Promoter methylation of the Wnt/beta-catenin signaling antagonist Dkk-3 is associated with poor survival in gastric cancer

Genomic and genetic alterations influence the progression of gastric cancer

Gastric cancer is one of the leading causes of cancer-related deaths worldwide, although the incidence has gradually decreased in many Western countries. Two main gastric cancer histotypes, intestinal and diffuse, are recognised. Although most of the described genetic alterations have been observed in both types, different genetic pathways have been hypothesized. Genetic and epigenetic events, including 1q loss of heterozygosity (LOH), microsatellite instability and hypermethylation, have mostly been reported in intestinal-type gastric carcinoma and its precursor lesions, whereas 17p LOH, mutation or loss of E-cadherin are more often implicated in the development of diffuse-type gastric cancer. In this review, we summarize the sometimes contradictory findings regarding those markers which influence the progression of gastric adenocarcinoma.

Expression and prognostic significance of gastric-specific annexin A10 in diffuse- and intestinal-type gastric carcinoma

BACKGROUND AND AIMS

Annexin A10 (ANXA10) and its liver-specific short isoform (ANXA10S) had tissue-restricted expression. The downregulation of ANXA10S is correlated with tumor progression and poor prognosis in hepatocellular carcinoma. The aim of the present study was to validate the tissue distribution and explore the role of the ANXA10 protein expression in gastric carcinoma.

METHODS

We examined the ANXA10 protein expression in human and animal tissues and 356 resected primary gastric carcinomas, using specific mouse and rabbit polyclonal antibodies, by immunohistochemical staining.

RESULTS

The ANXA10 protein is a nuclear protein specifically expressed in fetal and adult gastric mucosa and Brunner's gland across species, including humans, minipigs, woodchucks, and mice, and is commonly lost in gastric mucosa with intestinal metaplasia. The ANXA10 protein was expressed in 43.5% (155 cases) of gastric carcinomas; 74.2% (98/132) in the diffuse-type gastric carcinoma (DGC), 73.7% (28/38) in the mixed-type gastric carcinoma, and significantly lower in the intestinal-type gastric carcinoma (IGC) and indeterminate groups, 16.8% (28/167) and 5.3% (1/19), respectively (P<1×10(-8)). IGC with ANXA10 expression was correlated with a higher stage (P=0.049), particularly higher in stage IIIA/IIIB/IV IGC than lower-stage (IA/IB/II) tumors (P=0.005), but was not correlated with age, sex, and nodal status. In contrast, DGC with ANXA10 expression was associated with younger age, female patients, and importantly, lower tumor stage and lymph node metastasis (P=0.007, P=0.065, P=0.024, and P=0.0014, respectively). Moreover, DGC with ANXA10 expression had a better 5-year patient survival (P=0.0048), whereas IGC with ANXA10 expression had a lower 5-year survival (P=0.034).

CONCLUSIONS

The ANXA10 protein expression is a novel marker of gastric differentiation, and is differentially expressed in IGC and DGC, with opposite prognostic significance.

Epigenetic inactivation of T-box transcription factor 5, a novel tumor suppressor gene, is associated with colon cancer

