60Co radiation-induced transformation to anchorage independence of fibroblast from normal persons and patients with inherited predisposition to retinoblastoma.

Retinoblastoma (RB), cancer of the retina, occurs in an inherited form which not only predisposes the patient to bilateral RB, but also to the risk of developing secondary tumors of mesenchymal origin (osteosarcomas and fibrosarcomas). These tumors often arise in areas that were exposed to ionizing radiation during therapy and fibroblasts derived from patients with hereditary RB have been reported to be more sensitive than normal to the killing effects of ionizing radiation. Therefore, we compared diploid fibroblast cell lines derived from two hereditary RB patients (aged 1 and 3 years) with those of three normal persons (two newborns and a 2 year old) for their sensitivity to ionizing radiation-induced transformation to anchorage independence. The target cells were exposed to 60Co radiation (1.0-3.5 Gy), allowed to undergo an expression period (4-5 population doublings in 5 days), and assayed for ability to form colonies in 0.33% agar. There was no detectable difference between the RB cells' and the normal cells' response to the transforming action of the 60Co. Both kinds of cells showed a linear, dose-dependent increase in anchorage-independent cells from 100 to 800/10(6) cells assayed.