit angiogenesis in a number of cancers. We evaluated the role of ING4 in regulation of angiogenesis in patients with epithelial ovarian cancer.

METHODS

Semi-quantitative RT-PCR was used to determine ING4 mRNA levels in 40 ovarian cancer patients and 40 normal controls. Also, we used immunohistochemistry to evaluate (1) ING4 protein expression levels and (2) the level of MVD by staining CD34, a microvessel marker, in these patients. Through statistical analysis, the possible correlation between the ING4 expression and angiogenesis was explored.

RESULTS

ING4 mRNA and protein were significantly downregulated in all ovarian cancer patients compared to normal controls (P < 0.001). Endometrioid carcinoma tissue had significantly lower ING4 levels compared to serous or mucinous ovarian cancer. ING4 expression correlated negatively with stage and histological grade of ovarian cancers. MVD correlated negatively with ING4 protein and mRNA levels (ρ = -0.865; P < 0.001 and ρ = -0.724; P < 0.001, respectively).

CONCLUSIONS

Loss of ING4 may promote microvessel formation and plays a role in facilitating the development of ovarian cancer. Although the specific mechanisms are not yet understood, our data suggest that ING4 may be a promising target for the treatment for ovarian cancer.

Downregulation and translocation of nuclear ING4 is correlated with tumorigenesis and progression of head and neck squamous cell carcinoma

ING4 (inhibitor of growth gene 4) is a new member of the ING gene family and is implicated in chromatin remodeling and repression of cell growth. In order to explore the roles of ING4 in head and neck squamous cell carcinoma (HNSCC), ING4 expression was assessed in 214 cases of HNSCC by immunohistochemistry using tissue microarray, and in three oral SCC cell lines by immunohistochemistry and Western blotting. Expression of ING4 was also compared to clinicopathological variables, TUNEL assay staining, and the expression of several tumorigenic markers. We found nuclear expression of ING4 was gradually decreased from non-cancerous epithelium and dysplasia to HNSCC and was negatively correlated with a poorly-differentiated status, T staging, and TNM staging in HNSCC. In contrast, cytoplasmic expression of ING4 was significantly increased in HNSCC and was significantly associated with lymph node metastasis and 14-3-3η expression. In addition, nuclear expression of ING4 was positively correlated with p21 and p300 expression and with the apoptotic index. These results suggest that the decreases in nuclear ING4 may play important roles in tumorigenesis, progression and tumor differentiation in HNSCC. Increases in cytoplasmic ING4 may be due to 14-3-3η binding and may also be involved in malignant progression. Nuclear ING4 may modulate the transactivation of target genes, promoting apoptosis and cell cycle arrest through interactions with p300 and p21.

Deletion of the inhibitor of growth 4 (ING4) tumor suppressor gene is prevalent in human epidermal growth factor 2 (HER2)-positive breast cancer

Inhibitor of growth 4 (ING4) is a candidate tumor suppressor gene that was shown to be deleted in 10% to 20% of breast cancers by array comparative genome hybridization analysis. We developed fluorescent in situ hybridization to detect the ING4 gene directly in the tissue samples on tumor tissue microarrays. We evaluated the ING4 gene status in 1033 breast cancer tissue samples and observed that ING4 was deleted in 16.5% (170/1033) of all breast cancers. ING4 deletion was significantly associated with Her2 overexpression: of the tumors with ING4 deletion, 23.8% (39/164) were human epidermal growth factor 2 (HER2) positive, as compared with 14.1% (115/814) of the tumors without ING4 deletion (P = .002). In addition, the tumors with ING4 deletion were more likely to belong to the HER2 molecular subtype (estrogen receptor negative/progesterone receptor negative/human epidermal growth factor positive) of breast cancer, compared with the other subtypes (28.4% HER2 versus 15.7% all, P = .002). ING4 deletion did not affect survival outcome of all patients with breast cancer (P = .797) or of the patients with HER2-positive tumors (P = .792). We conclude that ING4 deletion in breast cancer is relatively common, as 1 in 6 breast cancer harbors ING4 deletion. Furthermore, ING4 deletion is more prevalent in HER2-positive tumors, suggesting a functional antagonistic relationship between the ING4 tumor suppressor and the HER2 oncogene. These results sustain the view that ING4 is a tumor suppressor in breast cancer and suggest that ING4 deletion may contribute to the pathogenesis of HER2-positive breast cancer.

