The interaction of the SRA domain of ICBP90 with a novel domain of DNMT1 is involved in the regulation of VEGF gene expression.

Inverted CCAAT box-binding protein of 90 kDa (ICBP90) is over-expressed in several types of cancer, including breast, prostate and lung cancers. In search for proteins that interact with the set and ring-associated (SRA) domain of ICBP90, we used the two-hybrid system and screened a placental cDNA library. Several clones coding for a new domain of DNMT1 were found. The interaction, between the ICBP90 SRA domain and the DNMT1 domain, has been confirmed with purified proteins by glutathione-S-transferase pull-down experiments. We checked whether ICBP90 and DNMT1 are present in the same macro-molecular complexes in Jurkat cells and immortalized human vascular smooth muscle cells (HVTs-SM1). Co-immunoprecipitation experiments showed that ICBP90 and DNMT1 are present in the same molecular complex, which was further confirmed by co-localization experiments as assessed by immunocytochemistry. Downregulation of ICBP90 and DNMT1 decreased VEGF gene expression, a major pro-angiogenic factor, whereas those of p16(INK4A) gene and RB1 gene were significantly enhanced. Together, these results indicate that DNMT1 and ICBP90 are involved in VEGF gene expression, possibly via an interaction of the SRA domain of ICBP90 with a novel domain of DNMT1 and an upregulation of p16(INK4A). They further suggest a new role of ICBP90 in the relationship between histone ubiquitination and DNA methylation in the context of tumoral angiogenesis and tumour suppressor genes silencing.

Allele-specific binding to the -308 single nucleotide polymorphism site in the tumour necrosis factor-alpha promoter.

Single nucleotide polymorphisms in the tumour necrosis factor alpha (TNF-alpha) promoter region may modulate TNF-alpha gene transcriptional activity by modifying the binding of transcription factors. Here we confirm that a specific DNA complex binds preferentially the variant TNF2 allele in various cell types and demonstrate that activating protein (AP)-2, myeloid zinc finger gene 1 (MZF-1) and Sp1 are not involved in this complex.

Higher LPS-stimulated TNF-alpha mRNA levels in peripheral blood mononuclear cells from non-Hodgkin's lymphoma patients.

OBJECTIVE: The aim of the present study was to investigate the capacity of normal immune blood cells from non-Hodgkin's lymphoma patients to produce tumor necrosis factor (TNF) after lipopolysaccharide (LPS) stimulation and the influence of the TNF (-308) polymorphism in this production. MATERIALS AND METHODS: A whole peripheral blood cell assay was utilized following LPS stimulation. At selected incubation times, supernatants were harvested for protein dosage, while mRNA was extracted and reverse-transcribed. The amount of TNF mRNA was quantified using real-time quantitative polymerase chain reaction (PCR) and genomic DNA was typed for TNF (-308) polymorphism. RESULTS: Upon LPS stimulation, TNF-secreted protein was slightly but not significantly increased in lymphoma patients when compared to controls. In contrast, the relative TNF mRNA amounts were significantly higher in lymphoma patients at 30 minutes (median 27.75 vs. 16.00; Mann-Whitney U-test p < 0.05), at 4 hours (52.00 vs. 31.00; p < 0.05), and at 24 hours (19.50 vs. 9.00; p < 0.05). In addition, patients carrying the variant TNF2 allele had higher relative TNF mRNA levels than TNF1 homozygotes (p = 0.02). CONCLUSION: The LPS-induced TNF mRNA levels are higher in peripheral blood cells (PBC) from lymphoma patients than from controls, while TNF protein secretion is not strikingly different. Altered regulation of TNF mRNA translation or TNF protein secretion may contribute to these observations. Taken together, an increased susceptibility for TNF gene transcription after LPS stimulation was observed in PBC (mainly in monocytes) from lymphoma patients, and especially those carrying the TNF2 allele.

Expression of genes coding for the tumor necrosis factor and lymphotoxin ligand-receptor system in non-Hodgkin's lymphomas.

Excessive production of the tumor necrosis factor (TNF) ligand-receptor system has been found to contribute to the severity of non-Hodgkin's lymphoma (NHL). We therefore investigated the expression of TNF, lymphotoxin alpha (LTalpha), lymphotoxin beta (LTbeta), and their receptor (p55, p75, LTbeta-R) transcripts within the tumor tissue in different NHL histological subtypes. The constitutive expression of genes coding for TNF-related ligands and receptors was found in almost all 31 NHL samples studied. Semi-quantitative reverse transcription/polymerase chain reaction and computed densitometry assays revealed that the amounts of TNF, LTalpha, p55, and LTbeta-R mRNA were higher in follicular NHL than in other histological entities. Therefore tumor cell immunopurification was performed in representative follicular NHL samples and consistent results were obtained. The pattern of LTbeta gene expression was different from that of the other molecules, indicating the existence of distinct mechanisms of gene regulation. These results indicate that the transcription of genes coding for the TNF ligand-receptor system in NHL tumor tissue is more widespread than originally thought and that the heterogeneity of their expressions might be related to histological features. The expression of TNF-related ligands and receptors in tumor tissues is likely to contribute to the clinicopathological features of lymphoid-derived malignancies.

Modulation of costimulatory molecules on follicular lymphoma cells by TNF and CD40.

