Plakoglobin regulates adipocyte differentiation independently of the Wnt/β-catenin signaling pathway

The scaffold protein 14-3-3ζ is an established regulator of adipogenesis and postnatal adiposity. We and others have demonstrated the 14-3-3ζ interactome to be diverse and dynamic, and it can be examined to identify novel regulators of physiological processes, including adipogenesis. In the present study, we sought to determine if factors that influence adipogenesis during the development of obesity could be identified in the 14-3-3ζ interactome found in white adipose tissue of lean or obese TAP-tagged-14-3-3ζ overexpressing mice. Using mass spectrometry, differences in the abundance of novel, as well as established, adipogenic factors within the 14-3-3ζ interactome could be detected in adipose tissues. One novel candidate was revealed to be plakoglobin, the homolog of the known adipogenic inhibitor, β-catenin, and herein, we report that plakoglobin is involved in adipocyte differentiation. Plakoglobin is expressed in murine 3T3-L1 cells and is primarily localized to the nucleus, where its abundance decreases during adipogenesis. Depletion of plakoglobin by siRNA inhibited adipogenesis and reduced PPARγ2 expression, and similarly, plakoglobin depletion in human adipose-derived stem cells also impaired adipogenesis and reduced lipid accumulation post-differentiation. Transcriptional assays indicated that plakoglobin does not participate in Wnt/β-catenin signaling, as its depletion did not affect Wnt3a-mediated transcriptional activity. Taken together, our results establish plakoglobin as a novel regulator of adipogenesis in vitro and highlights the ability of using the 14-3-3ζ interactome to identify potential pro-obesogenic factors.

14-3-3ζ regulates adipogenesis by modulating chromatin accessibility during the early stages of adipocyte differentiation

We previously established the scaffold protein 14-3-3ζ as a critical regulator of adipogenesis and adiposity, but the temporal specificity of its action during adipocyte differentiation remains unclear. To decipher if 14-3-3ζ exerts its regulatory functions on mature adipocytes or on adipose precursor cells (APCs), we generated Adipoq14-3-3ζKO and Pdgfra14-3-3ζKO mouse models. Our findings revealed a pivotal role for 14-3-3ζ in APC differentiation in a sex-dependent manner, whereby male and female Pdgfra14-3-3ζKO mice display impaired or potentiated weight gain, respectively, as well as fat mass. To better understand how 14-3-3ζ regulates the adipogenic transcriptional program in APCs, CRISPR-Cas9 was used to generate TAP-tagged 14-3-3ζ-expressing 3T3-L1 preadipocytes. Using these cells, we examined if the 14-3-3ζ nuclear interactome is enriched with adipogenic regulators during differentiation. Regulators of chromatin remodeling, such as DNMT1 and HDAC1, were enriched in the nuclear interactome of 14-3-3ζ, and their activities were impacted upon 14-3-3ζ depletion. The interactions between 14-3-3ζ and chromatin-modifying enzymes suggested that 14-3-3ζ may control chromatin remodeling during adipogenesis, and this was confirmed by ATAC-seq, which revealed that 14-3-3ζ depletion impacted the accessibility of up to 1,244 chromatin regions corresponding in part to adipogenic genes, promoters, and enhancers during the initial stages of adipogenesis. Moreover, 14-3-3ζ-dependent chromatin accessibility was found to directly correlate with the expression of key adipogenic genes. Altogether, our study establishes 14-3-3ζ as a crucial epigenetic regulator of adipogenesis and highlights the usefulness of deciphering the nuclear 14-3-3ζ interactome to identify novel pro-adipogenic factors and pathways.

The CDK12 inhibitor SR-4835 functions as a molecular glue that promotes cyclin K degradation in melanoma

CDK12 is a transcriptional cyclin-dependent kinase (CDK) that interacts with cyclin K to regulate different aspects of gene expression. The CDK12-cyclin K complex phosphorylates several substrates, including RNA polymerase II (Pol II), and thereby regulates transcription elongation, RNA splicing, as well as cleavage and polyadenylation. Because of its implication in cancer, including breast cancer and melanoma, multiple pharmacological inhibitors of CDK12 have been identified to date, including THZ531 and SR-4835. While both CDK12 inhibitors affect Poll II phosphorylation, we found that SR-4835 uniquely promotes cyclin K degradation via the proteasome. Using loss-of-function genetic screening, we found that SR-4835 cytotoxicity depends on a functional CUL4-RBX1-DDB1 ubiquitin ligase complex. Consistent with this, we show that DDB1 is required for cyclin K degradation, and that SR-4835 promotes DDB1 interaction with the CDK12-cyclin K complex. Docking studies and structure-activity relationship analyses of SR-4835 revealed the importance of the benzimidazole side-chain in molecular glue activity. Together, our results indicate that SR-4835 acts as a molecular glue that recruits the CDK12-cyclin K complex to the CUL4-RBX1-DDB1 ubiquitin ligase complex to target cyclin K for degradation.

