Electrophoretic Assessment of Aqueous and Serum Neurone-specific Enolase in Retinoblastoma and Ocular Malignant Melanoma

The isoenzyme pattern of enolase was examined in the aqueous humour and serum of patients with retinoblastoma (10 aqueous, 8 sera), malignant melanoma (4 aqueous, 25 sera), and normal subjects undergoing cataract surgery (25 aqueous, 30 sera). The assay we used allowed assessment of all three major isoenzymes, including the gamma gamma isoenzyme (neurone-specific enolase). No enolase was detectable in normal aqueous; alpha alpha isoenzyme was present in the aqueous of one patient with malignant melanoma, while aqueous from all patients with retinoblastoma contained both alpha alpha and gamma gamma. Normal serum contained only an alpha alpha band, while serum from patients with retinoblastoma contained alpha alpha, alpha gamma, and gamma gamma bands (7 sera, 87.5%), or alpha alpha only (1 patient, 12.5%). All sera from patients with malignant melanoma contained the alpha alpha band, with low levels of gamma gamma in 16 (60%). In a single patient with Coats's disease alpha alpha was present in the serum, but no enolase was detected in aqueous. Increased amounts of gamma-containing isoenzymes of enolase are found in both serum and aqueous from patients with retinoblastoma. In malignant melanoma there is often an increase in serum gamma gamma enolase. The assessment of aqueous and serum enolase patterns may be of value in the diagnosis of retinoblastoma and malignant melanoma.