FBXW7/hCDC4 is a general tumor suppressor in human cancer

The ubiquitin-proteasome system is a major regulatory pathway of protein degradation and plays an important role in cellular division. Fbxw7 (or hCdc4), a member of the F-box family of proteins, which are substrate recognition components of the multisubunit ubiquitin ligase SCF (Skp1-Cdc53/Cullin-F-box-protein), has been shown to mediate the ubiquitin-dependent proteolysis of several oncoproteins including cyclin E1, c-Myc, c-Jun, and Notch. The oncogenic potential of Fbxw7 substrates, frequent allelic loss in human cancers, and demonstration that mutation of FBXW7 cooperates with p53 in mouse tumorigenesis have suggested that Fbxw7 could function as a tumor suppressor in human cancer. Here, we carry out an extensive genetic screen of primary tumors to evaluate the role of FBXW7 as a tumor suppressor in human tumorigenesis. Our results indicate that FBXW7 is inactivated by mutation in diverse human cancer types with an overall mutation frequency of approximately 6%. The highest mutation frequencies were found in tumors of the bile duct (cholangiocarcinomas, 35%), blood (T-cell acute lymphocytic leukemia, 31%), endometrium (9%), colon (9%), and stomach (6%). Approximately 43% of all mutations occur at two mutational "hotspots," which alter Arg residues (Arg465 and Arg479) that are critical for substrate recognition. Furthermore, we show that Fbxw7Arg465 hotspot mutant can abrogate wild-type Fbxw7 function through a dominant negative mechanism. Our study is the first comprehensive screen of FBXW7 mutations in various human malignancies and shows that FBXW7 is a general tumor suppressor in human cancer.

A pseudogene long-noncoding-RNA network regulates PTEN transcription and translation in human cells

PTEN is a tumor suppressor gene that has been shown to be under the regulatory control of a PTEN pseudogene expressed noncoding RNA, PTENpg1. Here, we characterize a previously unidentified PTENpg1 encoded antisense RNA (asRNA), which regulates PTEN transcription and PTEN mRNA stability. We find two PTENpg1 asRNA isoforms, alpha and beta. The alpha isoform functions in trans, localizes to the PTEN promoter, and epigenetically modulates PTEN transcription by the recruitment of DNMT3a and EZH2. In contrast, the beta isoform interacts with PTENpg1 through an RNA:RNA pairing interaction, which affects PTEN protein output via changes of PTENpg1 stability and microRNA sponge activity. Disruption of this asRNA-regulated network induces cell cycle arrest and sensitizes cells to doxorubicin, suggesting a biological function for the respective PTENpg1 expressed asRNAs.

A randomized, controlled trial of a home environmental intervention: effect on efficacy and upset in caregivers and on daily function of persons with dementia

PURPOSE OF STUDY

The authors determined short-term effects of a home environmental intervention on self-efficacy and upset in caregivers and daily function of dementia patients. They also determined if treatment effect varied by caregiver gender, race, and relationship to patient.

DESIGN AND METHODS

Families (N = 171) of dementia patients were randomized to intervention or usual care control group. The intervention involved 5 90-min home visits by occupational therapists who provided education and physical and social environmental modifications.

RESULTS

Compared with controls, intervention caregivers reported fewer declines in patients' instrumental activities of daily living (p = .030) and less decline in self-care and fewer behavior problems in patients at 3 months post-test. Also, intervention spouses reported reduced upset (p = .049), women reported enhanced self-efficacy in managing behaviors (p = .038), and women (p = .049) and minorities (p = .037) reported enhanced self-efficacy in managing functional dependency.

IMPLICATIONS

The environmental program appears to have a modest effect on dementia patients' IADL dependence. Also, among certain subgroups of caregivers the program improves self-efficacy and reduces upset in specific areas of caregiving.