T-box transcription factor 5 (TBX5) is a member of a phylogenetically conserved family of genes involved in the regulation of developmental processes. The function of TBX5 in cancer development is largely unclear. We identified that TBX5 was preferentially methylated in cancer using methylation-sensitive arbitrarily primed PCR. We aim to clarify the epigenetic inactivation, biological function and clinical significance of TBX5 in colon cancer. Promoter methylation was evaluated by combined bisulfite restriction analysis and bisulfite genomic sequencing. Cell proliferation was examined by cell viability assay and colony formation assay, apoptosis by flow cytometry and cell migration by wound-healing assay. TBX5 target genes were identified by cDNA microarray analysis. Cox regression model and log-rank test were used to identify independent predictors of prognosis. TBX5 was silenced or downregulated in 88% (7/8) colon cancer cell lines, but was expressed in normal colon tissues. Loss of gene expression was associated with promoter methylation. The biological function of TBX5 in human colon cancer cells was examined. Re-expression of TBX5 in silenced colon cancer cell lines suppressed colony formation (P<0.001), proliferation (P<0.001), migration and induced apoptosis (P<0.01). Induction of apoptosis was mediated through cross-talk of extrinsic apoptosis pathway, apoptotic BCL2-associated X protein and Granzyme A signaling cascades. TBX5 suppressed tumor cell proliferation and metastasis through the upregulation of cyclin-dependent kinase inhibitor 2A, metastasis suppressor 1 and downregulation of synuclein gamma and metastasis-associated protein 1 family member 2. TBX5 methylation was detected in 68% (71/105) of primary colon tumors. Multivariate analysis showed that patients with TBX5 methylation had a significantly poor overall survival (P=0.0007). In conclusion, we identified a novel functional tumor suppressor gene TBX5 inactivated by promoter methylation in colon cancer. Detection of methylated TBX5 may serve as a potential biomarker for the prognosis of this malignancy.

DNA methylation predicts recurrence from resected stage III proximal colon cancer

BACKGROUND

In colorectal cancer (CRC), DNA methylation anomalies define distinct subgroups termed CpG island methylator phenotype 1 (CIMP1), CIMP2, and CIMP-negative. The role of this classification in predicting recurrence and disease-free survival (DFS) in resected stage III CRC was evaluated.

METHODS

Sporadic cancers from 161 patients were analyzed. Bisulfite pyrosequencing was used to examine the methylation of 2 global DNA methylation markers (LINE-1, Alu) and 9 loci (MINT1, MINT2, MINT31, P16, hMLH1, P14, SFRP1, SFRP2, and WNT5A). Mutations in BRAF and KRAS were assayed.

RESULTS

Gene hypermethylation clustered in discrete groups of patients, indicating the presence of CIMP. K-means clustering analysis identified 3 discrete subgroups: CIMP1 (n = 22, 13.7%), associated with proximal location and BRAF mutations; CIMP2 (n = 40, 24.8%), associated with KRAS mutations; and CIMP-negative (n = 99, 61.5%), associated with distal location. In proximal CRC, CIMP1 was correlated with a higher recurrence rate (53% for CIMP1, 18% for CIMP2, and 26% for CIMP-negative) and a worse DFS (P = .015). Also in proximal CRC, LINE-1 methylation was lower in patients whose cancer recurred compared with those whose cancer did not recur (P = .049). In multivariate analysis, CIMP1 and low LINE1 methylation were independent prognostic factors for DFS in proximal CRC (P = .008 for classification by K-means clustering analysis; P = .040 for LINE-1 methylation status).

CONCLUSIONS

DNA methylation is a useful biomarker of recurrence in resected stage III proximal but not distal CRC. However, as the number of CIMP1 cases was small in distal CRC, further study is required to validate our findings.

DNA methylation markers in colorectal cancer

Colorectal cancer (CRC) arises as a consequence of the accumulation of genetic and epigenetic alterations in colonic epithelial cells during neoplastic transformation. Epigenetic modifications, particularly DNA methylation in selected gene promoters, are recognized as common molecular alterations in human tumors. Substantial efforts have been made to determine the cause and role of aberrant DNA methylation ("epigenomic instability") in colon carcinogenesis. In the colon, aberrant DNA methylation arises in tumor-adjacent, normal-appearing mucosa. Aberrant methylation also contributes to later stages of colon carcinogenesis through simultaneous methylation in key specific genes that alter specific oncogenic pathways. Hypermethylation of several gene clusters has been termed CpG island methylator phenotype and appears to define a subgroup of colon cancer distinctly characterized by pathological, clinical, and molecular features. DNA methylation of multiple promoters may serve as a biomarker for early detection in stool and blood DNA and as a tool for monitoring patients with CRC. DNA methylation patterns may also be predictors of metastatic or aggressive CRC. Therefore, the aim of this review is to understand DNA methylation as a driving force in colorectal neoplasia and its emerging value as a molecular marker in the clinic.