CDK12 is hyperactivated and a synthetic-lethal target in BRAF-mutated melanoma

Melanoma is the deadliest form of skin cancer and considered intrinsically resistant to chemotherapy. Nearly all melanomas harbor mutations that activate the RAS/mitogen-activated protein kinase (MAPK) pathway, which contributes to drug resistance via poorly described mechanisms. Herein we show that the RAS/MAPK pathway regulates the activity of cyclin-dependent kinase 12 (CDK12), which is a transcriptional CDK required for genomic stability. We find that melanoma cells harbor constitutively high CDK12 activity, and that its inhibition decreases the expression of long genes containing multiple exons, including many genes involved in DNA repair. Conversely, our results show that CDK12 inhibition promotes the expression of short genes with few exons, including many growth-promoting genes regulated by the AP-1 and NF-κB transcription factors. Inhibition of these pathways strongly synergize with CDK12 inhibitors to suppress melanoma growth, suggesting promising drug combinations for more effective melanoma treatment.

Proteomic analysis of the actin cortex in interphase and mitosis

Many animal cell shape changes are driven by gradients in the contractile tension of the actomyosin cortex, a thin cytoskeletal network supporting the plasma membrane. Elucidating cortical tension control is thus essential for understanding cell morphogenesis. Increasing evidence shows that alongside myosin activity, actin network organisation and composition are key to cortex tension regulation. However, owing to a poor understanding of how cortex composition changes when tension changes, which cortical components are important remains unclear. In this article, we compared cortices from cells with low and high cortex tensions. We purified cortex-enriched fractions from cells in interphase and mitosis, as mitosis is characterised by high cortical tension. Mass spectrometry analysis identified 922 proteins consistently represented in both interphase and mitotic cortices. Focusing on actin-related proteins narrowed down the list to 238 candidate regulators of the mitotic cortical tension increase. Among these candidates, we found that there is a role for septins in mitotic cell rounding control. Overall, our study provides a comprehensive dataset of candidate cortex regulators, paving the way for systematic investigations of the regulation of cell surface mechanics.

This article has an associated First Person interview with the first author of the paper.

Summary: Contractile tension at the actomyosin cortex is a key determinant of cell shape. Cortices from cells with high and low tension were analysed using mass spectrometry, generating a dataset of candidate cortex mechanics regulators.

Triglyceride-derived fatty acids reduce autophagy in a model of retinal angiomatous proliferation

Dyslipidemia and autophagy have been implicated in the pathogenesis of blinding neovascular age-related macular degeneration (NV-AMD). VLDL receptor (VLDLR), expressed in photoreceptors with a high metabolic rate, facilitates the uptake of triglyceride-derived fatty acids. Since fatty acid uptake is reduced in Vldlr-/- tissues, more remain in circulation, and the retina is fuel deficient, driving the formation in mice of neovascular lesions reminiscent of retinal angiomatous proliferation (RAP), a subtype of NV-AMD. Nutrient scarcity and energy failure are classically mitigated by increasing autophagy. We found that excess circulating lipids restrained retinal autophagy, which contributed to pathological angiogenesis in the Vldlr-/- RAP model. Triglyceride-derived fatty acid sensed by free fatty acid receptor 1 (FFAR1) restricted autophagy and oxidative metabolism in photoreceptors. FFAR1 suppressed transcription factor EB (TFEB), a master regulator of autophagy and lipid metabolism. Reduced TFEB, in turn, decreased sirtuin-3 expression and mitochondrial respiration. Metabolomic signatures of mouse RAP-like retinas were consistent with a role in promoting angiogenesis. This signature was also found in human NV-AMD vitreous. Restoring photoreceptor autophagy in Vldlr-/- retinas, either pharmacologically or by deleting Ffar1, enhanced metabolic efficiency and suppressed pathological angiogenesis. Dysregulated autophagy by circulating lipids might therefore contribute to the energy failure of photoreceptors driving neovascular eye diseases, and FFAR1 may be a target for intervention.

RIOK2 phosphorylation by RSK promotes synthesis of the human small ribosomal subunit

Ribosome biogenesis lies at the nexus of various signaling pathways coordinating protein synthesis with cell growth and proliferation. This process is regulated by well-described transcriptional mechanisms, but a growing body of evidence indicates that other levels of regulation exist. Here we show that the Ras/mitogen-activated protein kinase (MAPK) pathway stimulates post-transcriptional stages of human ribosome synthesis. We identify RIOK2, a pre-40S particle assembly factor, as a new target of the MAPK-activated kinase RSK. RIOK2 phosphorylation by RSK stimulates cytoplasmic maturation of late pre-40S particles, which is required for optimal protein synthesis and cell proliferation. RIOK2 phosphorylation facilitates its release from pre-40S particles and its nuclear re-import, prior to completion of small ribosomal subunits. Our results bring a detailed mechanistic link between the Ras/MAPK pathway and the maturation of human pre-40S particles, which opens a hitherto poorly explored area of ribosome biogenesis.

