TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Cells: The nutrient medium for culturing human cells is a serum-free medium. The human cells are fibroblasts, spleen cells or thymus cells or a mixture of cell types capable of expressing p53 TSP and capable of being induced to express and secrete p53-dependent GIFs. The cells are induced to express and secrete the GIFs by being subjected to stress treatment, e.g. gamma irradiation.Preferred Growth Inhibitory Factors: The p53-dependent GIFs expressed and secreted by the cells are transforming growth factor-beta2 (TGF-beta2), inhibin-beta or a serine protease inhibitor. The GIF-containing composition is administered with a chemotherapeutic compound or while irradiating the subject with gamma radiation. ACTIVITY - Antiproliferative; cytostatic.    ADMINISTRATION - Administration of the products of the above process is, e.g., oral, parenteral or nasal. Daily dosage of active agent is especially 10 mug/kg to 10 mg/kg. The products are preferably administered with a chemotherapeutic compound or while irradiating the subject with gamma radiation    EXAMPLE - A fresh human spleen was gamma-irradiated (10 Gy), desegregated into a single-cell suspension in Dulbecco's modified Eagle's medium (DMEM) (5 x 107 cells/ml) and incubated at 37 degrees C for 7 hours. Cells were then removed by centrifugation and filtration of the supernatant through a 0.45 micro m filter. The conditioned medium was tested in a growth inhibition assay on DU145 cells.    Ten athymic nude mice were injected subcutaneously with a suspension of DU145 cells (0.1 ml of growth medium with 5 x 105 cells per site, 4 sites per mouse). Five of these mice were left untreated (control group), while 5 of the mice were injected intravenously (once a day for 6 days) with 0.15 ml of non-diluted conditioned media. The mice were examined weekly for tumor growth. Four weeks after injection, tumors developed in approximately half of the injected sites in the control group. In the experimental group, tumors appeared in only 3 of the 20 sites injected. The result indicates that factors secreted by irradiated splenocytes possess in vivo detectable anticancer activity.