Matrix metalloproteinases and tumor invasion: from correlation and causality to the clinic

Tumor cell invasion is now viewed as dysregulated physiologic invasion. Investigators have started to define the molecular events that are involved in this process. We find that there are many functional similarities with molecular events involved in physiologic process such as angiogenesis and wound healing. Matrix metalloproteinase activity is a common denominator in these pathologic conditions and in normal responses. Studies using endogenous metalloproteinase inhibitors suggest that targeting matrix metalloproteinase activity may prevent tumor cell dissemination. The development and pre-clinical testing of novel, low molecular weight matrix metalloproteinase inhibitors support this concept and suggest that an exciting new era of cancer therapy is on the horizon.

An alpaca nanobody neutralizes SARS-CoV-2 by blocking receptor interaction

SARS-CoV-2 enters host cells through an interaction between the spike glycoprotein and the angiotensin converting enzyme 2 (ACE2) receptor. Directly preventing this interaction presents an attractive possibility for suppressing SARS-CoV-2 replication. Here, we report the isolation and characterization of an alpaca-derived single domain antibody fragment, Ty1, that specifically targets the receptor binding domain (RBD) of the SARS-CoV-2 spike, directly preventing ACE2 engagement. Ty1 binds the RBD with high affinity, occluding ACE2. A cryo-electron microscopy structure of the bound complex at 2.9 Å resolution reveals that Ty1 binds to an epitope on the RBD accessible in both the 'up' and 'down' conformations, sterically hindering RBD-ACE2 binding. While fusion to an Fc domain renders Ty1 extremely potent, Ty1 neutralizes SARS-CoV-2 spike pseudovirus as a 12.8 kDa nanobody, which can be expressed in high quantities in bacteria, presenting opportunities for manufacturing at scale. Ty1 is therefore an excellent candidate as an intervention against COVID-19.

LUMA (LUminometric Methylation Assay)—A high throughput method to the analysis of genomic DNA methylation

Changes in genomic DNA methylation are recognized as important events in normal and pathological cellular processes, contributing both to normal development and differentiation as well as cancer and other diseases. Here, we report a novel method to estimate genome-wide DNA methylation, referred to as LUminometric Methylation Assay (LUMA). The method is based on combined DNA cleavage by methylation-sensitive restriction enzymes and polymerase extension assay by Pyrosequencing. The method is quantitative, highly reproducible and easy to scale up. Since no primary modification of genomic DNA, such as bisulfite treatment, is needed, the total assay time is only 6 h. In addition, the assay requires only 200-500 ng of genomic DNA and incorporates an internal control to eliminate the problem of varying amounts of starting DNA. The accuracy and linearity of LUMA were verified by in vitro methylated lambda DNA. In addition, DNA methylation levels were assessed by LUMA in DNA methyltransferase knock-out cell lines and after treatment with the DNA methyltransferase inhibitor (5-AzaCytidine). The LUMA assay may provide a useful method to analyze genome-wide DNA methylation for a variety of physiological and pathological conditions including etiologic, diagnostic and prognostic aspects of cancer.

Wrap53, a natural p53 antisense transcript required for p53 induction upon DNA damage

Antisense transcription is a widespread phenomenon in the mammalian genome. It is thought to play a role in regulation of gene expression, but its exact functional significance is largely unknown. We have identified a natural antisense transcript of p53, designated Wrap53, that regulates endogenous p53 mRNA levels and further induction of p53 protein by targeting the 5' untranslated region of p53 mRNA. siRNA knockdown of Wrap53 results in significant decrease in p53 mRNA and suppression of p53 induction upon DNA damage. Conversely, overexpression of Wrap53 increases p53 mRNA and protein levels. Blocking of potential Wrap53/p53 RNA hybrids reduces p53 levels nearly as efficiently as Wrap53 knockdown, strongly suggesting that Wrap53 regulates p53 via Wrap53/p53 RNA interaction. Furthermore, induction of Wrap53 sensitizes cells for p53-dependent apoptosis. This discovery not only reveals a regulatory pathway for controlling p53, but also proposes a general mechanism for antisense-mediated gene regulation in human cells.

