Frequent loss of RUNX3 gene expression in remnant stomach cancer and adjacent mucosa with special reference to topography

DNA methylation genome-wide analysis in remnant and primary gastric cancers

BACKGROUND

Although primary (PGC) and remnant gastric cancers (RGC) both originate from the same gastrointestinal organ, they have very distinct clinicopathological behaviors. We hypothesized that there would be distinct differences in DNA methylation patterns that would occur during carcinogenesis of RGC and PGC, and that the differences in methylation patterns may help identify the primary factor contributing to chronic inflammation in patients with RGC.

METHODS

We investigated the genome-wide DNA methylation patterns of PGC and RGC tissues from 48 patients using the Infinium HumanMethylation450 Beadchip assay. The results were validated by quantitative methylation-specific PCR (qMSP) in separate, independent cohorts.

RESULTS

We found that in our training cohort of 48 patients, the most variable genes from the gastric cancer tissues identified by the Infinium HumanMethylation450 Beadchip clustered the resultant heatmap into high and low methylation groups. On multivariate analysis, PGCs contributed significantly to the high methylation group (p = 0.004, OR 12.33), which suggested that the promoter methylation status in PGC is higher than that in RGC. Supporting this conclusion was the finding that in a separate qMSP analysis in a test cohort, the EPB41L3 gene, chosen because of its high β value on microarray analysis in the gastric cancer tissues, had significantly higher DNA promoter methylation in cancer tissues in the validation PGC tissues than in RGC.

CONCLUSIONS

This study demonstrated that promoter methylation status in PGC is higher than in RGC. This result may reflect the effects of the absence of Helicobacter pylori on the reduced DNA methylation in the remnant stomach.

Epigenetic inactivation of RUNX3 in colorectal cancer

PURPOSE

Emerging evidence indicates that runt-related transcription factor 3 (RUNX3) is an important tumor suppressor gene in several cancer types, including colorectal cancer (CRC). However, the clinical significance of RUNX3 inactivation in CRC remains unclear. The aim of this study was to examine the correlation between clinicopathologic factors and RUNX3 hypermethylation/expression in CRC.

METHODS

Sixty-two CRC patients who were treated at the Soonchunhyang University College of Medicine were recruited in this study. The hypermethylation of CpG islands in the RUNX3 promoter and the expression of RUNX3 mRNA were identified by methylation-specific polymerase chain reaction (PCR) and reverse transcriptase-PCR, respectively. The expression of RUNX3 was determined by immunohistochemical staining.

RESULTS

Of the 62 CRC tissue samples, 20 (32.3%) presented hypermethylated RUNX3 promoters. Aberrant RUNX3 hypermethylation was found to be associated with vascular (P = 0.006) and lymphatic (P = 0.002) invasion. Hypermethylation of RUNX3 was associated with poor survival outcomes (P = 0.038). However, expression of RUNX3 was not a prognostic factor (P = 0.363).

CONCLUSION

Hypermethylation of RUNX3 may be a predictor of a poor prognosis in CRC.

Runt-related Transcription Factor 3 Promoter Hypermethylation and Gastric Cancer Risk: A Meta-analysis

OBJECTIVE

The aim of this study was to investigate the correlation between runt-related transcription factor 3 (RUNX3) gene promoter hypermethylation and gastric cancer risk by meta-analysis.

METHODS

By searching Medline, PubMed, Embase, Cochrane, Ovid and CNKI electronic databases, the open published studies about the association between RUNX3 gene promoter hypermethylation and gastric cancer risk were screened. The hypermethylation rate in cancer tissue and autologous control tissue (normal gastric tissue of gastric cancer patients) were extracted from each included study. The odds ratio (OR) and corresponding 95% confidence interval (95% CI) of RUNX3 gene promoter hypermethylation in cancer tissue versus autologous control tissue of gastric cancer patients were pooled with random or fixed effect models. The publication bias was evaluated by Begg's funnel plot and Egger's line regression test.

