Mechanism-based epigenetic chemosensitization therapy of diffuse large B-cell lymphoma.

UNLABELLED: Although aberrant DNA methylation patterning is a hallmark of cancer, the relevance of targeting DNA methyltransferases (DNMT) remains unclear for most tumors. In diffuse large B-cell lymphoma (DLBCL) we observed that chemoresistance is associated with aberrant DNA methylation programming. Prolonged exposure to low-dose DNMT inhibitors (DNMTI) reprogrammed chemoresistant cells to become doxorubicin sensitive without major toxicity in vivo. Nine genes were recurrently hypermethylated in chemoresistant DLBCL. Of these, SMAD1 was a critical contributor, and reactivation was required for chemosensitization. A phase I clinical study was conducted evaluating azacitidine priming followed by standard chemoimmunotherapy in high-risk patients newly diagnosed with DLBCL. The combination was well tolerated and yielded a high rate of complete remission. Pre- and post-azacitidine treatment biopsies confirmed SMAD1 demethylation and chemosensitization, delineating a personalized strategy for the clinical use of DNMTIs. SIGNIFICANCE: The problem of chemoresistant DLBCL remains the most urgent challenge in the clinical management of patients with this disease. We describe a mechanism-based approach toward the rational translation of DNMTIs for the treatment of high-risk DLBCL.

Molecular targeting of the oncogene eIF4E in acute myeloid leukemia (AML): a proof-of-principle clinical trial with ribavirin.

The eukaryotic translation initiation factor eIF4E is elevated in 30% of malignancies including M4/M5 subtypes of acute myeloid leukemia (AML). The oncogenic potential of eIF4E arises from its ability to bind the 7-methyl guanosine (m(7)G) cap on mRNAs, thereby selectively enhancing eIF4E-dependent nuclear mRNA export and translation. We tested the clinical efficacy of targeting eIF4E in M4/M5 AML patients with a physical mimic of the m(7)G cap, ribavirin. Among 11 evaluable patients there were 1 complete remission (CR), 2 partial remissions (PRs), 2 blast responses (BRs), 4 stable diseases (SDs), and 2 progressive diseases (PDs). Ribavirin-induced relocalization of nuclear eIF4E to the cytoplasm and reduction of eIF4E levels were associated with clinical response. Lack of response or relapse coincided with continued or renewed nuclear localization of eIF4E. This first clinical study to target eIF4E in human malignancy demonstrates clinical activity and associated molecular responses in leukemic blasts. This trial is registered at ClinicalTrials.gov (NCT00559091).

Perspectives in PML: a unifying framework for PML function.

The promyeloctyic leukemia protein (PML) has established activities as a potent repressor of proliferation, and oncogenic transformation, a promoter of apoptosis, an inducer of senescence, and may act as an inhibitor of angiogenesis in mammalian systems. Loss of PML or its nuclear bodies is associated with many human disease states. At the molecular level, the PML protein, and its associated nuclear bodies, play roles in diverse events ranging from mRNA export to DNA repair. PML expression impacts on Akt survival signaling, p53/Mdm2 activity, and cell cycle progression, to name a few. However, there is no discrete set of molecular activities associated with the PML protein that underlie its biochemical and physiological effects. In this review, we postulate a possible molecular model of PML function that could provide a unifying underpinning for many of its disparate activities. In particular, we explore how the ability of PML to coordinately and combinatorially regulate gene expression post-transcriptionally, enables PML to have such broad ranging effects on cellular physiology.

Understanding and Targeting the Eukaryotic Translation Initiation Factor eIF4E in Head and Neck Cancer.

The eukaryotic translation initiation factor eIF4E is elevated in about 30% of human malignancies including HNSCC where its levels correlate with poor prognosis. Here, we discuss the biochemical and molecular underpinnings of the oncogenic potential of eIF4E. Studies in human leukemia specimens, and later in a mouse model of prostate cancer, strongly suggest that cells with elevated eIF4E develop an oncogene dependency to it, making them more sensitive to targeting eIF4E than normal cells. We describe several strategies that have been suggested for eIF4E targeting in the clinic: the use of a small molecule antagonist of eIF4E (ribavirin), siRNA or antisense oligonucleotide strategies, suicide gene therapy, and the use of a tissue-targeting 4EBP fusion peptide. The first clinical trial targeting eIF4E indicates that ribavirin effectively targets eIF4E in poor prognosis leukemia patients and more importantly leads to striking clinical responses including complete and partial remissions. Finally, we discuss the relevance of these findings to HNSCC.

