C/EBPß regulates homeostatic and oncogenic gastric cell proliferation.

Cancer of the stomach is among the leading causes of death from cancer worldwide. The transcription factor C/EBPß is frequently overexpressed in gastric cancer and associated with the suppression of the differentiation marker TFF1. We show that the murine C/EBPß knockout stomach displays unbalanced homeostasis and reduced cell proliferation and that tumorigenesis of human gastric cancer xenograft is inhibited by knockdown of C/EBPß. Cross-species comparison of gene expression profiles between C/EBPß-deficient murine stomach and human gastric cancer revealed a subset of tumors with a C/EBPß signature. Within this signature, the RUNX1t1 tumor suppressor transcript was down-regulated in 38 % of gastric tumor samples. The RUNX1t1 promoter was frequently hypermethylated and ectopic expression of RUNX1t1 in gastric cancer cells inhibited proliferation and enhanced TFF1 expression. These data suggest that the tumor suppressor activity of both RUNX1t1 and TFF1 are mechanistically connected to C/EBPß and that cross-regulation between C/EBPß-RUNX1t1-TFF1 plays an important role in gastric carcinogenesis. KEY MESSAGE: C/EBPß controls proliferation and differentiation balance in the stomach. Homeostatic differentiation/proliferation balance is altered in gastric cancer. RUNX1t1 is a C/EBPß-associated tumor suppressor. RUNX1t1 negatively regulates C/EBPß pro-oncogenic functions.

Interleukin-1B signalling leads to increased survival of gastric carcinoma cells through a CREB-C/EBPß-associated mechanism.

BACKGROUND: Polymorphisms in inflammation-related genes have been associated with a risk of gastric carcinoma (GC). However, the biological mechanisms underlying these associations are still elusive. Our objective was to determine whether chronic inflammation-associated IL1Β signalling, as seen in the context of Helicobacter pylori infection, could be linked to gastric carcinogenesis by modulating the behaviour of gastric epithelial cells. METHODS: The effect of IL1B was assessed by studying the expression and activation status of the IL1Β-activated transcription factors C/EBPß and CREB in GC cell lines. Interaction between CREB and C/EBPß was explored through interference RNA, chromatin immunoprecipitation and chemical inhibition. CREB and C/EBPß expression was analysed in 66 samples of primary GC and in normal gastric mucosa. GC cell growth was analysed in vitro by BrdU incorporation and in vivo employing a chicken embryo chorioallantoic membrane model. RESULTS: We found that IL1B regulates the expression/activation status of both C/EBPß and CREB in GC cells through an ERK1/2-dependent mechanism. Our results show that CREB is a direct transactivator of CEBPB, acting as an upstream effector in this regulatory mechanism. Furthermore, we found CREB to be overexpressed in 94 % of GC samples and significantly associated with C/EBPß expression (P < 0.05). Finally, we demonstrated both in vitro and in vivo that CREB can mediate IL1B-induced GC cell proliferation. CONCLUSIONS: Our results support the hypothesis that the effect of chronic inflammation on gastric carcinogenesis, as seen in the context of genetically susceptible individuals infected with Helicobacter pylori, includes the modulation of signalling pathways that regulate survival mechanisms in epithelial cells. IL1B is able to increase the expression/activation status of CREB and its target gene C/EBPß, which are mandatory for GC cell survival. Our results may help inform new strategies for the prevention and treatment of GC, including the control of chronic inflammation.

Hacking cell differentiation: transcriptional rerouting in reprogramming, lineage infidelity and metaplasia.

Initiating neoplastic cell transformation events are of paramount importance for the comprehension of regeneration and vanguard oncogenic processes but are difficult to characterize and frequently clinically overlooked. In epithelia, pre-neoplastic transformation stages are often distinguished by the appearance of phenotypic features of another differentiated tissue, termed metaplasia. In haemato/lymphopoietic malignancies, cell lineage ambiguity is increasingly recorded. Both, metaplasia and biphenotypic leukaemia/lymphoma represent examples of dysregulated cell differentiation that reflect a history of trans-differentiation and/or epigenetic reprogramming. Here we compare the similarity between molecular events of experimental cell trans-differentiation as an emerging therapeutic concept, with lineage confusion, as in metaplasia and dysplasia forecasting tumour development.

C/EBP alpha expression is associated with homeostasis of the gastric epithelium and with gastric carcinogenesis.