Cell death induced by dexamethasone in lymphoid leukemia is mediated through initiation of autophagy

Glucocorticoids are fundamental drugs used in the treatment of lymphoid malignancies with apoptotic cell death as the hitherto proposed mechanism of action. Recent studies, however, showed that an alternative mode of cell death, autophagy, is involved in the response to anticancer drugs. The specific role of autophagy and its relationship to apoptosis remains, nevertheless, controversial: it can either lead to cell survival or can function in cell death. We show that dexamethasone induced autophagy upstream of apoptosis in acute lymphoblastic leukemia cells. Inhibition of autophagy by siRNA-mediated repression of Beclin 1 expression inhibited apoptosis showing an important role of autophagy in dexamethasone-induced cell death. Dexamethasone treatment caused an upregulation of promyelocytic leukemia protein, PML, its complex formation with protein kinase B or Akt and a PML-dependent Akt dephosphorylation. Initiation of autophagy and the onset of apoptosis were both dependent on these events. PML knockout thymocytes were resistant to dexamethasone-induced death and upregulation of PML correlated with the ability of dexamethasone to kill primary leukemic cells. Our data reveal key mechanisms of dexamethasone-induced cell death that may inform the development of improved treatment protocols for lymphoid malignancies.

The tumor suppressor gene hCDC4 is frequently mutated in human T-cell acute lymphoblastic leukemia with functional consequences for Notch signaling

Notch signaling is of crucial importance in normal T-cell development and Notch 1 is frequently mutated in T-cell acute lymphoblastic leukemias (T-ALL), leading to aberrantly high Notch signaling. In this report, we determine whether T-ALL mutations occur not only in Notch1 but also in the F-box protein hCdc4 (Sel-10, Ago, or Fbxw7), a negative regulator of Notch1. We show that the hCDC4 gene is mutated in leukemic cells from more than 30% of patients with pediatric T-ALL and derived cell lines. Most hCDC4 mutations found were missense substitutions at critical arginine residues (Arg(465), Arg(479), and Arg(505)) localized in the substrate-binding region of hCdc4. Cells inactivated for hCdc4 and T-ALL cells containing hCDC4 mutations exhibited an increased Notch1 protein half-life, consistent with the proposed role of hCdc4 in ubiquitin-dependent proteolysis of Notch1. Furthermore, restoration of wild-type but not mutant hCdc4 in HCT 116 hCDC4-negative cells led to an increased Notch1 ubiquitylation and decreased Notch1 signaling. These results show that hCdc4 mutations interfere with normal Notch1 regulation in vivo. Finally, we found that mutations in hCDC4 and NOTCH1 can occur in the same cancers and that patients carrying hCDC4 and/or NOTCH1 mutations have a favorable overall survival. Collectively, these data show that mutation of hCDC4 is a frequent event in T-ALL and suggest that hCDC4 mutations and gain-of-function mutations in NOTCH1 might synergize in contributing to the development of pediatric T-ALL leukemogenesis.

Cloning of two candidate tumor suppressor genes within a 10 kb region on chromosome 13q14, frequently deleted in chronic lymphocytic leukemia

Previous studies have indicated the presence of a putative tumor suppressor gene on chromosome 13q14, commonly deleted in patients with B-cell chronic lymphocytic leukemia (B-CLL). We have previously defined a minimally deleted region of 130 kb centromeric to the marker D13S272, and constructed a PAC and cosmid contig encompassing this area. In the present study we have made a detailed restriction and transcriptional map of the region of interest. Using these tools we have screened a panel of 206 primary CLL clones and three cell lines. In five CLL cases we found limited deletions defining the region of interest to an area of no more than 10 kb. Two adjacent genes, termed Leu1 and Leu2 (leukemia-associated gene 1 and 2), were mapped to the minimally deleted region, with several patients showing deletion borders within these genes. The Leu1 and Leu2 genes show little homology to previously published genes at the nucleotide and expected translated amino acid sequence level. Mutational analysis of the Leu1 and 2 genes in 170 CLL samples revealed no small intragenic mutations or point mutations. However, in all cases of 13q14 loss examined, the first exon of both genes, which are only 300 bp apart, were deleted. We conclude that the Leu1 and Leu2 genes are strong candidates as tumor suppressor gene(s) involved in B-CLL leukemogenesis.