Ribavirin targets eIF4E dependent Akt survival signaling.

The eukaryotic translation initiation factor eIF4E is dysregulated in many cancers. eIF4E, through its mRNA export and translation functions, combinatorially modulates the expression of genes involved in Akt dependent survival signaling. For these activities, eIF4E must bind the 7-methyl guanosine (m(7)G) cap moiety on the 5'-end of mRNAs. We demonstrate that a physical mimic of the m(7)G cap, ribavirin, inhibits eIF4E dependent Akt survival signaling. Specifically, ribavirin impairs eIF4E mediated Akt activation via inhibiting the production of an upstream activator of Akt, NBS1. Consequently, ribavirin impairs eIF4E dependent apoptotic rescue. A ribavirin analog with distinct physico-chemical properties, tiazofurin, does not impair eIF4E activity indicating that only analogs that mimic the m(7)G cap will inhibit eIF4E function. Ribavirin represents a first-in-class strategy to inhibit eIF4E dependent cancers, through competition for m(7)G cap binding. Thus, ribavirin coordinately impairs eIF4E dependent pathways and thereby, potently inhibits its biological effects.

The eIF4E RNA regulon promotes the Akt signaling pathway.

Eukaryotic initiation factor 4E (eIF4E) promotes cellular proliferation and can rescue cells from apoptotic stimuli such as serum starvation. However, the mechanisms underlying apoptotic rescue are not well understood. In this study, we demonstrate that eIF4E overexpression leads to enhanced survival signaling through Akt and that eIF4E requires Akt1 to rescue serum-deprived fibroblasts. Furthermore, a mutant form of eIF4E (W73A), which is messenger RNA (mRNA) export competent but does not promote translation, rescues cells as readily as wild-type eIF4E. We show that eIF4E mediates Akt activation via up-regulation of Nijmegen breakage syndrome 1 (NBS1), a phosphoinositide-3 kinase-Akt pathway upstream activator. Additionally, eIF4E coordinately up-regulates the expression of downstream effectors of the Akt pathway, thereby amplifying Akt signaling effects. A negative regulator of eIF4E, the promyelocytic leukemia protein (PML), suppresses Akt activation and apoptotic rescue. These PML activities likely arise, at least in part, through its inhibition of eIF4E-mediated NBS1 mRNA export. In summary, eIF4E coordinately regulates gene expression to potentiate Akt activation, an activity required for apoptotic rescue.

Controlling gene expression through RNA regulons: the role of the eukaryotic translation initiation factor eIF4E.

The eukaryotic translation initiation factor eIF4E is a potent oncogene. In fact, its overexpression in human cancer often correlates with poor prognosis. Traditionally, eIF4E plays a role in translation initiation where it binds the 5' m7G cap found on mRNAs. More recent studies indicate that a significant fraction of eIF4E (up to 68%) resides in the nucleus where it regulates the nuclear export of specific mRNAs. Additionally, eIF4E may play a role in mRNA sequestration and stability in cytoplasmic processing bodies (P-bodies). Our recent studies suggest that eIF4E governs cell cycle progression and cellular proliferation by coordinately orchestrating the expression of several genes at the post-transcriptional level. Hence, eIF4E functions as a central node of an RNA regulon (described below), which plays an essential role in normal differentiation and development and is frequently dysregulated in cancer. Several cellular factors, such as the promyelocytic leukemia protein PML, modulate the function of this regulon by altering the activity of eIF4E. Here, the physiological implications of these observations are described and the clinical implications of directly targeting eIF4E, and the related regulon, are discussed.

eIF4E is a central node of an RNA regulon that governs cellular proliferation.

This study demonstrates that the eukaryotic translation initiation factor eIF4E is a critical node in an RNA regulon that impacts nearly every stage of cell cycle progression. Specifically, eIF4E coordinately promotes the messenger RNA (mRNA) export of several genes involved in the cell cycle. A common feature of these mRNAs is a structurally conserved, approximately 50-nucleotide element in the 3' untranslated region denoted as an eIF4E sensitivity element. This element is sufficient for localization of capped mRNAs to eIF4E nuclear bodies, formation of eIF4E-specific ribonucleoproteins in the nucleus, and eIF4E-dependent mRNA export. The roles of eIF4E in translation and mRNA export are distinct, as they rely on different mRNA elements. Furthermore, eIF4E-dependent mRNA export is independent of ongoing RNA or protein synthesis. Unlike the NXF1-mediated export of bulk mRNAs, eIF4E-dependent mRNA export is CRM1 dependent. Finally, the growth-suppressive promyelocytic leukemia protein (PML) inhibits this RNA regulon. These data provide novel perspectives into the proliferative and oncogenic properties of eIF4E.

