Reactivation of the homeotic tumor suppressor gene CDX2 by 5-aza-2'-deoxycytidine-induced demethylation inhibits cell proliferation and induces caspase-independent apoptosis in gastric cancer cells

CDX2 and Reg IV expression and correlation in gastric cancer

Background

Ectopic expression of CDX2 is associated with the development and progression of gastric cancer. Previous studies showed that CDX2 may be an upstream regulator of Reg IV expression in gastric cancer, and our previous report showed that Reg IV upregulated SOX9 expression and enhanced cell migration and invasion in gastric cancer cells. However, the regulatory roles of CDX2 have not been clarified in gastric cancer, and the correlation between CDX2 and Reg IV requires further study.

Methods

CDX2 and Reg IV were examined in gastric cancer specimens and paired adjacent tissues via real-time PCR and immunohistochemistry (IHC). The association between CDX2 and Reg IV was assessed using the χ²-test and Spearman’s rank correlation. To verify their relationship, knockdown and exogenous expression of CDX2 or Reg IV were performed in AGS and MKN-45 gastric cancer cells, and their expression was subsequently analyzed via a real-time PCR and western blotting. Wound-healing and Transwell assays were used to examine migration and invasion in AGS and MKN-45 cells following CDX2 silencing or overexpression.

Results

A positive correlation was observed between CDX2 and Reg IV expression at the mRNA and protein levels in gastric cancer tissues. CDX2 silencing significantly downregulated Reg IV expression, and CDX2 overexpression significantly upregulated Reg IV expression in AGS and MKN-45 cells. Neither Reg IV silencing nor overexpression had any effect on CDX2 protein expression in AGS or MKN-45 cells, even though both affected the expression of CDX2 mRNA. Functionally, CDX2 silencing significantly inhibited cell migration and invasion, and CDX2 overexpression significantly promoted cell migration and invasion in AGS and MKN-45 cells.

Conclusions

Our findings demonstrate that CDX2 expression was positively correlated with that of Reg IV in gastric cancer, and CDX2 promoted cell migration and invasion through upregulation of Reg IV expression in AGS and MKN-45 cells.

CDX2 in colorectal cancer is an independent prognostic factor and regulated by promoter methylation and histone deacetylation in tumors of the serrated pathway

Background

In colorectal cancer, CDX2 expression is lost in approximately 20% of cases and associated with poor outcome. Here, we aim to validate the clinical impact of CDX2 and investigate the role of promoter methylation and histone deacetylation in CDX2 repression and restoration.

Methods

CDX2 immunohistochemistry was performed on multi-punch tissue microarrays (n = 637 patients). Promoter methylation and protein expression investigated on 11 colorectal cancer cell lines identified two CDX2 low expressors (SW620, COLO205) for treatment with decitabine (DNA methyltransferase inhibitor), trichostatin A (TSA) (general HDAC inhibitor), and LMK-235 (specific HDAC4 and HDAC5 inhibitor). RNA and protein levels were assessed. HDAC5 recruitment to the CDX2 gene promoter region was tested by chromatin immunoprecipitation.

Results

Sixty percent of tumors showed focal CDX2 loss; 5% were negative. Reduced CDX2 was associated with lymph node metastasis (p = 0.0167), distant metastasis (p = 0.0123), and unfavorable survival (multivariate analysis: p = 0.0008; HR (95%CI) 0.922 (0.988–0.997)) as well as BRAF^V600E, mismatch repair deficiency, and CpG island methylator phenotype. Decitabine treatment alone induced CDX2 RNA and protein with values from 2- to 25-fold. TSA treatment ± decitabine also led to successful restoration of RNA and/or protein. Treatment with LMK-235 alone had marked effects on RNA and protein levels, mainly in COLO205 cells that responded less to decitabine. Lastly, decitabine co-treatment was more effective than LMK-235 alone at restoring CDX2.

