Chemotherapeutic response of tumor derived from human adenovirus 12--induced retinal tumor cell line in syngeneic CDF (F 344) rats.

The effect of two anticancer agents, vincristine (VCR) and cyclophosphamide (CTX), on an established cell line (EXP-5) derived from human adenovirus serotype 12 (Ad 12)--induced retinal tumor was studied in vitro and in vivo. VCR at a concentration of 5 and 10 micrograms/ml of culture medium and CTX at 50 and 100 micrograms/ml suppressed growth in vitro. EXP-5 cells were transplanted into the vitreous of 56 inbred CDF (F 344 strain) rats. The implants grew almost exclusively as intravitreous tumors within one month. When the tumor was full grown in the vitreous, VCR and CTX were administered intravenously, singly or in combination, on a schedule based on the protocol CCG-961 for localized unilateral retinoblastoma, Reese-Ellsworth group 5. At a dosage of 0.05 mg/kg, VCR was effective in reducing tumor size; at a dosage of 5 mg/kg, CTX did not reduce tumor size. Combined VCR/CTX therapy induced reduction of about two thirds in tumor size in 2 of 10 treated animals; in all 10 animals, the tumor became morphologically less distinct during the course of treatment although some characteristic features remained. Cytotoxic tumor changes (necrosis, fibrous proliferation, cell transformation, and bizarre giant cells) were observed in all treated animals. This model used the EXP-5 cell line grown in the vitreous, thereby providing a potential tool for evaluating growth and chemotherapeutic responsiveness of retinoblastoma.