NF45 and NF90 Regulate Mitotic Gene Expression by Competing with Staufen-Mediated mRNA Decay

In human cells, the expression of ∼1,000 genes is modulated throughout the cell cycle. Although some of these genes are controlled by specific transcriptional programs, very little is known about their post-transcriptional regulation. Here, we analyze the expression signature associated with all 687 RNA-binding proteins (RBPs) and identify 39 that significantly correlate with cell cycle mRNAs. We find that NF45 and NF90 play essential roles in mitosis, and transcriptome analysis reveals that they are necessary for the expression of a subset of mitotic mRNAs. Using proteomics, we identify protein clusters associated with the NF45-NF90 complex, including components of Staufen-mediated mRNA decay (SMD). We show that depletion of SMD components increases the binding of mitotic mRNAs to the NF45-NF90 complex and rescues cells from mitotic defects. Together, our results indicate that the NF45-NF90 complex plays essential roles in mitosis by competing with the SMD machinery for a common set of mRNAs.

SPIN90 associates with mDia1 and the Arp2/3 complex to regulate cortical actin organization

Cell shape is controlled by the submembranous cortex, an actomyosin network mainly generated by two actin nucleators: the Arp2/3 complex and the formin mDia1. Changes in relative nucleator activity may alter cortical organization, mechanics and cell shape. Here we investigate how nucleation-promoting factors mediate interactions between nucleators. In vitro, the nucleation-promoting factor SPIN90 promotes formation of unbranched filaments by Arp2/3, a process thought to provide the initial filament for generation of dendritic networks. Paradoxically, in cells, SPIN90 appears to favour a formin-dominated cortex. Our in vitro experiments reveal that this feature stems mainly from two mechanisms: efficient recruitment of mDia1 to SPIN90-Arp2/3 nucleated filaments and formation of a ternary SPIN90-Arp2/3-mDia1 complex that greatly enhances filament nucleation. Both mechanisms yield rapidly elongating filaments with mDia1 at their barbed ends and SPIN90-Arp2/3 at their pointed ends. Thus, in networks, SPIN90 lowers branching densities and increases the proportion of long filaments elongated by mDia1.

F-Actin Interactome Reveals Vimentin as a Key Regulator of Actin Organization and Cell Mechanics in Mitosis

Most metazoan cells entering mitosis undergo characteristic rounding, which is important for accurate spindle positioning and chromosome separation. Rounding is driven by contractile tension generated by myosin motors in the sub-membranous actin cortex. Recent studies highlight that alongside myosin activity, cortical actin organization is a key regulator of cortex tension. Yet, how mitotic actin organization is controlled remains poorly understood. To address this, we characterized the F-actin interactome in spread interphase and round mitotic cells. Using super-resolution microscopy, we then screened for regulators of cortex architecture and identified the intermediate filament vimentin and the actin-vimentin linker plectin as unexpected candidates. We found that vimentin is recruited to the mitotic cortex in a plectin-dependent manner. We then showed that cortical vimentin controls actin network organization and mechanics in mitosis and is required for successful cell division in confinement. Together, our study highlights crucial interactions between cytoskeletal networks during cell division.

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Comparison of the F-actin interactome in spread interphase and round mitotic cells

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Proteomics identifies vimentin and plectin as key regulators of the mitotic cortex

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Vimentin intermediate filaments localize under the actin cortex in mitosis

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Sub-cortical vimentin regulates actin cortex organization and mechanics in mitosis

Proteomic Analysis Reveals a Role for RSK in p120-catenin Phosphorylation and Melanoma Cell-Cell Adhesion

The RAS/mitogen-activated protein kinase (MAPK) signaling pathway regulates various biological functions, including cell survival, proliferation and migration. This pathway is frequently deregulated in cancer, including melanoma, which is the most aggressive form of skin cancer. RSK (p90 ribosomal S6 kinase) is a MAPK-activated protein kinase required for melanoma growth and proliferation, but relatively little is known about its function and the nature of its cellular partners. In this study, we used a proximity-based labeling approach to identify RSK proximity partners in cells. We identified many potential RSK-interacting proteins, including p120ctn (p120-catenin), which is an essential component of adherens junction (AJ). We found that RSK phosphorylates p120ctn on Ser320, which appears to be constitutively phosphorylated in melanoma cells. We also found that RSK inhibition increases melanoma cell-cell adhesion, suggesting that constitutive RAS/MAPK signaling negatively regulates AJ integrity. Together, our results indicate that RSK plays an important role in the regulation of melanoma cell-cell adhesion.

