Papers by Martine Roussel
Research Square (Research Square), Jun 6, 2023
GK and CD have patent applications in the field of immunotherapy. SG is a co-inventor on patent a... more GK and CD have patent applications in the field of immunotherapy. SG is a co-inventor on patent applications in the fields of cell or gene therapy for cancer, a consultant of TESSA Therapeutics, a scientific advisory board member of Be Biopharma, a member of the Data and Safety Monitoring Board (DSMB) of Immatics, and has received honoraria from Tidal, Catamaran Bio, and Sanofi within the last 2 years.
Cancer Research, Jul 15, 2008
Molecular and Cellular Biology, Apr 1, 2000
The ARF tumor suppressor protein stabilizes p53 by antagonizing its negative regulator, Mdm2 (Hdm... more The ARF tumor suppressor protein stabilizes p53 by antagonizing its negative regulator, Mdm2 (Hdm2 in humans). Both mouse p19 ARF and human p14 ARF bind to the central region of Mdm2 (residues 210 to 304), a segment that does not overlap with its N-terminal p53-binding domain, nuclear import or export signals, or C-terminal RING domain required for Mdm2 E3 ubiquitin ligase activity. The N-terminal 37 amino acids of mouse p19 ARF are necessary and sufficient for binding to Mdm2, localization of Mdm2 to nucleoli, and p53-dependent cell cycle arrest. Although a nucleolar localization signal (NrLS) maps within a different segment (residues 82 to 101) of the human p14 ARF protein, binding to Mdm2 and nucleolar import of ARF-Mdm2 complexes are both required for cell cycle arrest induced by either the mouse or human ARF proteins. Because many codons of mouse ARF mRNA are not recognized by the most abundant bacterial tRNAs, we synthesized ARF minigenes containing preferred bacterial codons. Using bacterially produced ARF polypeptides and chemically synthesized peptides conjugated to Sepharose, residues 1 to 14 and 26 to 37 of mouse p19 ARF were found to interact independently and cooperatively with Mdm2, while residues 15 to 25 were dispensable for binding. Paradoxically, residues 26 to 37 of mouse p19 ARF are also essential for ARF nucleolar localization in the absence of Mdm2. However, the mobilization of the p19 ARF-Mdm2 complex into nucleoli also requires a cryptic NrLS within the Mdm2 C-terminal RING domain. The Mdm2 NrLS is unmasked upon ARF binding, and its deletion prevents import of the ARF-Mdm2 complex into nucleoli. Collectively, the results suggest that ARF binding to Mdm2 induces a conformational change that facilitates nucleolar import of the ARF-Mdm2 complex and p53-dependent cell cycle arrest. Hence, the ARF-Mdm2 interaction can be viewed as bidirectional, with each protein being capable of regulating the subnuclear localization of the other.
Molecular and Cellular Biology, May 1, 1995
Cyclin D-dependent kinases act as mitogen-responsive, rate-limiting controllers of G 1 phase prog... more Cyclin D-dependent kinases act as mitogen-responsive, rate-limiting controllers of G 1 phase progression in mammalian cells. Two novel members of the mouse INK4 gene family, p19 and p18, that specifically inhibit the kinase activities of CDK4 and CDK6, but do not affect those of cyclin E-CDK2, cyclin A-CDK2, or cyclin B-CDC2, were isolated. Like the previously described human INK4 polypeptides, p16 INK4a/MTS1 and p15 INK4b/MTS2 , mouse p19 and p18 are primarily composed of tandemly repeated ankyrin motifs, each ca. 32 amino acids in length. p19 and p18 bind directly to CDK4 and CDK6, whether untethered or in complexes with D cyclins, and can inhibit the activity of cyclin D-bound cyclin-dependent kinases (CDKs). Although neither protein interacts with D cyclins or displaces them from preassembled cyclin D-CDK complexes in vitro, both form complexes with CDKs at the expense of cyclins in vivo, suggesting that they may also interfere with cyclin-CDK assembly. In proliferating macrophages, p19 mRNA and protein are periodically expressed with a nadir in G 1 phase and maximal synthesis during S phase, consistent with the possibility that INK4 proteins limit the activities of CDKs once cells exit G 1 phase. However, introduction of a vector encoding p19 into mouse NIH 3T3 cells leads to constitutive p19 synthesis, inhibits cyclin D1-CDK4 activity in vivo, and induces G 1 phase arrest.
