Increased cellular glutathione and protection by bone marrow stromal cells account for the resistance of non-acute promylocytic leukemia acute myeloid leukemia cells to arsenic trioxidein vivo

Abstract

Arsenic trioxide (ATO) is a novel agent for acute promylocytic leukemia (APL). Studies performed in vitro have demonstrated that ATO also induces cell-cycle arrest and apoptosis in multiple cancers, including non-APL acute myeloid leukemia (AML). To explore the potential use of ATO on non-APL AML, we treated the leukemic cells in vivo using a NOD/SCID animal model. Mice harboring HL-60 or NB-4 leukemia or primary AML-M2 cells were treated daily with 5 mug/g ATO intraperitoneally for a maximum of 6 weeks. Although ATO initially appeared to be effective on HL-60 cells, it failed to decrease the leukemic cells in bone marrow (BM) after the extended treatment (52.2 +/- 10.7% vs. 62.2 +/- 2.6% in the controls; P = 0.51); whereas the same treatment to NB-4 leukemic mice significantly decreased the percentage of leukemic cells in BM. ATO also failed to eradicate the primary AML cells in vivo. The reason for the treatment failure was that HL-60 cells quickly developed resistance in vivo. The drug resistance could be partly attributable to the increase of cellular glutathione as a result of compensatory response to ATO treatment because depletion of glutathione with buthionine sulfoximine reversed the drug resistance in vitro. Meanwhile, BM stromal cells also contributed to the drug resistance. Leukemic cells grown on an adherent layer of MS-5 stromal cells in the presence of ATO were more proliferative and less apoptotic and had increased expression cyclin D1, Bcl-xL and Bcl-2 and decreased expression of p21, likely protecting the leukemic cells from ATO cytotoxicity. Therefore, our study suggests that strategies to inhibit the compensatory increase of glutathione and block the interaction between leukemic cells and BM stromal cells should be employed before applying ATO to non-APL hematologic malignancies.

Factors Determining Sensitivity and Resistance of Tumor Cells to Arsenic Trioxide

“…This is further complicated by the conflicting data indicating that arsenic trioxide can up- and down-regulate the apoptosis-regulating bcl-2 , bcl-x L , and bax genes depending on the model system [18], [66]–[68]. Therefore, we attempted to clarify the role of the anti-apoptotic bcl-2 gene by treating bcl-2 transfected cells with arsenic trioxide.…”

Distinct roles of mesenchymal stem and progenitor cells during the development of acute myeloid leukemia in mice

“…It has been believed that the disease persistence is attributed to residual leukemia-initiating cells or leukemic stem cells (LSCs) that are protected by a specialized BM microenvironment, the so-called hematopoietic stem cell (HSC) niche. [5][6][7][8][9] These leukemic cells outcompete normal HSCs for the niche occupancy, 10 which ultimately causes disruption of normal hematopoiesis and mortality. Therefore, efforts have been put into untangling the complex interactions between leukemic cells and neighboring stromal cells.…”

Phase II study of arsenic trioxide and ascorbic acid for relapsed or refractory lymphoid malignancies: a Wisconsin Oncology Network study

“…A recent publication from Taiwan demonstrates that HL-60 cells quickly develop resistance to As 2 O 3 by compensatory increases in intracellular glutathione, and depletion of glutathione with buthionine sulfoximine (BSO) reversed the drug resistance in vitro . [36] While BSO is an attractive agent for glutathione depletion, availability of this agent for clinical use is limited. [37,38]…”