Apoptosis induced by arsenic trioxide in leukemia U937 cells is dependent on activation of p38, inactivation of ERK and the Ca2+-dependent production of superoxide

Abstract

The mechanism of the induction of apoptosis by arsenic trioxide (As 2 O 3 ), which was demonstrated recently to be an effective inducer of apoptosis in patients with leukemia, was examined in detail in human leukemia U937 cells. Upon treatment of U937 cells with 50 M of As 2 O 3 , complete inactivation of the kinases ERK1 and ERK2 was detected within 30 min. p38 was activated within 3 hr, and the maximum activity was detected at 6 hr, when DNA fragmentation remained undetectable. Experiments with transfected cells that expressed constitutively activated MEK1 and a specific inhibitor of p38 also suggested that inactivation of ERKs and activation of p38 might be associated with the induction of apoptosis by As 2 O 3 . In contrast to the inactivation of ERKs and the activation of p38, activation of JNK by Key words: arsenic trioxide; apoptosis; leukemia cells; superoxide; tumorArsenic has long been used in traditional Chinese medicine. Arsenic trioxide (As 2 O 3 ) was recently demonstrated to be an effective inducer of apoptosis in patients with relapsed acute promyelocytic leukemia (APL) and in patients with APL in whom all-trans-retinoic acid (ATRA) and conventional chemotherapy has failed. 1-4 Studies in vitro indicate that As 2 O 3 can induce apoptosis in myeloma cell lines, in plasma cells from myeloma patients, 5 in malignant lymphocytic cell lines 6,7 as well as primary cultures of lymphocytic leukemia and lymphoma cells, 6 in myeloid and B-cell leukemia cell lines, 8 in megakaryocytic leukemia cell lines, 9 in neuroblastoma cell lines 10 and in HPV16-immortalized human cervical epithelial cells. 11 The mechanism responsible for the induction of apoptosis has not been fully characterized, but As 2 O 3 induced apoptosis in NB4 cells, cloned from a relapsed patient with APL, by inducing loss of PML/RAR␣ protein 12 and by suppressing expression of the Bcl-2 protein. 13 Apoptosis induced by As 2 O 3 and by the organic arsenical melarsoprol in myeloid leukemia cell lines, such as the HL-60, KG-1 and U937 cell lines, was found, however, to be independent of the level of expression of PML and PML-RAR␣. 14 In contrast to its apparent curative effects, As 2 O 3 is known to be a carcinogen in human organs, such as skin and lung, and it has serious side effects such as fluid retention in patients. 15 Other chronic side effects include polyneuropathy, palmar keratosis and skin hyperpigmentation. 15 It is, therefore, desirable to develop other drugs that act by a similar mechanism to that of As 2 O 3 but lack the side effect. While the mechanism of the induction of apoptosis in tumor cells by As 2 O 3 is not well understood, As 2 O 3 has been used to mimic the effects of heat shock on cells. 16 When rat fibroblastic 3Y1 cells and rat PC12 cells are treated with As 2 O 3 , stress-induced kinases such as c-Jun N-terminal kinase (JNK) and p38 are activated. 17 To clarify the mechanism of induction of apoptosis in tumor cells by As 2 O 3 , we examined the effects of As 2 O 3 on the activities of mitogen-activated protein (M...

Neuroprotective Role of Quercetin against Arsenic Induced Oxidative Stress in Rat Brain

“…It is believed that damage due to arsenic is closely associated with oxidative stress induced by arsenic. As reported in earlier studies, arsenic is known to cause generation of free radicals, like reactive oxygen species (ROS) and reactive nitrogen species (RNS), as well as metabolic intermediates like dimethyl arsenic (DMA) peroxy radical [6][7][8][9][10][11].…”

Arsenic Trioxide Augments Chk2/p53-mediated Apoptosis by Inhibiting Oncogenic Wip1 Phosphatase

“…Activation of p38 MAPK has been shown to associate with ATO-induced apoptosis of human leukemic cell lines, U937 and K562 cells (31,32,35). To determine whether or not p38 MAPK is required for ATO-induced apoptosis of NB4 cells, the cells were untreated or treated with ATO (10 M) in the absence (DMSO alone) or presence of the p38 MAPK inhibitor SB203580 (10 M), and 24 h after incubation, apoptotic cells were scored (see "Experimental Procedures").…”

“…It has been shown that p38 MAPK stimulates p53 in response to various stress agents, including UV irradiation and anticancer drugs, and regulates both activation of p53-mediated transcription and p53-dependent apoptosis (29,30). ATO is known to activate p38 MAPK in various neoplastic cell lines, suggesting a role for this pathway in the regulation of ATO-induced responses in malignant cells (31)(32)(33)(34)(35).…”

Targeting Hsp90 by 17-AAG in leukemia cells: mechanisms for synergistic and antagonistic drug combinations with arsenic trioxide and Ara-C

“…We and others groups have previously demonstrated that generation of ROS is an important event that mediates ATO-induced apoptosis. 30,[47][48][49][50] It is known that increased ROS may lead to activation of the PI3K/Akt survival pathway, which likely reflects a cellular response to ROS stress in the attempt to survive the drug insult. Furthermore, a recent study suggests that the PI3K/Akt signaling pathway may contribute to resistance to ATO-induced apoptosis in human leukemia cell lines.…”