An α‐E‐catenin (CTNNA1) mutation in hereditary diffuse gastric cancer

Diffuse gastric cancers typically present as late‐stage tumours and, as a result, the 5 year survival rate is poor. Some gastric cancers are hereditary and these tend to be of the diffuse type; 30–40% of hereditary diffuse gastric cancers (HDGCs) can be explained by defective germline alleles of E‐cadherin (CDH1), but for the remaining families the factors driving susceptibility remain unknown. We had access to a large HDGC pedigree with no obvious mutation in CDH1, and applied exome sequencing to identify new genes involved in gastric cancer. We identified a germline truncating allele of α‐E‐catenin (CTNNA1) that was present in two family members with invasive diffuse gastric cancer and four in which intramucosal signet ring cells were detected as part of endoscopic surveillance. The remaining CTNNA1 allele was silenced in the two diffuse gastric cancers from the family that were available for screening, and this was also true for signet ring cells identified in endoscopic biopsies. Since α‐E‐catenin functions in the same complex as E‐cadherin, our results call attention to the broader signalling network surrounding these proteins in HDGC. We also detected somatic mutations in one tumour and found substantial overlap with genes mutated in sporadic gastric cancer, including PIK3CA, ARID1A, MED12 and MED23.     

TIMP4 expression is regulated by miR‐200b‐3p in prostate cancer cells

In prostate cancer TIMP4 expression level fluctuates with tumor progression. The mechanism and factors influencing its expression remain unclear. The aim of the study was to test the hypothesis on regulation of TIMP4 by microRNA‐200b‐3p. The levels of TIMP4 and miR‐200b‐3p expression were determined by real time PCR in 27 prostate carcinomas and eight benign prostatic hyperplasia samples. We found that miR‐200b‐3p positively correlated with TIMP4 expression in cancer samples (r = 0.46; p < 0.02). Moreover, mean miR‐200b‐3p level and TIMP4 expression were both higher in cancer tissues compared to benign prostatic hyperplasia samples (p > 0.05). Next, to test probable mechanisms of the regulation androgen‐sensitive human prostate adenocarcinoma cells (LNCaP) were transfected with synthetic‐miR‐200b‐3p or its synthetic antagonist. Modulation of miR‐200b‐3p in LNCaP cells had an impact on TIMP4 expression confirming the observation made in analyzed clinical samples. Two targets of miR‐200b‐3p: ZEB1 and ETS1 were investigated subsequently as potential regulators of TIMP4, however, no effect of their modulation on TIMP4 expression in LNCaP cells was found. Concluding, miR‐200b‐3p mediates regulation of TIMP4 expression in prostate cancer but exact mechanism needs to be investigated.     

miR‐1, regulated by LMP1, suppresses tumour growth and metastasis by targeting K‐ras in nasopharyngeal carcinoma

There is evidence to show that downregulation of miR‐1 expression is closely related to cancer progression, including in nasopharyngeal carcinoma (NPC). However, the molecular mechanisms underlying miR‐1 downregulation in NPC remain largely unknown, especially its association with Epstein–Barr virus (EBV). In this study we found that restoration of miR‐1 dramatically inhibited cell invasion in vitro, together with tumour growth and metastasis in vivo. Importantly, we found that LMP1, an Epstein–Barr virus (EBV)‐associated protein, suppressed miR‐1 expression. Furthermore, we identified K‐ras as a novel direct target of miR‐1. Our results demonstrated for the first time that miR‐1 was suppressed by LMP1 and its tumour‐suppressive effects were mediated chiefly by repressing K‐ras expression. We propose that miR‐1 could serve as an independent biomarker to identify patients with different clinical characteristics.     

Overexpression of miR‐17 in gastric cancer is correlated with proliferation‐associated oncogene amplification

The molecular mechanism underlying microRNA (miR)‐17 overexpression has not been clearly evaluated in gastric cancer. We aimed to evaluate the functional roles of miR‐17 in gastric cancer and test its viability as a therapeutic target. We conducted comparative genomic hybridization and expression array analyses on human gastric cancer tissue samples, as well as evaluating the functional roles of miR‐17 in gastric cancer cell lines and transgenic mice. miR‐17 overexpression in gastric cancer patients was associated with copy number gain of proliferation‐associated oncogenes such as MYC, CCNE1, ERBB2, and FGFR2. Copy number gain of MIR17HG gene (13q31.3) was rare, with an overall frequency of 2% in gastric cancers (1 of 51). miR‐17 knockdown suppressed the monolayer and anchorage‐independent growth of FGFR2‐amplified KATO‐III gastric cancer cells. mir‐17–92 TG/TG mice overexpressing the mir‐17–92 cluster under the villin promoter developed spontaneous benign tumors in the intestinal tract (log‐rank P for tumor‐free survival = 0.069). Taken together, miR‐17 overexpression in gastric cancer was rarely associated with MIR17HG gene amplification, but correlated with proliferation‐associated oncogene amplification. Therefore, miR‐17‐targeting approach may benefit patients with gastric cancers harboring proliferation‐associated oncogene amplification.     

E‐cadherin germline mutations define an inherited cancer syndrome dominated by diffuse gastric cancer

To extend earlier observations of germline E‐cadherin mutations in kindreds with an inherited susceptibility to diffuse gastric cancer, we searched for germline E‐cadherin mutations in five further families affected predominantly by diffuse gastric cancer and one family with a history of diffuse gastric cancer and early‐onset breast cancer. Heterozygous inactivating mutations were found in the E‐cadherin gene in each of these families. No mutation hotspots were identified. These results demonstrate that germline mutation of the E‐cadherin gene is a common cause of hereditary diffuse gastric cancer and suggest a role for these mutations in the incidence of breast cancer. Hum Mutat 14:249–255, 1999. © 1999 Wiley‐Liss, Inc.     

