Correlation Between Expression of the Cancer/Testis Antigen KK-LC-1 and Helicobacter pylori Infection in Gastric Cancer

BACKGROUND/AIM: Our previous study indicated that Kita-kyushu lung cancer antigen-1 (KK-LC-1) is a cancer/testis antigen (CTA) expressed in 82% of gastric cancer cases. Here, we investigated the relationship between KK-LC-1 expression and Helicobacter pylori infection in Japanese patients with gastric cancer. PATIENTS AND METHODS: We examined CTA expression in 25 surgical gastric cancer specimens and anti-H. pylori IgGs in the serum of each patient. RESULTS: KK-LC-1 was expressed in 80% of tumor samples, markedly higher than melanoma antigen gene (MAGE)-A1, MAGE-A3, MAGE-A4, synovial sarcoma, X breakpoint 4 (SSX4) and New York esophageal squamous cell carcinoma-1 (NY-ESO-1). Anti-H. pylori IgG titers from the KK-LC-1-positive patients were significantly higher (67.5±7.6) than those from KK-LC-1-negative patients (15.8±7.5, p<0.01) although there were no significant differences between patients positive and negative for MAGE-A1, -A3 and-A4, SSX4 and NY-ESO-1. CONCLUSION: As far as we are aware, this is the first report of a correlation between a carcinogen and CTA expression in clinical samples. KK-LC-1 was frequently expressed in gastric cancer caused by H. pylori infection. The risk diagnosis for gastric cancer might be more accurate if KK-LC-1 expression status were also considered.