Conclusion

CDX2 loss is an adverse prognostic factor and linked to molecular features of the serrated pathway. RNA/protein expression is restored in CDX2 low-expressing CRC cell lines by demethylation and HDAC inhibition. Importantly, our data underline HDAC4 and HDAC5 as new epigenetic CDX2 regulators that warrant further investigation.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0548-2) contains supplementary material, which is available to authorized users.

Homeobox protein CDX2 as a prognostic biomarker in solid malignancies: a meta-analysis

Background

CDX2 is a caudal-homeobox gene and its expression is abnormal in numerous tumour cell types. Nevertheless, its prognostic value for solid tumours requires further investigation. Hence, we conducted a meta-analysis to determine the significance of CDX2 as a prognostic biomarker in solid malignancies systematically.

Materials and Methods

We performed a systematic literature search in PUBMED and EMBASE up to May 2017. Retrospective studies comparing the prognostic value of different CDX2 levels in human malignancies were included. Data extractions and methodological assessments were performed separately by two investigators using a standard procedure. The statistical procedures were performed using Review Manager 5.3 and STATA/MP 14.0.

Results

A total of 26 retrospective studies met the inclusion criteria and comprised 5008 participants. Patients with CDX2 overexpression had significantly better 3-year, 5-year, 10-year and disease-free survival outcomes in solid malignancies, regardless of the cancer type, mean age, and source region. Nevertheless, there was no significant difference in the patients from Europe. The expression level of CDX2 was not statistically associated with cancer relapse. Moreover, our analysis showed that CDX2 overexpression is correlated to better responses to chemotherapy in patients with TNM IV stage cancers. The stability of the pooled outcomes was verified by sensitivity analysis. The funnel plots, Egger's test and Begg's test jointly confirmed that there was no publication bias.

Conclusions

Overexpression of CDX2 is a reliable biomarker of a better prognosis in solid malignancies.

SOX2 Inhibition Promotes Promoter Demethylation of CDX2 to Facilitate Gastric Intestinal Metaplasia

BACKGROUND

Gastric intestinal metaplasia (IM) is regarded as a premalignant lesion, conferring risks for gastric cancer development. An intestinal transcription factor, CDX2, plays a vital role in establishing and maintaining IM. SOX2, an HMG-box transcription factor, is expressed in normal gastric mucosa and downregulated in IM. Therefore, it is important to elucidate the mutual interaction of SOX2 and CDX2 in gastric IM.

AIMS

This study aims to evaluate the negative correlation between SOX2 and CDX2 in mRNA expression and promoter methylation and to illuminate the effect of SOX2 on the promoter methylation of CDX2.

METHODS

Immunohistochemistry, real-time PCR and methylation-specific polymerase chain reaction assays were performed to evaluate the expression and promoter methylation of SOX2 and CDX2 in IM tissues from patients. SOX2 knockdown and CDX2 overexpression were performed in GES-1 cells to further clarify the relationship between SOX2 and CDX2.

RESULTS

A negative correlation between SOX2 and CDX2 was found in 120 gastric IM specimens. Additionally, significant DNA demethylation of CDX2 promoter in clinical IM specimens was observed concomitantly with partial methylation of the SOX2 promoter. Furthermore, SOX2 knockdown in GES-1 cells triggered promoter demethylation of CDX2. Finally, the phenotype shift of gastric intestinal metaplasia in GES-1 cells, marked by MUC2 expression, was effectively induced by the combination of SOX2 RNAi and CDX2 overexpression.

CONCLUSIONS

Aberrant DNA methylation of SOX2 and CDX2 genes contributes to the development of IM. Notably, SOX2 may play a role in establishing and maintaining the methylation status of the CDX2 gene in gastric tissues and cells.