RESULTS

Finally, twenty three relevant studies were included in this meta-analysis. The hypermethylation rate in cancer tissue and autologous control tissue of gastric cancer patients were 0.56±0.16 and 0.18±0.22 respectively, which demonstrated a hypermethylation rate in cancer tissue significantly higher than that of autologous controls (P<0.05). A significant positive correlation of hypermethylation rate between cancer tissue and autologous control existed for the included 23 studies(r_pearson =0.62, P<0.05). For significant heterogeneity across the studies, the OR was pooled by random effects model. The combined OR was 8.06 with the 95% CI of 5.73~11.32, which indicated the hypermethylation frequency in cancer tissue was higher than that of autologous controls.

CONCLUSION

The RUNX3 gene promoter hypermethylation rate was much higher in cancer tissue than that of normal gastric tissue in patients with gastric cancer, which indicates a close association between gastric cancer and RUNX3 gene promoter hypermethylation. Furthermore, RUNX3 gene promoter hypermethylation may be a potential biomarker for gastric cancer diagnosis.

RUNX3 and p53: How Two Tumor Suppressors Cooperate Against Oncogenic Ras?

RUNX family members play pivotal roles in both normal development and neoplasia. In particular, RUNX1 and RUNX2 are essential for determination of the hematopoietic and osteogenic lineages, respectively. RUNX3 is involved in lineage determination of various types of epithelial cells. Analysis of mouse models and human cancer specimens revealed that RUNX3 acts as a tumor suppressor via multiple mechanisms. p53-related pathways play central roles in tumor suppression through the DNA damage response and oncogene surveillance, and RUNX3 is involved in both processes. In response to DNA damage, RUNX3 facilitates p53 phosphorylation by the ATM/ATR pathway and p53 acetylation by p300. When oncogenes are activated, RUNX3 induces ARF, thereby stabilizing p53. Here, we summarize the molecular mechanisms underlying the p53-mediated tumor-suppressor activity of RUNX3.

Association between RUNX3 promoter methylation and gastric cancer: a meta-analysis

Background

Runt-related transcription factor 3 (RUNX3) is a member of the runt-domain family of transcription factors and has been reported to be a candidate tumor suppressor in gastric cancer. However, the association between RUNX3 promoter methylation and gastric cancer remains unclear.

Methods

We systematically reviewed studies of RUNX3 promoter methylation and gastric cancer published in English or Chinese from January 2000 to January 2011, and quantified the association between RUNX3 promoter methylation and gastric cancer using meta-analysis methods.

Results

A total of 1740 samples in 974 participants from seventeen studies were included in the meta-analysis. A significant association was observed between RUNX3 promoter methylation and gastric cancer, with an aggregated odds ratio (OR) of 5.63 (95%CI 3.15, 10.07). There was obvious heterogeneity among studies. Subgroup analyses (including by tissue origin, country and age), meta-regression were performed to determine the source of the heterogeneity. Meta-regression showed that the trend in ORs was inversely correlated with age. No publication bias was detected. The ORs for RUNX3 methylation in well-differentiated vs undifferentiated gastric cancers, and in intestinal-type vs diffuse-type carcinomas were 0.59 (95%CI: 0.30, 1.16) and 2.62 (95%CI: 1.33, 5.14), respectively. There were no significant differences in RUNX3 methylation in cancer tissues in relation to age, gender, TNM stage, invasion of tumors into blood vessel or lymphatic ducts, or tumor stage.

Conclusions

This meta-analysis identified a strong association between methylation of the RUNX3 promoter and gastric cancer, confirming the role of RUNX3 as a tumor suppressor gene.

H. pylori-Eradication Therapy Increases RUNX3 Expression in the Glandular Epithelial Cells in Enlarged-Fold Gastritis

Helicobacter pylori (HP)-eradication therapy increases Runt domain transcription factor 3 (RUNX3) expression in the glandular epithelial cells in enlarged-fold gastritis. The aim of this study is to evaluate expression of the RUNX3 protein, the product of a gastric tumor suppression gene, and mutagenic oxidative stress in human gastric mucosal specimens obtained from patients with HP-induced enlarged-fold gastritis. Methods. RUNX3 expression was immunohistochemically scored and the degree of the mucosal oxidative stress was directly measured by the chemiluminescense (ChL) assay in the biopsy specimens. Results. RUNX3 expression was detected in the gastric epithelial cells. HP-eradication significantly increased RUNX3 expression in the glandular epithelium of the corpus, however, no change was observed in those of the antrum. A fourfold higher mucosal ChL value was observed in the corpus as compared with that in the antrum. HP-eradication significantly decreased the mucosal ChL values in both portions of the stomach to nearly undetectable levels. Conclusion. The glandular epithelium is exposed to a high level of carcinogenic oxidative stress and shows low levels of expression of the tumor suppressive molecule, RUNX3; however, this expression was restored after HP-eradication, suggesting the high risk of carcinogenesis associated with HP-induced enlarged-fold gastritis of the corpus.