Vaccination induces HIV broadly neutralizing antibody precursors in humans

Broadly neutralizing antibodies (bnAbs) can protect against HIV infection but have not been induced by human vaccination. A key barrier to bnAb induction is vaccine priming of rare bnAb-precursor B cells. In a randomized, double-blind, placebo-controlled phase 1 clinical trial, the HIV vaccine-priming candidate eOD-GT8 60mer adjuvanted with AS01B had a favorable safety profile and induced VRC01-class bnAb precursors in 97% of vaccine recipients with median frequencies reaching 0.1% among immunoglobulin G B cells in blood. bnAb precursors shared properties with bnAbs and gained somatic hypermutation and affinity with the boost. The results establish clinical proof of concept for germline-targeting vaccine priming, support development of boosting regimens to induce bnAbs, and encourage application of the germline-targeting strategy to other targets in HIV and other pathogens.

DLEU2, frequently deleted in malignancy, functions as a critical host gene of the cell cycle inhibitory microRNAs miR-15a and miR-16-1

The microRNAs miR-15a and miR-16-1 are downregulated in multiple tumor types and are frequently deleted in chronic lymphocytic leukemia (CLL), myeloma and mantle cell lymphoma. Despite their abundance in most cells the transcriptional regulation of miR-15a/16-1 remains unclear. Here we demonstrate that the putative tumor suppressor DLEU2 acts as a host gene of these microRNAs. Mature miR-15a/miR-16-1 are produced in a Drosha-dependent process from DLEU2 and binding of the Myc oncoprotein to two alterative DLEU2 promoters represses both the host gene transcript and levels of mature miR-15a/miR-16-1. In line with a functional role for DLEU2 in the expression of the microRNAs, the miR-15a/miR-16-1 locus is retained in four CLL cases that delete both promoters of this gene and expression analysis indicates that this leads to functional loss of mature miR-15a/16-1. We additionally show that DLEU2 negatively regulates the G1 Cyclins E1 and D1 through miR-15a/miR-16-1 and provide evidence that these oncoproteins are subject to miR-15a/miR-16-1-mediated repression under normal conditions. We also demonstrate that DLEU2 overexpression blocks cellular proliferation and inhibits the colony-forming ability of tumor cell lines in a miR-15a/miR-16-1-dependent way. Together the data illuminate how inactivation of DLEU2 promotes cell proliferation and tumor progression through functional loss of miR-15a/miR-16-1.

Diagnosis of Bernard-Soulier syndrome and Glanzmann's thrombasthenia with a monoclonal assay on whole blood

Two hereditary platelet disorders, Bernard-Soulier syndrome and Glanzmann's thrombasthenia, are characterized by selective deficiencies of platelet membrane glycoproteins. Murine monoclonal antibodies were developed against platelet membrane glycoprotein Ib and against the glycoprotein IIb/IIIa complex. A rapid whole blood assay for the deficiency of these glycoproteins was developed and used to study whole blood samples from six patients with Glanzmann's thrombasthenia and three patients with Bernard-Soulier syndrome. Patients with type I and type II Glanzmann's thrombasthenia were easily detectable with this assay. This permits the diagnosis of these disorders on 200 microliters of whole blood within 2 h of blood sampling.

Well-being, appraisal, and coping in African-American and Caucasian dementia caregivers: findings from the REACH study

Although there has been considerable interest in racial differences in family caregiving for persons with dementia, most research to date has either ignored racial diversity or based conclusions on small numbers of caregivers drawn primarily from single site studies. The current study utilized participants from four sites of the REACH (Resources for Enhancing Alzheimer's Caregiver Health) multi-site study to compare well-being, appraisal, and religious coping by race. African-American (n = 295) and Caucasian (n = 425) dementia caregivers from four cities (Birmingham, Memphis, Boston, and Philadelphia) were compared in their demographics, care recipient characteristics, mental and physical health, and psychosocial coping resources including appraisal and religious coping. African-American caregivers reported lower anxiety, better well-being, less use of psychotropic medications, more benign appraisals of stress and perceived benefits of caregiving, and greater religious coping and participation, than Caucasian caregivers. Self-rated health did not differ by race, but African-American caregivers reported more unhealthy behaviors than Caucasian caregivers. Some results were specific to site, possibly due to differences in recruitment strategies, inclusion/exclusion criteria, and regional differences. Adjustment for covariates, including caregiver relationship to the care recipient, gender, age, socioeconomic status, and care recipient behavioral problems, altered few of these differences. Results are discussed in terms of their relevance to psychosocial intervention programs for ethnically diverse caregivers.