Molecular and Cellular Biology, Nov 1, 2001
The ARF and p53 tumor suppressors mediate Myc-induced apoptosis and suppress lymphoma development... more The ARF and p53 tumor suppressors mediate Myc-induced apoptosis and suppress lymphoma development in E-myc transgenic mice. Here we report that the proapoptotic Bcl-2 family member Bax also mediates apoptosis triggered by Myc and inhibits Myc-induced lymphomagenesis. Bax-deficient primary pre-B cells are resistant to the apoptotic effects of Myc, and Bax loss accelerates lymphoma development in E-myc transgenics in a dose-dependent fashion. Eighty percent of lymphomas arising in wild-type E-myc transgenics have alterations in the ARF-Mdm2-p53 tumor suppressor pathway characterized by deletions in ARF, mutations or deletions of p53, and overexpression of Mdm2. The absence of Bax did not alter the frequency of biallelic deletion of ARF in lymphomas arising in E-myc transgenic mice or the rate of tumorigenesis in ARF-null mice. Furthermore, Mdm2 was overexpressed at the same frequency in lymphomas irrespective of Bax status, suggesting that Bax resides in a pathway separate from ARF and Mdm2. Strikingly, lymphomas from Bax-null E-myc transgenics lacked p53 alterations, whereas 27% of the tumors in Bax ؉/؊ E-myc transgenic mice contained p53 mutations or deletions. Thus, the loss of Bax eliminates the selection of p53 mutations and deletions, but not ARF deletions or Mdm2 overexpression, during Myc-induced tumorigenesis, formally demonstrating that Myc-induced apoptotic signals through ARF/Mdm2 and p53 must bifurcate: p53 signals through Bax, whereas this is not necessarily the case for ARF and Mdm2.
HAL (Le Centre pour la Communication Scientifique Directe), 2018
Purpose: Although most children with medulloblastoma are cured of their disease, Sonic Hedgehog (... more Purpose: Although most children with medulloblastoma are cured of their disease, Sonic Hedgehog (SHH) subgroup medulloblastoma driven by TRP53 mutations is essentially lethal. Casein kinase 1α (CK1α) phosphorylates and destabilizes GLI transcription factors, thereby inhibiting the key effectors of SHH signaling. We therefore tested a second-generation CK1α activator against TRP53-mutant, MYCN-amplified medulloblastoma. Experimental Design: The ability of this CK1α activator to block SHH signaling was determined in vitro using GLI reporter cells, granular precursor primary cultures, and PATCHED1 (PTCH1)mutant sphere cultures. While in vivo efficacy was tested using 2 different medulloblastoma mouse models: PTCH1 and ND2:SMOA1. Finally, the clinical relevance of CK1α activators was demonstrated using a TRP53-mutant, MYCN-amplified patient-derived xenograft. Results: SSTC3 inhibited SHH activity in vitro, acting downstream of the vismodegib target SMOOTHENED (SMO), and reduced the viability of sphere cultures derived from SHH medulloblastoma. SSTC3 accumulated in the brain, inhibited growth of SHH medulloblastoma tumors, and blocked metastases in a genetically engineered vismodegib-resistant mouse model of SHH medulloblastoma. Importantly, SSTC3 attenuated growth and metastasis of orthotopic patient-derived TRP53-mutant, MYCN-amplified, SHH subgroup medulloblastoma xenografts, increasing overall survival. Conclusions: Using a newly described small-molecule, SSTC3, we show that CK1a activators could address a significant unmet clinical need for patients with SMO inhibitor-resistant medulloblastoma, including those harboring mutations in TRP53.
