A murine IgG1 monoclonal antibody (mAb) was developed to recognize a sialylated sugar chain, designated as KL-6,
by immunizing a mouse with the human lung adenocarcinoma cell line VMRC-LCR. KL-6 is now classified as a human
MUC1 mucin protein, and regenerating type II pneumocytes are the primary cellular source of KL-6/MUC1 in the
affected lungs of patients with ILD. A cooperative study on KL-6 as a serum biomarker was initiated with the diagnostic
division of Eidia Co., Ltd. (Tokyo, Japan) in 1992. The findings of this study led to the development of an enzymelinked
immunosorbent assay (ELISA) that enabled the determination of the absolute amount of KL-6 in samples
collected in clinical practice. KL-6 has been approved by Japan’s Health Insurance Program as a diagnostic marker for
ILDs since 1999, and KL-6 levels are examined in more than 2,000,000 samples per year in Japan.
Interstitial lung diseases (ILDs) are a diverse group of pulmonary disorders characterized by various patterns of
inflammation and fibrosis in the interstitium of the lung. The identification of serum biomarkers for ILDs would greatly
improve current diagnostic methods. To date, various serum biomarkers have been tested for their use in ILDs. Among
these, biomarkers derived from type II pneumocytes have been of particular interest, because ILDs show a common
pathophysiological development, i.e., type II pneumocyte injury or remodeling. Krebs von den Lungen-6 (KL-6) discovered bu us, was approved as a diagnostic marker for interstitial pneumonitis in Japan in 1998, and in EU in 2012. The clinical utility of KL-6 is becoming higher and higher around world recent years.
Based on the results from a number of reports investigating KL-6/MUC1, the serum levels of KL-6/MUC1 are thought
to be useful for (1) detecting the presence of disease, (2) evaluating disease activity, and (3) predicting outcomes in
various types of ILDs.
Because the measurement of serum KL-6/MUC1 levels is rapid, inexpensive, reproducible, less invasive, and easier
to perform than surgical lung biopsy, high-resolution computed tomography, bronchoscopic examination, and
pulmonary function tests, we believe that this biomarker would provide a significant benefit to the clinical management
of patients with ILDs.
(1) Japanese Patent No. 2011158: Nobuoki Kohno received patent royalties/licensing fees from Eisai Co., Ltd.
(2) Nobuoki Kohno received the Commendation for Science and Technology by the Minister of Education, Culture,
Sports, Science and Technology in 2011.