Selective killing of human T-ALL cells: an integrated approach targeting redox homeostasis and the OMA1/OPA1 axis

Abstract

Approximately 20% of pediatric T-cell acute lymphoblastic leukemia (T-ALL) patients are currently incurable due to primary or secondary resistance to glucocorticoid-based therapies. Here we employed an integrated approach to selectively kill T-ALL cells by increasing mitochondrial reactive oxygen species (ROS) using NS1619, a benzimidazolone that activates the K+ (BK) channel, and dehydroepiandrosterone (DHEA), which blunts ROS scavenging through inhibition of the pentose phosphate pathway. These compounds selectively killed T-ALL cell lines, patient-derived xenografts and primary cells from patients with refractory T-ALL, but did not kill normal human thymocytes. T-ALL cells treated with NS1619 and DHEA showed activation of the ROS-responsive transcription factor NRF2, indicating engagement of antioxidant pathways, as well as increased cleavage of OPA1, a mitochondrial protein that promotes mitochondrial fusion and regulates apoptosis. Consistent with these observations, transmission electron microscopy analysis indicated that NS1619 and DHEA increased mitochondrial fission. OPA1 cleavage and cell death were inhibited by ROS scavengers and by siRNA-mediated knockdown of the mitochondrial protease OMA1, indicating the engagement of a ROS-OMA1-OPA1 axis in T-ALL cells. Furthermore, NS1619 and DHEA sensitized T-ALL cells to TRAIL-induced apoptosis. In vivo, the combination of dexamethasone and NS1619 significantly reduced the growth of a glucocorticoid-resistant patient-derived T-ALL xenograft. Taken together, our findings provide proof-of-principle for an integrated ROS-based pharmacological approach to target refractory T-ALL.

Targeted OMA1 therapies for cancer

“…The OMA1 and OPA1 promoter regions showed no apparent binding sites for HIF1A, which would coincide with a model in which hypoxia, or the oxidative stress associated with hypoxia, controls OMA1 activation rather than its expression . Indeed, the combined administration of the potassium channel opener NS1619 and the pentose phosphate pathway inhibitor DHEA (dehydroepiandrosterone) increased mitochondrial reactive oxygen species and activated NFE2L2 in malignant cells, which resulted in OMA1‐dependent cell death . XBP1 and NFE2L2 binding sites on the other hand suggest stress‐dependent gene regulation.…”

“…195 Indeed, the combined administration of the potassium channel opener NS1619 and the pentose phosphate pathway inhibitor DHEA (dehydroepiandrosterone) increased mitochondrial reactive oxygen species and activated NFE2L2 in malignant cells, which resulted in OMA1-dependent cell death. 196 XBP1 and NFE2L2 binding sites on the other hand suggest stress-dependent gene regulation. Interestingly, loss of OPA1 function in mice and rats resulted in augmented XBP1 and NFE2L2 activity, [197][198][199] which could indicate the presence of regulatory feedback loops adjusting OPA1 (and OMA1) protein levels to a variable baseline of cellular stress.…”

Nanoparticles as Tools to Target Redox Homeostasis in Cancer Cells

“…Consistent with this notion, we recently provided evidence for a ROS-based strategy to selectively kill T-cell acute lymphoblastic leukemia (T-ALL) cells and sensitize them to glucocorticoid-based therapies, while sparing healthy thymocytes [8]. Other evidence points to the anticancer efficacy of therapeutic strategies aimed at inducing oxidative stress [9,10].…”

“…To this effect, nanotechnologies may provide novel and powerful tools to both alter redox homeostasis in cancer cells and improve the targeting of anticancer drugs to tumor cells by exploiting the unique features of their microenvironment, which include high ROS levels and the acidic pH that results from the glycolytic rewiring of tumor metabolism (Warburg effect). Nanomedicine is based on the use of synthetic particles of 1-1000 nm diameter (nanoparticles, NPs), which can be classified into six main groups: carbon NPs, metal NPs, ceramic NPs, semiconductor Consistent with this notion, we recently provided evidence for a ROS-based strategy to selectively kill T-cell acute lymphoblastic leukemia (T-ALL) cells and sensitize them to glucocorticoid-based therapies, while sparing healthy thymocytes [8]. Other evidence points to the anticancer efficacy of therapeutic strategies aimed at inducing oxidative stress [9,10].…”

Oxidative resistance of leukemic stem cells and oxidative damage to hematopoietic stem cells under pro-oxidative therapy

“…Mitochondria are the main site for intracellular ROS generation. Therefore, targeting mitochondria is a reasonable strategy to disrupt the redox balance of the cells, induce oxidative stress and promote the apoptosis of leukemia cells 64 . A variety of mitochondrial inhibitors that can promote ROS generation are undergoing clinical trials for their role in leukemia treatment.…”