Predisposing germline mutations in high hyperdiploid acute lymphoblastic leukemia in children

High hyperdiploidy (HD) is the most common cytogenetic subtype of childhood acute lymphoblastic leukemia (ALL), and a higher incidence of HD has been reported in ALL patients with congenital cancer syndromes. We assessed the frequency of predisposing germline mutations in 57 HD-ALL patients from the California Childhood Leukemia Study via targeted sequencing of cancer-relevant genes. Three out of 57 patients (5.3%) harbored confirmed germline mutations that were likely causal, in NBN, ETV6, and FLT3, with an additional six patients (10.5%) harboring putative predisposing mutations that were rare in unselected individuals (<0.01% allele frequency in the Exome Aggregation Consortium, ExAC) and predicted functional (scaled CADD score ≥ 20) in known or potential ALL predisposition genes (SH2B3, CREBBP, PMS2, MLL, ABL1, and MYH9). Three additional patients carried rare and predicted damaging germline mutations in GAB2, a known activator of the ERK/MAPK and PI3K/AKT pathways and binding partner of PTPN11-encoded SHP2. The frequency of rare and predicted functional germline GAB2 mutations was significantly higher in our patients (2.6%) than in ExAC (0.28%, P = 4.4 × 10^-3 ), an observation that was replicated in ALL patients from the TARGET project (P = .034). We cloned patient GAB2 mutations and expressed mutant proteins in HEK293 cells and found that frameshift mutation P621fs led to reduced SHP2 binding and ERK1/2 phosphorylation but significantly increased AKT phosphorylation, suggesting possible RAS-independent leukemogenic effects. Our results support a significant contribution of rare, high penetrance germline mutations to HD-ALL etiology, and pinpoint GAB2 as a putative novel ALL predisposition gene.

Abstract 3502: Chemoproteomics provide insights into cell surface reprogramming during KRAS-mediated transformation

KRAS is among the most frequently mutated genes driving human cancers, including ~45% of colorectal cancers (CRC). Despite decades of research, mutant KRAS is considered undruggable, and is frequently associated with resistance to chemotherapy and other targeted therapies. While the effect of mutant KRAS on regulating intracellular signaling events is well studied, much less is known about its impact on the cell surface proteome (surfaceome), which constitutes the predominant therapeutic target for FDA-approved drugs. To study the cell surfaceome, we optimized a chemoproteomics approach that selectively isolates cell surface proteins and allows their relative quantification using mass spectrometry. When comparing normal intestinal cells to their counterparts expressing oncogenic KRAS (G12V), we identified 104 (~13%) and 170 (~22%) cell surface proteins that were significantly upregulated or downregulated, respectively, in KRAS-transformed cells. Overall, a myriad of proteins, including receptors, solute carriers, adhesion molecules, etc., were modulated by mutant KRAS, and their potential roles in KRAS-mediated transformation are currently being studied. We also found that most of the cell surface proteins were altered in response to transcriptional changes induced by KRAS signaling, and due to increased global endocytosis in KRAS-mutated cells. Our study suggests potential cell surface proteins that could be targeted in KRAS-mutant cells, which will be verified in subsequent studies using human CRC models. Our work helps assemble a global view of how oncogenic KRAS alters the spatial distribution of several cell surface proteins, and thereby potentially impacts tumor functions and therapeutic response.

Citation Format: Neethi Nandagopal, Léo Aubert, Sami Nourreddine, Geneviève Lavoie, Philippe Roux. Chemoproteomics provide insights into cell surface reprogramming during KRAS-mediated transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3502.

High-throughput screening in niche-based assay identifies compounds to target preleukemic stem cells

Current chemotherapies for T cell acute lymphoblastic leukemia (T-ALL) efficiently reduce tumor mass. Nonetheless, disease relapse attributed to survival of preleukemic stem cells (pre-LSCs) is associated with poor prognosis. Herein, we provide direct evidence that pre-LSCs are much less chemosensitive to existing chemotherapy drugs than leukemic blasts because of a distinctive lower proliferative state. Improving therapies for T-ALL requires the development of strategies to target pre-LSCs that are absolutely dependent on their microenvironment. Therefore, we designed a robust protocol for high-throughput screening of compounds that target primary pre-LSCs maintained in a niche-like environment, on stromal cells that were engineered for optimal NOTCH1 activation. The multiparametric readout takes into account the intrinsic complexity of primary cells in order to specifically monitor pre-LSCs, which were induced here by the SCL/TAL1 and LMO1 oncogenes. We screened a targeted library of compounds and determined that the estrogen derivative 2-methoxyestradiol (2-ME2) disrupted both cell-autonomous and non-cell-autonomous pathways. Specifically, 2-ME2 abrogated pre-LSC viability and self-renewal activity in vivo by inhibiting translation of MYC, a downstream effector of NOTCH1, and preventing SCL/TAL1 activity. In contrast, normal hematopoietic stem/progenitor cells remained functional. These results illustrate how recapitulating tissue-like properties of primary cells in high-throughput screening is a promising avenue for innovation in cancer chemotherapy.

