MondoA drives malignancy in B-ALL through enhanced adaptation to metabolic stress

Cancer cells are in most instances characterized by rapid proliferation and uncontrolled cell division. Hence, they must adapt to proliferation-induced metabolic stress through intrinsic or acquired antimetabolic stress responses to maintain homeostasis and survival. One mechanism to achieve this is reprogramming gene expression in a metabolism-dependent manner. MondoA (also known as Myc-associated factor X-like protein X-interacting protein [MLXIP]), a member of the MYC interactome, has been described as an example of such a metabolic sensor. However, the role of MondoA in malignancy is not fully understood and the underlying mechanism in metabolic responses remains elusive. By assessing patient data sets, we found that MondoA overexpression is associated with worse survival in pediatric common acute lymphoblastic leukemia (ALL; B-precursor ALL [B-ALL]). Using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) and RNA-interference approaches, we observed that MondoA depletion reduces the transformational capacity of B-ALL cells in vitro and dramatically inhibits malignant potential in an in vivo mouse model. Interestingly, reduced expression of MondoA in patient data sets correlated with enrichment in metabolic pathways. The loss of MondoA correlated with increased tricarboxylic acid cycle activity. Mechanistically, MondoA senses metabolic stress in B-ALL cells by restricting oxidative phosphorylation through reduced pyruvate dehydrogenase activity. Glutamine starvation conditions greatly enhance this effect and highlight the inability to mitigate metabolic stress upon loss of MondoA in B-ALL. Our findings give novel insight into the function of MondoA in pediatric B-ALL and support the notion that MondoA inhibition in this entity offers a therapeutic opportunity and should be further explored.

The Truncated Splice Variant of the Granulocyte-Macrophage-Colony-Stimulating Factor Receptor β- Chain in Peripheral Blood Serves as Severity Biomarker of Respiratory Failure in Newborns

BACKGROUND

The granulocyte-macrophage-colony-stimulating factor (GM-CSF) plays an important role in surfactant homeostasis. βC is a subunit of the GM-CSF receptor (GM-CSF-R), and its activation mediates surfactant catabolism in the lung. βIT is a physiological, truncated isoform of βC and is known to act as physiological inhibitor of βC.

OBJECTIVE

The aim of this study was to determine the ratio of βIT and βC in the peripheral blood of newborns and its association with the degree of respiratory failure at birth.

METHODS

We conducted a prospective cohort study in newborns with various degrees of respiratory impairment at birth. Respiratory status was assessed by a score ranging from no respiratory impairment (0) to invasive respiratory support (3). βIT and βC expression were determined in peripheral blood cells by real-time PCR. βIT expression, defined as the ratio of βIT and βC, was correlated with the respiratory score.

RESULTS

βIT expression was found in all 59 recruited newborns with a trend toward higher βIT in respiratory ill (score 2, 3) newborns than respiratory healthy newborns ([score 0, 1]; p = 0.066). Seriously ill newborns (score 3) had significantly higher βIT than healthy newborns ([score 0], p = 0.010). Healthy preterm infants had significantly higher βIT expression than healthy term infants (p = 0.019).

CONCLUSIONS

βIT is expressed in newborns with higher expression in respiratory ill than respiratory healthy newborns. We hypothesize that βIT may have a protective effect in postnatal pulmonary adaptation acting as a physiological inhibitor of βC and, therefore, maintaining surfactant in respiratory ill newborns.

Abstract B51: Adaptation to oncogene-induced metabolic stress by MondoA (MLXIP) drives common acute lymphoblastic leukemia (cALL) malignancy

MondoA (also known as MLXIP, MAX-like protein X interacting protein) is a metabolic stress sensor and a proglycolytic transcription factor potentially involved in metabolic addiction features of leukemia and the Warburg effect. MondoA dimerizes with MLX within the MYC interactome and promotes longevity in C. elegans (Johnson et al., 2014). The MYC interactome comprises the MYC/MAX/MNT/MLX/MLXIP transcription factor network: Its key players MYC, MNT and MLXIP differentially mediate proliferation, differentiation, or metabolism by heterodimerization with MAX or MLX. We previously described MondoA to promote malignancy of common precursor B-cell acute lymphoblastic leukemia (cALL). MondoA knockdown (MKD) in cALL cell lines in xenografted mice reduced the number of leukemic blasts (Sipol, 2014). Here we report that MondoA high expression was observed in ALL subtypes with no MYC overexpression. RNA-sequencing data of 132 primary ALL bone marrow samples confirmed the inverse correlation of MYC and MondoA. Interestingly, in subgroups of ALL with low MYC expression and high MondoA (cALL with BCR-ABL, cALL with TCF3-PBX, cALL with ETV6-RUNX1, and cALL with hyperdiploid karyotype), metabolic gene sets did not appear as upregulated. In contrast, cALL samples with high MYC expression and low MondoA (proB-ALL with MLL rearrangements and B-ALL with IGH-MYC fusion gene) demonstrated upregulation of pathways for oxidative phosphorylation and fatty acid metabolism in addition to targets of E2F, G2M checkpoints, and MYC targets. Using CRISPR/CAS9-mediated knockout (MKO), we demonstrate that MondoA dials down MYC-induced metabolic stress and increases leukemia stress resistance. By limiting mitochondrial pyruvate dehydrogenase (PDH) activity in PDHK1 (pyruvate dehydrogenase kinase 1)-dependent manner, MondoA decreases oxidative phosphorylation. In line with limiting effect of MondoA on oxidative phosphorylation, we observed that MondoA decreases ROS generation in B cells. In conclusion, MondoA is restricting MYC-target gene expression to promote leukemia cell survival by facilitating glycolysis and adaption to oxidative stress. MondoA limits pyruvate availability for the TCA cycle by decreasing PDH activity, thus ensuring consistent glycolytic flux, mediating the Warburg effect, and insuring integrity of leukemia metabolism and ROS balancing in response to oncogene activation.