Journal of Neuro-oncology, May 1, 2023
Purpose We and others have demonstrated that MYC-amplified medulloblastoma (MB) cells are suscept... more Purpose We and others have demonstrated that MYC-amplified medulloblastoma (MB) cells are susceptible to class I histone deacetylase inhibitor (HDACi) treatment. However, single drug treatment with HDACi has shown limited clinical efficacy. We hypothesized that addition of a second compound acting synergistically with HDACi may enhance efficacy. Methods We used a gene expression dataset to identify PLK1 as a second target in MB cells and validated the relevance of PLK1 in MB. We measured cell metabolic activity, viability, and cycle progression in MB cells after treatment with PLK1-specific inhibitors (PLK1i). Chou-Talalay synergy calculations were used to determine the nature of class I HDACi entinostat and PLK1i interaction which was validated. Finally, the clinical potential of the combination was assessed in the in vivo experiment. Results MYC-amplified tumor cells are highly sensitive towards treatment with ATP-competitive PLK1i as a monotherapy. Entinostat and PLK1i in combination act synergistically in MYC-driven MB cells, exerting cytotoxic effects at clinically relevant concentrations. The downstream effect is exerted via MYC-related pathways, pointing out the potential of MYC amplification as a clinically feasible predictive biomarker for patient selection. While entinostat significantly extended survival of mice implanted with orthotopic MYC-amplified MB PDX, there was no evidence of the improvement of survival when treating the animals with the combination. The combination of entinostat and PLK1i showed synergistic interaction in vitro, but not in vivo. Therefore, further screening of blood-brain barrier penetrating PLK1i is warranted to determine the true potential of the combination as no on-target activity was observed after PLK1i volasertib treatment in vivo.
Oncogene, Apr 5, 2023
Atypical teratoid/rhabdoid tumors (ATRTs) represent a rare, but aggressive pediatric brain tumor ... more Atypical teratoid/rhabdoid tumors (ATRTs) represent a rare, but aggressive pediatric brain tumor entity. They are genetically defined by alterations in the SWI/SNF chromatin remodeling complex members SMARCB1 or SMARCA4. ATRTs can be further classified in different molecular subgroups based on their epigenetic profiles. Although recent studies suggest that the different subgroups have distinct clinical features, subgroup-specific treatment regimens have not been developed thus far. This is hampered by the lack of pre-clinical in vitro models representative of the different molecular subgroups. Here, we describe the establishment of ATRT tumoroid models from the ATRT-MYC and ATRT-SHH subgroups. We demonstrate that ATRT tumoroids retain subgroup-specific epigenetic and gene expression profiles. High throughput drug screens on our ATRT tumoroids revealed distinct drug sensitivities between and within ATRT-MYC and ATRT-SHH subgroups. Whereas ATRT-MYC universally displayed high sensitivity to multi-targeted tyrosine kinase inhibitors, ATRT-SHH showed a more heterogeneous response with a subset showing high sensitivity to NOTCH inhibitors, which corresponded to high expression of NOTCH receptors. Our ATRT tumoroids represent the first pediatric brain tumor organoid model, providing a representative pre-clinical model which enables the development of subgroup-specific therapies.
Cancers, Jan 5, 2020
Medulloblastoma is an embryonal tumor that shows a predilection for distant metastatic spread and... more Medulloblastoma is an embryonal tumor that shows a predilection for distant metastatic spread and leptomeningeal seeding. For most patients, optimal management of medulloblastoma includes maximum safe resection followed by adjuvant craniospinal irradiation (CSI) and chemotherapy. Although CSI is crucial in treating medulloblastoma, the realization that medulloblastoma is a heterogeneous disease comprising four distinct molecular subgroups (wingless [WNT], sonic hedgehog [SHH], Group 3 [G3], and Group 4 [G4]) with distinct clinical characteristics and prognoses has refocused efforts to better define the optimal role of CSI within and across disease subgroups. The ability to deliver clinically relevant CSI to preclinical models of medulloblastoma offers the potential to study radiation dose and volume effects on tumor control and toxicity in these subgroups and to identify subgroup-specific combination adjuvant therapies. Recent efforts have employed commercial image-guided small animal irradiation systems as well as custom approaches to deliver accurate and reproducible fractionated CSI in various preclinical models of medulloblastoma. Here, we provide an overview of the current clinical indications for, and technical aspects of, irradiation of pediatric medulloblastoma. We then review the current literature on preclinical modeling of and treatment interventions for medulloblastoma and conclude with a summary of challenges in the field of preclinical modeling of CSI for the treatment of leptomeningeal seeding tumors.
