As observed previously in the conditioned medium (CM) of Kagura-2 cells, CM prepared from Kagura-1 cells, the another cell line of aflatoxin B
1 (AFB
1)-induced hepatoma, also contains very active neuronal differentiation factor(s) which convert PC12 cells to the sympathetic neuron-like cells. The factor(s) detected in Kagura-1 cell-CM are inactivated by heat, trypsin, acetic acid and dithiothreitol. Molecular weights of the factor (s) are ranging from 6, 000 to 14, 000 Da. These facts indicate that the factor(s) detected in Kagura-1 cell-CM are very similar or identical to those of Kagura-2 cells. In contrast, CM obtained from H4-II-E cells, one of the minimal deviation rat hepatomas, shows only slight activity for the neurite outgrowth of PC12 cells, although the cell extract contains the very active factor(s) as detected in those of AFB
1-induced hepatomas. The synthetic activities of the factor(s) in Balb/3T3, 3Y1, IMR-32 and HeLa cells are negligible except for NRK cells. The present data strongly suggest that the neuronal differentiation factor(s) are constitu-tively produced in rat hepatoma cells involving the minimal deviation H4-II-E cells, and secreted extracellularly in the AFBI-induced hepatoma cell lines.
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