Cytotoxic effect of xanthotoxol (8-hydroxypsoralen) on TCTC cells in vitro.

The effect of xanthotoxol (8-hydroxypsoralen) on proliferation of TCTC cells in vitro has been studied. Xanthotoxol at concentrations of 5 to 50 micrograms/ml inhibited the growth of cells. In cultures with xanthotoxol, decreased amount of cell protein, mitotic index, and decreased ability to form a colony, were observed. Moreover, xanthotoxol disturbed mitoses elevating the number of mitotic cells in the telophase stage. An increase of giant and multinuclear cells was also found. On the basis of these results it can be concluded, that 8-hydroxypsoralen which in comparison with other psoralens is not sensitive to photostimulation, inhibits the cell proliferation anyway. This fact shows that the mechanism of the psoralens activity is to some extent independent from the photostimulation.