Dysregulation of cyclin dependent kinase 6 expression in splenic marginal zone lymphoma through chromosome 7q translocations

The increased or inappropriate expression of genes with oncogenic properties through specific chromosome translocations is an important event in the pathogenesis of B-cell lymphoproliferative diseases. Recent studies have found deletions or translocations of chromosome 7q to be the most common cytogenetic abnormality observed in SLVL, a leukemic variant of SMZL, with the q21-q22 region being most frequently affected. In three patients with translocations between chromosomes 2 and 7, the cloning of the breakpoints at 7q21 revealed that each was located within a small region of DNA 3.6 kb upstream of the transcription start site of cyclin dependent kinase 6 (CDK6). In each case the translocation event was consistent with aberrant VJ recombination between the immunoglobulin light chain region (Ig kappa) on chromosome 2p12 and DNA sequences at 7q21, resembling the heptamer recombination site. The t(7;21) breakpoint in an additional patient with splenic marginal zone lymphoma (SMZL), resided 66 kb telomeric to the t(2;7) breakpoints juxtaposing CDK6 to an uncharacterized transcript. In two of the SLVL patient samples, the CDK6 protein was found to be markedly over expressed. These results suggest that dysregulation of CDK6 gene expression contributes to the pathogenesis of SLVL and SMZL.

A comparative evaluation of conventional and pretargeted radioimmunotherapy of CD20-expressing lymphoma xenografts

Radioimmunotherapy with anti-CD20 monoclonal antibodies is a promising new treatment approach for patients with relapsed B-cell lymphomas. However, the majority of patients treated with conventional radiolabeled anti-CD20 antibodies eventually have a relapse because the low tumor-to-blood and tumor-to-normal organ ratios of absorbed radioactivity limit the dose that can be safely administered without hematopoietic stem cell support. This study assessed the ability of a streptavidin-biotin "pretargeting" approach to improve the biodistribution of radioactivity in mice bearing Ramos lymphoma xenografts. A pretargeted streptavidin-conjugated anti-CD20 1F5 antibody was infused, followed 24 hours later by a biotinylated N-acetylgalactosamine-containing "clearing agent" and finally 3 hours later by (111)In-labeled DOTA-biotin. Tumor-to-blood ratios were 3:1 or more with pretargeting, compared with 0.5:1 or less with conventional (111)In-1F5. Tumor-to-normal organ ratios of absorbed radioactivity up to 56:1 were observed with pretargeting, but were 6:1 or less with conventional (111)In-1F5. Therapy experiments demonstrated that 400 microCi (14.8 MBq) or more of conventional (90)Y-1F5 was required to obtain major tumor responses, but this dose was associated with lethal toxicity in 100% of mice. In marked contrast, up to 800 microCi (29.6 MBq) (90)Y-DOTA-biotin could be safely administered by the pretargeting approach with only minor toxicity, and 89% of the mice were cured. These data suggest that anti-CD20 pretargeting shows great promise for improving current therapeutic options for B-cell lymphomas and warrants further preclinical and clinical testing.

Antibody Lineages with Vaccine-Induced Antigen-Binding Hotspots Develop Broad HIV Neutralization

The vaccine-mediated elicitation of antibodies (Abs) capable of neutralizing diverse HIV-1 strains has been a long-standing goal. To understand how broadly neutralizing antibodies (bNAbs) can be elicited, we identified, characterized, and tracked five neutralizing Ab lineages targeting the HIV-1-fusion peptide (FP) in vaccinated macaques over time. Genetic and structural analyses revealed two of these lineages to belong to a reproducible class capable of neutralizing up to 59% of 208 diverse viral strains. B cell analysis indicated each of the five lineages to have been initiated and expanded by FP-carrier priming, with envelope (Env)-trimer boosts inducing cross-reactive neutralization. These Abs had binding-energy hotspots focused on FP, whereas several FP-directed Abs induced by immunization with Env trimer-only were less FP-focused and less broadly neutralizing. Priming with a conserved subregion, such as FP, can thus induce Abs with binding-energy hotspots coincident with the target subregion and capable of broad neutralization.