Src kinase phosphorylates RUNX3 at tyrosine residues and localizes the protein in the cytoplasm

RUNX3 is a transcription factor that functions as a tumor suppressor. In some cancers, RUNX3 expression is down-regulated, usually due to promoter hypermethylation. Recently, it was found that RUNX3 can also be inactivated by the mislocalization of the protein in the cytoplasm. The molecular mechanisms controlling this mislocalization are poorly understood. In this study, we found that the overexpression of Src results in the tyrosine phosphorylation and cytoplasmic localization of RUNX3. We also found that the tyrosine residues of endogenous RUNX3 are phosphorylated and that the protein is localized in the cytoplasm in Src-activated cancer cell lines. We further showed that the knockdown of Src by small interfering RNA, or the inhibition of Src kinase activity by a chemical inhibitor, causes the re-localization of RUNX3 to the nucleus. Collectively, our results demonstrate that the tyrosine phosphorylation of RUNX3 by activated Src is associated with the cytoplasmic localization of RUNX3 in gastric and breast cancers.

Molecular pathology of RUNX3 in human carcinogenesis

A major goal of molecular biology is to elucidate the mechanisms underlying cancer development and progression in order to achieve early detection, better diagnosis and staging and novel preventive and therapeutic strategies. We feel that an understanding of Runt-related transcription factor 3 (RUNX3)-regulated biological pathways will directly impact our knowledge of these areas of human carcinogenesis. The RUNX3 transcription factor is a downstream effector of the transforming growth factor-beta (TGF-beta) signaling pathway, and has a critical role in the regulation of cell proliferation and cell death by apoptosis, and in angiogenesis, cell adhesion and invasion. We previously identified RUNX3 as a major gastric tumor suppressor by establishing a causal relationship between loss of function and gastric carcinogenesis. More recently, we showed that RUNX3 functions as a bona fide initiator of colonic carcinogenesis by linking the Wnt oncogenic and TGF-beta tumor suppressive pathways. Apart from gastric and colorectal cancers, a multitude of epithelial cancers exhibit inactivation of RUNX3, thereby making it a putative tumor suppressor in human neoplasia. This review highlights our current understanding of the molecular mechanisms of RUNX3 inactivation in the context of cancer development and progression.

Novel roles for MLH3 deficiency and TLE6-like amplification in DNA mismatch repair-deficient gastrointestinal tumorigenesis and progression

DNA mismatch repair suppresses gastrointestinal tumorgenesis. Four mammalian E. coli MutL homologues heterodimerize to form three distinct complexes: MLH1/PMS2, MLH1/MLH3, and MLH1/PMS1. To understand the mechanistic contributions of MLH3 and PMS2 in gastrointestinal tumor suppression, we generated Mlh3^−/−;Apc^1638N and Mlh3^−/−;Pms2^−/−;Apc^1638N (MPA) mice. Mlh3 nullizygosity significantly increased Apc frameshift mutations and tumor multiplicity. Combined Mlh3;Pms2 nullizygosity further increased Apc base-substitution mutations. The spectrum of MPA tumor mutations was distinct from that observed in Mlh1^−/−;Apc^1638N mice, implicating the first potential role for MLH1/PMS1 in tumor suppression. Because Mlh3;Pms2 deficiency also increased gastrointestinal tumor progression, we used array-CGH to identify a recurrent tumor amplicon. This amplicon contained a previously uncharacterized Transducin enhancer of Split (Tle) family gene, Tle6-like. Expression of Tle6-like, or the similar human TLE6D splice isoform in colon cancer cells increased cell proliferation, colony-formation, cell migration, and xenograft tumorgenicity. Tle6-like;TLE6D directly interact with the gastrointestinal tumor suppressor RUNX3 and antagonize RUNX3 target transactivation. TLE6D is recurrently overexpressed in human colorectal cancers and TLE6D expression correlates with RUNX3 expression. Collectively, these findings provide important insights into the molecular mechanisms of individual MutL homologue tumor suppression and demonstrate an association between TLE mediated antagonism of RUNX3 and accelerated human colorectal cancer progression.

