Biology subjects

Hoefler, G.

Publications and source records attributed to Hoefler, G..

7 recordsLinked to original sources

bioRxiv2026

EZH2 inactivation drives MAPK-dependent vulnerability to MEK inhibition in RAS-mutant CMML

Chronic myelomonocytic leukemia (CMML) is a heterogeneous hematologic malignancy with limited therapeutic options. Although RAS and RAS-modifying mutations (RASmut) are common and associated with poor prognosis, targeting RAS signaling has shown limited clinical success. Here, we define co-occurrence of RASmut and EZH2 inactivation (EZH2inact) as a distinct molecular subgroup of CMML characterized by aggressive disease biology. Mechanistically, RASmutEZH2inact drives selective MAPK/ERK hyperactivation in mature myeloid cells and hematopoietic stem and progenitor compartments. Transcriptomic analysis of a large independent myeloid neoplasm cohort (Beat-AML) further supports this finding, demonstrating selective activation of gene signatures of MAPK/ERK activation in RASmutEZH2inact cases. Functionally, this signaling activation promotes proliferation and myelomonocytic differentiation in human and murine models. Therapeutically, this MAPK/ERK upregulation confers increased sensitivity to MEK inhibition (MEKi). In a murine RasmutEzh2inact-driven CMML model, MEKi suppresses MAPK/ERK activity and reduces leukemic burden by impairing proliferation and myelomonocytic differentiation without inducing cell death. In primary human CMML samples ex vivo, MEKi shows stronger anti-proliferative effects in RASmutEZH2inact specimens compared with RASmut samples. Drug-sensitivity data from the Beat-AML cohort further supported this. Ultimately, these findings were confirmed in a patient-derived xenograft model, where MEKi reduced the leukemic burden by selectively inhibiting the proliferation of transplanted human RASmutEZH2inact leukemic cells. In summary, our data define RASmutEZH2inact CMML as a clinically relevant subgroup with selective MAPK/ERK hyperactivation and increased sensitivity to MEKi. They provide a mechanistic explanation for the limited efficacy of MEK inhibitors in unselected CMML and support molecularly guided use of MEK-targeted therapy in this patient population.

molecular biology↗

bioRxiv2026

Self-organized hemanoids derived from human iPSCs create a niche that produces definitive extraembryonic hematopoiesis.

Manufacturing red blood cells (RBCs) from human induced pluripotent stem cells (iPSCs) can improve our understanding of embryonic erythropoiesis, foster innovative treatments for RBC-related diseases, and ultimately address clinical blood supply shortages. However, existing systems face low efficiency, enucleation failure, and uncertainty about the develop-mental wave of cultured RBCs. We successfully used self-organized hemanoids to improve iPSC-derived RBC generation. Based on the hypothesis that cellular interactions and 3D organization promote hematopoietic cell fate, we aimed to thoroughly characterize hemanoids. We visualized the spatiotemporal emergence of hematopoiesis by generating a CD43-GFP reporter iPSC line. Imaging and spatial transcriptomics analysis provided de-tailed insight into the hemanoid architecture, identifying stromal cells and hepatoblasts as potential erythropoiesis-supportive elements. The developmental stage mirrors extraembryonic hematopoiesis. Given the difficulties of accessing these early stages in vivo, our system offers a platform not only for further clinical translation but also for exploring hu-man embryonic blood wave dynamics.

developmental biology↗

bioRxiv2026

RAS-mutant clones drive extramedullary acute myeloid leukemia

Extramedullary acute myeloid leukemia (eAML) represents a clinically challenging manifestation of acute myeloid leukemia (AML), but its molecular drivers remain poorly defined. We performed targeted sequencing in 85 eAML biopsies, representing one of the largest molecular analyses of eAML to date. We detected mutations in RAS or RAS-modifying genes (RASMUT; NRAS, KRAS, PTPN11, CBL, and NF1) in 41% of cases, representing a significant enrichment compared to bone marrow (BM) samples of more than 1300 AML patients not selected for eAML. Analysis of paired eAML and BM specimens revealed expansion and/or de-novo appearance of RASMUT clones at the extramedullary site. Functional studies using primary murine leukemia cells and CRISPR/Cas9-engineered isogenic human leukemia cell lines demonstrated that RASMUT increase the migration and invasion of leukemic cells compared to RAS-wildtype controls. Consistently, RASMUT cells showed increased infiltration into the chorioallantoic membrane of chicken embryos and demonstrated enhanced extramedullary growth after injection into immunocompromised mice. RNA sequencing revealed increased expression of junctional adhesion molecule-like (JAML) and activation of PI3K/AKT signaling in RASMUT cells. JAML silencing and pharmacologic AKT inhibition reversed the RASMUT-driven effects on leukemic cell migration, demonstrating a causal role of the JAML-PI3K/AKT axis in RASMUT-driven eAML formation. In conclusion, these findings delineate the molecular landscape of extramedullary AML and show that RASMUT are enriched within this AML subform. They further demonstrate that RASMUT actively contribute to leukemic tissue infiltration through activation of a RASMUT-JAML-PI3K/AKT axis, highlighting AKT signaling as a potential therapeutic vulnerability in RASMUT-associated eAML.