Frequency analysis and clinical characterization of different types of spinocerebellar ataxia in Serbian patients.

The relative frequencies of different spinocerebellar ataxias (SCAs) vary widely among different ethnic groups, presumably due to a founder effect. We investigated the relative prevalence of SCA1-3, 6-8, 12, 17; dentate-rubro-pallidoluysian atrophy; and Friedreich's ataxia (FRDA) in Serbian patients with adult-onset (>20 years of age) hereditary and sporadic SCAs, and compared clinical features of patients with genetically confirmed SCAs. A total of 108 patients from 54 families (38 apparently dominant [ADCA] and 16 apparently recessive) with adult-onset hereditary ataxia and 75 apparently sporadic patients were assessed. Of 38 families with ADCA, 13 (34%) were positive for an expansion in an SCA1 and 5 families (13%) for an expansion in an SCA2 allele. In 20 families (53%), no expansions have been identified in any of the analyzed genes. Gaze palsy, spasticity, and hyperreflexia were significantly more common in SCA1, whereas slow saccades, hypotonia, hyporeflexia, and dystonia prevailed in SCA2 patients. Among the 16 families with an apparently recessive mode of ataxia inheritance, 4 (25%) were identified as having the FRDA mutation. Ataxia-causing mutations were identified in 8 (10.6%) of patients with apparently sporadic adult-onset ataxia.

Further evidence that ribavirin interacts with eIF4E.

This commentary discusses the recent reports in RNA by Yan and colleagues and Westman and colleagues of the apparent failure of ribavirin to bind to recombinant eIF4E and inhibit 7-methyl guanosine cap-dependent exogenous mRNA translation of cell extracts in vitro. Measuring binding by using affinity chromatography of matrix-immobilized proteins and by using protein emission fluorescence spectroscopy in the presence of nucleotide ligands, as well as limitations of using cell extracts for the assessment of mechanisms of mRNA translation are discussed. Possible reasons for the discordant findings of Yan and colleagues and Westman and colleagues are suggested, and direct observation of the specific binding of ribavirin to eIF4E by using mass spectrometry is presented.

Population data on 14 STR loci from population of Serbia and Montenegro (new and renewed data).

A renewed and new population study of fourteen short tandem repeat loci (TH01, TPOX, CSF1P0, vWA, FES/FPS, F13A01, D13S317, D7S820, D16S539, LPL, F13B, CD4, D5S818 and D8S1179) were performed in a sample of 296-531 unrelated individuals from Serbia and Montenegro. Population data were compared to previously published data from Vojvodina province and neighboring Croatia.

eIF4E promotes nuclear export of cyclin D1 mRNAs via an element in the 3'UTR.

The eukaryotic translation initiation factor eIF4E is a critical modulator of cellular growth with functions in the nucleus and cytoplasm. In the cytoplasm, recognition of the 5' m(7)G cap moiety on all mRNAs is sufficient for their functional interaction with eIF4E. In contrast, we have shown that in the nucleus eIF4E associates and promotes the nuclear export of cyclin D1, but not GAPDH or actin mRNAs. We determined that the basis of this discriminatory interaction is an approximately 100-nt sequence in the 3' untranslated region (UTR) of cyclin D1 mRNA, we refer to as an eIF4E sensitivity element (4E-SE). We found that cyclin D1 mRNA is enriched at eIF4E nuclear bodies, suggesting these are functional sites for organization of specific ribonucleoproteins. The 4E-SE is required for eIF4E to efficiently transform cells, thereby linking recognition of this element to eIF4E mediated oncogenic transformation. Our studies demonstrate previously uncharacterized fundamental differences in eIF4E-mRNA recognition between the nuclear and cytoplasmic compartments and further a novel level of regulation of cellular proliferation.

Ribavirin suppresses eIF4E-mediated oncogenic transformation by physical mimicry of the 7-methyl guanosine mRNA cap.