Methylation status of homeobox genes in common human cancers

Approximately 300 homeobox loci were identified in the euchromatic regions of the human genome, of which 235 are probable functional genes and 65 are likely pseudogenes. Many of these genes play important roles in embryonic development and cell differentiation. Dysregulation of homeobox gene expression is a frequent occurrence in cancer. Accumulating evidence suggests that as genetics disorders, epigenetic modifications alter the expression of oncogenes and tumor suppressor genes driving tumorigenesis and perhaps play a more central role in the evolution and progression of this disease. Here, we described the current knowledge regarding homeobox gene DNA methylation in human cancer and describe its relevance in the diagnosis, therapeutic response and prognosis of different types of human cancers.

Methylation of promoter region of CDX2 gene in colorectal cancer

The incidence of colorectal cancer is on the increase owing to changes in daily diet. In the present study, the methylation status of caudal type homeobox transcription factor 2 (CDX2) gene in lesion tissue of colorectal cancer (CRC) was investigated. Additionally, the correlation between the promoter methylation of CDX2 gene, CRC and gene expression in patients with CRC and normal population was examined. Between April 2014 and May 2015 78 cases with CRC were enrolled in the study. Using methylation-specific polymerase chain reaction (PCR), the promoter methylation of CDX2 in normal tissues and colorectal tissues was examinned. Through the fluorescence quantitative PCR technique, the expression levels of CDX2 gene were determined in a normal population and lesion tissue of patients with CRC. At the same time, we evaluated the levels of the CDX2 gene product in the normal population and lesion tissue of patients with CRC. The results showed that the methylation rate of the promoter region of CDX2 gene in normal colorectal tissue was 43.5%, whereas that in the lesion tissue of CRC was 78.5%. The result was statistically significant (P<0.05). The quantity of mRNA and protein expression of CDX2 gene in colorectal and normal tissue was significantly different (P<0.05). In conclusion, the methylation of the CDX2 gene promoter region was associated with risk of CRC, i.e., methylation of the promoter region of CDX2 gene favors the occurrence of CRC.

Methylation status of the FHIT gene in the transformed human mesenchymal F6 stem cell line

The fragile histidine triad (FHIT) gene is known to be a tumor suppressor gene and the abnormal methylation of FHIT has been identified in leukemia and several solid tumors. The transformation of the tumor F6 cell line from human fetal mesenchymal stem cells (FMSCs) was first reported in a previous study that also identified the presence of a population of cancer stem cells in the F6 cell line. However, the existence of the epigenetic changes during the transformation process have yet to be elucidated. To confirm the role of the FHIT gene in the transformation process of FMSC, the expression level and methylation status of the FHIT gene was examined in F6 tumor cells and FMSCs. Additionally, the alteration in cell morphology, the cell cycle and apoptosis in F6 cells following 5-Aza-CdR treatment was assessed. It was found that the FHIT gene was expressed in FMSCs, but not in F6 cells. The methylation-specific PCR results demonstrated that the promoter methylation of FHIT genes existed in the F6 cell line. Subsequent to treatment with 5-Aza-CdR the expression of FHIT genes was restored in F6 cells. In addition, the morphology of F6 cells was altered, and the cell cycle was arrested in the G₂ phase, with the initiation of apoptosis. Overall, the present findings demonstrated that the FHIT gene was methylated in F6 cells and demethylation treatment lead to changes in the biological characteristics, thereby promoting the apoptosis of F6 cells. FHIT gene methylation may be one of the molecular events involved in the development and transformation of FMSCs into F6 tumor cells.

