The glycolytic enzyme enolase (2-phospho-D-glycerate hydrolyase) exists as several dimeric isoenzymes (αα, αβ, ββ, γγ) composed of three distinct subunits: α, β, γ. Three isoenzymes are found in the human brain: αα, αβ, and γγ. The heterologous αγ isoenzyme and the homologous γγ isoenzyme are known as neuron-specific enolases (NSE), as these isoenzymes initially were detected in neurons and neuroendocrine cells. This ELISA detects both the αγ and γγ forms by using monoclonal antibodies specific to the γ enzyme subunit.
NSE levels are low in the normal healthy population, as well as in people with benign disease. Lung cancer is one of the most common cancer forms with incidences of about 50-100 per 100,000 people. Approximately 20% of lung cancers are of the small cell variety. NSE has been shown to be a valuable tumor marker of neuroendocrine origin, particularly in small cell lung cancer and neuroblastoma.