Nature Communications, Feb 10, 2023
Acta Neuropathologica, Jun 10, 2020
Pediatric brain tumors are the leading cause of cancer-related death in children. Patient-derived... more Pediatric brain tumors are the leading cause of cancer-related death in children. Patient-derived orthotopic xenografts (PDOX) of childhood brain tumors have recently emerged as a biologically faithful vehicle for testing novel and more effective therapies. Herein, we provide the histopathological and molecular analysis of 37 novel PDOX models generated from pediatric brain tumor patients treated at St. Jude Children's Research Hospital. Using a combination of histopathology, whole-genome and whole-exome sequencing, RNA-sequencing, and DNA methylation arrays, we demonstrate the overall fidelity and inter-tumoral molecular heterogeneity of pediatric brain tumor PDOX models. These models represent frequent as well as rare childhood brain tumor entities, including medulloblastoma, ependymoma, atypical teratoid rhabdoid tumor, and embryonal tumor with multi-layer rosettes. PDOX models will be valuable platforms for evaluating novel therapies and conducting pre-clinical trials to accelerate progress in the treatment of brain tumors in children. All described PDOX models and associated datasets can be explored using an interactive web-based portal and will be made freely available to the research community upon request.
The Cerebellum, Nov 25, 2017
Epigenetics is the process by which gene expression is regulated by events other than alterations... more Epigenetics is the process by which gene expression is regulated by events other than alterations of the genome. This includes DNA methylation, histone modifications, chromatin remodeling, microRNAs, and long non-coding RNAs. Methylation of DNA, chromatin remodeling, and histone modifications regulate the chromatin and access of transcription factors to DNA and in turn gene transcription. Alteration of chromatin is now recognized to be deregulated in many cancers. Medulloblastoma is an embryonal tumor of the cerebellum and the most common malignant brain tumor in children, that occurs only rarely in adults. Medulloblastoma is characterized by four major molecularly and histopathologically distinct groups, wingless (WNT), sonic hedgehog (SHH), group 3 (G3), and group 4 (G4), that, except for WNT, are each now subdivided in several subgroups. Gene expression array, next-generation sequencing, and methylation profiling of several hundred primary tumors by several consortia and independent groups revealed that medulloblastomas harbor a paucity of mutations most of which occur in epigenetic regulators, genetic alterations in oncogenes and tumor suppressors, in addition to copy number alterations and chromosome gains and losses. Remarkably, some tumors have no reported mutations, suggesting that some genes required for oncogenesis might be regulated by epigenetic mechanisms which are still to be uncovered and validated. This review will highlight several epigenetic regulators focus-i n g m a i n l y o n h i s t o n e m o d i f i e r s i d e n t i f i e d i n medulloblastoma.
Proceedings of the National Academy of Sciences of the United States of America, Jul 18, 1995
Three gene products, including Myc and the D-and E-type G1 cyclins, are rate limiting for G1 prog... more Three gene products, including Myc and the D-and E-type G1 cyclins, are rate limiting for G1 progression in mammalian fibroblasts. Quiescent mouse NIH 3T3 fibro- blasts engineered to express a mutant colony-stimulating factor (CSF-1) receptor (CSF-1R 809F) fail to synthesize c-myc and cyclin Dl mRNAs upon CSF-1 stimulation and remain arrested in early G, phase. Ectopic expression of c-myc or either of three D-type cyclin genes, but not cyclin E, resensi- tized these cells to the mitogenic effects of CSF-1, enabling them to proliferate continuously in liquid culture and to form colonies in agar in response to the growth factor. Rescue by cyclin Dl was enhanced by c-myc but not by cyclin E and was reversed by infecting cyclin DI-reconstituted cells with a retroviral vector encoding catalytically inactive cyclindependent kinase 4. Induction of cyclin Dl mRNA by CSF-1 was restored in cells forced to express c-myc, and vice versa, suggesting that expression of the two genes is interdependent. Cells reconstituted with c-myc were prevented from entering S phase when microinjected with a monoclonal antibody to cyclin Dl, and conversely, those rescued by cyclin Dl were inhibited from forming CSF-1-dependent colonies when chal- lenged with a dominant-negative c-myc mutant. Cyclin D mutants defective in binding to the retinoblastoma protein were impaired in rescuing mitogenic signaling. Therefore, Myc and D-type cyclins collaborate during the mitogenic response to CSF-1, whereas cyclin E functions in a separate pathway.
