Biology subjects

Labbe, D. P.

Publications and source records attributed to Labbe, D. P..

6 recordsLinked to original sources

bioRxiv2026

Iron Metabolism as a Therapeutic Vulnerability in Stem Cell-Like Castration-Resistant Prostate Cancer

Prostate cancer is the second most common malignancy among men, with androgen deprivation therapy (ADT) serving as the standard treatment due to the hormone sensitivity of prostate tumors. However, therapeutic resistance frequently develops, leading to castration-resistant prostate cancer (CRPC), an aggressive and lethal disease. A recently defined subtype, stem cell-like CRPC (CRPC-SCL), accounts for approximately 25% of CRPC cases and demonstrates poor responsiveness to ADT. CRPC-SCL is characterized by the expression of Cluster of Differentiation 44 (CD44), a glycoprotein that promotes hyaluronic acid binding and uptake. Within CRPC-SCL patient-derived xenograft (PDX) model, CD44 high (CD44hi) cells exhibit enhanced tumorigenicity and proliferative capacity. Importantly, iron metabolism emerges as a critical regulator of this population: CD44hi cells maintain elevated intracellular iron, which sustains CD44 expression and stem cell-like properties by modulating H3K9me2 modification. Leveraging this vulnerability, inhibition of the iron-regulatory factor NRF2 was shown to increase intracellular free iron and selectively induce ferroptosis in CD44hi cells. These findings highlight the therapeutic potential of targeting iron metabolism to induce ferroptosis as a novel treatment strategy for CRPC-SCL.

cancer biology↗

bioRxiv2025

EZH2-TTP-mTORC1 Axis Drives Phenotypic Plasticity and Therapeutic Vulnerability in Lethal Prostate Cancer

Phenotypic plasticity is a recognized mechanism of therapeutic resistance in prostate cancer (PCa), however current knowledge of driver mechanisms and therapeutic interventions are limited. Using genetically engineered mouse models (GEMMs) devoid of Pten and Rb1, we previously demonstrated the chromatin reprogramming factor enhancer of zeste homolog 2 (EZH2) as an important regulator of alternative transcription programs promoting phenotypic plasticity. Here, using a multi-omics approach we demonstrate that EZH2 regulates multilineage cell states dependent on the RNA binding protein Tristetraprolin (TTP) that mediates RNA stability and activation of translation. Combined chemical inhibition of EZH2 and PI3K/mTORC1 resulted in superior anti-tumor activity in murine and human phenotypic plastic models and was most significant when this combination was used with castration or enzalutamide. Together, these data indicate phenotypic plasticity dependence on coordination between EZH2, TTP and mTORC1 signaling that represent novel therapeutic dependencies for this lethal PCa phenotype. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=194 SRC="FIGDIR/small/669104v1_ufig1.gif" ALT="Figure 1"> View larger version (66K): org.highwire.dtl.DTLVardef@5ef713org.highwire.dtl.DTLVardef@af402forg.highwire.dtl.DTLVardef@19eedcforg.highwire.dtl.DTLVardef@10ee421_HPS_FORMAT_FIGEXP M_FIG C_FIG Significance StatementEZH2 plays a key role in driving cell state transitions in neuroendocrine prostate cancer (NEPC), guiding cancer cells towards a more aggressive, therapy-resistant cell type. This transformation creates a specific vulnerability, as NEPC cells become highly reliant on both EZH2 and PI3K/mTORC1-translation signaling. Targeting this dependency, we demonstrate that combining EZH2 with PI3K/mTORC1 inhibition provides effective suppression of NEPC cell growth, offering a promising therapeutic strategy for treating this challenging and aggressive prostate cancer subtype.

cancer biology↗

bioRxiv2021

SOCS3-mediated activation of p53-p21-NRF2 axis and cellular adaptation to oxidative stress in SOCS1-deficient hepatocellular carcinoma

SOCS1 and SOCS3 genes, frequently repressed in hepatocellular carcinoma (HCC), function as tumor suppressors in hepatocytes. However, TCGA transcriptomic data revealed that SOCS1-low/SOCS3-high specimens displayed more aggressive HCC than SOCS1-low/SOCS3-low cases. We show that hepatocyte-specific Socs1-deficient livers upregulate Socs3 expression following genotoxic stress. Whereas deletion of Socs1 or Socs3 increased HCC susceptibility, ablation of both genes attenuated HCC growth. SOCS3 promotes p53 activation in SOCS1-deficient livers, leading to increased expression of CDKN1A (p21WAF1/CIP1), which coincides with elevated expression and transcriptional activity of NRF2. Deleting Cdkn1a in SOCS1-deficient livers diminished NRF2 activation, oxidative stress and HCC progression. Elevated CDKN1A expression and enrichment of antioxidant response genes also characterized SOCS1-low/SOCS3-high HCC. SOCS1 expression in HCC cell lines reduced oxidative stress, p21 expression and NRF2 activation. Our findings demonstrate that SOCS1 controls the oncogenic potential of SOCS3-driven p53-p21-NRF2 axis and suggest that NRF2-mediated antioxidant response represents a drug target in SOCS1-deficient HCC.

