[Arsenic Trioxide-Induced Death of Neuroblastoma Cells Involves Activation of Bax and Does Not Require p53]
>>Clinical Cancer Research Vol. 10, 3179-3188, May 1, 2004
Arsenic Trioxide-Induced Death of Neuroblastoma Cells Involves Activation of Bax and Does Not Require p53
Jenny Karlsson1, Ingrid Øra1,3, Isabella Pörn-Ares2 and Sven Påhlman1
1 Divisions of Molecular Medicine and 2 Experimental Pathology, Departments of Laboratory Medicine, Malmö, and 3 Pediatrics, Oncology-Hematology Section, Lund University Hospital, Lund, Sweden
Purpose: On the basis of clinical studies showing that arsenic trioxide (As2O3), via an apoptotic mechanism, and with minimal toxicity induces complete remission in patients with refractory acute promyelocytic leukemia and that multidrug-resistant and p53-mutated neuroblastoma cells are sensitive to As2O3 both in vitro and in vivo, we searched for molecular mechanisms involved in the As2O3-induced neuroblastoma cell death.
Experimental Design: We have studied the effect of As2O3 on the expression and cellular localization of proteins involved in drug-induced death in two neuroblastoma cell lines with intact p53 and two with mutated p53, the latter two displaying multidrug resistance.
Results: As2O3 provoked Bax expression in all tested neuroblastoma cell lines, including SK-N-BE(2) cells with mutated p53 and LA-N-1 cells, which have a deleted p53. In all cell lines exposed to As2O3, p21 Bax was proteolytically cleaved in a calpain-dependent way into the more proapoptotic p18 Bax, which was detected exclusively in a mitochondria-enriched subcellular fraction. As2O3 also caused an increase of cytoplasmic cytochrome c, translocation of antiapoptosis-inducing factor to the nuclei, and a slight activation of caspase 3. However, inhibition of caspase 3 did not prevent cell death, whereas inhibition of Bax cleavage was associated with a decreased As2O3-induced cell death.
Conclusions: We show that multidrug-resistant neuroblastoma cells die after exposure to As2O3, independent of functional p53, suggesting activation of a cytotoxic pathway different from that induced by conventional chemotherapeutic agents. We further propose that proteolytic activation of Bax is an important event in As2O3-induced cell death. <<
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