Targeting c-met in sonic hedgehog medulloblastomas

Medulloblastoma (MB), a cerebellar tumour primarily diagnosed in children, is the most common malignant brain tumour consisting of four molecular subgroups: Wingless (WNT), Sonic Hedgehog (SHH), Group 3 and Group 4. Although the 70-75% of MB patients survive the disease, the current therapeutic regimen, which comprises surgical resection, chemotherapy and cranial irradiation, is worryingly associated with severe side effects in these young patients. Thus, identifying new and more precise therapeutic strategies is needed to overcome medulloblastoma progression and dissemination as well as the eradication of the disease. Over the last few years, various tyrosine kinase signalling pathways have been identified to play important roles in medulloblastoma tumorigenesis. Active c-MET kinase has been detected as a marker of SHH-driven MB and several inhibitors provided pre-clinical evidence for an effective therapy for SHH-MB patients.In this PhD project, we firstly confirmed that c-MET is highly expressed in SHH MBs; next, the efficacy of multiple commercially available c-MET kinase inhibitors against several in vitro SHH-MB cell lines was evaluated to identify the most potent in the MB cells context and to provide a detailed explanation of how they induce cell death in MB cells. We showed that the highly selective c-MET inhibitor tivantinib outperformed the c-MET inhibitors foretinib and crizotinib in impairing cell viability in both 2D and 3D cell models by inducing a strong apoptotic response, which was more prominent in TP53-/- MB SHH cells compared to TP53wt cells, where it showed primarily mitotic delay. We observed a complex and diverse pharmacological response to c-MET inhibitors; while tivantinib strongly induce mitotic cell death, through downregulation of MCL-1 protein, foretinib and crizotinib causes mitotic slippage, phenomenon frequently correlated to aneuploidy and drug-resistance. However, we demonstrated that use of BH-3 mimetics can reverse this effect and cause cell death. Taken together, this first set of data substantiate the rational use of c-MET inhibitors for SHH-driven MB but the pharmacological heterogeneity in response to c-MET inhibitors should be highly considered when designing novel effective therapies for MBs. Finally, we demonstrated that tivantinib had synergistic anti-proliferative in vitro SHH-MB cells effects, when combined with either first-line chemotherapy for MB or small-molecule, supporting the possibility of new therapeutic approaches aimed to lower doses of drugs and to limit drug toxicities as well as side effects

SMaRT lncRNA controls translation of a G-quadruplex-containing mRNA antagonizing the DHX36 helicase

Guanine-quadruplexes (G4) included in RNA molecules exert several functions in controlling gene expression at post-transcriptional level; however, the molecular mechanisms of G4-mediated regulation are still poorly understood. Here, we describe a regulatory circuitry operating in the early phases of murine muscle differentiation in which a long non-coding RNA (SMaRT) base pairs with a G4-containing mRNA (Mlx-γ) and represses its translation by counteracting the activity of the DHX36 RNA helicase. The time-restricted, specific effect of lnc-SMaRT on the translation of Mlx-γ isoform modulates the general subcellular localization of total MLX proteins, impacting on their transcriptional output and promoting proper myogenesis and mature myotube formation. Therefore, the circuitry made of lnc-SMaRT, Mlx-γ, and DHX36 not only plays an important role in the control of myogenesis but also unravels a molecular mechanism where G4 structures and G4 unwinding activities are regulated in living cells

The association between prenatal atrioventricular septal defects and chromosomal abnormalities

Objective Atrioventricular septal defect is associated with a high risk of a chromosomal abnormality, particularly trisomy 21. The aim of this study is to assess the rate of trisomy 21 in fetuses diagnosed with an atrioventricular septal defect and to examine the influence of prior screening on the rate of trisomy 21. Methods Electronic ultrasound database was searched to identify fetuses diagnoses with an atrioventricular septal defect from 2002 to 2014. Rate of trisomy 21 and other aneuploidies was calculated among fetuses with normal situs. The prevalence of trisomy 21 and other aneuploidies was assessed in women with low and high first trimester risk for trisomy 21, using a cut-off value of 1:150 and 1:250. Results A total 110 fetuses with a diagnosis of atrioventricular septal defect were identified. Among the 98 fetuses with normal situs, the prevalence of trisomy 21 was 46% (95%CI: 36-56%). Using a 1:150 threshold, the rate of trisomy 21 within the low-risk group was 41% (95%CI: 27-57%) while in the high-risk group it was 70% (95% CI: 52-83%), significantly higher than in the low risk group (p = 0.028). Similar results were obtained when the 1:250 threshold was applied (66% versus 41%, p = 0.055). Conclusions The rate of trisomy 21 among fetuses identified with an atrioventricular septal defect in the second trimester is high even in those that undergo first trimester combined screening. Some fetuses with a high-risk screening result show a normal karyotype. Therefore, an offer of an invasive procedure to check fetal karyotyping is indicated. Knowledge of these rates may be helpful for parents in the decision making process