Genes & Development, Aug 1, 2004
Unknown mechanisms govern degradation of the p19 Arf tumor suppressor, an activator of p53 and in... more Unknown mechanisms govern degradation of the p19 Arf tumor suppressor, an activator of p53 and inhibitor of ribosomal RNA processing. Kinetic metabolic labeling of cells with [ 3 H]-leucine indicated that p19 Arf is a relatively stable protein (half-life ∼6 h) whose degradation depends upon the ubiquitin-proteasome pathway. Although p19 Arf binds to the Mdm2 E3 ubiquitin protein ligase to activate p53, neither of these molecules regulates p19 Arf turnover. In contrast, the nucleolar protein nucleophosmin/B23, which binds to p19 Arf with high stoichiometry, retards its turnover, and Arf mutants that do not efficiently associate with nucleophosmin/B23 are unstable and functionally impaired. Mouse p19 Arf , although highly basic (22% arginine content), contains only a single lysine residue absent from human p14 ARF , and substitution of arginine for lysine in mouse p19 Arf had no effect on its rate of degradation. Mouse p19 Arf (either wild-type or lacking lysine) and human p14 ARF undergo N-terminal polyubiquitination, a process that has not as yet been documented in naturally occurring lysine-less proteins. Re-engineering of the p19 Arf N terminus to provide consensus sequences for N-acetylation limited Arf ubiquitination and decelerated its turnover.
F1000 biology reports, Mar 1, 2011
Medulloblastoma, a cancer of the posterior fossa, is the most common malignant brain tumor in chi... more Medulloblastoma, a cancer of the posterior fossa, is the most common malignant brain tumor in children. Although 80% of patients with average-risk medulloblastoma are cured, their quality of life is often compromised by treatment-related side effects. Recently, molecular and genomic studies have shown medulloblastoma to be a heterogeneous disease made up of distinct disease subtypes. The importance of this finding is that response to therapy appears to be subtype-specific. Nevertheless, most patients are still treated according to risk stratification methods based on the clinically defined presence or absence of disseminated disease, which take no account of these newly defined subtypes. The potential, however, to vastly reduce therapy-mediated toxicity to patients with tumor subtypes that have good outcomes, while improving therapy through targeting for the poor responders, is now palpable. Critical to this effort will be the ongoing refinement of our understanding of medulloblastoma subgroups at the molecular level and the development of mouse models that faithfully recapitulate tumor subtypes.
Nature
Medulloblastoma (MB) comprises a group of heterogeneous paediatric embryonal neoplasms of the hin... more Medulloblastoma (MB) comprises a group of heterogeneous paediatric embryonal neoplasms of the hindbrain with strong links to early development of the hindbrain 1-4. Mutations that activate Sonic hedgehog signalling lead to Sonic hedgehog MB in the upper rhombic lip (RL) granule cell lineage 5-8. By contrast, mutations that activate WNT signalling lead to WNT MB in the lower RL 9,10. However, little is known about the more commonly occurring group 4 (G4) MB, which is thought to arise in the unipolar brush cell lineage 3,4. Here we demonstrate that somatic mutations that cause G4 MB converge on the core binding factor alpha (CBFA) complex and mutually exclusive alterations that affect CBFA2T2, CBFA2T3, PRDM6, UTX and OTX2. CBFA2T2 is expressed early in the progenitor cells of the cerebellar RL subventricular zone in Homo sapiens, and G4 MB transcriptionally resembles these progenitors but are stalled in developmental
Neuro-Oncology
Germline loss-of-function (LOF) mutations in Elongator complex protein 1 (ELP1) are found in 15-2... more Germline loss-of-function (LOF) mutations in Elongator complex protein 1 (ELP1) are found in 15-20% of childhood SHH medulloblastoma (MB) and are exceedingly rare in non-SHH-MB or other cancers. ELP1 germline carriers that develop SHH-MB harbor frequent somatic PTCH1 mutations and universally sustain loss-of-heterozygosity of the remaining ELP1 allele through chromosome 9q deletion. ELP1 functions as a scaffolding subunit of the Elongator complex that is required for posttranscriptional modification of tRNAs and maintenance of efficient translational elongation and protein homeostasis. However, the molecular, biochemical, and cellular mechanisms by which ELP1/Elongator LOF contribute to SHH-MB tumorigenesis remain largely unknown. Herein, we report that mice harboring germline Elp1 monoallelic loss (i.e., Elp1+/-) exhibit hallmark features of malignant predisposition in developing cerebellar granule neuron progenitors (GNPs), the lineage-of-origin for SHH-MB. Elp1+/- GNPs are charac...
