gastric cancer ( gc ) is identified to be the second widespread neoplasm around the world ( 1 ) . in spite of advances in surgical treatment and chemotherapy , environmental factors such as infection and diet have been considered to play critical roles in gc . although the genetic supposed to encompass an impressive capacity in gc development , this aspect has not been proved comprehensively ( 3 ) . moreover , there is an association between infection of h pylori and the possibility of gc occurrence ( 4 , 5 ) in addition ; several studies have demonstrated smoking can be one of the causes of gc ( 6 , 7 ) . cyclooxygenase ( cox ) known as prostaglandin endoproxide h synthase ( pghs ) and is a rate - limiting enzyme in prostaglandin synthesis . it converts free arachidonic acid into important prostanoids ( pgs ) and eicosanoids such as prostaglandin h2 ( 8) . three different isoforms of human cox , cox-1 , 
 cox-2 and cox-3 with independent genes and different expression pattern have been reported ( 9 ) . normally , cox-2 is undetectable in most of tissues but it can be activated by several inducers like cytokines , growth factor , tumor promoters and lipopolysacharides ( lps ) . some studies reported its stimulation by cigarette smoking leading to carcinogenesis ( 10 , 11 ) . it is also accounted for inflammatory responses and tumor progression ( 12 ) . over expression of cox-2 is considered to be an indispensable part of tumor development , angiogenesis , metastasis and inhibition of apoptosis ( 13 ) . additionally , the expression of cox-2 is controlled by convoluted signaling pathways such as -catenin signal transduction ( 14 ) . the involvement of important nuclear proteins like nf-b , cre , pea3 and nf - il-6 in interacting with the cox-2 promoter region is essential for regulating the expression of the gene ( 15 ) . elevated level of cox-2 has been related to development of many human cancers such as colorectal and breast ( 1618 ) and in particular gastric cancer ( 19 , 20 ) . the vulnerability to the progression of human cancers like prostate and breast can be as a consequence of genetics variations such as single nucleotide polymorphisms ( snp ) ( 21 , 22 ) . regarding the cox-2 gene , only a few polymorphisms observed in its promoter region appeared to have an efficient impact on the gene transcription ( 23 ) . nevertheless , the difference in mrna expression level of the gene under the existence of carcinogens among individuals is due to different patterns of snps in the operative regions of the gene ( 24 , 25 ) . an acknowledged polymorphism in the promoter region of cox-2 gene , featured by a guanine ( g ) to cytosine ( c ) transition at position 765 ( -765 g > c ) performs disruptions in a positive transcription activator , stimulatory protein 1 ( 24 ) . unfortunately , limited studies have been performed to date to scrutinize cox-2 polymorphisms in different forms of cancer and various diseases ( 2629 ) . it has been demonstrated that in iranian population , gastric cancer incidence is high and the rate of this disease have increased about two fold when compared with the data of 40 years ago ( 30 ) . this study was performed to investigate the influence of age and gender on association between -765 g > c cox-2 genetic polymorphism and the development of gastric adenocarcinoma among iranian samples . this study was executed between two groups of healthy people with no clinical presentation of cancer including 91 subjects and individuals with evident gastric adenocarcinomas ( n=91 ) . blood samples were stored in a -20 c freezer . using a standard salting - out protocol optical density ( od ) and concentration was measured using nanophotometer at 260 and 280 nm . a 157 bp dna segment was amplified using the following primers : forward 5-attctggcctcgccgcttc-3 and reverse 5-ctccttgtttcttggaaagagacg-3. pcr reactions were carried out using 10 l of prime taq premix ( 2x ) ( genet bio , korea ) , 0.7 l of each forward and reverse primers , 0.5 l genomic dna and 8.1 l ddh2o in a total volume of 20 l under following thermal conditions : 94 c for 5 min intended for the initial denaturation , 94 c ( 1 min ) for denaturation , 59 c ( 1 min ) for annealing and 72 c ( 1 min ) for extension repeating 35 cycles ( master cycler gradient eppendorf , usa ) . 9 l pcr reaction products were subjected to 0.7 l bsh1236i restriction endonuclease ( fermentas , vilnius , lithuania ) , 2 l of r buffer and 2.3 l of ddh2o for 11 h at 37 c. 3% agarose gel was utilized for electrophoresis and then dna fragments were separated based on their specific length . in all samples , c cox-2 polymorphism , the wild - type homozygous -765gg was cut into fragments of 134 bp and 23 bp , however the uncut homozygous -765 cc was 157 bp . the presence of all the three fragments ( 157 , 134 and 23 bp ) showed a heterozygous -765 gc . the 23 bp fragment was not identified in the agarose gel due to primer - dimer band . pcr - rflp analysis of -765 g > c cox-2 polymorphism ; lane 1 : 20 bp dna ladder ; lane 2 : pcr product ( undigested ) ; lane 3 : homozygous -765 cc genotype ; lanes 4 , 6 : homozygous -765 gg genotype ; lane5 : heterozygous-765 gc genotype . in this study , overall , 91 gastric adenocarcinoma patients ( 44 female and 47 male , mean age : 60.515.1 ) and 91 control normal ( 47 female and 44 male , mean age : 36.112.5 ) were enrolled . mean  standard deviation age of case and control groups there was a statistically significant difference between increasing of age and gastric adenocarcinoma risk ( odds ratio=1.12 , 95% ci=1.08 - 1.16 ; p < 0.001 ) . the frequency of the -765 > cc , gc and gg genotypes were 4.4% , 61.5% and 34% in controls and 4.4% , 68.1% and 27.5% in gastric adenocarcinoma patients respectively . however , differences were considered significant ( p=0.04 ) for female patients with c carrier genotypes ( sum : gc and cc ) and gastric adenocarcinoma when compared with male patients ( p=0.65 ) and control groups ( p=0.65 ) . based on the present results , we found that age and gender are important factors which are involved on association between -765 g > c cox-2 genetic polymorphism and gastric adenocarcinoma risk . although cox-1 is constitutively expressed , cox-2 expression is associated with various pathophysiological conditions , including inflammatory diseases and different cancers such as adenocarcinoma tissues and gastric precancerous ( 31 , 32 ) . molecular mechanisms and other pathways that are responsible for over expression of cox-2 protein has not elucidate completely . the current consensus is that both transcriptional and post - transcriptional events are important ( 33 ) . many studies suggest an important role of cox-2 in the carcinogenesis pathway including in the inhibition of apoptosis , tumor growth , angiogenesis , invasion and metastasis ( 34 ) . one of the most important polymorphism in cox-2 gene consisted on g / c transversion 765 nucleotides upstream from the transcription start ( 35 ) . for these reasons previously pereira et al have investigated the influence of the cox2 -765 g > c polymorphism on gastric cancers ( 36 , 37 ) . they have reported not only a nearly 3-fold increased risk of progression from gastric lesions into gastric cancer , but also described an associated between c - allele and gastric cancers . demonstrated that cox2- 765 g allele promoter polymorphism is associated with most kinds of gastric cancers ( 34 ) . in the present study , we investigated the presence of this nucleotide variant and recognized allelic frequencies of g-765c in the iranians for the first time , similar to those formerly reported in other studies ( 5 , 23 , 32 ) . we found no statistically significant between the presence of cc , gc and cc genotypes 765 g > c polymorphisms and risk of gastric cancer . however , we observed a border line statistically significant ( p=0.043 ) for female subjects with c- carrier genotypes when compared with male subjects ( p=0.645 ) and control groups ( p=0.653 ) . these results appear that gender may be a risk factor for the development of gastric adenocarcinoma related to cox-2 polymorphism in iranian samples . although the frequency of gc genotype is much higher than other similar published studies ( 5 , 26 , 34 ) , the frequency of gg ( 27.5% ) and c - carrier ( 72.5% ) genotypes are similar to indian population ( 5 ) . thus , it can be concluded that cox2 -765g / c polymorphism perhaps play a similar role in susceptibility to gastric cancer between asian populations . we found that , age factor can be excessively marker for gc because we observe a statistically significant difference between increasing of age and gc risk ( or=1.125 , 95ci=1.089 - 1.162 ) . in general , cox2 -765g / c polymorphisms possibly play a role in cancer development under specific situation or in specific populations . finally , we conclude that age and gender are important factors which can be involved on association between -765 g > c cox-2 genetic polymorphism and gastric adenocarcinoma risk in iranian samples .
aimthe purpose of this study was to investigate the possible influence of age and gender on association between -765 g > c cox-2 genetic polymorphism and gastric adenocarcinoma risk in iranian patients.backgroundthe promoter polymorphism of cox-2 gene -765 g > c has been described to play an important role in many cancers such as gastric cancer.patients and methodswe carried out single - nucleotide polymorphism analysis in iranian samples including 91 patients and 91 control normal using pcr- rflp technique.resultsstatistical analysis revealed no significant association between gg , gc and cc genotypes and risk of gastric adenocarcinoma 
 . however differences were considered significant ( p=0.043 ) for female subjects with c carrier genotypes ( gc and cc ) and gastric adenocarcinoma when compared with male patients ( p=0.645 ) and control groups ( p=0.653 ) . 
 also , there was a statistically significant difference between increasing of age and susceptibility for gastric adenocarcinoma ( odd ratio=1.125 , 95% ci=1.089 - 1.162).conclusionthese results suggested that iranian c carrier females can be more susceptible for gastric adenocarcinoma in comparison with control group . also increasing of age should be considered as a risk factor for this disease .