cancer biology↗

bioRxiv2025

Tissue architecture and immune niches govern ctDNA release in colorectal cancer

Circulating tumor DNA (ctDNA) is central to liquid biopsy-based cancer detection, yet its release into the bloodstream varies widely and remains poorly understood. To define the tissue-level determinants of ctDNA shedding in colorectal cancer (CRC), we integrated tumor-informed plasma sequencing with detailed histopathology, immunophenotyping, spatial transcriptomics, and in situ mutation detection in resectable stages (I-III). ctDNA detectability increased with tumor burden, and high ctDNA shedders exhibited a distinct architectural and microenvironmental phenotype characterized by expanded necrotic pseudolumina, frequent epithelial barrier disruption, and dense myeloid infiltration. Spatial profiling revealed stress-associated malignant programs and a myeloid-rich immune-luminal niche. In situ sequencing confirmed plasma-detected mutations within pseudoluminal debris, identifying these structures as focal reservoirs of shed DNA. These findings provide a mechanistic framework linking tissue architecture, immune remodelling, and spatially organized cell death to ctDNA release with implications for refining liquid biopsy applications.

cancer biology↗

bioRxiv2024

Non-shivering thermogenesis is intact upon brown-adipocyte specific loss of ATGL and HSL due to white adipose tissue browning

Intracellular fatty acids (FAs) activate and fuel non-shivering thermogenesis (NST) via uncoupling protein 1 (UCP1). Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) control FA availability. Since mice lacking ATGL in brown adipose tissue (BAT) exhibit intact recruitable adrenergic thermogenesis, we hypothesized that HSL-mediated FA release is sufficient to activate UCP1-dependent NST. We demonstrate that mice with inducible brown adipocyte-specific loss of ATGL and HSL (iBDKO) exhibit normal recruitable adrenergic thermogenesis upon prolonged cold exposure. Mechanistically, we show that BAT thermogenic capacity is impaired in cold-adapted iBDKO mice due to diminished mitochondrial numbers. Increased browning of white adipose tissue (WAT) in iBDKO mice indicates a shift in thermogenesis from BAT to WAT. Consistently, the loss of ATGL and HSL in BAT and WAT disrupts thermogenesis in both depots, resulting in blunted UCP1-dependent NST. Our study highlights the metabolic adaptability of adipose tissue and the critical role of intracellular lipolysis in regulating thermogenesis.

physiology↗

bioRxiv2020

Adipose Triglyceride Lipase is needed for homeostatic control of Sterol Element-Binding Protein-1c driven hepatic lipogenesis

Sterol Regulatory Element-Binding Protein-1c (SREBP-1c) is translated as an inactive precursor-protein that is proteolytically activated to promote fatty-acid (FA) biosynthesis, when unsaturated (u)FAs are scarce. During fasting, however, lipogenesis is low, and adipose-tissue lipolysis supplies the organism with FAs. Adipose TriGlyceride Lipase (ATGL) is the rate-limiting enzyme for lipolysis, and it preferentially hydrolyzes uFAs. Therefore, we hypothesized that ATGL-derived FAs may suppress the proteolytic activation of SREBP-1c in the liver. Here we show that (i) SREBP-1c is inactive during fasting but active after refeeding, (ii) uFA species liberated by ATGL suppress SREBP-1c activation in vitro, (iii) SREBP-1c is hyper-activated in livers of mice lacking ATGL, and (iv) pharmacological inhibition of ATGL selectively activates SREBP-1c in hepatocytes. Our findings highlight an ATGL/SREBP-1c axis, instrumental to coordinate lipogenesis and lipolysis, whose homeostatic regulation is crucial to avoid severe diseases including diabetes, cardiomyopathy, and even cancer.

biochemistry↗

bioRxiv2020

Loss of malate-aspartate shuttle component SLC25A12 induces pulmonary metastasis

BackgroundAspartate biosynthesis and its delivery to the cytosol can be crucial for tumor growth in vivo. However, the impact of aspartate synthesis on metastasis has not been studied. We previously described that loss-of-aspartate glutamate carrier 1 (SLC25A12 or AGC1), an important component of the malate-aspartate shuttle, impairs cytosolic aspartate levels, NAD+/NADH ratio, mitochondrial respiration, and tumor growth. Here, we report the impact of AGC1-knockdown on metastasis. ResultsAGC1 expression is positively correlated with worse patient prognosis in many cancers. AGC1-knockdown in mouse lung carcinoma and melanoma cell lines leads to increased pulmonary metastasis following subcutaneous or intravenous injections, respectively. On the other hand, conventional in vitro metastasis assays show no indication of increased metastasis capacity of AGC1-knockdown cells. ConclusionThis study highlights that certain branches of metabolism impact tumor growth and tumor metastasis differently. In addition, it also argues that commonly known metastasis indicators, including EMT genes, cell migration, or colony formation do not always reflect the metastatic capacity in vivo.

cancer biology↗