RSK regulates activated BRAF signalling to mTORC1 and promotes melanoma growth

The Ras/mitogen-activated protein kinase (MAPK) signalling cascade regulates various biological functions, including cell growth, proliferation and survival. As such, this pathway is often deregulated in cancer, including melanomas, which frequently harbour activating mutations in the NRAS and BRAF oncogenes. Hyperactive MAPK signalling is known to promote protein synthesis, but the mechanisms by which this occurs remain poorly understood. Here, we show that expression of oncogenic forms of Ras and Raf promotes the constitutive activation of the mammalian target of rapamycin (mTOR). Using pharmacological inhibitors and RNA interference, we find that the MAPK-activated protein kinase RSK (p90 ribosomal S6 kinase) is partly required for these effects. Using melanoma cell lines carrying activating BRAF mutations, we show that ERK/RSK signalling regulates assembly of the translation initiation complex and polysome formation, as well as the translation of growth-related messenger RNAs containing a 5'-terminal oligopyrimidine (TOP) motif. Accordingly, we find that RSK inhibition abrogates tumour growth in mice. Our findings indicate that RSK may be a valuable therapeutic target for the treatment of tumours characterized by deregulated MAPK signalling, such as melanoma.

PKC isoforms interact with and phosphorylate DNMT1

Background

DNA methyltransferase 1 (DNMT1) has been shown to be phosphorylated on multiple serine and threonine residues, based on cell type and physiological conditions. Although recent studies have suggested that protein kinase C (PKC) may be involved, the individual contribution of PKC isoforms in their ability to phosphorylate DNMT1 remains unknown. The PKC family consists of at least 12 isoforms that possess distinct differences in structure, substrate requirement, expression and localization.

Results

Here we show that PKCα, βI, βII, δ, γ, η, ζ and μ preferentially phosphorylate the N-terminal domain of human DNMT1. No such phosphorylation of DNMT1 was observed with PKCε. Using PKCζ as a prototype model, we also found that PKC physically interacts with and phosphorylates DNMT1. In vitro phosphorylation assays conducted with recombinant fragments of DNMT1 showed that PKCζ preferentially phosphorylated the N-terminal region of DNMT1. The interaction of PKCζ with DNMT1 was confirmed by GST pull-down and co-immunoprecipitation experiments. Co-localization experiments by fluorescent microscopy further showed that endogenous PKCζ and DNMT1 were present in the same molecular complex. Endogenous PKCζ activity was also detected when DNMT1 was immunoprecipitated from HEK-293 cells. Overexpression of both PKCζ and DNMT1 in HEK-293 cells, but not of either alone, reduced the methylation status of genes distributed across the genome. Moreover, in vitro phosphorylation of DNMT1 by PKCζ reduced its methytransferase activity.

Conclusions

Our results indicate that phosphorylation of human DNMT1 by PKC is isoform-specific and provides the first evidence of cooperation between PKCζ and DNMT1 in the control of the DNA methylation patterns of the genome.

Improvement of Antitumor Activity by Gene Amplification with a Replicating but Nondisseminating Adenovirus

Gene therapy is a promising approach for cancer treatment; however, efficacy of current vectors remains insufficient. To improve the success of suicide gene therapy, we constructed a replication-competent adenoviral vector that has its protease gene deleted and expresses bacterial cytosine deaminase fused with bacterial uracil phosphoribosyltransferase (CU). The prodrug, 5-fluorocytosine, is transformed into the highly toxic and tissue-diffusible 5-fluorouracil by CU in infected cells. This vector is incapable of producing infectious particles but is able to undergo a single round of replication, thereby increasing transgene copy number and expression. In the presence of 5-FC, compared with the first-generation vector (AdCU), the replication-competent vector, Ad(dPS)CU-IRES-E1A, was significantly more efficacious for in vitro tumor cell killing and in bystander assays, whereas 25-fold fewer viral particles were required in a three-dimensional spheroid model. For in vivo experiments, in which virus was injected into preestablished intracranial glioma xenografts, followed by 5-FC treatment, mice receiving Ad(dPS)CU-IRES-E1A had significantly smaller tumors at 35 days postinjection as well as significantly longer median survival than mice treated with the replication-deficient, protease-deleted vector [Ad(dPS)CU]. In an immunocompetent syngeneic model, Ad(dPS)CU + 5-FC-treated mice had a median survival of only 23 days, whereas Ad(dPS)CU-IRES-E1A + 5-FC-treated animals had a survival of 57.1% at 365 days. In conclusion, Ad(dPS)CU-IRES-E1A in the presence of 5-FC produces more potent tumoricidal effects than its replication-deficient counterparts.

