Effect of carcinogenic polycyclic aromatic hydrocarbons on mouse embryonic cells in culture: induction of spindle-shaped cells.

In cultured mouse embryonic cells (MECs) treated with benzo[a]pyrene (B[a]P), there appeared unusual type of fibroblasts, spindle-shaped cells (SP cells), which were characterized by their narrow bipolar shape, long cellular processes and optically distinct cell borders. Appearance of SP cells was massive and irreversible. The amount of SP cells increased with increasing concentrations of B[a]P, while early cytotoxicity did not. In various polycyclic aromatic hydrocarbons (PAHs) tested, only potent carcinogens (7,12-dimethylbenz[a]anthracene (DMBA), 3-methylcholanthrene (MCA), B[a]P, and dibenz[a,e]pyrene (DB[a,e]P) induced SP cells. Among them, PAH having higher Iball's index induced SP cells at lower concentration and at an earlier time. Weak or non-carcinogenic PAHs including 3-hydroxybenzo[a]-pyrene (3-OH-B[a]P) did not induce SP cells. alpha-Napthoflavon (alpha NF) suppressed the induction of SP cell by carcinogenic PAH. SP cells did not appear spontaneously under various abnormal culture conditions. These results indicate that carcinogenic PAHs induce the appearance of a specific type of fibroblast, SP cells in MEC cultures in accordance with their carcinogenicity.