Involvement of reactive oxygen species in adaphostin-induced cytotoxicity in human leukemia cells

Abstract

Adaphostin (NSC 680410), an analog of the tyrphostin AG957, was previously shown to induce Bcr/abl down-regulation followed by loss of clonogenic survival in chronic myelogenous leukemia (CML) cell lines and clinical samples. Adaphostin demonstrated selectivity for CML myeloid progenitors in vitro and remained active in K562 cells selected for imatinib mesylate resistance. In the present study, the mechanism of action of adaphostin was investigated in greater detail in vitro. Initial studies demonstrated that adaphostin induced apoptosis in a variety of Bcr/ abl ؊ cells, including acute myelogenous leukemia (AML) blasts and cell lines as well as chronic lymphocytic leukemia (CLL) samples. Further study demonstrated that adaphostin caused intracellular peroxide production followed by DNA strand breaks and, in cells containing wild-type p53, a typical DNA damage response consisting of p53 phosphorylation and up-regulation. Importantly, the antioxidant N-acetylcysteine (NAC) blunted these events, whereas glutathione depletion with buthionine sulfoximine (BSO) augmented them. Collectively, these results not only outline a mechanism by which adaphostin can damage both myeloid and lymphoid leukemia cells, but also indicate that this novel agent might have a broader spectrum of activity than originally envisioned. IntroductionChronic myelogenous leukemia (CML) is almost universally associated with a t(9;22) chromosomal translocation that juxtaposes the Bcr and Abl genes. 1,2 Because the resulting kinase, p210 Bcr/abl , is found exclusively in malignant hematopoietic cells, there has been considerable interest in identifying inhibitors of this enzyme. Several classes of p210 Bcr/abl inhibitors have been identified, including the 2-phenylaminopyrimidine derivative imatinib mesylate, 3 the pyrido [2,3-d]pyrimidine derivative PD180970, 4 and the tyrphostin AG957. 5 Clinical studies performed to date have established that imatinib mesylate is highly active in chronic-phase CML. 6,7 In contrast, patients with CML in blast crisis or t(9;22) ϩ acute lymphocytic leukemia (ALL) tend to have shorter remissions. 8,9 At the time of relapse, cells from the latter patients exhibit imatinib mesylate resistance in vitro. 10 Although the molecular basis of imatinib mesylate resistance remains somewhat controversial, 11,12 there is considerable interest in overcoming this resistance. Potential strategies include combining imatinib mesylate with conventional cytotoxic agents 13 or arsenic trioxide 9 as well as using Bcr/abl kinase inhibitors that are unaffected by alterations that cause imatinib mesylate resistance. 14,15 The tyrphostin AG957 was originally identified as an inhibitor of p210 Bcr/abl kinase that is not competitive with adenosine triphosphate (ATP). 5 Subsequent studies demonstrated that adaphostin, the adamatyl ester analog of AG957, has a longer serum half-life and displays greater antiproliferative effects against Bcr/abl ϩ leukemia cells in the National Cancer Institute (NCI) hollow fiber assay. Recent comparison of th...

Restoration of SHIP-1 activity in human leukemic cells modifies NF-κB activation pathway and cellular survival upon oxidative stress

“…Indeed, recent data suggest that ROS regulate T-cell apoptosis (Hildeman, 2004), and cytotoxicity of some compounds used in antileukemic chemotherapy, like arsenic or adaphostin, is based on ROS production (Chandra et al, 2003;Chou and Dang, 2005). Furthermore, SHIP-1 was recently described as an inhibitor of c-Jun N-terminal kinase (JNK) cascade, a critical mediator of cell death (Robson et al, 2004).…”

“…This unexpected result might be of importance as many chemotherapies are based on ROS-induced cell death (Chandra et al, 2003;Chou and Dang, 2005). Some recent reports are in agreement with our results.…”

“…Moreover, some compounds used in chemotherapies induce cell death through ROS generation (Chandra et al, 2003;Chou and Dang, 2005). During inflammation, ROS are also produced by activated phagocytic cells through NADPH oxidase (Ambruso et al, 2004).…”

Potentiation of reactive oxygen species is a marker for synergistic cytotoxicity of MS-275 and 5-azacytidine in leukemic cells

“…In addition, given data from several groups indicating that MS-275 as a single agent or combined with other anti-tumor agents generates reactive oxygen species (ROS) in certain tumor cell lines (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32), the potentiation of ROS with the combined exposure was studied. Our findings show that the production of ROS in AML and ALL cells is an indicator for the synergistic, cytotoxic effects of MS-275 and 5-azacytidine.…”

Xylodiol from Xylopia langsdorfiana induces apoptosis in HL60 cells

“…A role for oxidative stress in the induction of apoptosis is suggested by the observations that low levels of ROS induce apoptosis whereas antioxidants such as N-acetylcysteine (NAC) inhibit cell death. Additionally, ROS generation occurs following the treatment of cells with various agents, including chemotherapeutic drugs (Chandra et al, 2003).…”