The role of DNA hypomethylation in the control of stromelysin gene expression

Genome-wide DNA hypomethylation is a critical mechanism underlying neoplastic transformation. Thus, genes that are suppressed in normal tissues or in specific cell types may become aberrantly expressed in neoplasia. To determine whether DNA methylation can modulate matrix metalloproteinase (mmp) gene expression, we have used a genetically engineered cell line in which both key DNA methyltransferase genes, Dnmt-1 and Dnmt-3b, were removed by homologous recombination. We found that cells bearing a dual knock-out of both Dnmt-1 and Dnmt-3b genes induced de novo expression of mmp-3 gene, but not that of mmp-1 and mmp-2. Furthermore, treatment of the wild-type cells with DNA methylase inhibitors 5-aza-dC and zebularine also induced mmp-3 gene expression. On the other hand, in vitro methylation of the mmp-3 promoter suppressed its transcriptional activity. Finally, we found that induction of mmp-3 and mmp-10 gene expression by hypomethylation was cell-specific, suggesting that epigenetic changes may predispose cells to express stromelysin genes.

Suicide gene therapy with an adenovirus expressing the fusion gene CD::UPRT in human glioblastomas: different sensitivities correlate with p53 status

BACKGROUND

Several gene therapy strategies have been designed for cancer treatment. Intra-tumoral injection of adenoviruses expressing pro-drug-converting enzymes is one such strategy. Although the efficacy of these therapies was tested in animal models, little work has been devoted to the determination of critical variables for success. In this work, we aimed at better understanding variables that affect the cytosine deaminase::uracil phosphoribosyl transferase (CD::UPRT)-based strategy in two human glioblastomas.

METHODS

We have constructed two adenoviruses expressing either CD or the fusion protein CD::UPRT. We have tested their anti-tumor activity in combination with 5-fluorocytosine (5-FC) in the glioblastoma cell lines U87 and U251, which are p53-wt and p53-deficient, respectively. Anti-tumor activity has also been investigated in spheroid structures.

RESULTS

The superiority of CD::UPRT over CD was confirmed in both glioblastoma cells. We found that the pro-drug concentration required for anti-tumor activity was 9-fold higher in U251 than in U87, while multiplicity of infection (MOI) as low as 6 was sufficient to achieve 50% killing. Bystander activity was observed with as few as 2 and 6% transduced cells for U87 and U251, respectively. Differences in sensitivity between U87 and U251 were not due to differences in transduction, transgene expression, or intercellular transport, but were related to 5-FU sensitivity and p53 status. Also, it is noteworthy that, in contrast to U87, U251 spheroids barely responded to the treatment, whereas their monolayer counterparts were very sensitive.

CONCLUSIONS

Our study has shown that p53 status is important for CD::UPRT/5-FC treatment. Moreover, this study demonstrated that the three-dimensional spheroid model is a more stringent in vitro model for suicide gene therapy evaluation than are monolayer cultures.

Cryopreservation of intact human articular cartilage

Damaged articular cartilage (AC) impairs joint function and many treatment techniques are being investigated to determine their long term results. Successful cryopreservation of AC can provide a reliable source of intact matrix with viable chondrocytes to maintain the cartilage over long periods of time. This study investigated the application of an established cryopreservation protocol to determine the recovery of intact chondrocytes from human AC. Ten millimeter diameter osteochondral dowels were harvested from two human donors. The cryopreservation protocol was performed and the samples were rapidly warmed from varying experimental holding temperatures (-10, -20, -30, -40 degrees C), with and without plunging into liquid nitrogen, using 1 M dimethyl sulfoxide as cryoprotectant. The cartilage was stained with membrane integrity dyes and viewed under fluorescence microscopy. The percent of intact chondrocytes was compared to fresh controls. Low recovery of intact chondrocytes was recorded from all temperature levels with and without cryoprotectant. The results of this experiment demonstrated that the cryopreservation procedure used to achieve moderate success with intact sheep AC was not successful with intact human AC and further investigation is required.

Standard anatomical medullary locking (AML) versus tricalcium phosphate-coated AML femoral prostheses

OBJECTIVES

To compare the preliminary rate and amount of bony ingrowth and calcar resorption between patients receiving either a standard anatomical medullary locking (AML) or a tricalcium phosphate (TCP)-coated AML femoral prosthesis and to compare preliminary clinical results.

DESIGN

A prospective, randomized, double-blind clinical trial.

SETTING

An acute care tertiary institution.

