Urinary laminin-γ2 is a novel biomarker of non-muscle invasive urothelial carcinoma

Lack of appropriate biomarkers has hampered early detection of urothelial cancer (UC), therefore, development of biomarkers for its diagnosis at earlier stages is of importance. Laminin-332 (Ln-332, formerly Ln-5), a component of basement membranes, consists of Ln-alpha 3, Ln-beta 3, and Ln-gamma 2 polypeptides. However, monomeric Ln-gamma 2 alone is frequently expressed in malignant neoplasms. If Ln-gamma 2 is also expressed in UC and secreted into the urine, its detection could be useful for UC diagnosis. Here, we evaluated Ln-gamma 2 levels from 60 patients with urinary diseases (including UC) by Western blotting, and detected it in approximately 53% of UC cases. Using immunohistochemistry, we confirmed Ln-gamma 2 expression in UC tissues that were positive for Ln-gamma 2, whereas Ln-alpha 3 expression was absent. We next developed a sandwich enzyme-linked immunosorbent assay and applied it for screening 39 patients with non-muscle invasive UC and 61 patients with benign urologic diseases. The Ln-gamma 2 levels were higher in UC patients than in those with benign urologic diseases. Ln-gamma 2 was detected even in patients with earlier stages of UC, such as Ta, T1, or carcinoma in situ. The sensitivity of Ln-gamma 2 testing for UC was 97.4%, and the specificity was 45.9%, using a cut-off of 0.5 mu g/g.crn. Ln-gamma 2 had greater diagnostic value for detecting non-muscle invasive UC compared to conventional urine cytology and available biomarkers for UC, and may be useful as a urine biomarker for the diagnosis and monitoring of UC.