Gastric Cancer: Molecular Pathology State

Despite the progressive decrease observed in the past fifty years, gastric cancer (GC) is the fourth of the world rankings incidence of various types of cancer and is the second as a cause of cancer-related death. There is distinct geographical variation in gastric cancer incidence with the highest rates reported from Japan, Korea and Eastern Asia. Other high incidence areas are Eastern Europe and parts of Latin America, while Western Europe, Africa, Australia and the US generally have low incidence rates. In the last decade there has been a downward trend in the incidence and mortality from this cancer. The reasons are to be found in the improvement of food both as regards its preservation procedures and the variability in the diet and for the decrease of infection by Helicobacter pylori (H. pylori). H. pylori infection is strongly associated with risk for stomach cancer. Likely, this association is supported by the strong link between this bacterium infections and precancerous lesions, including chronic atrophic gastritis and dysplasia. The development of gastric cancer is characterized by multistage process in which several alterations of genetic and epigenetic nature accumulate. These alterations are mainly related to abnormalities of growth factors and receptors, DNA mismatch repair genes, angiogenic factors, transcription factors, adaptor proteins, cell cycle regulators, and many other macromolecular cell components. All these abnormalities identify from one side the molecular and biological aspect of gastric cancer cells and from the other might suggest possible strategies for therapeutic intervention

Role of Gastrokine 1 in Gastric Cancer

Gastric cancer (GC) has high incidence (> 1.000.000 new cases/year) and mortality rate in several countries and is still one of the most frequent and lethal (> 600.000 dead/year) neoplasia with an average surviving of five years (less than 20%) (Pisani et al., 1990; Lands et al., 1998). It is already well known that infection of gastric antrum mucosal with the bacterium Helicobacter pylori is the cause of the chronic inflammation that leads to intestinal-type gastric cancer in the majority of the cases. The H. pylori infection is widespread but only a small number of the total population of infected individuals might eventually develop adenocarcinoma (around 3/10,000 individuals per year or 2.1% for lifetime infection) 27 (Correa & Piazuelo, 2008). Risk factors influencing the outcome of H. pylori–associated pathology include bacterial cytotoxic heterogeneity, diet, and geographic differences. The phenomenon of decreased gastric cancer incidence in Africa compared with other regions where H. pylori is endemic 28 (Holcombe, 1992) is probably due to the different diet of these populations compared to the western countries. This discrepancy has been partially attributed to helminth co-infection that likely modifies the characteristic proinflammatory type 1 T-helper 1 cell response, to a T-helper 2–predominant response 29 (Whary et al., 2005), typified by the release of non-inflammatory cytokines and reduced incidence of H. pylori–associated glandular atrophy, an early marker of cancer development. The identification of novel genes regulated by H. pylori in vivo, particularly those contributing to these early stages of gastric cancer, would facilitate improved understanding of the differential susceptibility to this pathogen. The different susceptibility among individuals to H. pylori infection is still not yet defined. Some works, however, suggested that the polymorphisms in host genetic factors like the proinflammatory cytokines interleukin-1, interleukin-8, and tumor necrosis factor may play a relevant role 30 (El-Omar et al., 2003). The evolution of intestinal tumours is characterized by a progression of several sequential steps that starts with gastritis and then progresses to mucosal atrophy (atrophic gastritis), intestinal metaplasia, dysplasia and carcinoma with subsequent metastatic dissemination (Correa, 1992, 1995). The diffuse-type has instead a poorer prognosis and develops through unknown genetic and morphological events from normal gastric epithelium. No preceding steps have been identi_ed in the pathogenesis of diffuse carcinoma other than the chronic gastritis. The pathogenesis of gastric cancer remains poorly understood although it is evident that several environmental factors, such as H. pylori infection can be one of the causes leading to this disease. In fact, the risk to develop gastric cancer is increased in patients with H. pylori infections probably as the result of a combination of genetic and environmental factors in which the infection by H. pylori is of particular relevance, especially when the inflammation involves the gastric body region with respect to the antrum (Correa, 1995; Goldstone et al., 1996; Nabewera & Logan, 1999). Generally, this condition is associated to different degrees of atrophy and alterations of the secretor function that, in the long term, became associated to gastric carcinoma (Forman et al., 1991; Parsonnet et al., 1997; Watanabe et al., 1998). Diffuse adenocarcinoma shows an increased propensity for intra and transmural spread and is therefore associated with a poorer prognosis. Unfortunately, the histological classification of an individual gastric adenocarcinoma is not clear-cut with a tumour often comprising a mixture of intestinal and diffuse tissue types. Under these considerations, we think that there is an urgent necessity to dispose of an efficient tool for the detection of early stage gastric cancer like the identification of highly sensitive and specific biomarkers that will aid disease diagnosis and ensure early clinical intervention, thereby preventing mortality and reducing morbidity (Boussioutas & Taupin, 2001). Since most of GC (around 73%) is developed at antrum/pylorus, proteins secreted by antrum/pylorus mucosa might play a critical role in maintaining normal gastric mucosa structure and function