Transcription factors from the CCAAT/enhancer-binding protein (C/EBP) family are fundamental for the control of differentiation and proliferation of many adult tissues. C/EBP alpha has a crucial role in inducing terminal differentiation and is an established tumor suppressor gene in several cancer models. The objective of this study was to analyze the putative role of C/EBP alpha in gastric carcinoma (GC). We analyzed the expression of C/EBP alpha in normal and neoplastic gastric tissues, and assessed the role of C/EBP alpha on proliferation and differentiation of GC cells. In normal gastric mucosa, C/EBP alpha is expressed in the foveolar epithelium and co-localizes with the gastric differentiation marker trefoil factor 1 (TFF1). The expression of C/EBP alpha was found to be lost in 30% of GC cases. To evaluate the role of C/EBP alpha in cell proliferation and differentiation, we transfected GC cells with a full-length C/EBP alpha protein. We observed a significant decrease in proliferation in C/EBP alpha-transfected cells. This was accompanied by a decrease in Cyclin D1, an increase in P27 expression, and an increased expression of TFF1. Finally, we showed that inhibition of the Ras/MAPK pathway leads to increased C/EBP alpha and TFF1 expression, and decreased cell proliferation and cyclin D1 expression in GC cells. Our results suggest that C/EBP alpha (together with other members of the C/EBP family) has an active role in the control of differentiation and proliferation in normal gastric mucosa. In GC, loss of C/EBP alpha may be associated with the switch from a cellular differentiation to a cellular proliferation program, presumably as a consequence of Ras/MAPK pathway activation.

Tumor necrosis factor alpha extended haplotypes and risk of gastric carcinoma.

The tumor necrosis factor alpha (TNFA)-308*A allele has been found to confer an increased risk of gastric carcinoma. Inconsistency in risk estimates across populations lead us to hypothesize about the presence of an alternative causal locus in the same chromosomal region. A suitable approach is to determine the tumor necrosis factor haplotypic structure in order to clarify whether the association between the *A allele and the increased risk of gastric carcinoma is etiologic or secondary to linkage disequilibrium. Firstly, we assessed the association between the TNFA-308G>A polymorphism and the risk of gastric carcinoma in a population from Northern Portugal (508 gastric carcinoma patients, 713 controls); secondly, we genotyped five microsatellite loci (TNFa, b, c, d, e) flanking the TNFA-308G>A locus to establish the haplotypic structure associated with this single-nucleotide polymorphism in cases (122 patients) and controls (169 individuals). We found a significant association between the *A allele and increased risk of gastric carcinoma (odds ratio, 1.7; 95% confidence interval, 1.3-2.2) confirming previous results in our population. Regarding the *A allele-associated haplotypes, the most relevant difference was found for the H1A haplotype present in 33.1% of the cases and 12.5% of the controls. We also observed haplotypes associated with the *A allele that were found only in cases or controls. A population differentiation test showed that the gastric carcinoma and the control groups were significantly different for the *A allele haplotypic structure. This suggests that the association between the TNFA-308G>A polymorphism and increased risk of gastric carcinoma is dependent on linkage disequilibrium with an as yet unidentified locus.

NOD2/CARD15 and TNFA, but not IL1B and IL1RN, are associated with Crohn's disease.

BACKGROUND: NOD2/CARD15 was described as the first susceptibility gene to Crohn's disease (CD). Polymorphisms in the TNFA gene and in the IL1 gene cluster, which are associated with an enhanced chronic inflammatory response, may also play a role in the development of CD. The aim of this study was to determine the association of polymorphisms in the CARD15, TNFA, IL1B, and IL1RN genes with risk of development of CD and with the clinicopathological profile of CD patients. METHODS: In a case-control study including 235 CD patients and 312 controls (929 controls for TNFA genotyping), the CARD15 (R702W, G908R, and 1007fs), TNFA (-308G/A and -857C/T), IL1B (-511C/T), and IL1RN (intron 2 variable number of tandem repeats) polymorphisms were genotyped. RESULTS: We observed a significant association between CD and the CARD15 polymorphisms, with an odds ratio (OR) of 2.9 [95% confidence interval (CI), 1.9 to 4.6] for carriers of 1 variant allele and an OR of 11.8 (95% CI, 3.5 to 40.4) for carriers of 2 variant alleles. Patients with CARD15 polymorphisms had more frequently ileal or ileocolonic disease location, stricturing phenotype, abdominal surgery, and no extraintestinal manifestations. The TNFA-308A/A genotype was associated with susceptibility to CD with an OR of 3.0 (95% CI, 1.2 to 7.2). TNFA-308A/A homozygotes showed a higher frequency of erythema nodosum and arthritis, colonic disease location, and absence of abdominal surgery. No associations were found with the TNFA-857, IL1B-511, and the IL1RN VNTR polymorphisms. CONCLUSIONS: These findings suggest that CARD15 and TNFA-308 genetic polymorphisms are associated with increased risk of CD displaying distinct clinicopathological profiles.