PATIENTS

Between January 1993 and March 1995, 92 patients underwent primary total hip arthroplasty (THA). They were randomized to 2 groups of 46--a control group or a treatment group. Of the 46 subjects enrolled in each group, no significant differences were seen preoperatively with respect to age, sex, diagnosis, clinical and radiographic assessment. Seventy-one patients were followed up for 24 months.

INTERVENTIONS

Insertion of either a standard AML femoral implant (control group) or a TCP-coated AML femoral implant (treatment group).

OUTCOME MEASURES

The degree of hypertrophy, calcar atrophy and the number of spot welds on standard postoperative radiographs at 6, 12 and 24 months. Clinically, assessment according to the Société internationale de chirurgie orthopédique et de traumatologie (SICOT) scale and a 100-point visual analogue scale (VAS) for pain.

RESULTS

There were no prosthetic stem revisions in either group at the 24-month follow-up. Radiographically, bony ingrowth was not significantly different in the TCP-coated stem, by chi2 analysis of the degree of hypertrophy and number of spot welds present. Also by chi2 analysis, the degree of calcar atrophy was not significantly different between groups. The mean VAS score for pain at 24 months was 12.5 for the control and 12.1 for the treatment group. No significant differences were seen in any of the clinical categories of the SICOT Scale over the 24-month interval.

CONCLUSION

The objective of TCP-coating--to increase the rate and amount of bony ingrowth while reducing the rate of calcar resorption in non-cemented THA--was not achieved by 24 months postoperatively in our study.

Changing trends in mortality and admissions to hospital for elderly patients with congestive heart failure in Montreal

BACKGROUND

Congestive heart failure (CHF) is a common disease requiring admission to hospital among elderly people and is associated with a high mortality rate. The objective of this study was to examine trends in CHF mortality and admissions to hospital in Montreal between 1990 and 1997 for individuals aged 65 years or more.

METHODS

We obtained information about deaths from the Quebec Death Certificate Registry database and information about admissions to hospital from the Quebec Med-Echo database. Patients with a primary diagnosis that was classified as ICD-9 code 428 were considered cases of CHF.

RESULTS

Although age-adjusted rates of mortality from CHF did not change significantly between 1990 and 1997, the annual rate of admission to hospital for CHF increased from 92 per 10,000 population in 1990/91 to 124 per 10,000 population in 1997/98 (p < 0.01). Deaths due to CHF, expressed as a proportion of all cardiovascular deaths, increased among women from 5.6% in 1990 to 6.2% in 1997 (p = 0.01). The rate of readmission for all causes following a first admission for CHF during that year rose over the study period from 16.6% to 22.0% within one month (p < 0.001) and from 46.7% to 49.4% within 6 months (p = 0.03). Conversely, mean annual length of stay per admission decreased from 16.4 days in 1990/91 to 12.2 days in 1997/98.

INTERPRETATION

The increase in rates of admission to hospital for CHF and the stable rates of CHF mortality suggest that the management of CHF and its antecedents has improved in recent years.

Habitat partitioning between woodland caribou and moose in Ontario: the potential role of shared prédation risk

This paper explores mechanisms of coexistence for woodland caribou (Rangifer tarandus caribou) and moose (Akes alces) preyed upon by gray wolves (Canis lupus) in northern Ontario. Autocorrelation analysis of winter track locations showed habitat partitioning by caribou and moose. Numbers of Delaunay link edges for moose-wolves did not differ significantly from what would be expected by random process, but those for caribou-wolves were significantly fewer. Thus, habitat partitioning provided implicit refuges that put greater distances between caribou and wolves, presumably decreasing predation on the caribou. Yet, direct competition cannot be ruled out; both apparent and direct competition may be involved in real-life situations. A synthesis including both explanations fits ecological theory, as well as current understanding about caribou ecology.

The use of prescription claims databases in pharmacoepidemiological research: the accuracy and comprehensiveness of the prescription claims database in Québec

Despite the potential benefits of using prescription claims databases for pharmacoepidemiological research, little work has been reported on the nature of available information or its accuracy. The purpose of this study was to describe information contained within the prescription claims database in Québec, and to assess the accuracy of drug information that might be used to monitor drug exposure and physician prescribing. The comprehensiveness of the prescriptions claims database was assessed by examining 1,917,214 records of dispensed prescriptions for a regionally stratified random sample of 65,349 Québec elderly in 1990. We found that values in key fields (individual identifiers, drug, quantity, date dispensed and duration) were missing or out of range in 0-0.4% of records. The accuracy of data were examined in 723 prescriptions filled by 306 elderly patients attending one internal medicine clinic. Of these prescriptions, 83% were filled by the patient and correctly identified the patient and drug and in 89% of these 599 records, the prescribing physician was correctly identified. The quantity and duration of the prescriptions were accurate in 69.1% and 72.1% of records, respectively. We conclude that the prescription claims database in Québec may represent one of the most accurate means of determining drugs dispensed to individuals. There may be limitations in using this database for dosing information.

