THE OCCURRENCE OF SERUM AUTOANTIBODIES AGAINST ENOLASE IN CANCER-ASSOCIATED RETINOPATHY

Cancer-associated retinopathy (CAR) is an uncommon paraneoplastic dise ase in which degeneration of the retina occurs as a remote effect of c ancer in a distant part of the body. Immunoreactivity of sera from CAR patients and controls have been analyzed. Immunostaining of human ret inal proteins showed that a soluble protein of M(r) similar to 46 kDa (p46) is labeled by antibodies from several CAR patients with various types of cancer (lung, breast, bladder, prostate, salivary gland, and gastrointestinal tract cancer and chronic lymphocytic leukemia), These sera did not show reactivity with the 23-kDa protein previously assoc iated with CAR, To identify and further characterize p46, the retinal protein was purified to homogeneity by anion-exchange chromatography a nd preparative gel electrophoresis. Protein sequence analysis of the p eptides from p46 revealed a high homology with human enolase, an impor tant glycolytic enzyme. Although enolase has been previously identifie d as a product of several types of tumors, and enolase activity has be en detected in the sera of some cancer patients, the existence of auto antibodies directed to enolase has not been described. This is the fir st report of the presence of serum antibodies to retinal enolase in th e patients with cancer and the CAR syndrome, When antibodies of specif ic isotypes (IgG, IgM, and IgA) were measured, IgG1 isotype was domina nt. The significance of these antibodies for the disease process is un der investigation. (C) 1996 Academic Press, Inc.