Cellular Interaction of Human Eukaryotic Elongation Factor 1A Isoforms

Besides its canonical role in protein synthesis, the eukaryotic translation elongation factor 1A (eEF1A) is also involved in many other cellular processes such as cell survival and apoptosis. We showed that eEF1A phosphorylation by C-Raf in vitro occurred only in the presence of eEF1A1 and eEF1A2, thus suggesting that both isoforms interacted in cancer cells (heterodimer formation). This hypothesis was recently investigated in COS-7 cells where fluorescent recombinant eEF1A isoforms colocalized at the level of cytoplasm with a FRET signal more intense at plasma membrane level. Here, we addressed our attention in highlighting and confirming this interaction in a different cell line, HEK 293, normally expressing eEF1A1 but lacking the eEF1A2 isoform. To this end, His-tagged eEF1A2 was expressed in HEK 293 cells and found to colocalize with endogenous eEF1A1 in the cytoplasm, also at the level of cellular membranes. Moreover, FRET analysis showed, in this case, the appearance of a stronger signal mainly at the level of the plasma membrane. These results confirmed what was previously observed in COS-7 cells and strongly reinforced the interaction among eEF1A isoforms. Moreover, the formation of eEF1A heterodimer in cancer cells could also be important for cytoskeleton rearrangements rather than for phosphorylation, most likely occurring during cell survival and apoptosis

Role of Gastrokine 1 in Gastric Cancer

Gastric cancer (GC) has high incidence (> 1.000.000 new cases/year) and mortality rate in several countries and is still one of the most frequent and lethal (> 600.000 dead/year) neoplasia with an average surviving of five years (less than 20%) (Pisani et al., 1990; Lands et al., 1998). It is already well known that infection of gastric antrum mucosal with the bacterium Helicobacter pylori is the cause of the chronic inflammation that leads to intestinal-type gastric cancer in the majority of the cases. The H. pylori infection is widespread but only a small number of the total population of infected individuals might eventually develop adenocarcinoma (around 3/10,000 individuals per year or 2.1% for lifetime infection) 27 (Correa & Piazuelo, 2008). Risk factors influencing the outcome of H. pylori–associated pathology include bacterial cytotoxic heterogeneity, diet, and geographic differences. The phenomenon of decreased gastric cancer incidence in Africa compared with other regions where H. pylori is endemic 28 (Holcombe, 1992) is probably due to the different diet of these populations compared to the western countries. This discrepancy has been partially attributed to helminth co-infection that likely modifies the characteristic proinflammatory type 1 T-helper 1 cell response, to a T-helper 2–predominant response 29 (Whary et al., 2005), typified by the release of non-inflammatory cytokines and reduced incidence of H. pylori–associated glandular atrophy, an early marker of cancer development. The identification of novel genes regulated by H. pylori in vivo, particularly those contributing to these early stages of gastric cancer, would facilitate improved understanding of the differential susceptibility to this pathogen. The different susceptibility among individuals to H. pylori infection is still not yet defined. Some works, however, suggested that the polymorphisms in host genetic factors like the proinflammatory cytokines interleukin-1, interleukin-8, and tumor necrosis factor may play a relevant role 30 (El-Omar et al., 2003). The evolution of intestinal tumours is characterized by a progression of several sequential steps that starts with gastritis and then progresses to mucosal atrophy (atrophic gastritis), intestinal metaplasia, dysplasia and carcinoma with subsequent metastatic dissemination (Correa, 1992, 1995). The diffuse-type has instead a poorer prognosis and develops through unknown genetic and morphological events from normal gastric epithelium. No preceding steps have been identi_ed in the pathogenesis of diffuse carcinoma other than the chronic gastritis. The pathogenesis of gastric cancer remains poorly understood although it is evident that several environmental factors, such as H. pylori infection can be one of the causes leading to this disease. In fact, the risk to develop gastric cancer is increased in patients with H. pylori infections probably as the result of a combination of genetic and environmental factors in which the infection by H. pylori is of particular relevance, especially when the inflammation involves the gastric body region with respect to the antrum (Correa, 1995; Goldstone et al., 1996; Nabewera & Logan, 1999). Generally, this condition is associated to different degrees of atrophy and alterations of the secretor function that, in the long term, became associated to gastric carcinoma (Forman et al., 1991; Parsonnet et al., 1997; Watanabe et al., 1998). Diffuse adenocarcinoma shows an increased propensity for intra and transmural spread and is therefore associated with a poorer prognosis. Unfortunately, the histological classification of an individual gastric adenocarcinoma is not clear-cut with a tumour often comprising a mixture of intestinal and diffuse tissue types. Under these considerations, we think that there is an urgent necessity to dispose of an efficient tool for the detection of early stage gastric cancer like the identification of highly sensitive and specific biomarkers that will aid disease diagnosis and ensure early clinical intervention, thereby preventing mortality and reducing morbidity (Boussioutas & Taupin, 2001). Since most of GC (around 73%) is developed at antrum/pylorus, proteins secreted by antrum/pylorus mucosa might play a critical role in maintaining normal gastric mucosa structure and function

