Claudin 18.2 expression in various tumor types and its role as a potential target in advanced gastric cancer

Background: Alterations in claudin expression can impair tight junction function, influence signaling pathways, and act as a tumor-promoting event in some epithelial cancers. Recently, zolbetuximab, a highly potent and tumor cell-selective therapeutic antibody against claudin 18.2, has been developed and investigated in clinical trials. Methods: We conducted a prospective study using claudin 18.2 immunohistochemistry in 430 consecutive patients with advanced gastrointestinal, genitourinary, or rare cancers between June 2012 and March 2016. Results: Claudin 18.2 expression was evaluated in 96.3% of the patients (414/430) using immunohistochemistry. In total, 4.1% (17/414) of the patients were claudin 18.2-positive, including patients with pancreatic (16.7%, 1/6), gastric (14.1%, 12/85), biliary tract (6.3%, 1/16), genitourinary/miscellaneous (2.2%, 1/46), and colorectal (0.9%, 2/203) cancers. Twelve of 17 patients positive for claudin 18.2 had gastric cancers (GCs); this subgroup showed no statistical differences by gender, age, disease extent, primary tumor site, pathologic differentiation, human epidermal growth factor receptor 2, or Epstein-Barr virus status with or without claudin 18.2 expression. However, claudin 18.2 was more frequently positive in intestinal-type compared with diffuse-type as assessed by Lauren classification (P=0.026). There was no significant difference in overall survival (OS) between patients with and without claudin 18.2 expression (P=0.101). Conclusions: Our results add to the emerging literature about claudin 18.2 expression in various cancer types and support the need for extended clinical exploration of zolbetuximab.