The RBCC gene RFP2 (Leu5) encodes a novel transmembrane E3 ubiquitin ligase involved in ERAD

RFP2, a gene frequently lost in various malignancies, encodes a protein with RING finger, B-box, and coiled-coil domains that belongs to the RBCC/TRIM family of proteins. Here we demonstrate that Rfp2 is an unstable protein with auto-polyubiquitination activity in vivo and in vitro, implying that Rfp2 acts as a RING E3 ubiquitin ligase. Consequently, Rfp2 ubiquitin ligase activity is dependent on an intact RING domain, as RING deficient mutants fail to drive polyubiquitination in vitro and are stabilized in vivo. Immunopurification and tandem mass spectrometry enabled the identification of several putative Rfp2 interacting proteins localized to the endoplasmic reticulum (ER), including valosin-containing protein (VCP), a protein indispensable for ER-associated degradation (ERAD). Importantly, we also show that Rfp2 regulates the degradation of the known ER proteolytic substrate CD3-delta, but not the N-end rule substrate Ub-R-YFP (yellow fluorescent protein), establishing Rfp2 as a novel E3 ligase involved in ERAD. Finally, we show that Rfp2 contains a C-terminal transmembrane domain indispensable for its localization to the ER and that Rfp2 colocalizes with several ER-resident proteins as analyzed by high-resolution immunostaining. In summary, these data are all consistent with a function for Rfp2 as an ERAD E3 ubiquitin ligase.

Identification of a novel gene,FGFR1OP2, fused toFGFR1 in 8p11 myeloproliferative syndrome

The 8p11 myeloproliferative syndrome (EMS) is an aggressive hematological malignancy caused by the fusion of diverse partner genes to fibroblast growth factor receptor 1 (FGFR1). The partner proteins promote dimerization and ligand-independent activation of FGFR1-encoded tyrosine kinase, deregulating hemopoiesis in a manner analogous to BCR-ABL in chronic myeloid leukemia. Here, we describe the identification of a new FGFR1 fusion gene in a patient who presented with T-cell lymphoblastic lymphoma in conjunction with an acquired ins(12;8)(p11;p11p22). Initial FISH analysis and Southern blotting confirmed that FGFR1 was disrupted. Using 5'-RACE PCR, we identified part of a novel gene, FGFR1OP2, at chromosome band 12p11 that was fused to exon 9 of FGFR1.FGFR1OP2 is predicted to be translated into an evolutionarily conserved protein containing coiled-coil domains but no other recognizable motifs. The presence of the chimeric gene was confirmed by RT-PCR, genomic DNA PCR, and FISH. These data further support the central role of deregulated FGFR1 in the pathogenesis of EMS.

Particulate Array of Well-Ordered HIV Clade C Env Trimers Elicits Neutralizing Antibodies that Display a Unique V2 Cap Approach

The development of soluble envelope glycoprotein (Env) mimetics displaying ordered trimeric symmetry has ushered in a new era in HIV-1 vaccination. The recently reported native, flexibly linked (NFL) design allows the generation of native-like trimers from clinical isolates at high yields and homogeneity. As the majority of infections world-wide are of the clade C subtype, we examined responses in non-human primates to well-ordered subtype C 16055 trimers administered in soluble or high-density liposomal formats. We detected superior germinal center formation and enhanced autologous neutralizing antibodies against the neutralization-resistant (tier 2) 16055 virus following inoculation of liposome-arrayed trimers. Epitope mapping of the neutralizing monoclonal antibodies (mAbs) indicated major contacts with the V2 apex, and 3D electron microscopy reconstructions of Fab-trimer complexes revealed a horizontal binding angle to the Env spike. These vaccine-elicited mAbs target the V2 cap, demonstrating a means to accomplish tier 2 virus neutralization by penetrating the dense N-glycan shield.

