Synchronization of cultured retinoblastoma cells for high-resolution chromosomes showing up to 1000 bands.

A method that allows high-resolution cytogenetic analysis of retinoblastoma cells in primary culture and subpassages is described. This method is based on the addition of high concentrations of bromodeoxyuridine or thymidine to obtain chromosomes subsequently banded to show 600-1000 bands. The results are compared with the standard harvest after 24 hours or long-term culture, and with low-temperature synchronization after long-term culture. After blocking with bromodeoxyuridine or thymidine, the chromosomes are significantly longer than after cold synchronization or after the unsynchronized techniques. When they are GTG, RHG, or GBG banded, more than 40% of the mitoses are in the earlier phases with chromosomes showing more than 600 bands per haploid set. This method significantly improves the general quality of retinoblastoma tumor cell chromosomes and increases diagnostic and prognostic accuracy.