Can a patient smart card improve decision making in a clinical setting?

In the health field, clinical information is the raw material for the clinician delivering health services. Therefore, the clinical information available to the physician is often incomplete or even non¿existent upon consultation. Furthermore, the reconstruction of the medical history, which is the most important source of data for the clinician to establish a diagnosis and initiate a treatment, suffers from many constraints. The smart card, like the one used in Quebec's project, could ease the physician's decision-making by allowing fast access to accurate and pertinent data. The smart card is a major asset in the present health system.

[Effect of patient education on neuroleptic treatment of young psychotic patients]

This study verifies the effect of the neuroleptic treatment teaching module, the French translation of the Medication Management Module produced by the social skills training programs. Twenty patients from an outpatient clinic (with schizophreniform or schizoaffective schizophrenia) were assigned at random to a test group (n = 10) or a control group (n = 10). The pre-test evaluation found that the two groups were the same with regard to 13 significant parameters. The experimenters used French translations of well-known instruments, and the double-blind method was applied to their respective observations throughout the study. Results were obtained by applying the neuroleptic treatment teaching module three hours per week for two to three months. The post-test evaluation revealed that patients who had been exposed to the education module had an improved understanding of schizophrenia and the medication required to treat it than patients who had not been exposed. The dose of medication prescribed between pre- and post-test evaluations were able to more effectively stabilize patients who had received education than patients who had not. Nevertheless, the education module continues to have no significant effect on the symptomatology (according to the Brief Psychiatric Rating Scale) and final SAS-II social scores of schizophrenics.

A reproducible porcine vertebral fracture for biomechanical testing of spinal fixation devices

To evaluate vertebral fracture fixation devices in the laboratory, it is necessary to produce identical and unstable fractures either in anatomic specimen or animal models. Consistent achievement of this goal has not been reported in the literature. This report presents a technique for the study of reproducibility for a particular vertebral fracture model. A precise anterior defect was created in a vertebra of each specimen drawn from a homogeneous population of mature sow spines. The spines were loaded to failure. Fracture reproducibility was shown by measurement of load and displacement, and confirmed by roentgenographic evaluation. The technique is easily applied to human specimens. Because there is a plethora of fracture fixation devices based on hooks, wires, or, more recently, plates and pedicle screws, the reliability of comparative testing of these devices in the laboratory requires an appropriate and reproducible fracture.

Zopiclone versus flurazepam in insomnia: prolonged administration and withdrawal

Zopiclone (7.5 mg), a cyclopyrrolone derivative with a 6.5 h half-life, and flurazepam (30 mg) were compared to placebo in a randomized double-blind study involving 36 adult patients suffering from insomnia. All previous psychotropic drugs were discontinued 1 week prior to the study. During 4 weeks, 12 patients received zopiclone, 12 flurazepam and the others placebo. Thereafter, all patients received single-blind placebo for 3 nights. Rapidity of sleep onset, sleep duration, frequency of nocturnal awakenings, psychomotor coordination and side-effects were assessed daily with a questionnaire and a symptom checklist. The results of the study suggest that zopiclone 7.5 mg was at least as potent as flurazepam 30 mg in inducing and maintaining sleep. Both drugs maintained their efficacy during the 4 weeks of treatment. However, the two drugs differed in that flurazepam impaired psychomotor coordination whereas zopiclone did not demonstrate daytime protracted effects on psychomotor performance. Upon discontinuation of drug treatment, score values of the different sleep parameters under study returned to the baseline values. Side-effects were mild and consistent with earlier studies.

A primary choroid plexus papilloma of the cerebellopontine angle

Papillomas of the choroid plexus arising in and occupying the cerebellopontine angle are rare. Such a case occurring in a 41-year-old woman is reported. The signs and symptoms are described. The literature is reviewed.

Perception and conservation of length: comparative study of Rwandese and French-Canadian children

3 groups of children (64 urban French-Canadians, 62 rural schooled Rwandese, 64 rural unschooled Rwandese) were tested on their conservation and perception of length in order to determine whether Piaget's (1969) interpretation of the relation between the two tasks might be generalized to children differing in ethnic origin, urbanization, and schooling The results did not confirm Piaget's main findings on the importance of the upper protruding line and on the superiority of preoperational over operational children in the perceptual estimation of length. In spite of wide difference between the three groups on the perceptual task (overestimation of the variable line by French-Canadians, overestimation of the standard by schooled Rwandese, no systematic error in unschooled Rwandese) and on the conceptual task (operational level attained first by French-Canadians, then by schooled Rwandese and finally by unschooled Rwandese), the perception of length was not decisively influenced by the protrusion of the upper line and was significantly better for operational than for preoperational children for all three groups.