Use of routine ureteral stents in cesarean hysterectomy for placenta accreta

OBJECTIVE: To evaluate benefits of use of ureteral stents in association with cesarean hysterectomy in case of placenta accreta. METHODS: This was a single center, cohort study. Clinical records of singleton pregnancies with placenta accreta who underwent cesarean hysterectomy were included in the study. For this study, pregnancies with diagnoses of placenta accreta, increta, or percreta were considered under the umbrella term of placenta accreta. For all women with placenta accreta, delivery was planned via cesarean hysterectomy at 340-356 weeks, without any attempt to remove the placenta. Reasons for earlier delivery included vaginal bleeding and spontaneous onset of labor. The primary outcome was the incidence of unintentional urinary tract injury. Outcomes were compared in a cohort of women who had planned the placement of ureteral stents and in those who did not. RESULTS: Forty-four singleton gestations with confirmed placenta accreta at the time of cesarean hysterectomy were included in the study. Twenty-four (54.5%) of the included women had the placing of ureteral stents prior to cesarean, while 20 (45.5%) did not. At histological confirmation, most of them had placenta accreta (17/44, 38.6%), 14 placenta increta (31.8%), and 13 placenta percreta (29.6%). Urinary tract injuries occurred in eight cases (18.2%), six in the ureteral stents and two in the non-ureteral stents group (25 versus 10%; p = .21). All the injuries were bladder injuries, while no cases of ureteral injury were recorded. All injuries were recognized intraoperatively. CONCLUSION: In case of placenta accreta, the use of ureteral stents in association with cesarean hysterectomy does not reduce the risk of urinary tract injury

Drug resistance in Medulloblastoma is driven by YB-1, ABCB1 and a seven-gene drug signature

Therapy resistance represents an unmet challenge in the treatment of medulloblastoma. Accordingly, the identification of targets that mark drug-resistant cell populations, or drive the proliferation of resistant cells, may improve treatment strategies. To address this, we undertook a targeted approach focused on the multi-functional transcription factor YB-1. Genetic knockdown of YB-1 in Group 3 medulloblastoma cell lines diminished cell invasion in 3D in vitro assays and increased sensitivity to standard-of-care chemotherapeutic vincristine and anti-cancer agents panobinostat and JQ1. For vincristine, this occurred in part by YB-1-mediated transcriptional regulation of multi-drug resistance gene ABCB1, as determined by chromatin immunoprecipitation. Whole transcriptome sequencing of YB-1 knockdown cells identified a role for YB-1 in the regulation of tumourigenic processes, including lipid metabolism, cell death and survival and MYC and mTOR pathways. Stable cisplatin- and vincristine-tolerant Group 3 and SHH cell lines were generated to identify additional mechanisms driving resistance to standard-of-care medulloblastoma therapy. Next-generation sequencing revealed a vastly different transcriptomic landscape following chronic drug exposure, including a drug-tolerant seven-gene expression signature, common to all sequenced drug-tolerant cell lines, representing therapeutically targetable genes implicated in the acquisition of drug tolerance. Our findings provide significant insight into mechanisms and genes underlying therapy resistance in medulloblastoma

Pre-therapeutic efficacy of the CDK inhibitor dinaciclib in medulloblastoma cells