cancer biology↗

bioRxiv2021

MYC drives aggressive prostate cancer by disrupting transcriptional pause release at androgen receptor targets

c-MYC (MYC) is a major driver of prostate cancer tumorigenesis and progression. Although MYC is overexpressed in both early and metastatic disease and associated with poor survival, its impact on prostate transcriptional reprogramming remains elusive. We demonstrate that MYC overexpression significantly diminishes the androgen receptor (AR) transcriptional program (the set of genes directly targeted by the AR protein) in luminal prostate cells without altering AR expression. Importantly, analyses of clinical specimens revealed that concurrent low AR and high MYC transcriptional programs accelerate prostate cancer progression toward a metastatic, castration-resistant disease. Data integration of single-cell transcriptomics together with ChIP-seq revealed an increased RNA polymerase II (Pol II) promoter-proximal pausing at AR-dependent genes following MYC overexpression without an accompanying deactivation of AR-bound enhancers. Altogether, our findings suggest that MYC overexpression antagonizes the canonical AR transcriptional program and contributes to prostate tumor initiation and progression by disrupting transcriptional pause release at AR-regulated genes. STATEMENT OF SIGNIFICANCEAR and MYC are key to prostate cancer etiology but our current understanding of their interplay is scarce. Here we show that the oncogenic transcription factor MYC can pause the transcriptional program of the master transcription factor in prostate cancer, AR, while turning on its own, even more lethal program.

genomics↗

bioRxiv2019

Protein Tyrosine Phosphatase 1B Regulates MicroRNA-208b-Argonaute 2 Association and Thyroid Hormone Responsiveness in Cardiac Hypertrophy

Elevated reactive oxygen species (ROS) production plays an important role in the pathogenesis of several diseases, including cardiac hypertrophy. While the regulation of diverse sources of ROS is well characterized in the heart, the redox-sensitive targets that contribute to redox signaling remain largely undefined. We now report that protein tyrosine phosphatase 1B (PTP1B) is reversibly oxidized and inactivated in hearts undergoing hypertrophy and that gene deletion of PTP1B in mouse hearts cause an hypertrophic phenotype that is critically exacerbated in mice subjected to pressure overload. Furthermore, we show that PTP1B dephosphorylates Tyr393 on argonaute 2, a key component of the RNA-induced silencing complex, and sustains gene silencing in the heart. Our results indicate that PTP1B inactivation and argonaute 2 Tyr393 phosphorylation specifically prevents argonaute 2 from interacting with miR-208b. Phosphorylation and inactivation of argonaute 2 in PTP1B cKO mice revealed a mechanism by which defective miR-208b-mediated repression of thyroid hormone receptor-associated protein 1 (THRAP1/MED13) contributes to thyroid hormone-mediated cardiac hypertrophy. In support of this conclusion, inhibiting the synthesis of triiodothyronine (T3), using propylthiouracil, rescued TAC-induced hypertrophy and improved myocardial contractility and systolic function in PTP1B cKO mice. Together, our data illustrate that PTP1B activity exerts a cardioprotective effect in the heart and that redox signaling is tightly linked to thyroid hormone responsiveness and to microRNA-mediated gene silencing in pathological hypertrophy.

cell biology↗

bioRxiv2019

Targeting EZH2 Increases Therapeutic Efficacy of Check-Point Blockade in Models of Prostate Cancer

Prostate cancers are considered immunologically cold tumors given the very few patients who respond to checkpoint inhibitor therapy (CPI). Recently, enrichment of interferon (IFN) response genes predicts a favorable response to CPI across various disease sites. The enhancer of zeste homolog-2 (EZH2) is over-expressed in prostate cancer and is known to negatively regulate IFN response genes. Here, we demonstrate that inhibition of EZH2 catalytic activity in prostate cancer models derepresses expression of double-strand RNA (dsRNA), associated with upregulation of genes involved in antigen presentation, Th-1 chemokine signaling, and interferon (IFN) response, including PD-L1. Similarly, application of a novel EZH2 derived gene signature to human prostate sample analysis indicated an inverse correlation between tumor EZH2 activity/expression with T-cell inflamed and IFN gene signatures and PD-L1 expression. EZH2 inhibition combined with PD-1 CPI significantly enhances antitumor response that is dependent on up-regulation of tumor PD-L1 expression. Further, combination therapy significantly increases intratumoral trafficking of activated CD8+ T-cells and M1 tumor associated macrophages (TAMs) with concurrent loss of M2 TAMs. Our study identifies EZH2 as a potent inhibitor of antitumor immunity and responsiveness to CPI. This data suggests EZH2 inhibition as a novel therapeutic direction to enhance prostate cancer response to PD-1 CPI.

cancer biology↗