Citation Format: Alexandra Sipol, Erik Hameister, Andreas Petry, Agnes Görlach, Jürgen Ruland, Guenther Richter, Stefan Burdach, Poul Sorensen. Adaptation to oncogene-induced metabolic stress by MondoA (MLXIP) drives common acute lymphoblastic leukemia (cALL) malignancy [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B51.

Transcriptome based individualized therapy of refractory pediatric sarcomas: feasibility, tolerability and efficacy

Survival rates of pediatric sarcoma patients stagnated during the last two decades, especially in adolescents and young adults (AYAs). Targeted therapies offer new options in refractory cases. Gene expression profiling provides a robust method to characterize the transcriptome of each patient’s tumor and guide the choice of therapy.

Twenty patients with refractory pediatric sarcomas (age 8-35 years) were assessed with array profiling: ten had Ewing sarcoma, five osteosarcoma, and five soft tissue sarcoma. Overexpressed genes and deregulated pathways were identified as actionable targets and an individualized combination of targeted therapies was recommended. Disease status, survival, adverse events (AEs), and quality of life (QOL) were assessed in patients receiving targeted therapy (TT) and compared to patients without targeted therapy (non TT).

Actionable targets were identified in all analyzed biopsies. Targeted therapy was administered in nine patients, while eleven received no targeted therapy. No significant difference in risk factors between these two groups was detected. Overall survival (OS) and progression free survival (PFS) were significantly higher in the TT group (OS: P=0.0014, PFS: P=0.0011). Median OS was 8.83 versus 4.93 months and median PFS was 6.17 versus 1.6 months in TT versus non TT group, respectively. QOL did not differ at baseline as well as at four week intervals between the two groups. TT patients had less grade 1 AEs (P=0.009). The frequency of grade 2-4 AEs did not differ.

Overall, expression based targeted therapy is a feasible and likely beneficial approach in patients with refractory pediatric sarcomas that warrants further study.

Abstract 2462: MondoA mediates in vivo aggressiveness of common ALL and may serve as a T-cell immunotherapy target

Oncogene addiction provides ideal targets for immunotherapy. We previously described MondoA (also known as MLXIP, MAX like protein X interacting protein) as a metabolic stress sensor, required for leukemogenesis. Here we report on the expression of MondoA in common acute lymphoblastic leukemia (cALL) compared to other malignancies, its role in malignancy of cALL in vivo, downstream pathways and correlation with relapse risk. Given the non-accessibility of transcription factors by drugs or chimeric antigen receptor transgenic T cells (CARs), we tested the targetability of MondoA by allo-restricted, peptide specific T cells.

Our human/murine xenotransplantation model with immunodeficient RAG2-/-gc-/- mice was used (Richter et al. 2009). NALM6 and 697 cALL lines were lentivirally transduced with MondoA short hairpin RNA (shRNA). Upon successful MondoA knock down (KD), KD and control lines were injected into the mice; CD10+ blasts in blood, spleen and marrow were assessed. MondoA specific T cells were generated by priming of donor HLAA0201 negative (A2-) T-cells with A2+ dendritic cells bearing MondoA peptides, multimer-based sorting and subcloning of A2-CD8+ T-cells. For priming of T cells, five MondoA peptides were chosen by SYMPEITHI, BIMAS and NetCTL1.2. analyses. Peptide 428 stabilized best A2 expression on TAP-deficient T2 cells. Specificity and functionality of T cell clones were tested by ELISpot interferon gamma (IFg) and granzyme B assays with six MondoA+ leukemia lines (A2+, A2-). Off target effects of MondoA specific T-cell clones were assessed by IFg reactivity against the MondoA expressing A2+ NALM6 cell line vs. A2+ and A2- EBV immortalized lymphoblastoid cell lines from six donors. Peptide homology was assessed with BLAST algorithms in SWISSPROT.

We found MondoA to be most strongly expressed in pediatric cALL and AML. Moreover MondoA expression was high in gastrointestinal stromal tumors and alveolar rabdomyosarcoma. MondoA KD in cALL cell lines and their subsequent analysis in xenograft mice resulted in a reduced number of leukemic blasts in blood, marrow and spleen. Spleen size and weight normalized in treated mice after MondoA KD. Further microarray analysis revealed an induction of aerobic glycolysis switch genes and hypoxia-response by MondoA. Consequently, HIF1A stabilization required MondoA expression and tied to these results, MondoA overexpression correlated with relapse risk; its expression was 63% higher in the very high-risk group as compared to the non-high-risk group of cALL. Therapeutically, MondoA-derived peptide antigens and A2+ cALL lines were successfully recognized and killed by specific, allo-restricted CD8+ T cells.

In conclusion, our findings demonstrate that MondoA maintains leukemic burden and aggressiveness of cALL in vivo possibly by modulating metabolic and hypoxia stress response. Moreover, we identified MondoA as a promising target for immunotherapy of cALL.

Citation Format: Alexandra Sipol, Thomas G. P. Grunewald, Juliane Schmaeh, David Schirmer, Monique L. den Boer, Rebeca Alba Rubío, Michaela Baldauf, Caroline Wernicke, Hans-Jochem Kolb, Martin Horstmann, Gunnar Cario, Guünther Richter, Stefan Burdach. MondoA mediates in vivo aggressiveness of common ALL and may serve as a T-cell immunotherapy target. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2462.