Overexpression of caudal type homeobox transcription factor 2 inhibits the growth of the MGC-803 human gastric cancer cell line in vivo

Caudal type homeobox transcription factor 2 (CDX2) is important in intestinal cell fate specification and multiple lines of evidence have substantiated that CDX2 is important in carcinogenesis of the digestive tract. The CDX2 regulatory network is intricate and remains to be fully elucidated in gastric cancer. The aim of the present study was to examine the effects of CDX2 on the growth of the MGC-803 human gastric cancer cell line in vivo, and to elucidate the mechanism involved. The effects of the overexpression of CDX2 in xenograft tumors of MGC-803 cells was investigated in nude mice through the injection of CDX2 recombinant lentiviral vectors. The tumor size was measured using vernier callipers. The expression levels of CDX2, survivin, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), cyclin D1, s-phase kinase-associated protein 2 (Skp2) and c-Myc in the tumor cells were analyzed by western blotting and semi-quantitative reverse transcription polymerase chain reaction. The apoptotic rates were determined using a terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay. The overexpression of CDX2 was observed in the group subjected to the injection of CDX2 recombinant lentiviral vectors. CDX2 had an inhibitory effect on the MGC-803 human gastric cancer cell line and promoted tumor cell apoptosis in vivo. Furthermore, the overexpression of CDX2 upregulated the expression of Bax and downregulated the expression levels of survivin, Bcl-2, cyclin D1, Skp2 and c-Myc in the tumor tissues. These results indicated that CDX2 may serve as a tumor suppressor in gastric cancer, and inhibits gastric cancer cell growth by suppressing the nuclear factor-κB signaling pathway.

Methylation-associated silencing of miR-495 inhibit the migration and invasion of human gastric cancer cells by directly targeting PRL-3

Phosphatase of regenerating liver-3 (PRL-3) is believed to be associated with cell motility, invasion, and metastasis. Our previous work found that PRL-3 is highly overexpressed in gastric cancer (GC) tissue with peritoneal metastasis and directly involved in the pathogenesis of GC peritoneal metastasis. Moreover, we further found that the down-regulation of endogenous miR-495 expression plays a causative role in over expression of PRL-3 in GC peritoneal metastasis. However, the molecular regulation mechanisms by which endogenous miR-495 expression is down-regulated and PRL-3 promotes GC peritoneal metastasis remain to be clearly elucidated. Some studies have shown that the promoter methylation is closely related to the miRNA gene expression. Therefore, in present study, based on our previous findings, we will analysis whether DNA methylation is a major cause of the down-expression of endogenous miR-495, which results in PRL-3 overexpression in GC peritoneal metastasis. Methylation specific PCR (MSP) and sodium bisulfite sequencing method (BSP) detected miR-495 gene promoter methylation status. We treated GC cell lines with 5-Aza-2'-deoxycytidine (5-Aza-dC) to make the gene promoter methylation inactivation. By treating with 5-Aza-dC the migration and invasion of GC cells were significantly inhibited. And the miR-495 was overexpressing, corresponds to the mRNA and protein levels of PRL-3 were reduced, the ability of invasion and metastasis was inhibited. This study suggest that miR-495 have tumor suppressor properties and are partially silenced by DNA hypermethylation in GC, will provide new strategies for prevention and treatment of GC peritoneal metastasis.

Extracts of endophytic fungus xkc-s03 from Prunella vulgaris L. spica inhibit gastric cancer in vitro and in vivo

Prunella vulgaris L. belongs to the Prunella genus and has been proven effective in the treatment of gastric cancer, however, the therapeutic activity of the endophytic fungi is not yet well understood. The results of the present study suggest that the ethyl acetate extract (S03-EA) of the endophytic fungus XKC-S03, isolated from Prunella vulgaris L. spica, is a potent anticancer agent with the potential to treat gastric cancer. In the present study, the effects of S03-EA on gastric cancer in vitro and in vivo were determined using the 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan assay and the human gastric cancer SGC 7901 cell xenograft model. The tumor tissue was fixed with 10% formaldehyde solution and the levels of the apoptotic proteins, B-cell lymphoma protein-2 (Bcl-2), Bcl-2-associated X protein (Bax) and pro-angiogenic vascular endothelial growth factor (VEGF), were measured by immunohistochemistry. The results indicated that treating SGC 7901 cells with petroleum ether (S03-PE), ethyl acetate (S03-EA) or dichloromethane (S03-DM) extracts from the XKC-S03 fermentation broth inhibited cell proliferation. S03-EA demonstrated the best activity, with a half maximal inhibitory concentration of 25.89 μg/ml and dose-dependent suppression of the SGC 7901 tumor cells in vivo, without any evident adverse effects. In addition, the 100-mg/kg/day S03-EA-treated tumor tissue revealed a downregulation of Bcl-2 and VEGF expression and an upregulation of Bax expression. In conclusion, the S03-EA extract of XKC-S03, isolated from Prunella vulgaris L. spica, exhibits a growth-suppressive activity on gastric cancer in vitro and in vivo.

