High-dose ascorbate and arsenic trioxide selectively kill acute myeloid leukemia and acute promyelocytic leukemia blasts in vitro

Abstract

The use of high-dose ascorbate (ASC) for the treatment of human cancer has been attempted several decades ago and has been recently revived by several in vitro and in vivo studies in solid tumors. We tested the cytotoxic effects of ASC, alone or in combination with arsenic trioxide (ATO) in acute myeloid leukemia (AML) and acute promyelocytic leukemia (APL). Leukemic cell lines and primary blasts from AML and APL patients were treated with graded concentrations of ASC, alone or in association with standard concentration (1 μM) of ATO. The ASC/ATO combination killed myeloid blasts, including leukemic CD34+ cells, while sparing CD34+ progenitors obtained from normal cord blood and bone marrow. Actually, approximately one-third (11/36) of primary AML cases were highly sensitive to the ASC/ATO combination. The mechanism of cell killing appeared to be related to increased oxidative stress and overproduction of ROS in a non-quantitative fashion, which resulted in induction of apoptosis. These effects were reverted by the addition of the antioxidant N-Acetyl-Cysteine (NAC). In the APL NB4 model, ASC induced direct degradation of the PML and PML/RARA proteins via caspase activation, while the transcriptional repressor DAXX was recruited in re-constituted PML nuclear bodies. Our findings encourage the design of pilot studies to explore the potential clinical benefit of ASC alone or in combination with ATO in advanced AML and APL.

The role of TP53 in acute myeloid leukemia: Challenges and opportunities

“…In addition, ATO enhances wild‐type TP53 activity and upregulates its target genes, thereby inducing apoptosis and inhibiting the proliferation of tumor cells . In recent AML pilot studies, researchers combined ascorbate (ASC) and ATO, resulting in the depletion of myeloid blasts, including leukemic CD34+ cells, whereas only slightly decreasing cell viability in CD34+ progenitors obtained from normal cord blood and bone marrow . The proapoptotic affect of ASC/ATO treatment appeared to be dependent on increased oxidative stress and reactive oxygen species (ROS) overproduction .…”

“…168 The proapoptotic affect of ASC/ATO treatment appeared to be dependent on increased oxidative stress and reactive oxygen species (ROS) overproduction. 168 A plausible mechanism for combinatorial benefit with ASC is its capacity to undergo auto-oxidation and therefore increase intracellular ROS levels, especially under the low catalase concentrations present in certain malignant cells. 168,169,172 Furthermore, recent studies have demonstrated that the cholesterol-lowering drugs statins (Atorvastatin/Lipitor) can act as degradation inducers for the stable, misfolded mutant TP53 protein.…”

PML/RARa Interferes with NRF2 Transcriptional Activity Increasing the Sensitivity to Ascorbate of Acute Promyelocytic Leukemia Cells

“…A series of in vitro and in vivo studies revived the interest of high doses of ascorbate (ASC) as an anticancer agent. In particular, studies from our group and others revealed that, when administered in pharmacologic doses corresponding to the millimolar (mM) range, ASC behaves as a powerful pro-oxidant, generating hydrogen peroxide-dependent cytotoxicity towards a variety of cancer cells in vitro without adversely affecting normal cells [15][16][17][18]. A different view of the potential action of vitamin C in cancer came from the discovery of its importance for the activation of the ten-eleven translocation (TET) and Jumonji dioxygenases that are involved in active demethylation of DNA and histones, respectively [19,20].NRF2 is tightly regulated to assure cell homeostasis: In normal conditions low levels of NRF2 are maintained by the association with Kelch-like ECH-associated protein 1 (Keap1) in a complex with E3 ubiquitin ligase Cullin 3-Ring-box protein 1 (CUL3-RBX1) and degradation by proteasome [21,22].…”

Antitumor efficacy of arsenic/interferon in preclinical models of chronic myeloid leukemia resistant to tyrosine kinase inhibitors

“…In vitro, we showed that the ATO/IFN combination treatment inhibited proliferation of imatinib‐resistant CML cell lines and synergistically induced their apoptosis. This is consistent with the fact that ATO alone or in combination with other drugs exhibits potent antitumor effects in several hematological cancers . Most importantly, the superiority of the ATO/IFN combination as a treatment in TKI‐resistant CML models was emphasized in vivo by the use of the T315I‐CML murine model.…”

“…This is consistent with the fact that ATO alone or in combination with other drugs exhibits potent antitumor effects in several hematological cancers. [30][31][32][33] Most importantly, the superiority of the ATO/IFN combination as a treatment in TKI-resistant CML models was emphasized in vivo by the use of the T315I-CML murine model. In contrast to imatinib treatment, which was not expected to have any favorable Cancer August 15, 2019 effects, daily or weekday ATO/IFN treatment led to a significant increase in the survival of primary TKI-resistant T315I mice along with a reduction of leukemic cell infiltration, although WBC counts remained highly abnormal and spleen weights were not affected.…”