Gastric Cancer

Gastric or stomach cancer is the second most frequent death cause of cancer, after lung cancer, around the world. Almost two-thirds of cases occur in Eastern Europe, South America, and Asia with 42% in China alone. In the United States, in 2009, an estimated 21,130 new cases of gastric cancer were diagnosed and were associated with 10,620 deaths (Jemal et al., 2009), and it is one of the most common cancers in Europe ranking fifth after lung, prostate, colorectal, and bladder cancers in men and breast, colorectal, lung, and cancer of the corpus uteri in women. Sex-dependent ratio is (the male-to-female ratio in incidence rates) about 1.6:1 (Boyle and Ferlay, 2005).

There are geographic and ethnic differences in gastric cancer incidence in the world and in its trends for each population with time. The incidence patterns observed among immigrants change according to where they live. These factors indicate the close association of gastric cancer with modifiable factors such as diet. Substantial evidence from ecological, case-control, and cohort studies strongly suggest that the risk of cancer increases with a high intake of various traditional salt-preserved foods as well as salt per se and that this risk could be decreased with a high intake of fruit and vegetables (Kono and Hirohata, 1996). Also, there is some evidence that the intake of green tea and vitamin C is associated with the risk of gastric cancer. A recent report of a joint World Health Organization (WHO) and Food and Agriculture Organization (FAO) Expert Consultation concluded that salt-preserved food and salt probably increase the risk of gastric cancer, whereas fruit and vegetables probably decrease the risk (Petersen, 2003). Genetic factors are also important for the risk of gastric cancer. Approximately 10% of cases show a genetic component. Other established nondietary factors include cigarette smoking (Anton-Culver et al., 1993) and infection with the Helicobacter pylori. Although H. pylori lives in between the mucosal and the epithelial cells of the human stomach without adverse consequences, the presence of H. pylori is associated with an increased risk of gastric adenocarcinoma (Linz et al., 2007).

The potential of the marine algae has been the driving force for the researchers to focus on the benefits of algae (Barros et al., 2005; Puglisi et al., 2004). The prevention of gastric cancer therefore represents one of the most important aspects of any cancer control strategy in around the world. Hence, radical scavenging compounds such as polysaccharides from seaweeds can be used indirectly to reduce cancer formation in human body.

Porphyran is sulfated polysaccharides from marine algae. Kwon and Nam purified polysaccharides from Porphyra haitanesis and evaluated its anticancer activity on AGS human adenocarcinoma cell (Kwon and Nam, 2006). It has been known that specific IGF-IR inhibition with neutralizing antibody, antagonistic peptide, or selective kinase inhibitor has activity against diverse tumor cell types and is one of the causes of antiprolifera-tive/proapoptotic molecular induction (Li et al., 2004; Saxena and Moorthy, 2007). In the study, the effect of IGF-I on porphyran-treated AGS cells was determined, and the result they declared that porphyran-induced apoptosis is involved in the IGF-IR-mediated signaling pathway in AGS gastric cancer cells. Moreover a porphyran purified from Porphyra yezoensis confirmed its apoptotic activity on AGS human adenocarcinoma cell line (Kwon and Nam, 2007). Porphyran that was isolated from red alga P. yezoensis also shows the apoptotic activity on AGS cell line. Further, Kwon and Nam declared that porphyran from different marine algae showed same apoptotic activity on AGS cell line by following mitochondrial pathway (Kwon and Nam, 2007).

Hwang et al. declared that polysaccharide extracted from Capsosiphon fulvescens inhibited alcohol-induced cell death and reduced the expressions of cyclooxygenase-2 (COX-2) and the inducible form of nitric oxide (iNOS), proteins related to ulcers (Hwang et al., 2008). They proved that polysaccharide from marine algae also can be used as cancer protection agent.

Moreover, fucoidan is a fucan sulfate occurring in brown marine algae. Shibata et al. studied the inhibitory effect of Cladosiphon fucoidan on H. pylori adhesion to human stomach (Shibata et al., 1999). Their researches proved that fucoidan inhibited bacterial binding to human gastric cell. It was also shown that this fucoidan blocks both Leb- and sulfatide-mediated attachment of H. pylori to gastric cells.

Hiroe et al. reported that glycoprotein which extracted from brown alga ''Laminaria japonica induces apoptosis on AGS adenocarcinoma cells.'' They declared that glycoprotein extracted from L. japonica inhibited AGS cell growth by following multiple apoptotic (extinct and instinct) pathways. Treatment of glycolipid caused some changes in the Fas receptor pathway and the mitochondrial pathway (Go et al., 2010).

Besides, acetone + methylane chloride and methanol extract of Carpo-peltis affinis, Sargassum tortile, Sargassum horneri, Sargassum fulvellum, Col-pomenia sinuosa, Sargassum yezoense, and Sargassum hemiphyllum inhibit the AGS cells' growth (Choi et al., 2006). Besides methanol extract of marine algae L. japonica, Porphyra tenera, Gelidium amansii, and Ecklonia cava has inhibitory activity on AGS cell growth (Choi et al., 2006). Their mechanism to inhibitions has not been clarified yet.

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