Biology subjects

Grebien, F.

Publications and source records attributed to Grebien, F..

5 recordsLinked to original sources

bioRxiv2023

Small molecule STAT3/5 inhibitors exhibit therapeutic potential in acute myeloid leukemia and extra-nodal natural killer/T cell lymphoma

The oncogenic transcription factors STAT3, STAT5A and STAT5B are essential to steer hematopoiesis and immunity, but their enhanced expression and activation drives the development or progression of blood cancers. Current therapeutic strategies focus on blocking upstream tyrosine kinases, but frequently occurring resistance often leads to disease relapse, emphasizing the need for more targeted therapies. Here we evaluate JPX-0700 and JPX-0750, which are STAT3/5-specific covalent cysteine binders that lead to growth arrest of acute myeloid leukemia (AML) and natural killer/T cell lymphoma (NKCL) cell lines in vitro and in vivo, as well as reduce cell viability of primary AML blasts ex vivo. Our non-PROTAC small molecular weight degraders selectively reduce STAT3/5 activation and total protein levels, as well as downstream target oncogene expression, exhibiting nanomolar to low micromolar efficacy. We found that both AML and NKCL cells hijack STAT3/5 signaling through either upstream activating mutations in tyrosine kinases, activating gain-of-function mutations in STAT3, mutational loss of negative STAT regulators, or genetic gains in anti-apoptotic, pro-proliferative or epigenetic-modifying STAT3/5 targets. Moreover, we have shown synergistic inhibitory action of JPX-0700 and JPX-0750 upon combinatorial use with approved chemotherapeutics (doxorubicin, daunorubicin, cytarabine), epigenetic enzyme blocker vorinostat, tyrosine kinase inhibitor cabozantinib or BCL-2 inhibitor venetoclax. Importantly, JPX-0700 or JPX-0750 treatment reduced leukemic cell growth in human AML/NKCL xenograft mouse models without adverse side effects. These potent small molecule degraders of STAT3/5 could propel further clinical development for use in AML and NKCL patients.

cancer biology↗

bioRxiv2023

TET2 lesions enhance the aggressiveness of CEBPA-mutant AML by rebalancing GATA2 expression

The myeloid transcription factor CEBPA is recurrently biallelically mutated (i.e., double mutated; CEBPADM) in acute myeloid leukemia (AML) with a combination of hypermorphic N-terminal mutations (CEBPANT), promoting expression of the leukemia-associated p30 isoform, and amorphic C-terminal mutations. The most frequently co-mutated genes in CEBPADM AML are GATA2 and TET2, however the molecular mechanisms underlying this co-mutational spectrum are incomplete. By combining transcriptomic and epigenomic analyses of CEBPA-TET2 co-mutated patients with models thereof, we identify GATA2 as a conserved target of the CEBPA-TET2 mutational axis, providing a rationale for the mutational spectra in CEBPADM AML. Elevated CEBPA levels, driven by CEBPANT, mediate recruitment of TET2 to the Gata2 distal hematopoietic enhancer thereby increasing Gata2 expression. Concurrent loss of TET2 in CEBPADM AML induces a competitive advantage by increasing Gata2 promoter methylation, thereby rebalancing GATA2 levels. Of clinical relevance, demethylating treatment of Cebpa-Tet2 co-mutated AML restores Gata2 levels and prolongs disease latency.

cancer biology↗

bioRxiv2022

STAT5 Gain-of-Function Variants Promote Precursor T-Cell Receptor Activation to Drive T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive immature T-cell cancer. Hotspot mutations in JAK-STAT pathway members IL7R, JAK1 and JAK3 were analyzed in depth. However, the role of STAT5A or STAT5B mutations promoting their hyperactivation is poorly understood in the context of T-cell cancer initiation and acute leukemia progression. Importantly, the driver mutation STAT5BN642H encodes the most frequent activating STAT5 variant in T-ALL associated with poor prognosis. Here, we show that hyperactive STAT5 promotes early T-cell progenitor (ETP)-ALL-like cancer in mice and upregulated genes involved in T-cell receptor signaling (TCR), even in absence of surface TCR promoting. Importantly, these genes were also overexpressed in human T-ALL and other STAT5-dependent T-cell cancers. Moreover, human T-ALL cells were sensitive to pharmacologic inhibition by dual STAT3/5 degraders or ZAP70 tyrosine kinase blockers. Thus, we define STAT5 target genes in T-ALL that promote pre-TCR signaling mimicry. We propose therapeutic targeting using selective ZAP70 or STAT3/5 inhibitors in a subgroup of T-ALL patients with prominent IL-7R-JAK1/3-STAT5 activity. SignificanceWe provide detailed functional characterizations of hyperactive STAT5A or STAT5B in thymic T-cell development and transformation. We found that hyperactive STAT5 transcribes T-cell-specific kinases or pre-TCR signaling hubs to promote T-ALL. Biomolecular and next-generation-sequencing methods, transgenesis and pharmacologic interference revealed that hyperactive STAT5 is a key oncogenic driver that can be targeted in T-ALL using STAT3/5 or SYK family member tyrosine kinase inhibitors. Conflict of interestThe authors declare no potential conflicts of interest.

cancer biology↗

bioRxiv2020

Biomolecular Condensation Drives Leukemia Caused by NUP98-Fusion Proteins

NUP98-fusion proteins cause acute myeloid leukemia via unknown molecular mechanisms. All NUP98-fusion proteins share an intrinsically disordered region (IDR) featuring >35 repeats of Phenylalanine-Glycine (FG) in the NUP98 N-terminus. Conversely, different C-terminal NUP98-fusion partners are often transcriptional and epigenetic regulators. Given these structural features we hypothesized that mechanisms of oncogenic transformation by NUP98-fusion proteins are hard-wired in their protein interactomes. Affinity purification coupled to mass spectrometry of five distinct NUP98-fusion proteins revealed a conserved set of interactors that was highly enriched for proteins involved in biomolecular condensation. We developed biotinylated isoxazole-mediated condensome mass spectrometry (biCon-MS) to show that NUP98-fusion proteins alter the global composition of biomolecular condensates. In addition, an artificial FG-repeat containing fusion protein was able to phenocopy the induction of leukemic gene expression as mediated by NUP98-KDM5A. Thus, we propose that IDR-containing fusion proteins have evolved to uniquely combine biomolecular condensation with gene control to induce cancer. AML, NUP98, fusion protein, AP-MS, LLPS, biCon-MS, condensate

cancer biology↗

bioRxiv2020

Ablation of MYB-dependent leukaemia phenotype in MLL-driven AML correlates with increased expression of MAFB.

The transcription factor MYB plays a pivotal role in haematopoietic homeostasis and its aberrant expression is involved in the genesis and maintenance of acute myeloid leukaemia (AML). Our previous work has demonstrated that not all AML types display the same dependency on MYB expression and that MYB dependence is dictated by the nature of the driver mutation. However, whether this difference in MYB dependency is a general trend in AML still remains to be further elucidated. In this study, we investigate the importance of MYB in human leukaemia by performing siRNA-mediated knock-down in cell line models of AML with different driver lesions. We show that the characteristic reduction in proliferation and the concomitant induction of myeloid differentiation that is observed in MLL-fusion-driven leukaemia upon MYB suppression is not seen in AML cells with a complex karyotype. By performing transcriptome analysis, we demonstrate that a strong activation of MAFB expression driven by MYB ablation is restricted to MYB-dependent cells. In line with these observations, stratification of publicly available patient data reveals a reciprocal relationship between the expression of MYB and MAFB, highlighting a novel connection between those two factors in AML.

cancer biology↗