Approximately one million people every year are diagnosed with colorectal cancer worldwide, and about five hundred thousand of these people subsequently perish from the disease. Colorectal cancer is thought to develop through a series of early and later stages (called cancer initiation and progression, respectively). Deaths from colorectal cancer are particularly tragic because the disease can usually be cured if discovered before full-blown progression. However, our knowledge of how these tumors progress remains very limited. DNA mismatch repair is known to be an important process in preventing ∼15% of colorectal cancer initiation. In this study we describe how two of these genes (Mlh3 and Pms2) that have partial functional redundancy and therefore individually are rarely mutated are also important in preventing colorectal cancer progression. Additionally, we describe a new gene (Tle6-like) that, when overactive, makes these cancers progress more rapidly. The overall goal of this study is to understand colorectal cancer progression better so that we can come up with new ways to block it at the later stage.

Lack of RUNX3 regulation in human gastric cancer

It has been proposed that the transcription factor RUNX3 is the product of a gastric tumour suppressor gene. We examined RUNX3 expression in gastric biopsies from 105 patients with different histological presentations. Surprisingly, immunohistochemical staining detected RUNX3 protein expression only in infiltrating leukocytes but not in the gastric epithelium. Using laser capture microdissection and quantitative reverse transcription-polymerase chain reaction, we confirmed that the level of RUNX3 mRNA expression in the gastric epithelium was very low and was influenced neither by H. pylori infection nor by neoplastic transformation. Instead, RUNX3 was highly expressed in the gastric stroma and the level of expression correlated with the magnitude of H. pylori-induced gastric inflammation. The low level of RUNX3 expression in gastric epithelium and the absence of downregulation in gastric cancer do not support the hypothesis that RUNX3 functions as a gastric tumour suppressor gene.

Frequent silencing of RUNX3 in esophageal squamous cell carcinomas is associated with radioresistance and poor prognosis

Radiotherapy is an effective treatment for some esophageal cancers, but the molecular mechanisms of radiosensitivity remain unknown. RUNX3, a novel tumor suppressor of gastric cancer, functions in transforming growth factor (TGF)-beta-dependent apoptosis. We obtained paired samples from 62 patients with advanced esophageal cancers diagnosed initially as T3 or T4 with image diagnosis; one sample was obtained from a biopsy before presurgical radiotherapy, and the other was resected in surgical specimens after radiotherapy. RUNX3 was repressed in 67.7% cases of the pretreatment biopsy samples and 96.7% cases of the irradiated, resected samples. The nuclear expression of RUNX3 was associated with radiosensitivity and a better prognosis than cytoplasmic or no RUNX3 expression (P<0.003); cytoplasmic RUNX3 expression was strictly associated with radioresistance. RUNX3 was downregulated and its promoter was hypermethylated in all radioresistant esophageal cancer cell lines examined. Stable transfection of esophageal cancer cells with RUNX3 slightly inhibited cell proliferation in vitro, enhanced the antiproliferative and apoptotic effects of TGF-beta and increased radiosensitivity in conjunction with Bim induction. In contrast, transfection of RUNX3-expressing cells with a RUNX3 antisense construct or a Bim-specific small interfering RNA induced radioresistance. Treatment with 5-aza-2'-deoxycytidine restored RUNX3 expression, increased radiosensitivity and induced Bim in both control and radioresistant cells. These results suggest that RUNX3 silencing promotes radioresistance in esophageal cancers. Examination of RUNX3 expression in pretreatment specimens may predict radiosensitivity, and induction of RUNX3 expression may increase tumor radiosensitivity.

