Reactivation of epigenetically silenced miR-512 and miR-373 sensitizes lung cancer cells to cisplatin and restricts tumor growth

MicroRNAs (miRs) regulate a variety of cellular processes, and their impaired expression is involved in cancer. Silencing of tumor-suppressive miRs in cancer can occur through epigenetic modifications, including DNA methylation and histone deacetylation. We performed comparative miR profiling on cultured lung cancer cells before and after treatment with 5'aza-deoxycytidine plus Trichostatin A to reverse DNA methylation and histone deacetylation, respectively. Several tens of miRs were strongly induced by such 'epigenetic therapy'. Two representatives, miR-512-5p (miR-512) and miR-373, were selected for further analysis. Both miRs were secreted in exosomes. Re-expression of both miRs augmented cisplatin-induced apoptosis and inhibited cell migration; miR-512 also reduced cell proliferation. TEAD4 mRNA was confirmed as a direct target of miR-512; likewise, miR-373 was found to target RelA and PIK3CA mRNA directly. Our results imply that miR-512 and miR-373 exert cell-autonomous and non-autonomous tumor-suppressive effects in lung cancer cells, where their re-expression may benefit epigenetic cancer therapy.

Ensembl 2009

The Ensembl project (http://www.ensembl.org) is a comprehensive genome information system featuring an integrated set of genome annotation, databases, and other information for chordate, selected model organism and disease vector genomes. As of release 51 (November 2008), Ensembl fully supports 45 species, and three additional species have preliminary support. New species in the past year include orangutan and six additional low coverage mammalian genomes. Major additions and improvements to Ensembl since our previous report include a major redesign of our website; generation of multiple genome alignments and ancestral sequences using the new Enredo-Pecan-Ortheus pipeline and development of our software infrastructure, particularly to support the Ensembl Genomes project (http://www.ensemblgenomes.org/).

The PI3K inhibitor LY294002 prevents p53 induction by DNA damage and attenuates chemotherapy-induced apoptosis

The p53 tumor suppressor plays a key role in the natural protection against cancer. Activation of p53 by DNA-damaging agents can contribute to successful elimination of cancer cells via chemotherapy-induced apoptosis. The phosphatidylinositol-3 kinase (PI3K) pathway, triggered in normal cells upon exposure to growth factors, regulates a cascade of proliferation and survival signals. The PI3K pathway is abnormally active in many cancers, thus making it an attractive target for inactivation in an attempt to achieve better cancer therapy. We report here that exposure to LY294002, a potent PI3K inhibitor, aborts the activation of p53 by several drugs commonly used in cancer chemotherapy. Concomitantly, LY294002 attenuates p53-dependent, chemotherapy-induced apoptosis of cancer cells. These findings invoke an unexpected positive role for PI3K in p53 activation by anticancer agents, and suggest that the efficacy of PI3K inhibitors in cancer therapy may be greatly affected by the tumor p53 status.

Characterization of two peptide epitopes on Mdm2 oncoprotein that affect p53 degradation

Phosphorylation of Mdm2, in response to DNA damage, resulted in prevention of p53 degradation in the cytoplasm as well as reduction of its binding with monoclonal antibody (mAb) 2A10. Using a 15-mer phage-peptide library, we identified two 2A10-epitopes on human Mdm2 (hdm2): at positions 255-266 (LDSEDYSLSEEG) and 389-400 (QESDDYSQPSTS). Synthetic peptides corresponding to the above sites, inhibit the binding of mAb2A10 to Mdm2 with high (4.5 x 10(-9)M) and moderate affinity (1.1 x 10(-7)M), respectively. Phospho-derivatives of these peptides, and of single human Mdm2 mutations S260D or S395D resulted in a considerable reduction in their binding with mAb2A10. These results provide a molecular explanation for the observation that reactivity of Mdm2 with mAb2A10 is inhibited by phosphorylation.