MicroRNA-9 regulates the expression of peroxisome proliferator-activated receptor δ in human monocytes during the inflammatory response

PPARδ is involved in the inflammatory response and its expression is induced by cytokines, however, limited knowledge has been produced regarding its regulation. Since recent findings have shown that microRNAs, which are small non-coding RNAs that regulate gene expression, are involved in the immune response, we set out to investigate whether PPARδ can be regulated by microRNAs expressed in monocytes. Bioinformatic analysis identified a putative miR-9 target site within the 3′-UTR of PPARδ that was subsequently verified to be functional using reporter constructs. Primary human monocytes stimulated with LPS showed a downregulation of PPARδ and its target genes after 4 h while the expression of miR-9 was induced. Analysis of pro-inflammatory (M1) and anti-inflammatory (M2) macrophages showed that human PPARδ mRNA as well as miR-9 expression was higher in M1 compared to M2 macrophages. Furthermore, treatment with the PPARδ agonist, GW501516, induced the expression of PPARδ target genes in the pro-inflammatory M1 macrophages while no change was observed in the anti-inflammatory M2 macrophages. Taken together, these data suggest that PPARδ is regulated by miR-9 in monocytes and that activation of PPARδ may be of importance in M1 pro-inflammatory but not in M2 anti-inflammatory macrophages in humans.

Identification of four new translocations involving FGFR1 in myeloid disorders

The 8p11 myeloproliferative syndrome (EMS) is associated with three translocations, t(8;13)(p11;q12), t(8;9)(p11;q33), and t(6;8)(q27;p11), that fuse unrelated genes (ZNF198, CEP110, and FOP, respectively) to the entire tyrosine kinase domain of FGFR1. In all cases thus far examined (n = 10), the t(8;13) results in an identical mRNA fusion between ZNF198 exon 17 and FGFR1 exon 9. To determine if consistent fusions are also seen in the variant translocations, we performed RT-PCR on four cases and sequenced the products. For two patients with a t(8;9), we found that CEP110 exon 15 was fused to FGFR1 exon 9. For two patients with a t(6;8), we found that FOP exon 5 (n = 1) or exon 7 (n = 1) was fused to FGFR1 exon 9. To determine if FGFR1 might be involved in other myeloid disorders with translocations of 8p, we developed a two-color FISH assay using two differentially labeled PAC clones that flank FGFR1. Disruption of this gene was indicated in a patient with a t(8;17)(p11;q25) and Ph-negative chronic myeloid leukemia in association with systemic malignant mast cell disease, a patient with acute myeloid leukemia with a t(8;11)(p11;p15), and two cases with T-cell lymphoma, myeloproliferative disorder, and marrow eosinophilia with a t(8;12)(p11;q15) and ins(12;8)(p11;p11p21), respectively. For the patient with the t(8;11), the chromosome 11 breakpoint was determined to be in the vicinity of NUP98. We conclude that 1) all mRNA fusions in EMS result in splicing to FGFR1 exon 9 but breakpoints in FOP are variable, 2) two-color FISH can identify patients with EMS, and 3) the t(8;17)(p11;q25), t(8;11)(p11;p15), t(8;12)(p11;q15), and ins(12;8)(p11;p11p21) are novel karyotypic changes that most likely involve FGFR1.

Inactivation of FBXW7/hCDC4-β expression by promoter hypermethylation is associated with favorable prognosis in primary breast cancer

INTRODUCTION

Mutational inactivation of the FBXW7/hCDC4 tumor suppressor gene (TSG) is common in many cancer types, but infrequent in breast cancers. This study investigates the presence and impact of FBXW7/hCDC4 promoter methylation in breast cancer.

METHODS

FBXW7/hCDC4-β expression and promoter methylation was assessed in 161 tumors from two independent breast cancer cohorts. Associations between methylation status and clinicopathologic characteristics were assessed by Fisher's exact test. Survival was analyzed using the Kaplan-Meier method in addition to modeling the risk by use of a multivariate proportional hazard (Cox) model adjusting for possible confounders of survival.

