Isotachophoretic determination of phosphate splitting from Amifostine and p-nitrophenyl phosphate in serum and neuroblastoma cells.

Amifostine WR-2721; H2N-(CH2)3-NH-(CH2)2-S-PO3H2] is used as a protecting agent in the chemotherapy of neuroblastoma. It is supposed that Amifostine will be transformed into its active form, the free thiol (WR-1065), easier by normal cells than by tumour cells. Analytical capillary isotachophoresis was used to determine the dephosphorylation of Amifostine in serum and on neuroblastoma cells and peripheral blood cells. Furthermore, the biological effects of Amifostine and its free thiol, on cell proliferation of neuroblastoma cells were measured in combination with Carboplatin. It was found that neuroblastoma cells did not split phosphate less efficiently than normal peripheral blood cells. Furthermore, neither Amifostine (as expected) nor the free thiol (not expected according to the theory) were able to inhibit the effects of Carboplatin. Therefore, the current hypothesis concerning the mode of action of Amifostine must be questioned.