The MLL-Menin Interaction is a Therapeutic Vulnerability in NUP98 -rearranged AML

Chromosomal translocations involving the NUP98 locus are among the most prevalent rearrangements in pediatric acute myeloid leukemia (AML). AML with NUP98 fusions is characterized by high expression of HOXA and MEIS1 genes and is associated with poor clinical outcome. NUP98 fusion proteins are recruited to their target genes by the mixed lineage leukemia (MLL) complex, which involves a direct interaction between MLL and Menin. Here, we show that therapeutic targeting of the Menin–MLL interaction inhibits the propagation of NUP98-rearrranged AML both ex vivo and in vivo. Treatment of primary AML cells with the Menin inhibitor revumenib (SNDX-5613) impairs proliferation and clonogenicity ex vivo in long-term coculture and drives myeloid differentiation. These phenotypic effects are associated with global gene expression changes in primary AML samples that involve the downregulation of many critical NUP98 fusion protein-target genes, such as MEIS1 and CDK6. In addition, Menin inhibition reduces the expression of both wild-type FLT3 and mutated FLT3-ITD, and in combination with FLT3 inhibitor, suppresses patient-derived NUP98-r AML cells in a synergistic manner. Revumenib treatment blocks leukemic engraftment and prevents leukemia-associated death of immunodeficient mice transplanted with NUP98::NSD1 FLT3-ITD-positive patient-derived AML cells. These results demonstrate that NUP98-rearranged AMLs are highly susceptible to inhibition of the MLL–Menin interaction and suggest the inclusion of AML patients harboring NUP98 fusions into the clinical evaluation of Menin inhibitors

The Intricacies of Inflammatory Bowel Disease: A Preliminary Study of Redox Biology in Intestinal Organoids

We evaluated the redox status, precisely glutathione levels, which have a major impact in cellular detoxification and antioxidant defence in IBD-derived and healthy intestinal organoids. Therefore, we wanted to explore the differences in terms of their redox balance and mitochondrial fitness. To this end, we introduced a Grx1-roGFP2 construct into the organoids by lentiviral transduction before performing a stress assay by treating the organoids with hydrogen peroxide and examined the GSH/GSSG ratio using confocal imaging. Using ratio imaging, we could detect statistically significant differences between healthy and IBD-derived samples. To gain more insight, we also performed a GSH/GSSG assay, which directly measured glutathione levels. This analysis revealed that both organoid lines had higher levels of oxidized glutathione due to the stress treatment demonstrated by a lower GSH/GSSG ratio compared to the untreated control. Nevertheless, the results showed no significant difference between healthy and IBD-derived organoids. We further challenged organoids with hydrogen peroxide after incubation with MitoTracker® to see if mitochondrial fitness might be different in IBD-derived organoids. However, these results were also very comparable. In summary, our preliminary findings indicate that both organoid lines demonstrate a well-functioning system in terms of analysis but show no clear difference between healthy and IBD-derived samples

ABCC1 and glutathione metabolism limit the efficacy of BCL-2 inhibitors in acute myeloid leukemia

Abstract The BCL-2 inhibitor Venetoclax is a promising agent for the treatment of acute myeloid leukemia (AML). However, many patients are refractory to Venetoclax, and resistance develops quickly. ATP-binding cassette (ABC) transporters mediate chemotherapy resistance but their role in modulating the activity of targeted small-molecule inhibitors is unclear. Using CRISPR/Cas9 screening, we find that loss of ABCC1 strongly increases the sensitivity of AML cells to Venetoclax. Genetic and pharmacologic ABCC1 inactivation potentiates the anti-leukemic effects of BCL-2 inhibitors and efficiently re-sensitizes Venetoclax-resistant leukemia cells. Conversely, ABCC1 overexpression induces resistance to BCL-2 inhibitors by reducing intracellular drug levels, and high ABCC1 levels predicts poor response to Venetoclax therapy in patients. Consistent with ABCC1-specific export of glutathionylated substrates, inhibition of glutathione metabolism increases the potency of BCL-2 inhibitors. These results identify ABCC1 and glutathione metabolism as mechanisms limiting efficacy of BCL-2 inhibitors, which may pave the way to development of more effective therapies

The Intricacies of Inflammatory Bowel Disease: A Preliminary Study of Redox Biology in Intestinal Organoids

We evaluated the redox status, precisely glutathione levels, which have a major impact in cellular detoxification and antioxidant defence in IBD-derived and healthy intestinal organoids. Therefore, we wanted to explore the differences in terms of their redox balance and mitochondrial fitness. To this end, we introduced a Grx1-roGFP2 construct into the organoids by lentiviral transduction before performing a stress assay by treating the organoids with hydrogen peroxide and examined the GSH/GSSG ratio using confocal imaging. Using ratio imaging, we could detect statistically significant differences between healthy and IBD-derived samples. To gain more insight, we also performed a GSH/GSSG assay, which directly measured glutathione levels. This analysis revealed that both organoid lines had higher levels of oxidized glutathione due to the stress treatment demonstrated by a lower GSH/GSSG ratio compared to the untreated control. Nevertheless, the results showed no significant difference between healthy and IBD-derived organoids. We further challenged organoids with hydrogen peroxide after incubation with MitoTracker® to see if mitochondrial fitness might be different in IBD-derived organoids. However, these results were also very comparable. In summary, our preliminary findings indicate that both organoid lines demonstrate a well-functioning system in terms of analysis but show no clear difference between healthy and IBD-derived samples

ABCC1 and glutathione metabolism limit the efficacy of BCL-2 inhibitors in acute myeloid leukemia

The BCL-2 inhibitor Venetoclax is a promising agent for the treatment of acute myeloid leukemia (AML). However, many patients are refractory to Venetoclax, and resistance develops quickly. ATP-binding cassette (ABC) transporters mediate chemotherapy resistance but their role in modulating the activity of targeted small-molecule inhibitors is unclear. Using CRISPR/Cas9 screening, we find that loss of ABCC1 strongly increases the sensitivity of AML cells to Venetoclax. Genetic and pharmacologic ABCC1 inactivation potentiates the anti-leukemic effects of BCL-2 inhibitors and efficiently re-sensitizes Venetoclax-resistant leukemia cells. Conversely, ABCC1 overexpression induces resistance to BCL-2 inhibitors by reducing intracellular drug levels, and high ABCC1 levels predicts poor response to Venetoclax therapy in patients. Consistent with ABCC1-specific export of glutathionylated substrates, inhibition of glutathione metabolism increases the potency of BCL-2 inhibitors. These results identify ABCC1 and glutathione metabolism as mechanisms limiting efficacy of BCL-2 inhibitors, which may pave the way to development of more effective therapies