The N-myc gene product in primary retinoblastomas.

The N-myc gene product in retinoblastomas was examined using the antisera against the N-myc gene product, which was produced as a fusion protein by Escherichia coli. The N-myc gene product was detected not only in the retinoblastoma cell line Y79 but also in primary retinoblastomas as a pair of bands of approximately 62 kilodaltons (KD) by immunoblotting. Immunohistochemical analysis showed positively stained cells with the antibody against the N-myc gene product in a few rosettes or fleuretts containing area of the tumor. The nuclei of the cells were positively stained. The N-myc gene product was not detected in the normal part of the retina or in other parts of the eye. The results suggested that the level of the N-myc gene product may be inversely correlated with the differentiation of retinoblastoma cells and that the detection of the N-myc gene product may be useful in the diagnosis of retinoblastoma. Because the undifferentiated form of retinoblastoma carries a worse prognosis than the differentiated forms, the level of the N-myc gene product may be related to the aggressiveness of the tumor cells. It remains to be seen whether metastatic retinoblastoma has a higher concentration of the N-myc gene product.