Enhanced Cytotoxic Effects of Arenite in Combination with Active Bufadienolide Compounds against Human Glioblastoma Cell Line U-87.

The cytotoxicity of a trivalent arsenic derivative (arsenite, AsIII) combined with arenobufagin or gamabufotalin was evaluated in human U-87 glioblastoma cells. Synergistic cytotoxicity with upregulated intracellular arsenic levels was observed, when treated with AsIII combined with arenobufagin instead of gamabufotalin. Apoptosis and the activation of caspase-9/-8/-3 were induced by AsIII and further strengthened by arenobufagin. The magnitude of increase in the activities of caspase-9/-3 was much greater than that of caspase-8, suggesting that the intrinsic pathway played a much more important role in the apoptosis. An increase in the number of necrotic cells, enhanced LDH leakage, and intensified G2/M phase arrest were observed. A remarkable increase in the expression level of γH2AX, a DNA damage marker, was induced by AsIII+arenobufagin. Concomitantly, the activation of autophagy was observed, suggesting that autophagic cell death associated with DNA damage was partially attributed to the cytotoxicity of AsIII+arenobufagin. Suppression of Notch signaling was confirmed in the combined regimen-treated cells, suggesting that inactivation of Jagged1/Notch signaling would probably contribute to the synergistic cytotoxic effect of AsIII+arenobufagin. Given that both AsIII and arenobufagin are capable of penetrating into the blood-brain barrier, our findings may provide fundamental insight into the clinical application of the combined regimen for glioblastoma.

Speciation of arsenic trioxide metabolites in blood cells and plasma of a patient with acute promyelocytic leukemia.

Arsenic trioxide (As(2)O(3)) has been widely accepted as the second-best choice for the treatment of relapsed and refractory acute promyelocytic leukemia (APL) patients. However, a few studies have been conducted on a detailed speciation of As(2)O(3) metabolites in blood samples of patients. To clarify the speciation of arsenic, the blood samples were collected at various time points from a patient with APL after remission induction therapy and during consolidation therapy. The total amounts of arsenic in blood cells and plasma, and the plasma concentrations of inorganic arsenic and methylated metabolites were determined by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography/ICP-MS, respectively. The total amounts of arsenic in the blood cells were 4-10 times higher than those in plasma. Among all arsenic metabolites, the pentavalent arsenate (As(V)) in plasma was more readily eliminated. During the drug-withdrawal period, the initial plasma concentrations of trivalent arsenic (As(III)) declined more rapidly than those of methylarsonic acid and dimethlyarsinic acid, which are known as the major methylated metabolites of As(III). On the other hand, during the consecutive administration in the consolidation therapy period, the plasma concentrations of total arsenic and arsenic metabolites increased with time. In conclusion, these results may support the idea that methylated metabolites of As(2)O(3) contribute to the efficacy of arsenic in APL patients. These results also suggest that detailed studies on the pharmacokinetics as well as the pharmacodynamics of As(2)O(3) in the blood cells from APL patients should be carried out to provide an effective treatment protocol.