The c-fos proto-oncogene is a target for transactivation by the p53 tumor suppressor

The p53 tumor suppressor gene is mutated in over 50% of human cancers, resulting in inactivation of the wild-type (wt) p53 protein. The most notable biochemical feature of p53 is its ability to act as a sequence-specific transcriptional activator. Through use of the suppression subtractive hybridization differential screening technique, we identified c-fos as a target for transcriptional stimulation by p53 in cells undergoing p53-mediated apoptosis. Overexpression of wt p53 induces c-fos mRNA and protein. Moreover, in vivo induction of c-fos in the thymus following whole-body exposure to ionizing radiation is p53 dependent. p53 responsiveness does not reside in the basal c-fos promoter. Rather, a distinct region within the c-fos gene first intron binds specifically to p53 and confers upon the c-fos promoter the ability to become transcriptionally activated by wt p53. Identification of c-fos as a specific target for transcriptional activation by p53 establishes a direct link between these two pivotal regulatory proteins and raises the possibility that c-fos contributes to some of the biological effects of p53.

p53 activates the CD95 (APO-1/Fas) gene in response to DNA damage by anticancer drugs

Chemotherapeutic drugs cause DNA damage and kill cancer cells mainly by apoptosis. p53 mediates apoptosis after DNA damage. To explore the pathway of p53-dependent cell death, we investigated if p53-dependent apoptosis after DNA damage is mediated by the CD95 (APO-1/Fas) receptor/ligand system. We investigated hepatoma, gastric cancer, colon cancer, and breast cancer cell lines upon treatment with different anticancer agents known to act via p53 accumulation. Cisplatin, mitomycin, methotrexate, mitoxantrone, doxorubicin, and bleomycin at concentrations present in the sera of patients during therapy led to an upregulation of both CD95 receptor and CD95 ligand. Induction of the CD95 ligand occurred in p53 wild-type (wt), p53 mutant (mt), and p53 deficient (p53(-/-)) cell lines and at wt and mt conformation of temperature-sensitive p53 mutants. In contrast, upregulation of the CD95 receptor was observed only in cells with wt p53, not in cells with mt or without any p53. Restitution of inducible wt p53 function restored the ability of p53(-/-) Hep3B cells to upregulate the CD95 receptor in response to anticancer drugs. This rendered the cells sensitive to CD95-mediated apoptosis. In an attempt to understand how CD95 expression is regulated by p53, we identified a p53-responsive element within the first intron of the CD95 gene, as well as three putative elements within the promoter. The intronic element conferred transcriptional activation by p53 and cooperated with p53-responsive elements in the promoter of the CD95 gene. wt p53 bound to and transactivated the CD95 gene, whereas mt p53 failed to induce apoptosis via activation of the CD95 gene. These observations provide a mechanistic explanation for the ability of p53 to contribute to tumor progression and to resistance of cancer cells to chemotherapy.

N-(N-benzylpiperidin-4-yl)-2-[18F]fluorobenzamide: a potential ligand for PET imaging of sigma receptors

Four nitro- and fluorobenzamides (1-4) have been synthesized in good yields from nitro- and fluoro-substituted benzoyl chloride with 4-amino-1-benzylpiperidine. In vitro studies showed that these compounds have high affinities to sigma receptors. N-(N-Benzylpiperidin-4-yl)-2-fluorobenzamide (3), in particular, bound to sigma receptors with high affinity (Ki = 3.4 nM, guinea pig brain membranes) and high selectivity (sigma-2/sigma-1 = 120). It was, therefore, labeled with 18F and evaluated as a sigma receptor radioligand. N-(N-Benzylpiperidin-4-yl)-2-[18F]fluorobenzamide (3a) was synthesized in one step by nucleophile substitution of the 2-nitro precursor (1) with [18F]fluoride in DMSO at 140 degrees C for 20 min followed by purification with HPLC in 4-10% yield (decay corrected). The synthesis time was 90 min and the specific activity was 0.4-1.0 Ci/mumol. Tissue distribution in mice revealed that the uptakes of 3a in the brain, heart, liver, lungs, spleen, kidneys and small intestine were high, and the radioactivity in these organs remained constant from 60 to 120 min post-injection. The radioactivity in the bone did not significantly increase, suggesting in vivo defluorination may not be the major route of metabolism of 3a in mice. Blocking studies with haloperidol in rats indicated that the uptake of compound 3a in the rat brain was selective to haloperidol-sensitive sigma sites. These results suggest that compound 3a is a potent sigma receptor radioligand and may be a potential ligand for PET imaging of sigma receptors in humans.