Prognostic relevance of Wnt-inhibitory factor-1 (WIF1) and Dickkopf-3 (DKK3) promoter methylation in human breast cancer

BACKGROUND

Secreted Wnt signaling antagonists have recently been described as frequent targets of epigenetic inactivation in human tumor entities. Since gene silencing of certain Wnt antagonists was found to be correlated with adverse patient survival in cancer, we aimed at investigating a potential prognostic impact of the two Wnt antagonizing molecules WIF1 and DKK3 in breast cancer, which are frequently silenced by promoter methylation in this disease.

METHODS

WIF1 and DKK3 promoter methylation were assessed by methylation-specific PCR with bisulfite-converted DNA from 19 normal breast tissues and 150 primary breast carcinomas. Promoter methylation was interpreted in a qualitative, binary fashion. Statistical evaluations included two-sided Fisher's exact tests, univariate log-rank tests of Kaplan-Meier curves as well as multivariate Cox regression analyses.

RESULTS

WIF1 and DKK3 promoter methylation were detected in 63.3% (95/150) and 61.3% (92/150) of breast carcinoma samples, respectively. In normal breast tissues, WIF1 methylation was present in 0% (0/19) and DKK3 methylation in 5.3% (1/19) of samples. In breast carcinomas, WIF1 methylation was significantly associated with methylation of DKK3 (p = 0.009). Methylation of either gene was not associated with clinicopathological parameters, except for DKK3 methylation being associated with patient age (p = 0.007). In univariate analysis, WIF1 methylation was not associated with clinical patient outcome. In contrast, DKK3 methylation was a prognostic factor in patient overall survival (OS) and disease-free survival (DFS). Estimated OS rates after 10 years were 54% for patients with DKK3-methylated tumors, in contrast to patients without DKK3 methylation in the tumor, who had a favorable 97% OS after 10 years (p < 0.001). Likewise, DFS at 10 years for patients harboring DKK3 methylation in the tumor was 58%, compared with 78% for patients with unmethylated DKK3 (p = 0.037). Multivariate analyses revealed that DKK3 methylation was an independent prognostic factor predicting poor OS (hazard ratio (HR): 14.4; 95% confidence interval (CI): 1.9-111.6; p = 0.011), and short DFS (HR: 2.5; 95% CI: 1.0-6.0; p = 0.047) in breast cancer.

CONCLUSION

Although the Wnt antagonist genes WIF1 and DKK3 show a very similar frequency of promoter methylation in human breast cancer, only DKK3 methylation proves as a novel prognostic marker potentially useful in the clinical management of this disease.

Expression of the new target GS mRNA and protein of Wnt signaling pathway in gastric cancerous tissue

AIM: To investigate the new target of Wnt signaling pathway GS mRNA and protein expression in cancerous tissue from patients with gastric carcinoma and to evaluate its clinic significance.

METHODS: Fluorescent quantitative PCR (FQ-PCR) was used to detect the GS mRNA expression in cancerous tissue and paracancerous normal mucosa from 52 patients with gastric carcinoma. Immunohistochemistry (SP method) was used to detect GS expressions in paraffin-embedded gastric carcinoma tissues of 97 cases, paracancerous normal mucosa of 30 cases and 10 intestinal metaplasia tissues.

RESULTS: The expression of GS mRNA was significantly higher in cancerous tissue from patients with gastric carcinoma than in normal tissue (25.508 ± 5.090 vs 13.001 ± 2.040, P < 0.05). GS protein expression was closely related to the pathologic parameters, such as histological type, Lauren classification and distant metastasis (χ² = 26.994, 54.929, 5.173, all P < 0.05). However, there was no significant correlation between GS expression and lymph node metastasis, tumor size, TNM staging, age and gender of patients.

CONCLUSION: GS mRNA and protein expression is significantly correlated with the biological behavior of gastric carcinoma. The high expression of GS may be related with the occurrence and progress of gastric cancer.