Structural characterization of recombinant humangastrokine-1: biochemical properties of the purified protein

Gastric cancer (GC) is one of the most leading cause of cancer death. The high mortality is due to late diagnosis, although the gastric infection by Helicobacter pylori represents one of the most significant risk factors for this type of cancer. Gastrokine-1 (GKN1) is expressed in normal gastric tissue, while it is scarcely present in samples from patients infected by H. pylori, and completely absent in GC tissues and cell lines. Therefore, GKN1 could be a potential marker for GC diagnosis and a possible tumor suppressor. In order to get more insights into the molecular mechanisms on the pathology of GC, this study was directed to better understand the structural features and the biological activity of this protein. In details, this study was directed to: 1) synthesis of recombinant mature GKN1 by cloning, expression and purification; 2) characterization of structural and biochemical properties of recombinant GKN1 by circular dichroism, fluorescence spectroscopy, and limited proteolysis; 3) evaluation of the effect of recombinant GKN1 on gastric cancer cell lines growth; 4) construction of a 3D structural model of the protein. The first protocol for biosynthesis and purification of native human GKN1 in the homologous expression system of Pichia pastoris was settled. The use of biochemical analytical methods such as limited proteolysis led to the identification of exposed amino acid residues on the protein surface. The resistance of GKN1 to the action of proteolytic enzymes was somehow explanatory of its stability in the harsh stomach environment. Spectroscopic studies (fluorescence and circular dichroism) showed that the protein is endowed by a non-proper globular structure due probably to the presence of two domains. These domains showed a different behaviour toward chemical and physical denaturant. The results well correlate with predicted GKN1 secondary structure and 3D structure model. Finally, the recombinant protein showed anti-proliferative properties on gastric cancer cell lines. Our findings contribute to a preliminary clarification of the role of GKN1 in the pathogenesis of gastric cancer

Role of human GKN1 on APP processing in gastric cancer

Gastrokine 1 (GKN1) is highly expressed in gastric tissue and is secreted into the stomach but is not expressed in gastric cancer. GKN1 belongs to the BRICHOS domain family and plays a major role in maintaining gastric mucosa integrity. We previously demonstrated that a recombinant human GKN1 protein was able to interact with the amyloid precursor protein (APP) and was endowed with an anti-amyloidogenic property because it inhibited polymerization of the Aβ(1-40) peptide released from APP upon its partial hydrolysis. Here, we report that GKN1 can act as a physiological suppressor of Aβ production in gastric cancer cells. GKN1 blocked the access of γ-secretase to APP, thereby facilitating the cleavage of APP by α- and β-secretases. GKN1 directly interacted with APP C-terminal fragments, C83 and C99. In addition, it did not affect γ-secretase activity in gastric cancer cells because it did not alter Notch1 processing. GKN1-mediated inhibition of APP processing might represent a new approach for the prevention and therapy of Alzheimer's disease (AD)

Overexpression of gastrokine 1 in gastric cancer cells induces Fas-mediated apoptosis.