A novel p53-inducible gene, PAG608, encodes a nuclear zinc finger protein whose overexpression promotes apoptosis

The biological effects of the p53 tumor suppressor protein are elicited, at least in part, through sequence-specific transactivation of a battery of target genes. The differential display method was employed towards identifying additional p53 target genes, with emphasis on genes whose induction may contribute to p53-mediated apoptosis. We report here the cloning of a novel p53-inducible gene, designated PAG608. PAG608 transcripts are induced by DNA damage in a p53-dependent manner. PAG608 encodes a nuclear zinc finger protein, which appears to localize preferentially to nucleoli when expressed at moderate levels in transfected cells. Transient overexpression of PAG608 in human tumor-derived cells leads to distinctive changes in nuclear morphology, and can promote apoptosis. Together with additional p53 target genes, PAG608 may therefore play a role in mediating the biological activities of p53.

Stroke caregivers: do they feel prepared?

A pilot study was administered to determine if stroke caregivers felt they were adequately educated, trained, and prepared to care for their stroke survivor upon discharge. The convenience sample consisted of 26 stroke caregivers from four Indiana facilities with established therapy/rehabilitation units and two Indiana stroke clubs. Subjects were divided into groups according to the amount of time after discharge in the caregiver role (1-3 days, 10-14 days, greater than 3 months). Survey results were obtained by phone interviews and by self-administration. Compilation of data occurred over 5 months, and interpretation involved visual inspection and frequency distributions. Overall preparedness for the newer caregivers was a 4 (prepared); whereas, the more experienced caregivers' average score was a 3 (somewhat prepared). This study can help rehabilitation staff in their efforts to prepare caregivers for assisting stroke survivors at home.

Influence of biological response modifiers: measurement of tumor blood flow and temperature

Human recombinant interferon-alpha-2b (IFN) is known to inhibit growth of both normal and tumor cells and to stimulate immune effector cell function. We have previously shown that IFN and other biological response modifiers augment accumulation of radiolabeled antibodies in tumors. This investigation demonstrates that 30 min post i.m. administration of IFN significantly (p < 0.01) enhances tumor perfusion in tumor-bearing mice and persists for a much longer time than in normal tissue, which, in part, may contribute to the enhanced tumor uptake of radiolabeled monoclonal antibodies within 1.5 h of their administration. Histological examinations of tumors obtained from animals receiving IFN 72 h previously did not show changes in inflammatory cells. Our investigation shows that laser Doppler flowmetry and color Doppler imaging can provide an excellent means of measuring tumor perfusion changes in small living animals where radioactive tracers cannot be used.

Technetium-99m-labeled monoclonal antibodies: influence of technetium-99m binding sites

A number of 99mTc-labeled monoclonal antibodies (Mabs) are being evaluated for diagnostic applications. Preparations are carried out using both direct and indirect (bifunctional chelating agent, BFCA) labeling procedures in which nonspecific 99mTc binding has been postulated.

METHODS

By using the ascorbic acid (AA) reduction mediated direct labeling procedure and diaminotetrathiol (N2S4) as a BFCA method, we examined the role of specific binding sites and aliphatic E amino groups of lysine as nonspecific binding sites for 99mTc.