Enhanced tumor suppression by an ING4/IL-24 bicistronic adenovirus-mediated gene cotransfer in human non-small cell lung cancer cells

ING4 as a member of inhibitor of growth (ING) tumor suppressor family has potent inhibitory effects on a variety of tumors. Interleukin-24 (IL-24), a cytokine-tumor suppressor, also shows broad-spectrum and tumor-specific antitumor activities. In this report, we constructed an ING4/IL-24 bicistronic adenovirus (Ad-ING4-IL-24) and assessed its combined effect on in vitro and in vivo A549 human non-small cell lung cancer cells. We demonstrated that ING4 and IL-24 combination treatment by adenovirus-mediated ING4 and IL-24 coexpression induced additive growth suppression and apoptosis as well as an overlapping effect on upregulation of P21, P27, Fas, Bax and cleaved Caspases-8, 9, 3 and downregulation of Bcl-2 in in vitro A549 lung carcinoma cells. Moreover, Ad-ING4-IL-24 treatment additively inhibited in vivo A549 lung carcinoma subcutaneous (s.c.) xenografted tumor growth and reduced CD34 and microvessel density in A549 xenografted tumors in athymic nude mice. The enhanced antitumor activity elicited by Ad-ING4-IL-24 was closely associated with the coordinate activation of extrinsic and intrinsic apoptotic pathways and additive inhibition of tumor angiogenesis. Thus, our results indicate that cancer gene therapy combining two or more tumor suppressors such as ING4 and IL-24 may constitute a novel and effective therapeutic strategy for lung carcinoma and other cancers.

Citrullination of inhibitor of growth 4 (ING4) by peptidylarginine deminase 4 (PAD4) disrupts the interaction between ING4 and p53

Gene expression is regulated by a number of interrelated posttranslational modifications of histones, including citrullination. For example, peptidylarginine deminase 4 (PAD4) converts peptidyl arginine to citrulline in histone H3 and can repress gene expression. However, regulation of gene expression through citrullination of non-histone proteins is less well defined. Herein, we identify a tumor suppressor protein, inhibitor of growth 4 (ING4), as a novel non-histone substrate of PAD4. ING4 is known to bind p53 via its nuclear localization signal (NLS) region and to enhance transcriptional activity of p53. We show that PAD4 preferentially citrullinates ING4 in the same NLS region and thereby disrupts the interaction between ING4 and p53. A citrulline-mimicking Arg-NLS-Gln ING4 mutant, which has all Arg residues in the NLS mutated to Gln, loses its affinity for p53, can no longer promote p53 acetylation, and results in repression of downstream p21 expression. In addition, we found that citrullination leads to increased susceptibility of ING4 to degradation, likely impacting p53-independent pathways as well. These findings elucidate an interaction between posttranslational citrullination, acetylation, and methylation and highlight an unusual mechanism whereby citrullination of a non-histone protein impacts gene regulation.

Role of alternative splicing events in gastric carcinogenesis

Alternative splicing affects many essential biologic processes and is the basis for a number of pathologic conditions, including cancer. Inherited and acquired changes in pre-mRNA splicing have been documented to play a significant role in human disease development. Many cancer-associated genes are regulated by alternative splicing. In this review, we will summarize the evidence supporting the association between alternative splicing and gastric carcinogenesis. The potential significance of alternative splicing events as a target for the diagnosis and treatment of gastric cancer will also be discussed.

The altered expression of ING5 protein is involved in gastric carcinogenesis and subsequent progression

