Cone cell-specific genes expressed in retinoblastoma.

Retinoblastoma, an intraocular tumor that occurs in children, has long been regarded, on the basis of morphological criteria, as a malignancy of the photoreceptor cell lineage. Here it is shown that when this tumor is grown in vitro, the cells express highly specialized photoreceptor cell genes. Transcripts for the transducin alpha subunit, TC alpha, which is specific to the cone cell, as well as transcripts for the red or green cone cell photopigment, were found in seven out of seven low-passage retinoblastoma cell lines. No marker genes specific to rod cell were expressed, suggesting that retinoblastoma has a cone cell lineage.