Alterations of tumor suppressor and tumor-related genes in the development and progression of gastric cancer

The development and progression of gastric cancer involves a number of genetic and epigenetic alterations of tumor suppressor and tumor-related genes. The majority of differentiated carcinomas arise from intestinal metaplastic mucosa and exhibit structurally altered tumor suppressor genes, typified by p53, which is inactivated via the classic two-hit mechanism, i.e. loss of heterozygosity (LOH) and mutation of the remaining allele. LOH at certain chromosomal loci accumulates during tumor progression. Approximately 20% of differentiated carcinomas show evidence of mutator pathway tumorigenesis due to hMLH1 inactivation via hypermethylation of promoter CpG islands, and exhibit high-frequency microsatellite instability. In contrast, undifferentiated carcinomas rarely exhibit structurally altered tumor suppressor genes. For instance, while methylation of E-cadherin is often observed in undifferentiated carcinomas, mutation of this gene is generally associated with the progression from differentiated to undifferentiated carcinomas. Hypermethylation of tumor suppressor and tumor-related genes, including APC, CHFR, DAP-kinase, DCC, E-cadherin, GSTP1, hMLH1, p16, PTEN, RASSF1A, RUNX3, and TSLC1, can be detected in both differentiated and undifferentiated carcinomas at varying frequencies. However, the significance of the hypermethylation varies according to the analyzed genomic region, and hypermethylation of these genes can also be present in non-neoplastic gastric epithelia. Promoter demethylation of specific genes, such as MAGE and synuclein γ, can occur during the progressive stages of both histological types, and is associated with patient prognosis. Thus, while the molecular pathways of gastric carcinogenesis are dependent on histological background, specific genetic alterations can still be used for risk assessment, diagnosis, and prognosis.

Phosphorylation, acetylation and ubiquitination: the molecular basis of RUNX regulation

The RUNX family members play pivotal roles in normal development and neoplasia. RUNX1 and RUNX2 are essential for hematopoiesis and osteogenesis, respectively, while RUNX3 is involved in neurogenesis, thymopoiesis and functions as a tumor suppressor. Inappropriate levels of RUNX activity are associated with leukemia, autoimmune disease, cleidocranial dysplasia, craniosynostosis and various solid tumors. Therefore, RUNX activity must be tightly regulated to prevent tumorigenesis and maintain normal cell differentiation. Recent work indicates that RUNX activity is controlled by various extracellular signaling pathways, and that phosphorylation, acetylation and ubiquitination are important post-translational modifications of RUNX that affect its stability and activity. Defining the precise roles, these modifications that play in the regulation of RUNX function may reveal not only how the RUNX proteins are regulated but also how they are assembled into other regulatory machineries.

Possible involvement of RUNX3 silencing in the peritoneal metastases of gastric cancers

PURPOSE

Our previous results suggested that a lack of RUNX3 function contributed to human gastric carcinogenesis, but the role of RUNX3 in progression and metastasis remains unclear. We examined RUNX3 expression in clinical samples of peritoneal metastases in gastric cancers. Changes in metastatic potential were assessed in animal experiments using stable RUNX3 transfectants of gastric cancer cells. Finally, global expression changes were analyzed using a cDNA microarray.

EXPERIMENTAL DESIGN AND RESULTS

Significant down-regulation of RUNX3 through methylation on the promoter region was observed in primary tumors (75%) as well as in all clinical peritoneal metastases of gastric cancers (100%) compared with normal gastric mucosa. Stable transfection of RUNX3 inhibited cell proliferation slightly, and modest transforming growth factor-beta (TGF-beta)-induced antiproliferative and apoptotic effects were observed. Interestingly, it strongly inhibited peritoneal metastases of gastric cancers in animal model (P < 0.01). Furthermore, we did globally analyzed expression profiles of approximately 21,000 genes in parent cells and stable transfectant of RUNX3 using a cDNA microarray. Microarray analysis identified approximately 28 candidate genes under the possible downstream control of RUNX3, some of these genes were considered to be possibly involved in peritoneal metastases, which were related to signal transduction (vav3, TOLL-like receptor, MAPKK, MET, S1 00A1 1, and cathepsin E), apoptosis (caspase 9), immune responses (CD55 and TLR1O), and cell adhesion (sialyltransferase 1 and galectin 4). Some of the genes are involved in the TGF-beta signaling pathway.

CONCLUSION

These results indicate that silencing of RUNX3 affects expression of important genes involved in aspects of metastasis including cell adhesion, proliferation, apoptosis, and promoting the peritoneal metastasis of gastric cancer. Identification of such genes could suggest new therapeutic modalities and therapeutic targets.