Connexin 32 and 43 promoter methylation in Helicobacter pylori-associated gastric tumorigenesis

AIM

To explore the mechanism of abnormal Connexin (Cx) 32 and Cx43 expression in the gastric mucosa after Helicobacter pylori (H. pylori) infection.

METHODS

Biopsy specimens of gastric mucosa in different gastric carcinogenesis stages with H. pylori infection, that is, non-atrophic gastritis (NAG; n = 24), chronic atrophic gastritis (CAG; n = 25), intestinal metaplasia (IM; n = 28), dysplasia (DYS; n = 24), and gastric cancer (GC; n = 30), as well as specimens of normal gastric mucosa without H. pylori infection (NGM; n = 25), were confirmed by endoscopy and pathological examination. Cx32 and Cx43 mRNA expression was detected by real-time polymerase chain reaction (PCR). Cx32 and Cx43 promoter CpG island methylation status was determined by methylation-specific PCR (MSP), bisulfite PCR sequencing (BSP) and MassArray methods.

RESULTS

The relative mRNA expression levels in the gastric mucosa of patients with NGM, NAG, CAG, IM, DYS and GC were 0.146 ± 0.011, 0.133 ± 0.026, 0.107 ± 0.035, 0.039 ± 0.032, 0.037 ± 0.01 and 0.03 ± 0.011 for Cx32; and 0.667 ± 0.057, 0.644 ± 0.051, 0.624 ± 0.049, 0.555 ± 0.067, 0.536 ± 0.058 and 0.245 ± 0.121 for Cx43, respectively, which were gradually decreasing and significantly different (GC vs NGM: P < 0.001 for Cx32, P < 0.001 for Cx43). The promoter methylation levels in the gastric mucosa from NGM to GC stages by MSP were 38.8% ± 9.0%, 43.1% ± 9.4%, 56.5% ± 3.1%, 64.4% ± 9.7%, 72.5% ± 4.2% and 79.6% ± 6.8% for Cx32; and 49.0% ± 3.9%, 58.1% ± 5.0%, 66.5% ± 7.9%, 74.0% ± 8.8%, 78.3% ± 3.6% and 88.7% ± 6.2% for Cx43, respectively, which were gradually increasing and significantly different (P = 0.039, P = 0.019). The promoter methylation levels by BSP and MassArray exhibited similar trends. Cx32 and Cx43 mRNA expression was negatively correlated with promoter methylation status and gastric carcinogenesis stages (P < 0.001, P = 0.016).

CONCLUSION

Cx32 and Cx43 mRNA expression decreased gradually during H. pylori infection-associated gastric carcinogenesis, and it is associated with hypermethylation of these genes' promoter.

Integrated Analysis of Dysregulated miRNA-gene Expression in HMGA2-silenced Retinoblastoma Cells