RESULTS

Labeling yields for the direct and N2S4 "regular" preparations averaged 73% +/- 2.8% and 91% +/- 2%, for the "specific" preparations, 60% +/- 3.5% and 75% +/- 2% and for the "nonspecific" preparations 13% +/- 1.0% and 16% +/- 1% respectively. All preparations were evaluated in tumor-bearing mice. The control and specific preparations permitted excellent scintigraphic visualization of tumors; the percentages of specific preparations in the tumors being 2.1% +/- 0.5% and 3.1% +/- 0.4%, respectively. With nonspecific preparations, tumors were not visualized and the percentages of administered radioactivity per gram of tumor were only 0.9% +/- 0.2% and 0.9% +/- 0.3%, respectively.

CONCLUSIONS

In these 99mTc labeling procedures, the amino group-mediated nonspecific binding of 99mTc to Mabs can be as high as 16% and contributes to increased liver uptake and decreased tumor uptake of radioactivity.

Structural perturbations of monoclonal antibodies following radiolabelling: in vitro evaluation of different techniques

Antibodies are labelled routinely with direct labelling techniques in which some of the native disulphide groups are reduced to sulphydryls. Using polyacrylamide gel electrophoresis (PAGE) as an analytical tool and human polyclonal IgG (HIgG) labelled with 99Tcm by the ascorbic acid (AA), stannous chloride (SnCl2) and 2-mercaptoethanol (2-ME) techniques, we have quantitatively determined any fragmentation of the protein and the radioactivity associated with fragments. HIgG labelled with 99Tcm by two bifunctional chelating agents provided the vital comparison. The results indicated that in the bifunctional chelating agent (BFCA) methods 65 and 61% of the activity was associated with protein with an apparent molecular weight of 150,000 D. The corresponding numbers for the AA, SnCl2 and 2-ME methods were 46.4, 21 and 3.9%. With 2-ME, 96% of the activity was associated with low molecular weight fragments. Although monoclonal antibody fragmentation may not affect immunoreactivity of the protein, it may influence biodistribution.

p53-mediated cell death: relationship to cell cycle control

M1 clone S6 myeloid leukemic cells do not express detectable p53 protein. When stably transfected with a temperature-sensitive mutant of p53, these cells undergo rapid cell death upon induction of wild-type (wt) p53 activity at the permissive temperature. This process has features of apoptosis. In a number of other cell systems, wt p53 activation has been shown to induce a growth arrest. Yet, wt 53 fails to induce a measurable growth arrest in M1 cells, and cell cycle progression proceeds while viability is being lost. There exists, however, a relationship between the cell cycle and p53-mediated death, and cells in G1 appear to be preferentially susceptible to the death-inducing activity of wt p53. In addition, p53-mediated M1 cell death can be inhibited by interleukin-6. The effect of the cytokine is specific to p53-mediated death, since apoptosis elicited by serum deprivation is refractory to interleukin-6. Our data imply that p53-mediated cell death is not dependent on the induction of a growth arrest but rather may result from mutually incompatible growth-regulatory signals.

Three unique base pair changes in a family with Gaucher disease

Single-stranded cDNA was prepared from RNA obtained from a patient with type 1 Gaucher disease. The cDNA was amplified in vitro and analyzed by sequencing. Three base-pair changes were identified which included a G to C transversion at nucleotide 3119 of the active gene (Asp140----His), an A to C transversion at nucleotide 3170 (Lys157----Gln) and a G to A change at nucleotide 5309 (Glu326----Lys). To study the mode of inheritance of the three different base-pair changes, genomic DNA was prepared from blood or skin fibroblasts of several family members. Genomic glucocerebrosidase DNA sequences were amplified and subjected to hybridization with allele-specific oligonucleotides (ASOs). The hybridization profiles demonstrated that two of the base-pair changes originated from the mother and were transmitted to her two affected sons and to a grandchild, while the third base-pair change, originating from the father, was transmitted to his two affected sons, a carrier daughter and a second grandchild. Tests of other patients with Gaucher disease failed to disclose the presence of the three base-changes. This is a unique family with three base-pair changes tightly linked to Gaucher disease.

