EXPRESSION OF A PHOTORECEPTOR PROTEIN, RECOVERIN, AS A CANCER-ASSOCIATED RETINOPATHY AUTOANTIGEN IN HUMAN LUNG-CANCER CELL-LINES

Recently, a photoreceptor protein, recoverin, has been recognised as a n autoantigen of cancer-associated retinopathy (CAR), a rare paraneopl astic neurological syndrome often associated with patients with small- cell lung cancer (SCLC). Although until quite recently the specific ex pression of recoverin in cancer cells had not been indicated, Polans e t al. (Polans AS, Witkowska D, Haley TL, Amundson D, Baiter L, Adamus G 1995, Proc. Natl. Acad. Sci. USA, 92, 9176-9180) demonstrated the sp ecific expression of recoverin in lung tumour and primary cultured tum our cells from a CAR patient. We examined the expression of recoverin in human lung cancer cell lines by reverse transcription polymerase ch ain reaction (PCR), Northern blotting and Western immunoblotting. Reco verin was expressed in only one SCLC cell line from a patient with CAR . The sequence of recoverin cDNA from the cells was identical to the h uman recoverin sequence. These findings strongly support the hypothesi s that the ectopic expression of wild-type recoverin in SCLC induces t he cancer-retina immunological cross-reaction, leading to visual loss in CAR.