ING5 can interact with p53, thereby inhibiting cell growth and inducing apoptosis. To clarify the roles of ING5 in gastric tumorigenesis and progression, its expression was examined by immunohistochemistry on a tissue microarray containing gastric nonneoplastic mucosa (n = 119), dysplasia (n = 50), and carcinomas (n = 429), with its comparison with clinicopathologic parameters of the carcinomas. ING5 expression was analyzed in gastric carcinoma tissues and cell lines (MKN28, MKN45, AGS, GT-3 TKB, and KATO-III) by Western blot and reverse transcriptase-polymerase chain reaction. ING5 protein was found to distribute to the nuclei of gastric carcinoma cells with similar messenger RNA levels. An increased expression of ING5 messenger RNA was observed in gastric carcinoma in comparison with paired mucosa (P < .05). Lower expression of nuclear ING5 was detected in gastric dysplasia and carcinoma than that in nonneoplastic mucosa (P < .05). Gastric nonneoplastic mucosa and metastatic carcinoma showed more expression of cytoplasmic ING5 than did gastric carcinoma and dysplasia (P < .05). Nuclear ING5 expression was negatively correlated with tumor size, depth of invasion, lymph node metastasis, and clinicopathologic staging (P < .05), whereas cytoplasmic ING5 was positively associated with depth of invasion, venous invasion, lymph node metastasis, and clinicopathologic staging (P < .05). Nuclear ING5 was more expressed in older than younger carcinoma patients (P < .05). There was a higher expression of nuclear ING5 in intestinal-type than diffuse-type carcinoma (P < .05), whereas it was the converse for cytoplasmic ING5 (P < .05). Survival analysis indicated that nuclear ING5 was closely linked to favorable prognosis of carcinoma patients (P < .05), albeit not independent. It was suggested that aberrant ING5 expression may contribute to pathogenesis, growth, and invasion of gastric carcinomas and could be considered as a promising marker to gauge aggressiveness and prognosis of gastric carcinoma.

Enhanced antitumor activity by combining an adenovirus harboring ING4 with cisplatin for hepatocarcinoma cells

The inhibitor of growth (ING) family proteins have been defined as candidate tumor suppressors. ING4 as a novel member of the ING family has potential tumor-suppressive effects. In this study, we explored the combined effect of adenovirus-mediated ING4 (Ad-ING4) gene transfer plus chemotherapy drug cisplatin (CDDP) on SMMC-7721 human hepatocarcinoma cells in vitro and in vivo, and its underlying mechanism. We demonstrated that Ad-ING4 plus CDDP induced synergistic growth inhibition, enhanced apoptosis, and had an additive effect on upregulation of Fas, Bax, Bak, cleaved Bid, cleaved caspase-8, caspase-9, caspase-3 and cleaved PARP, and on downregulation of Bcl-2 and Bcl-X_L in SMMC-7721 hepatocarcinoma cells. Moreover, Ad-ING4 plus CDDP synergistically suppressed in vivo SMMC-7721 hepatocarcinoma subcutaneous (s.c.) xenografted tumor growth and reduced tumor vessel CD34 expression and microvessel density (MVD) in athymic nude mice. Most importantly, Ad-ING4 plus CDDP did not have overlapping toxicities in HL-7702 normal human liver cells and normal liver tissues of mice. The in vitro and in vivo enhanced antitumor effect elicited by Ad-ING4 plus CDDP was closely associated with the cooperative regulation of extrinsic and intrinsic apoptotic pathways and synergistic inhibition of tumor angiogenesis. Thus, our results indicate that Ad-ING4 plus CDDP is a potential combined treatment strategy for hepatocarcinoma.

ING Genes Work as Tumor Suppressor Genes in the Carcinogenesis of Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer in the world. The evolution and progression of HNSCC are considered to result from multiple stepwise alterations of cellular and molecular pathways in squamous epithelium. Recently, inhibitor of growth gene (ING) family consisting of five genes, ING1 to ING5, was identified as a new tumor suppressor gene family that was implicated in the downregulation of cell cycle and chromatin remodeling. In contrast, it has been shown that ING1 and ING2 play an oncogenic role in some cancers, this situation being similar to TGF-β. In HNSCC, the ING family has been reported to be downregulated, and ING translocation from the nucleus to the cytoplasm may be a critical event for carcinogenesis. In this paper, we describe our recent results and briefly summarize current knowledge regarding the biologic functions of ING in HNSCC.