Gastrokine 1 (GKN1) is involved in the replenishment of the surface lumen epithelial cell layer, in maintaining the mucosal integrity, and could play a role in cell proliferation and differentiation. In fact, after injury of the gastric mucosa, restoration may occur very rapidly in the presence of GKN1. In contrast, if the protein is downregulated, the repair process may be hampered; however, application of GKN1 to gastrointestinal cells promoted epithelial restoration. Because GKN1 possesses some mitogenic effects on intestinal epithelial cells (IEC- 6) whereas this protein was also capable of inhibiting proliferation in gastric cancer cells (MKN28), we decided to study its involvement in apoptosis to understand the role of GKN1 in the modulation of inflammatory damage or tumorigenesis in gastric mucosa. We found by cytofluorimetry, Western blot and RT-PCR that the overexpression of GKN1 in gastric cancer cell lines (AGS and MKN28) stimulated the expression of Fas receptor. Moreover, compared to control cells, a significant increase of apoptosis, evaluated by TUNEL, was observed when GKN1 transfected cells were treated with a monoclonal antibody (IgM) anti-Fas. The activation of Fas expression was also observed by the overexpression of GKN1 in other cancer cell lines. Moreover, in GKN1-overexpressing gastric cancer cells exposed to FasL, the activation of caspase-3 was also observed by Western blot and fluorescence assays. Our data represent the first report for GKN1 as modulator of apoptotic signals and suggest that GKN1 might play an important role for tissue repair during the early stages of neoplastic transformation

Role of Gastrokine 1 in Gastric Cancer: A Potential Diagnostic Marker and Antitumor Drug

Gastric cancer is still one of the prevalent leading causes of cancer-related deaths worldwide. The high mortality rate is mainly due to late-stage diagnosis, which has a very poor prognosis (five-year survival rates are as little as 3-10%). By contrast, early stage gastric cancer is highly curable with five-year survival rates exceeding 90%. Early detection is therefore the single most important factor influencing the outcome for gastric cancer patients. However, there are currently no biomarkers of acceptable sensitivity and specificity to detect early stage gastric cancer. Gastric infection with Helicobacter pylori (H. pylori) seems to be a risk factor for gastric cancer. Epidemiological studies have shown that patients that test serum positive to H. pylori infection are associated with a three- to six-fold increase in the risk of gastric cancer, findings that are compatible with pathological links between H. pylori-associated gastritis, pre-cancerous lesions, and subsequent cancer of the stomach. In a previous study, moving from genomic to proteomic investigation, we have identified a protein, gastrokine 1 (GKN1), a stomach-secreted protein previously named AMP-18 (18kDa Antrum Mucosa Protein) that was highly expressed in normal tissues and significantly down-regulated in H. pylori positive patients with respect to H. pylori negative subjects. In addition, we have also found that GKN1 is normally expressed in gastric mucosa but not in primary tumours, both at the transcriptional and translational levels. On the basis of these findings, we propose that GKN1 can be used as a new molecular marker that could be useful to predict early cell transformation and might be a potential novel target for gastric cancer therapeutics. Moreover, we have also found that recombinant GKN1 affect cancer cell growth and that the transient expression of GKN1 in human gastric cancer also inhibits cell growth and induces apoptosis, thus suggesting the importance of GKN1 in preventing cancer development in gastric tissues. Finally, we hypothesize that GKN1 might act as a tumor suppressor and thus foresee its importance as an antitumor drug

An overview on factors underlying gastric cancer; strategies for its management with particular reference to diet

The incidence of stomach cancer and the number of victims of this disease have decreased dramatically over the last 60 years. However, gastric cancer still remains a very serious disease that requires further studies to enlarge knowledge on its causes and to prevention methods. To date, the causes of gastric cancer are still not yet well known but it is clear that some people are more prone than others to develop this disease. Gastric cancer affects mostly adults aged 55 and over and men in percentage double than women. Stomach ulcer apparently does not increase the risk of gastric cancer however, Helicobacter pylori, usually due to inflammation and gastric ulcers, may be an important risk factor for this disease. Moreover, patients who have undergone stomach surgery or suffering from pernicious anemia, achlorhydria or atrophic gastritis (that typically produce a reduction in the amount of acid) are subject to a higher risk of gastric cancer. Exposure in workplaces to certain agents such as dust or fumes is linked to a higher risk than average of developing stomach cancer. Smoking also contributes to increase this risk. Moreover, epidemiological studies and animal models, conducted for years, have shown that some eating habits can increase the risk of cancer. Other studies instead report that fresh foods (especially fruits and vegetables) play a protective function against gastric cancer. For this reason, this paper provides an overview of the possible causes of gastric cancer and the different therapeutic approaches, focusing in particular on the effects of diet