Evaluation of γ-enolase as a tumor marker for lung cancer

The alpha-enolase and gamma-enolase in tumor tissues and sera of patients with lung cancer were determined with an enzyme immunoassay system. Tissue gamma-enolase in small cell carcinoma of the lung (SCCL, n = 11), large cell carcinoma (n = 11), and non-SCCL (except for large cell carcinoma) (n = 34) were enhanced approximately 35-fold, ninefold, and fourfold, respectively; tissue gamma/alpha + gamma value of SCCL was significantly higher than that of normal lung tissue (P less than 0.01). Serum gamma-enolase level was elevated (greater than 6.0 ng/ml) in 14/18, 3/10, and 15/60 patients with SCCL, large cell carcinoma, and non-SCCL (except for large cell carcinoma), respectively, and serum gamma/alpha + gamma value of SCCL was significantly higher than that of healthy subjects (P less than 0.01). Immunohistochemically, the gamma-enolase was positive in 29/31 of the lung cancers. Serum gamma-enolase value is a useful tumor marker for staging and monitoring treatment of patients with lung cancer, and serum gamma/alpha + gamma value may be useful for differential diagnosis of SCCL from non-SCCL or in differentiating lung cancers possessing neuroendocrine features from other lung cancers.