Biology subjects

Alexe, G.

Publications and source records attributed to Alexe, G..

7 recordsLinked to original sources

bioRxiv2026

Tabular foundation model predicts alternative lengthening of telomeres (ALT) and identifies SMARCAL1 as a target in ALT-driven cancers

Alternative lengthening of telomeres (ALT) is a telomerase-independent pathway used by aggressive cancers to maintain their replicative immortality. Because ALT is absent from normal human cells, it is an appealing target for cancer therapy, but the lack of ability to determine ALT status at scale has hindered discovery. Here, we developed ALTitude, a machine learning method from a tabular foundation model that infers ALT from cell line whole genome sequencing data, without need for paired germline analysis. We deployed ALTitude across the DepMap, doubling the number of known ALT+ cancer models. Systematic integration of ALTitude with CRISPR-Cas9 screens yielded the selective dependency on SMARCAL1 in ALT+ cell lines, where we show it stabilizes the ALT phenotype. Acute depletion of SMARCAL1 leads to G2/M arrest, mitotic catastrophe, and cell death. These data provide a valuable resource for studying ALT-related genomic features and present SMARCAL1 as a therapeutic target for ALT+ malignancies.

cancer biology↗

bioRxiv2025

Chromatin Perturbation Promotes Susceptibility to Hypomethylating Agents

Cancer-directed drugs are often clinically deployed without definitive understanding of their molecular mechanisms of action (MOA). Hypomethylating agents (HMAs), which result in the degradation of the DNA methyltransferase 1 (DNMT1), have been deployed for decades in the treatment of haematological malignancies1,2. The precise mechanism of action of these drugs, however, has been debated, rendering the design of rational combination therapies challenging. Here, we identified the deubiquitinating enzyme USP48 as a crucial regulator of posttranslational histone modification in the context of DNA demethylation. USP48 loss selectively enhances response to DNMT1 inhibition, leading to a rapid induction of cell death. We demonstrate that USP48 is localized at sites of DNA damage and deubiquitinates H2A variants and proteins important for DNA damage repair. Functionally, loss of USP48 triggers an increase in chromatin accessibility upon HMA treatment, rendering AML cells more susceptible to DNA damage. Our results support USP48 as a posttranslational histone modifier for chromatin stability and DNA damage in response to HMA-related DNA demethylation. These findings propose USP48 as a new target for combination therapy with HMAs for acute myeloid leukaemia (AML).

cancer biology↗

bioRxiv2025

CDK8 Inhibition Releases the Muscle Differentiation Block in Fusion-driven Alveolar Rhabdomyosarcoma

Alveolar rhabdomyosarcoma (aRMS) is a fusion-driven pediatric cancer with poor survival and limited therapeutic options. To uncover novel vulnerabilities, we employed complex-based analysis of the DepMap functional genomic data, identifying CDK8 as a dependency in aRMS. Both CDK8 knockout and pharmacologic inhibition impaired tumor cell growth and induced myogenic differentiation in vitro and in vivo. Compared to genetic loss, CDK8 inhibition induced more dynamic transcriptional changes. With a genome-scale CRISPR-Cas9 drug modifier screen, we determined that the maximal anti-tumor activity of the CDK8 inhibitor requires the presence of the Mediator kinase module and transcriptional cooperation with the SAGA complex. We further identified SIX4 as a key transcription factor mediating CDK8 inhibitor-induced transcriptional activation of myogenic differentiation genes and tumor cell proliferation. These findings suggest a distinct gain-of-function mechanism of the CDK8 inhibitor and establish a strong rationale for CDK8 inhibition as a differentiation-inducing therapeutic strategy in aRMS. STATEMENT OF SIGNIFICANCEWe provide a framework for uncovering therapeutic targets by network-based analysis of functional genomic screens. We identify CDK8 as a druggable target in aRMS and determine that CDK8 inhibition drives myogenic differentiation and impairs tumor progression via a collaborative mechanism involving the Mediator kinase module, SAGA complex, and SIX4.

cancer biology↗

bioRxiv2025

Riboflavin drives nucleotide biosynthesis and iron-sulfur metabolism to promote acute myeloid leukemia