Retinoblastoma (RB) is a primary childhood eye cancer. HMGA2 shows promise as a molecule for targeted therapy. The involvement of miRNAs in genome-level molecular dys-regulation in HMGA2-silenced RB cells is poorly understood. Through miRNA expression microarray profiling, and an integrated array analysis of the HMGA2-silenced RB cells, the dysregulated miRNAs and the miRNA-target relationships were modelled. Loop network analysis revealed a regulatory association between the transcription factor (SOX5) and the deregulated miRNAs (miR-29a, miR-9*, miR-9-3). Silencing of HMGA2 deregulated the vital oncomirs (miR-7, miR-331, miR-26a, miR-221, miR-17~92 and miR-106b∼25) in RB cells. From this list, the role of the miR-106b∼25 cluster was examined further for its expression in primary RB tumor tissues (n = 20). The regulatory targets of miR-106b∼25 cluster namely p21 (cyclin-dependent kinase inhibitor) and BIM (pro-apoptotic gene) were elevated, and apoptotic cell death was observed, in RB tumor cells treated with the specific antagomirs of the miR-106b∼25 cluster. Thus, suppression of miR-106b∼25 cluster controls RB tumor growth. Taken together, HMGA2 mediated anti-tumor effect present in RB is, in part, mediated through the miR-106b∼25 cluster.

microRNA-32 inhibits the proliferation and invasion of the SGC-7901 gastric cancer cell line in vitro

microRNAs (miRNAs) are a class of endogenously expressed, small non-coding RNAs, which suppress their target mRNAs at the post-transcriptional level. miRNAs play key roles in tumor metastasis. The aim of the present study was to investigate the expression of miRNA-32 (miR-32) on the biological behavior of the human gastric cancer cell line, SGC-7901. SGC-7901 cells were transfected with miR-32-mimic, miR-32-inhibitor and empty plasmid vectors using Lipofectamine™ 2000. The expression of GFP was observed by fluorescent microscopy and miR-32 gene expression was detected by quantitative polymerase chain reaction. The cell counting kit-8 assay was performed to evaluate the effect of miR-32 expression on cell proliferation in vitro. Alterations in the migration and metastatic potential of SGC-7901 cells, prior to and following miR-32 gene transfection, were assayed by cell chemotactic migration and invasion tests. The results of the current study showed that the proliferation rate of the transfected SGC-7901 cells overexpressing miR-32 is reduced and cell chemotactic migration and invasion potentials is markedly reduced following miR-32-mimic transfection (P<0.05). In addition, the results demonstrated that overexpression of miR-32 greatly inhibits the proliferation and decreases the migration and invasion capabilities of SGC-7901 cells in vitro.

Iron-ascorbate-mediated lipid peroxidation causes epigenetic changes in the antioxidant defense in intestinal epithelial cells: impact on inflammation

Introduction

The gastrointestinal tract is frequently exposed to noxious stimuli that may cause oxidative stress, inflammation and injury. Intraluminal pro-oxidants from ingested nutrients especially iron salts and ascorbic acid frequently consumed together, can lead to catalytic formation of oxygen-derived free radicals that ultimately overwhelm the cellular antioxidant defense and lead to cell damage.

Hypothesis

Since the mechanisms remain sketchy, efforts have been exerted to evaluate the role of epigenetics in modulating components of endogenous enzymatic antioxidants in the intestine. To this end, Caco-2/15 cells were exposed to the iron-ascorbate oxygen radical-generating system.

Results

Fe/Asc induced a significant increase in lipid peroxidation as reflected by the elevated formation of malondialdehyde along with the alteration of antioxidant defense as evidenced by raised superoxide dismutase 2 (SOD2) and diminished glutathione peroxidase (GPx) activities and genes. Consequently, there was an up-regulation of inflammatory processes illustrated by the activation of NF-κB transcription factor, the higher production of interleukin-6 and cycloxygenase-2 as well as the decrease of IκB. Assessment of promoter’s methylation revealed decreased levels for SOD2 and increased degree for GPx2. On the other hand, pre-incubation of Caco-2/15 cells with 5-Aza-2′-deoxycytidine, a demethylating agent, or Trolox antioxidant normalized the activities of SOD2 and GPx, reduced lipid peroxidation and prevented inflammation.

Conclusion

Redox and inflammatory modifications in response to Fe/Asc -mediated lipid peroxidation may implicate epigenetic methylation.