Molecular aspects of Gaucher disease

Gaucher disease is the most common sphingolipid storage disorder. Due to its high prevalence it may appear with a nonrelated neurological disease and be misinterpreted as Gaucher type 3. A family is described in which 2 Gaucher brothers presented different clinical signs. Molecular analysis has shown that both carried two mutated alleles. One allele had a G to C transversion at nucleotide 3119 of the active gene (Asp140-His) while the other presented two base pair changes, an A to C transversion at nucleotide number 3170 (Lys157-Gly), and a G-A transition at nucleotide number 5309 (Glu324-Lys). Therefore, both presented the same type of Gaucher disease which was accompanied with a nonrelated neurological disease in one of them. Molecular diagnosis of 161 patients has provided a relative abundance of different mutations among Jewish and non-Jewish patients and allowed some genotype-phenotype correlation. Differential expression of the murine glucocerebrosidase activator gene (the prosaposine) has been demonstrated using Northern technique and in situ hybridization. High expression levels were observed in the brain and testes. In the testes the prosaposine expression was confined to the supporting cells. In the female gonad prosaposine expression has also been shown, in the corpus luteum. In a 12 1/2-day-old embryo, prosaposine gene expression was detected mainly in brain stem, in dorsal ganglia and in the genital ridge.

Prevalent and rare mutations among Gaucher patients

Sequence analysis of gcs cDNA (encoding glucocerebrosidase) or genomic fragments originated from Gaucher patients revealed novel mutations. Two rare mutations were found in a type-2 non-Jewish Gaucher patient: a G----A transition (Gly325----Arg) at nucleotide (nt) 5306 of the active gene and a T----G transversion (Cys342----Gly) at nt 5357. These mutations were not found in any other patient. A G----C transversion (Asp409----His) at nt 5957 was identified in two non-Jewish patients, and was designated TL. Two recombinant alleles were found. One recombinant allele designated recTL contained four single-nt mutations. These mutations included: (1) a G----C transversion at nt 5957 (Asp409----His) (the TL mutation); (2) a T----C transition at nt 6433 (Leu444----Pro) creating a new NciI site (NciI mutation); (3) a G----C transversion at nt 6468 (Ala456----Pro; 456 mutation); and (4) a G----C transversion at amino acid (aa) 460 (nt 6482), not associated with any aa change. Sequence analysis indicated that at least part of exon 9, intron 9 and exon 10 of the recombinant gene derived from the pseudogene. The other recombinant gene, designated recNciI, contained a mutation at aa 444 (NciI mutation), and mutations 456 and 460 described above; at least exon 10 of this gene originated from the pseudogene. We hypothesize that the presence of the pseudogene close to the active gene causes transfer of mutations into the active gene via gene conversion or nonhomologous recombination, thus accounting for the high frequency of mutations observed in the gcs gene.

Characterization of mutations in Gaucher patients by cDNA cloning

Mutated cDNA clones containing the entire coding sequence of human glucocerebrosidase were isolated from libraries originated from Gaucher patients. Sequence analysis of a mutated cDNA derived from a type II Gaucher patient revealed a C-to-G transversion causing a substitution of an arginine for a proline at residue 415. This change creates a new cleavage site for the enzyme HhaI in the mutated cDNA. Allele-specific oligonucleotide hybridization made it possible to show that this mutation exists in the genomic DNA of the patient. From a cDNA library originated from a type I Gaucher patient, a mutated allele was cloned that contains a T-to-C transition causing a substitution of proline for leucine at residue 444 and creating a new NciI site. This mutation is identical to that described by S. Tsuji and colleagues in genomic DNA from type I, type II, and type III patients. Since the new NciI site generates RFLP, it was used to test the existence of this mutated allele in several Gaucher patients by Southern blot analysis. This allele was found in type I (Jewish and non-Jewish), type II, and type III Gaucher patients. These findings led us to conclude that the patient suffering from type II disease (denoted GM1260) carried both mutations described above. Any one of the amino acid changes described reduces the glucocerebrosidase activity as tested by transfection of COS cells with expression vectors harboring the mutated cDNAs. The base changes in the two mutated cDNAs do not affect the electrophoretic mobility of the corresponding polypeptides on an SDS polyacrylamide gel.