Riboflavin is a diet-derived vitamin in higher organisms that serves as a precursor for flavin mononucleotide and flavin adenine dinucleotide, key cofactors that participate in oxidoreductase reactions. Here, using proteomic, metabolomic and functional genomics approaches, we describe a specific riboflavin dependency in acute myeloid leukemia and demonstrate that, in addition to energy production via oxidative phosphorylation, a key biological role of riboflavin is to enable nucleotide biosynthesis and iron-sulfur cluster metabolism. Genetic perturbation of riboflavin metabolism pathways or exogenous depletion in physiological culture medium induce nucleotide imbalance and DNA damage responses, as well as impair the stability and activity of proteins which utilize [4Fe-4S] iron-sulfur clusters as cofactors. We identify a window of therapeutic opportunity upon riboflavin starvation or chemical riboflavin metabolism perturbation and demonstrate that this strongly synergizes with BCL-2 inhibition. Our work identifies riboflavin as a critical metabolic dependency in leukemia, with functions beyond energy production.

cancer biology↗

bioRxiv2025

Rewiring the fusion oncoprotein EWS/FLI1 in Ewing sarcoma with bivalent small molecules

Deregulated transcription is a defining hallmark of cancer, especially pediatric malignancies, which are frequently driven by fusion transcription factors. Targeting transcription factors directly has been challenging as they lack druggable pockets. Recently, chemically induced proximity has enabled the rewiring of transcriptional activators to drive expression of pro-apoptotic genes using bivalent small molecules. Targeting fusion transcription factors, such as EWS/FLI1 in Ewing sarcoma, with these compounds, may open new therapeutic avenues. Here, we develop a small molecule, EB-TCIP, that recruits FKBP12F36V-tagged EWS/FLI1 to DNA sites bound by the transcriptional regulator BCL6, leading to rapid expression of BCL6 target genes. EB-TCIP activity is dependent on ternary complex formation and specific to cells that express FKBP-EWS/FLI1. This proof-of-concept study demonstrates that EWS/FLI1 can be relocalized on chromatin to induce genes that are ordinarily regulated by a transcriptional repressor. Insights herein will guide the development of bivalent molecules that rewire fusion transcription factors.

cancer biology↗

bioRxiv2021

Mitochondrial Dysfunction is a Driver for SP-2509 Drug Resistance in Ewing Sarcoma

Expression of the fusion oncoprotein EWS/FLI causes Ewing sarcoma, an aggressive pediatric tumor characterized by widespread epigenetic deregulation. These epigenetic changes are targeted by novel lysine specific demethylase-1 (LSD1) inhibitors, which are currently in early phase clinical trials. Single agent targeted therapy often induces resistance, and successful clinical development requires knowledge of resistance mechanisms, enabling the design of effective combination strategies. Here, we used a genome-scale CRISPR-Cas9 loss-of-function screen to identify genes whose knockout (KO) conferred resistance to the LSD1 inhibitor SP- 2509 in Ewing sarcoma cell lines. Multiple genes required for mitochondrial electron transport chain (ETC) complexes III and IV function were hits in our screen. We validated this finding using genetic and chemical approaches including CRISPR KO, ETC inhibitors, and mitochondrial depletion. Further global transcriptional profiling revealed that altered complex III/IV function disrupted the oncogenic program mediated by EWS/FLI and LSD1 and blunted the transcriptomic response to SP-2509. These findings demonstrate that mitochondrial dysfunction modulates SP-2509 efficacy and suggest that new therapeutic strategies combining LSD1 with agents which prevent mitochondrial dysfunction may benefit patients with this aggressive malignancy.

cancer biology↗

bioRxiv2020

Targeting serine hydroxymethyltransferases 1 and 2 for T-cell acute lymphoblastic leukemia therapy.

Despite progress in the treatment of acute lymphoblastic leukemia (ALL), T-cell ALL (T-ALL) has limited treatment options particularly in the setting of relapsed/refractory disease. Using an unbiased genome-scale CRISPR-Cas9 screen we sought to identify pathway dependencies for T-ALL which could be harnessed for therapy development. Disruption of the one-carbon folate, purine and pyrimidine pathways scored as the top metabolic pathways required for T-ALL proliferation. We used a recently developed inhibitor of SHMT1 and SHMT2, RZ-2994, to characterize the effect of inhibiting these enzymes of the one-carbon folate pathway in T-ALL and found that T-ALL cell lines were differentially sensitive to RZ-2994, with a S/G2 cell cycle arrest. The effects of SHMT1/2 inhibition were rescued by formate supplementation. Loss of both SHMT1 and SHMT2 was necessary for impaired growth and cell cycle arrest, with suppression of both SHMT1 and SHMT2 impairing leukemia progression in vivo. RZ-2994 decreased leukemia burden in vivo and remained effective in the setting of methotrexate resistance in vitro. This study highlights the significance of the one-carbon folate pathway in T-ALL and supports further development of SHMT inhibitors for treatment of T-ALL and other cancers.

cancer biology↗