The eukaryotic translation initiation factor eIF4E is deregulated in many human cancers, and its overexpression in cells leads to malignant transformation. Oncogenic properties of eIF4E are directly linked to its ability to bind 7-methyl guanosine of the 5' mRNA. Here, we observe that the antiviral guanosine analogue ribavirin binds to eIF4E with micromolar affinity at the functional site used by 7-methyl guanosine mRNA cap, competes with eIF4E:mRNA binding, and, at low micromolar concentrations, selectively disrupts eIF4E subcellular organization and transport and translation of mRNAs posttranscriptionally regulated by eIF4E, thereby reducing levels of oncogenes such as cyclin D1. Ribavirin potently suppresses eIF4E-mediated oncogenic transformation of murine cells in vitro, of tumor growth of a mouse model of eIF4E-dependent human squamous cell carcinoma in vivo, and of colony formation of eIF4E-dependent acute myelogenous leukemia cells derived from human patients. These findings describe a specific, potent, and unforeseen mechanism of action of ribavirin. Quantum mechanical and NMR structural studies offer directions for the development of derivatives with improved cytostatic and antiviral properties. In all, ribavirin's association with eIF4E may provide a pharmacologic means for the interruption of posttranscriptional networks of oncogenes that maintain and enhance neoplasia and malignancy in human cancer.

Prevalence of the fragile X syndrome in Yugoslav patients with non-specific mental retardation.

Mutations at two fragile sites, FRAXA and FRAXE, loci are caused by an expansion of a CGG/GCC trinucleotide repeat and are characterized by mental retardation. Here we report molecular screening survey of 97 unrelated individuals diagnosed with non-specific mental retardation (MR), which produced positive test for FRAXA in two boys and none positive for the FRAXE mutation. In addition, we studied allelic frequency distribution for the FRAXA locus in this group of mentally retarded patients, as well as in the 99 healthy subjects of Yugoslav population. The distribution of FMR1 CGG repeat size in both groups was similar: the most common allele contained 29 repeats (32.86% in the healthy population and 54.54% in MR population), followed by the allele with 28 CGG repeats (21.43% in the healthy and 12.2% in MR population). Premutation alleles with more than 45 repeats were not found in control nor in the MR group.

Aberrant eukaryotic translation initiation factor 4E-dependent mRNA transport impedes hematopoietic differentiation and contributes to leukemogenesis.

The eukaryotic translation initiation factor 4E (eIF4E) acts as both a key translation factor and as a promoter of nucleocytoplasmic transport of specific transcripts. Traditionally, its transformation capacity in vivo is attributed to its role in translation initiation in the cytoplasm. Here, we demonstrate that elevated eIF4E impedes granulocytic and monocytic differentiation. Our subsequent mutagenesis studies indicate that this block is a result of dysregulated eIF4E-dependent mRNA transport. These studies indicate that the RNA transport function of eIF4E could contribute to leukemogenesis. We extended our studies to provide the first evidence that the nuclear transport function of eIF4E contributes to human malignancy, specifically in a subset of acute and chronic myelogenous leukemia patients. We observe an increase in eIF4E-dependent cyclin D1 mRNA transport and a concomitant increase in cyclin D1 protein levels. The aberrant nuclear function of eIF4E is due to abnormally large eIF4E bodies and the loss of regulation by the proline-rich homeodomain PRH. We developed a novel tool to modulate this transport activity. The introduction of IkappaB, the repressor of NF-kappaB, leads to suppression of eIF4E, elevation of PRH, reorganization of eIF4E nuclear bodies, and subsequent downregulation of eIF4E-dependent mRNA transport. Thus, our findings indicate that this nuclear function of eIF4E can contribute to leukemogenesis by promoting growth and by impeding differentiation.

Poly(A) tailing of ancient DNA: a method for reproducible microsatellite genotyping.

Microsatellites could be of great potential use in the analysis of ancient remains, but so far such analyses have failed to be reproducible mainly because of the high degree of ancient DNA (aDNA) degradation. During PCR, annealing of the primers to the complementary sequences of microsatellites occurs together with cross-annealing of partially degraded repeated sequences. This could create chimeric alleles that do not correspond to the authentic ones. Here we report a simple method for processing aDNA fragments prior to PCR that greatly reduces the production of chimeric alleles. This approach eliminates aDNA molecules broken within the repeats as targets for Taq polymerase by adding poly(A) tails at the 3(') ends of the DNA fragments, which disrupts the homology in the region and thus prevents annealing out of register. We have analyzed one dinucleotide- (D6S337) and two trinucleotide-containing loci (IT15 and SCA1) using poly(A)-tailed and the same untreated aDNA as template. aDNAs were isolated from 28 human remains, 600 and 7000 years of age. In repeated experiments with untreated aDNAs we obtained three to five times more alleles compared to poly(A)-tailed aDNAs. According to our results, modification of aDNA by poly(A) tailing is an efficient pretreatment for accurate genotyping.