Functional impact of cancer-associated mutations in the tumor suppressor protein ING4

Inhibitor of growth 4 (ING4) is a member of the ING family of tumor suppressor proteins. In this study, we have analyzed the impact of two mutations in ING4 associated with human tumors (Y121N and N214D), testing their behavior in a series of functional, biochemical and structural analyses. We report that the N214D mutation dramatically dampened the ability of ING4 to inhibit proliferation, anchorage-independent growth or cell migration or to sensitize to cell death. In turn, the Y121N mutant did not differ significantly from wild-type ING4 in our assays. Neither of the mutations altered the normal subcellular localization of ING4, showing predominantly nuclear accumulation. We investigated the molecular basis of the defect in the activity of the N214D mutant. The folding and ability to bind histone marks of ING4 was not significantly altered by this mutation. Instead, we found that the functional impairment of the N214D mutant correlates with reduced protein stability due to increased proteasome-mediated degradation. In summary, our data demonstrates that a point mutation of ING4 associated to human tumors leads to the loss of several essential functions of ING4 pertinent to tumor protection and highlight the importance of ING4 function to prevent tumorigenesis.

Down-regulation of ING4 is associated with initiation and progression of lung cancer

AIMS

Tumour suppressor ING4 is one of ING family genes, which are involved in cell cycle arrest, gene transcription regulation, DNA repair and apoptosis. ING4 inhibition has been reported in various tumours, including gliomas, breast tumours, and stomach adenocarcinoma. The aim was to evaluate ING4 expression in lung cancers.

METHOD AND RESULTS

By immunohistochemistry of 246 lung tumour tissues, reduced ING4 nuclear and cytoplasmic expression were both revealed in lung cancer and associated with tumour grade. Interestingly, compared with normal tissues, we found more tumours with ING4 expression in the cytoplasm higher than in the nucleus. Nuclear ING4 inhibition correlated with the tumour stage and lymph node metastasis. Consistent with these findings, semiquantitative reverse transcriptase-polymerase chain reaction and Western blotting demonstrated decreased ING4 mRNA and expression in 100% (50/50) tumour tissues. Furthermore, ING4 expression was lower in grade III than in grades I-II tumours. Reduced ING4 mRNA correlated with lymph node metastasis.

CONCLUSIONS

Our results indicate that overall inhibition of ING4 expression and ING4 expression higher in cytoplasm than in nucleus of tumour cells may be involved in the initiation and progression of lung cancers, and thus, analysis for ING4 expression may be useful as a clinical diagnostic and prognostic tool for lung cancer.

A dominant mutant allele of the ING4 tumor suppressor found in human cancer cells exacerbates MYC-initiated mouse mammary tumorigenesis

ING4 is a candidate tumor suppressor gene that is deleted in 10% to 20% of human breast cancers and is mutated in various human cancer cell lines. To evaluate whether ING4 has a tumor-suppressive role in breast tissue, we overexpressed it in mouse mammary glands using a transplant system. Ectopic expression of ING4 suppressed MYC-induced mammary hyperplasia, but not tumorigenesis. In the same model system, we show that a COOH-terminal truncation mutant of ING4 found in human cancer cells could act alone to induce abnormal gland structures resembling mammary hyperplasia, which did not progress to tumors. However, coexpression of the ING4 mutant with MYC increased the penetrance and metastasis of MYC-initiated mammary tumors, giving rise to tumors with more organized acinar structures. Similarly, in vitro expression of the ING4 mutant in MCF10A mammary epithelial cells reinforced tight junctional structures. Our results provide direct functional evidence that ING4 could suppress the early stages of breast cancer and that dominant mutant alleles of ING4 might contribute to malignant development.

Inhibitor of growth tumor suppressors in cancer progression

The inhibitor of growth (ING) family of tumor suppressors has five members and is implicated in the control of apoptosis, senescence, DNA repair, and cancer progression. However, little is known about ING activity in the regulation of cancer progression. ING members and splice variants seem to behave differently with respect to cancer invasion and metastasis. Interaction with histone trimethylated at lysine 4 (H3K4me3), hypoxia inducible factor-1 (HIF-1), p53, and nuclear factor kappa-B (NF-kappaB) are potential mechanisms by which ING members exert effects on invasion and metastasis. Subcellular mislocalization, rapid protein degradation, and to a lesser extent ING gene mutation are among the mechanisms responsible for inappropriate ING levels in cancer cells. The aim of this review is to summarize the different roles of ING family tumor suppressors in cancer progression and the molecular mechanisms involved.