Clinical implications of N-cadherin expression in gastric cancer

Neo-expression of N-cadherin in cancer cells is regarded as a significant event in tumor progression via epithelial-mesenchymal transition (EMT). No reports have detailed the clinical impact of N-cadherin expression in gastric cancer. We retrospectively examined the co-expression of N-cadherin and E-cadherin in human gastric carcinoma and analyzed the clinicopathological significance of N-cadherin expression. One hundred and forty-six gastric cancer patients who received curative gastrectomy were enrolled. E-cadherin and N-cadherin immunoreactivity in cancer tissue was evaluated by the avidin-biotin-peroxidase complex technique. The correlation between N-cadherin and E-cadherin expression and clinicopathological parameters were analyzed. N-cadherin-positive and -negative expression were found in 31 and 115 patients, respectively. N-cadherin expression positively correlated with hematogenous recurrence (P < 0.01) and negatively correlated with patients' postoperative outcomes (P < 0.05). Moreover, only in the E-cadherin-preserved group was prognostic significance found according to N-cadherin expression (P < 0.01). We could not show a significant relationship between N-cadherin expression and EMT in gastric cancer. However, neo N-cadherin expression significantly affected patient's survival in gastric cancer. Therefore, we concluded that neo N-cadherin expression may be a useful prognostic marker independent of E-cadherin expression.     

Hypoxic inactivation of glycogen synthase kinase‐3β promotes gastric tumor growth and angiogenesis by facilitating hypoxia‐inducible factor‐1 signaling

Since the molecular mechanism of hypoxic adaptation in cancer cells is cell‐type specific, we investigated whether glycogen synthase kinase‐3β (GSK‐3β) activation is involved in hypoxia‐induced gastric tumor promotion. Stable gastric cancer cell lines (SNU‐638, SNU‐484, MKN1, and MKN45) were cultured under hypoxic conditions. Cells overexpressing wild‐type GSK‐3β (WT‐GSK‐3β) or kinase‐dead mutant of GSK‐3β (KD‐GSK‐3β) were generated and used for cell culture and animal studies. In cell culture experiments, hypoxia decreased GSK‐3β activation in gastric cancer cells. Cell viability and the expressions of HIF‐1α protein and VEGF mRNA in gastric cancer cells were higher in KD‐GSK‐3β transfectants than in WT‐GSK‐3β transfectants under hypoxic conditions, but not under normoxic conditions. Gastric cancer xenografts showed that tumor growth, microvessel area, HIF‐1α activation, and VEGF expression were higher in KD‐GSK‐3β tumors than in WT‐GSK‐3β tumors in vivo. In addition, the expression of hypoxia‐induced HIF‐1α protein was regulated by GSK‐3β at the translational level. Our data suggest that GSK‐3β is involved in hypoxic adaptation of gastric cancer cells as an inhibitory upstream regulator of the HIF‐1α/VEGF signaling pathway.     

Involvement of α‐ and β‐catenins and E‐cadherin in the development of mammary phyllodes tumours

Tsang J Y S, Mendoza P, Lam C C F, Yu A M C, Putti T C, Karim R Z, Scolyer R A, Lee C S, Tan P H & Tse G M
(2012) Histopathology  61, 667–674 Involvement of α‐ and β‐catenins and E‐cadherin in the development of mammary phyllodes tumours Aims: Phyllodes tumours (PT) are rare but clinically important fibroepithelial tumours of the breast. β‐Catenin, a key component in Wnt signalling, has been shown to be important in the development of PT. It also functions as a component of the cadherin complex, which may therefore be implicated in PT pathogenesis. By assessing stromal α‐catenin, β‐catenin and E‐cadherin expression in 158 PT cases using immunohistochemistry and examining associations with clinicopathological features, we aimed to determine the role of these proteins in PT pathogenesis. Methods and results: Cytoplasmic β‐catenin correlated with α‐catenin expression. A significantly higher expression of both markers was observed in borderline than in benign PT (P = 0.003 and <0.001, respectively), but a lower level was found in malignant PT. Cytoplasmic E‐cadherin expression was significantly higher in borderline and malignant than in benign PT (P = 0.001 and 0.012, respectively), but was not correlated with other markers. Both E‐cadherin and α‐catenin showed stronger correlations with histological parameters than β‐catenin. α‐Catenin showed a significant correlation with recurrence (P = 0.005 and 0.016, respectively). Conclusions: α‐ and β‐catenins may be important in the early stages of PT development, while E‐cadherin may be required for malignant development. The correlation of α‐catenin expression with tumour recurrence may be relevant in predicting PT behaviour.     

De novo CDH1 mutation in a family presenting with early-onset diffuse gastric cancer

In this report, we describe the first concluded case of a de novo germline mutation in CDH1 in a hereditary diffuse gastric cancer (HDGC) kindred. The incident case was a woman with a personal history of Hodgkin's lymphoma and diffuse gastric cancer, who was then confirmed to have a CDH1 mutation (c.1792 C>T (R598X)). The patient's mother was found to have the same CDH1 germline mutation; however, neither maternal grandparent was found to carry the mutation, thus leading to a conclusion that the proband's mother's mutation is of de novo origin. This case highlights the importance of recognition of the HDGC syndrome and of testing for CDH1 germline mutations in young individuals with diffuse gastric cancer without a family history of the disease.