Medulloblastoma (MB) is the most common aggressive paediatric brain tumour and, despite the recent progress in the treatments of MB patients, there is still an urgent need of complementary or alternative therapeutic options for MB infants. Cyclin Dependent Kinase inhibitors (CDKi) are at the front-line of novel targeted treatments for multiple cancers and the CDK4/6 specific inhibitor palbociclib has been pre-clinically identified as an effective option for MB cells. Herein, we identified the pan-CDKi dinaciclib as a promising alternative to palbociclib for the suppression of MB cells proliferation. We present evidence supporting dinaciclib’s ability to inhibit MB cells in vitro proliferation at considerably lower doses than palbociclib. Sequencing data and pathway analysis suggested that dinaciclib is a potent cell death inducer in MB cells. We found that dinaciclib-induced apoptosis is triggered by CDK9 inhibition and the resultant reduction in RNA pol II phosphorylation, which leads to the downregulation of the oncogenic marker MYC, and the anti-apoptotic protein MCL-1. Specifically, we demonstrated that MCL-1 is a key apoptotic mediator for MB cells and co-treatment of dinaciclib with BH3 mimetics boosts the therapeutic efficacy of dinaciclib. Together, these findings highlight the potential of multi-CDK inhibition by dinaciclib as an alternative option to CDK4/6 specific inhibition, frequently associated with drug resistance in patients

The loop structure and the RNA helicase p72/DDX17 influence the processing efficiency of the mice miR-132

miRNAs are small RNAs that are key regulators of gene expression in eukaryotic organisms. The processing of miRNAs is regulated by structural characteristics of the RNA and is also tightly controlled by auxiliary protein factors. Among them, RNA binding proteins play crucial roles to facilitate or inhibit miRNA maturation and can be controlled in a cell, tissue and species-specific manners or in response to environmental stimuli. In this study we dissect the molecular mechanism that promotes the overexpression of miR-132 in mice over its related, co-transcribed and co-regulated miRNA, miR-212. We have shown that the loop structure of miR-132 is a key determinant for its efficient processing in cells. We have also identified a range of RNA binding proteins that recognize the loop of miR-132 and influence both miR-132 and miR-212 processing. The DEAD box helicase p72/DDX17 was identified as a factor that facilitates the specific processing of miR-132

The P-Loop Domain of Yeast Clp1 Mediates Interactions Between CF IA and CPF Factors in Pre-mRNA 3′ End Formation

Cleavage factor IA (CF IA), cleavage and polyadenylation factor (CPF), constitute major protein complexes required for pre-mRNA 3′ end formation in yeast. The Clp1 protein associates with Pcf11, Rna15 and Rna14 in CF IA but its functional role remained unclear. Clp1 carries an evolutionarily conserved P-loop motif that was previously shown to bind ATP. Interestingly, human and archaean Clp1 homologues, but not the yeast protein, carry 5′ RNA kinase activity. We show that depletion of Clp1 in yeast promoted defective 3′ end formation and RNA polymerase II termination; however, cells expressing Clp1 with mutant P-loops displayed only minor defects in gene expression. Similarly, purified and reconstituted mutant CF IA factors that interfered with ATP binding complemented CF IA depleted extracts in coupled in vitro transcription/3′ end processing reactions. We found that Clp1 was required to assemble recombinant CF IA and that certain P-loop mutants failed to interact with the CF IA subunit Pcf11. In contrast, mutations in Clp1 enhanced binding to the 3′ endonuclease Ysh1 that is a component of CPF. Our results support a structural role for the Clp1 P-loop motif. ATP binding by Clp1 likely contributes to CF IA formation and cross-factor interactions during the dynamic process of 3′ end formation

Feed-Forward Microprocessing and Splicing Activities at a MicroRNA–Containing Intron

The majority of mammalian microRNA (miRNA) genes reside within introns of protein-encoding and non-coding genes, yet the mechanisms coordinating primary transcript processing into both mature miRNA and spliced mRNA are poorly understood. Analysis of melanoma invasion suppressor miR-211 expressed from intron 6 of melastatin revealed that microprocessing of miR-211 promotes splicing of the exon 6–exon 7 junction of melastatin by a mechanism requiring the RNase III activity of Drosha. Additionally, mutations in the 5′ splice site (5′SS), but not in the 3′SS, branch point, or polypyrimidine tract of intron 6 reduced miR-211 biogenesis and Drosha recruitment to intron 6, indicating that 5′SS recognition by the spliceosome promotes microprocessing of miR-211. Globally, knockdown of U1 splicing factors reduced intronic miRNA expression. Our data demonstrate novel mutually-cooperative microprocessing and splicing activities at an intronic miRNA locus and suggest that the initiation of spliceosome assembly may promote microprocessing of intronic miRNAs