The proline-rich homeodomain protein, PRH, is a tissue-specific inhibitor of eIF4E-dependent cyclin D1 mRNA transport and growth.

The translation initiation factor eIF4E is involved in the modulation of cellular growth. In the nucleus, where eIF4E is associated with PML nuclear bodies, eIF4E mediates nucleocytoplasmic transport of specific transcripts, and this contributes to its transformation activity. Surprisingly, we found that a trans cription factor, the proline-rich homeodomain protein PRH, is a negative regulator of eIF4E in myeloid cells, interacting with eIF4E through a conserved binding site typically found in translational regulators. Through this interaction, PRH inhibits eIF4E-dependent mRNA transport and subsequent transformation. These activities of PRH are independent of its transcriptional functions. Further, we found that 199 homeodomain proteins contain potential eIF4E-binding sites. Thus, there could be many tissue-specific regulators of eIF4E. These findings provide a model for regulation of a general factor, eIF4E, in tissue- specific contexts, and suggest that its regulation is important in differentiation and development.

[Duchenne's and Becker's muscular dystrophy: analysis of phenotype-genotype correlation in 28 patients] ]. / Disenova i Bekerova misicna distrofija: analiza korelacije fenotip-genotip kod 28 bolesnika.

Duchenne's and Becker's muscular dystrophy (DMD & BMD) is a X linked disease caused by mutations in the dystrophic gene. DMD is the malign form of the disease, which significantly shortens the lifetime of the patient, while BMD has late onset with slow progression. Sixty five percent of DMD and BMD cases are caused by deletion of one or more exons in the dystrophic gene, while duplications cause these diseases in 6 to 7% of the cases. There are two hot spots for deletions and duplications. These are exons in the proximal part of the gene (3rd to 18th) and exons of a distal part of the gene (45th to 52nd). The remaining 30% of DMD and BMD cases are caused by point mutations, small deletions or inversions in the dystrophic gene. The correlation between the severity of the disease and the position of deletion shows that most of the out of frame deletions cause DMD phenotype, while in frame deletions result in BMD phenotype. We report on the results of 28 non-related DMD and BMD patients. In 57% of cases deletions were detected and all were found in the distal hot spot of the gene. These results suggest that in most of the cases, out of frame deletions produce DMD phenotype while in frame deletions result in BMD phenotype. This is in compliance with data from literature.

[Analysis of mutations in the chromosome 17p11.2 region in patients with Charcot-Marie-Tooth type 1 disease and in patients with tomaculous neuropathy]. / Analiza mutacija u regionu hromozoma 17p11.2 kod osoba s oboljenjem Sarko-Mari-Tut, tip jedan, i osoba obolelih od tomakulozne neuropatije.

Charcot-Marie-Tooth type 1A disease (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP) are common inherited disorders of the peripheral nervous system associated with duplication and deletion, respectively, of the 17p11.2 segment including the gene of peripheral myelin protein 22. We studied 48 subjects belonging to 29 families with clinical and electrophysiological signs of definite CMT1, 20 patients with suspected CMT phenotype, and 17 patients and healthy members of their families with HNPP. Blood sampling and DNA isolation, PCR, restriction analysis, southern blotting were performed using standard procedures. Of 48 patients with diagnosis of definite CMT1 in 25 (52%) we found a 1.5 Mb tandem duplication in chromosome 17p11.2. These duplications were not found in any of 20 sporadic cases with the clinical phenotype of CMT but without reliable electrophysiological data. Only 13 (44.8%) of 29 unrelated CMT1 patients from the first group had 17p11.2 duplications. Three of 4 sporadic cases (75%) with definite CMT1 had 17p11.2 duplications. Of 17 patients from 6 families with HNPP deletion of 17p11.2 segment was found in 15 (88.2%), as well as in 5 (83.3%) of six unrelated cases. Detection of CMT1A/HNPP recombination hotspot is a simple and reliable DNA diagnostic method, which is useful only for the patients with clinically already verified CMT1, and HNPP for further genetic counselling of patients and members of their families.