RESULTS

Methylation of the promoter and loss of mRNA expression was found both in cell lines and primary tumors (43% and 51%, respectively). Using Cox modeling, a trend was found towards decreased hazard ratio (HR) for death in women with methylation of FBXW7/hCDC4-β in both cohorts (HR 0.53 (95% CI 0.23 to 1.23) and HR 0.50 (95% CI 0.23 to 1.08), respectively), despite an association between methylation and high-grade tumors (P = 0.017). Interestingly, in subgroups of patients whose tumors are p53 mutated or lymph-node positive, promoter methylation identified patients with significantly improved survival (P = 0.048 and P = 0.017, respectively).

CONCLUSIONS

We demonstrate an alternative mechanism for inactivation of the TSG FBXW7/hCDC4, namely promoter specific methylation. Importantly, in breast cancer, methylation of FBXW7/hCDC4-β is related to favorable prognosis despite its association with poorly differentiated tumors. Future work may define whether FBXW7/hCDC4 methylation is a biomarker of the response to chemotherapy and a target for epigenetic modulation therapy.

AmotL2 disrupts apical-basal cell polarity and promotes tumour invasion

The establishment and maintenance of apical-basal cell polarity is essential for the functionality of glandular epithelia. Cell polarity is often lost in advanced tumours correlating with acquisition of invasive and malignant properties. Despite extensive knowledge regarding the formation and maintenance of polarity, the mechanisms that deregulate polarity in metastasizing cells remain to be fully characterized. Here we show that AmotL2 expression correlates with loss of tissue architecture in tumours from human breast and colon cancer patients. We further show that hypoxic stress results in activation of c-Fos-dependent expression of AmotL2 leading to loss of polarity. c-Fos/hypoxia-induced p60 AmotL2 interacts with the Crb3 and Par3 polarity complexes retaining them in large vesicles and preventing them from reaching the apical membrane. The resulting loss of polarity potentiates the response to invasive cues in vitro and in vivo in mice. These data provide a molecular mechanism how hypoxic stress deregulates cell polarity during tumour progression.

Dexamethasone-induced apoptosis in acute lymphoblastic leukemia involves differential regulation of Bcl-2 family members

BACKGROUND AND OBJECTIVES

The mechanism of glucocorticoid -induced apoptosis is not fully understood and early predictive assays based on apoptotic markers for clinical outcome in acute lymphoblastic leukemia (ALL) are scarce. The aim of this study was to characterize the involvement of Bcl-2 family members and caspase activation in dexamethasone(Dex)-induced apoptosis in ALL.

DESIGN AND METHODS

Primary childhood ALL samples, the pre-B ALL cell line RS(4;11), and the T-ALL cell line CCRF-CEM were used. The involvement of Bcl-2 family members was evaluated by flow cytometry, immunocytochemistry, and western and northern blotting. Apoptosis was analyzed by annexin V and TMRE staining. Caspase activity was evaluated by a fluorometric assay.

RESULTS

Dex induced significant down-regulation of the anti-apoptotic Bcl-2 family members Bcl-2 and Bcl-xL, differential activation of the pro-apoptotic Bak and Bax, loss of Delta psi m and cytochrome c release. Dex-induced apoptosis also involved early activation of caspases 2 and -3. Inhibition of caspase activity did not, however, protect against Dex-induced Bak/Bax activation, loss of Delta psi m or cell death. In 12 primary ALL samples Dex-induced apoptosis was associated with activation of Bax (p=0.045) and down-regulation of Bcl-2 (p=0.016) and/or Bcl-xL (p=0.004). Furthermore, ex vivo Dex-sensitivity was associated with an early treatment response to polychemotherapy (p=0.026).

INTERPRETATION AND CONCLUSIONS

The differential regulation of pro- and anti-apoptotic Bcl-2 family members appears to be a key event in the execution of Dex-induced apoptosis in ALL cell lines, and also indicates a role for these proteins in primary ALL cells.