Pediatric high-grade glioma (pHGG) is a major contributor to cancer-related death in children.In ... more Pediatric high-grade glioma (pHGG) is a major contributor to cancer-related death in children.In vitroandin vivodisease models reflecting the intimate connection between developmental context and pathogenesis of pHGG are essential to advance understanding and identify therapeutic vulnerabilities. We established 21 patient-derived pHGG orthotopic xenograft (PDOX) models and eight matched cell lines from diverse groups of pHGG. These models recapitulated histopathology, DNA methylation signatures, mutations and gene expression patterns of the patient tumors from which they were derived, and included rare subgroups not well-represented by existing models. We deployed 16 new and existing cell lines for high-throughput screening (HTS).In vitroHTS results predicted variablein vivoresponse to inhibitors of PI3K/mTOR and MEK signaling pathways. These unique new models and an online interactive data portal to enable exploration of associated detailed molecular characterization and HTS chemic...
F1000 - Post-publication peer review of the biomedical literature, 2020
Targeting oncogenic pathways holds promise for brain tumor treatment, but inhibition of Sonic Hed... more Targeting oncogenic pathways holds promise for brain tumor treatment, but inhibition of Sonic Hedgehog (SHH) signaling has failed in SHH-driven medulloblastoma. Cellular diversity within tumors and reduced lineage commitment can undermine targeted therapy by increasing the probability of treatment-resistant populations. Using single-cell RNA-seq and lineage tracing, we analyzed cellular diversity in medulloblastomas in transgenic, medulloblastoma-prone mice, and responses to the SHH-pathway inhibitor vismodegib. In untreated tumors, we find expected stromal cells and tumor-derived cells showing either a spectrum of neural progenitor-differentiation states or glial and stem cell markers. Vismodegib reduces the proliferative population and increases differentiation. However, specific cell types in vismodegib-treated tumors remain proliferative, showing either persistent SHHpathway activation or stem cell characteristics. Our data show that even in tumors with a single pathway-activating mutation, diverse mechanisms drive tumor growth. This diversity confers early resistance to targeted inhibitor therapy, demonstrating the need to target multiple pathways simultaneously.
Blood, 1988
The SV40-immortalized mouse macrophage cell line, BAC1.2F5, is strictly dependent on CSF-1 for it... more The SV40-immortalized mouse macrophage cell line, BAC1.2F5, is strictly dependent on CSF-1 for its survival and proliferation in culture. Introduction of a retroviral vector containing a 1.6 kilobase (kb) pair human CSF-1 cDNA into these cells abrogated their growth factor dependence but did not render the cells tumorigenic in nude mice. The infected macrophages contained multiple copies of the vector provirus, expressed both membrane-bound and secreted forms of CSF-1, and exhibited constitutive down modulation of the murine CSF-1 receptor. Because insertion of the v-fms gene has previously been shown to abrogate factor dependence and induce tumorigenicity in BAC1.2F5 macrophages, the failure of these cells to express a fully transformed phenotype after persistent stimulation by endogenous CSF-1 suggests that the v-fms and c-fms gene products provide different signals for cell proliferation.
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Papers by Martine Roussel