The human glucocerebrosidase gene and pseudogene: structure and evolution

We report the sequence of the entire human gene encoding beta-glucocerebrosidase and that of the associated pseudogene. The gene contains 11 exons extending from base pair 355 to base pair 7232 in the overall sequence. The gene promoter contains TATA- and CAT-like boxes upstream of the major 5' end of the glucocerebrosidase RNA. The two TATA boxes lie between nucleotides (-23)-(-27) and (-33)-(-39) and the two possible CAT boxes reside between nucleotides (-90)-(-94) and (-96)-(-99) in relation to the major 5' end of the mRNA. The functionality of the promoter region was monitored by coupling it to the bacterial gene coding for chloramphenicol acetyltransferase (CAT) and assaying the expression of the enzyme in cells transfected with this vector. The glucocerebrosidase promoter not only directs synthesis of the bacterial enzyme but also exhibits the same pattern of tissue-specific expression as that of the endogenous gene. An apparently tightly linked pseudogene is approximately 96% homologous to the functional gene. However, introns 2, 4, 6, and 7 have large "deletions" consisting of Alu sequences 313, 626, 320, and 277 bp in length, respectively. It is entirely possible that the ancestral gene lacks these sequences and that they have been inserted into the introns of the functioning gene. There is also a 55-bp deletion from a part of exon 9 flanked by a short inverted repeat. The sequence data should facilitate development of methods for diagnosis of Gaucher disease at the molecular level.

Efficient in vitro and in vivo expression of human glucocerebrosidase cDNA

A human glucocerebrosidase cDNA clone was isolated from a human chronic myelogenous leukemia (line K562) cDNA library using a 36-nucleotide-long synthetic probe (GC-36). The 2.4-kb cDNA contains 184 bp of 5' nontranslated sequences, the complete coding region, and 546 bp of 3' nontranslated sequences followed by 100 bp of poly(A). A primer extension experiment indicated that the cDNA is at least 51 bp shorter than the mRNA at the 5' end. In normal human placenta as well as in fibroblasts from Gaucher's disease patients, a major mRNA species of 2.6 kb hybridizes with the cDNA probe. The amounts of the glucocerebrosidase mRNA in normal placenta and Gaucher's cells are comparable. The cDNA was linked to the SP6 promoter and transcribed in vitro. The resultant RNA, when translated in a cell-free system, yielded a polypeptide of 55 kD, which is the size expected from the coding sequence. The cDNA was inserted into an SV40 shuttle vector, under the transcription control of the SV40 early promoter. COS-M6 cells were transfected with this construct and the biological activity of the cDNA was assayed by monitoring the increase in glucocerebrosidase activity, using 4-methyl umbiliferyl glucopyranoside as a substrate. There was a two- to three-fold increase in enzymatic activity in the transfected cells, compared to nontransfected cells. These results prove the authenticity of the glucocerebrosidase cDNA and provide the basis for experiments to understand the nature of the genetic alterations responsible for Gaucher's disease.

Startle reflex habituation in children with cerebral palsy

Two groups of children (9 with cerebral palsy and 10 normals, matched for sex and age) participated in a study of the startle reflex. Each child was instructed to press a button as soon as possible after the onset of a visual stimulus on a box on the table at which they were seated. During some of the trials, a sudden and intense auditory stimulus (85 dB) was presented concomitantly with the onset of the visual stimulus, and effects on reaction time recorded. Mean reaction time of normal children was significantly faster than that of the group with cerebral palsy. The magnitude of disruption associated with the first startle stimulus presentation was signicantly greater for cerebral palsied children. The course between groups of habituation to the startle stimuli was not significantly different. Data support the hypothesis that startle reflexes of children with cerebral palsy are more marked than are those of normal children.