 We will approach 50 gastric cancer patients treated in Rabin Medical Center, and ask for their consent to approach first degree relatives for participating in the study. For each gastric cancer patient 4 relatives will be asked to signed an informed consent and undergo the study procedures. For each participant a matched control for age, sex and background diseases, out of consecutive gastro esophageal reflux disease GERD patients undergoing gastroscopy, will be asked to join the study. Thus, we will screen 50 gastric cancer patients, 200 first degree relatives of gastric cancer patients, and 200 controls. 