Fig. 2: Cultured human glioma cells release an apoptosis-stimulating ferritin in vitro.

a Ferritin is detectable in culture supernatants (GBM-CM) collected from human glioma-derived cells⁷ after 24 h of serum-free culture (inset: dot blot of GBM-CM [1.5 µg of total protein] immunoreacted with monoclonal anti-ferritin Ab rH02¹⁵). Upon 24 h of incubating primary rat hepatocytes under serum-free conditions in native GBM-CM [8.5 µg of total protein/mL], a significant (p < 0.05) shift of the percentage of apoptotic cells was observed (black bars), which was suppressed by anti-FTH antibody rH02 (hatched bar). b The ferritin was purified from GBM-CM according to a protocol described elsewhere⁸ (left inset: dot blot of purified ferritin [0.5 µg] immunoreacted with Ab rH02). Treatment of serum-free primary rat hepatocyte cultures for 48 h with 100 ng/ml of the purified GBM ferritin (GBM, closed bar) also had a significant (p < 0.05) apoptosis-stimulating effect that was suppressed by anti-FTH Ab rH02 (hatched bar). In contrast, a 48-h exposure of primary rat hepatocytes to 100 ng/mL of a ferritin purified from newborn mouse astrocyte culture supernatants¹⁶ had no effect (NBA). (b right inset: NBA culture supernatants [10 µg of total protein] immunoreacted with Ab rH02). Bars represent the mean ± SD of N ≥ 3 independent experiments. *P < 0.05 compared with the control or as indicated; Student’s double-sided t-test for independent samples.