TNF has recently been implicated in the formation of germinal center cells in lymphoid organs. Follicular lymphoma (FL) is thought to represent the pathological counterpart of germinal center B-cell. High levels of TNF and its soluble receptors were found in the plasma of FL patients whereas the transcripts of these molecules were previously found to be present in FL patients lymph nodes. We therefore studied here the effects of TNF on the expression of costimulatory molecules implicated in the cytotoxic T cell response on purified FL cells. In contrast to results described with B-type chronic lymphocytic leukemia, also characterized by high levels of circulating TNF, none of the tested samples showed a regulation of CD80, CD86, CD27 and CD70 in response to TNF. To confirm that the lack of regulation of these molecules was not due to the FL cells inability to modulate their expression, we therefore analyzed costimulatory molecules expression after CD40 pathway stimulation. After culture with human CD40L-transfected L-cells, an up-regulation of CD80, CD86 and CD70 expression was observed, while TNF addition in this model did not influence these changes. In this context, the CD27 molecule was down-regulated except in a single case, where its expression was increased. Taken together, this data demonstrates that in vitro expression of costimulatory molecules such as CD80, CD86, CD27 and CD70, which are implicated in the anti-tumoral response, can be regulated by CD40 ligand but not by TNF.

CD40 regulation of death domains containing receptors and their ligands on lymphoma B cells.

Within the tumour necrosis factor (TNF) family the induction of apoptosis is restricted to some ligand-receptors pairs, including TNF-TNF receptor type I (TNFRI/p55), FasL-Fas, TNF-related apoptosis-inducing ligand (TRAIL) and its death-receptors (DR)-4 and -5. The pair CD40L-CD40 belongs to the same family but rescues B cells from apoptosis. To investigate how these opposing actions are cross-linked, purified follicular lymphoma (FL) cells were activated upon a human CD40L-transfected murine fibroblastic layer, then RNA messengers for the above molecules were analysed using RT-PCR. The observed down-modulation of TRAIL and up-regulation of TNF and Fas transcripts might account for CD40-CD40L-mediated FL cell survival.

Genetic polymorphisms in the tumor necrosis factor locus influence non-Hodgkin's lymphoma outcome.

Systemic release of tumor necrosis factor (TNF) and lymphotoxin-alpha (LTalpha) has been found to contribute to the severity of non-Hodgkin's lymphoma (NHL). We investigated whether genetic polymorphisms in the TNF locus, previously shown to influence TNF and LTalpha genes expression, might contribute to these cytokines production and to the clinical course of NHL. Genomic DNA from 273 lymphoma patients was typed for TNF (-308) polymorphism using an allele-specific polymerase chain reaction (PCR) and for LTalpha (+252) polymorphism with a PCR-based restriction fragment length polymorphism. The presence of the TNF allele involved in increased TNF gene transcription was associated with higher plasma levels of this cytokine at the time of lymphoma diagnosis (chi2 test, P = .013). An extended haplotype analysis showed that the presence of at least two TNF or LTalpha high-producer alleles constituted a risk factor for first-line treatment failure (chi2 test, P = .021), shorter progression-free survival (log-rank test, P = .0007), and overall survival (log-rank test, P = .012). In the subgroup of 126 patients with diffuse large-cell lymphoma, the presence of two or more TNF/LTalpha high producing alleles contributed significantly to a higher rate of relapse and progression (log-rank test, P = .045 and P = .027). In multivariate Cox regression models including the variables of the International Prognostic Index, the TNF/LTalpha haplotype status was found to be an independent risk factor for progression-free survival (relative risk 2.33, 95% confidence interval [1.17 to 4.64], P = . 0053) and overall survival (relative risk 1.92, 95% confidence interval [0.63 to 5.80], P = .081) of large-cell lymphoma patients. These results indicate that genetic polymorphism leading to increased TNF production influences the outcome of NHL and suggest a pathophysiological role for the genetic control of the immune response in lymphoid malignancies.

A new death receptor 3 isoform: expression in human lymphoid cell lines and non-Hodgkin's lymphomas.

Two isoforms encoding the full-length transmembrane death receptor 3 (DR3) were isolated from mRNAs of a panel of human cell lines and tumor tissues obtained from patients with follicular non-Hodgkin's lymphoma. A new DR3 variant (DR3 beta) was characterized by 2 insertions of respectively 20- and 7-base pairs (bp) which result in a predictive translated polypeptide differing from the described DR3 molecule by a 28 amino-acid stretch in the extracellular domain. DR3 was shown to be expressed in all cell lines and lymphoma samples tested, whereas DR3 beta expression was restricted to lymphoid T-cell and immature B-cell lines and to selected cases with follicular lymphoma. These data provide new insight into the molecular heterogeneity of DR3, suggesting the presence of several receptor isoforms that can participate in lymphoid cell homeostasis.

Identification of two lymphotoxin beta isoforms expressed in human lymphoid cell lines and non-Hodgkin's lymphomas.

Two isoforms of lymphotoxin beta (LTbeta) were isolated from mRNAs of a panel of human lymphoid cell lines and tumor tissues obtained from patients with non-Hodgkin's lymphoma (NHL). The truncated LTbeta mRNA variant lacked 46 base pairs complementary to the complete sequence of exon 2, suggesting that both isoforms are produced by an alternative splicing mechanism. Skipping out of exon 2 causes a reading frame shift and a premature stop codon in the LTbeta mRNA variant. The predictive translated polypeptide would correspond to a severely shortened LTbeta protein that would lack the majority of the extracellular domain of the native molecule, thus impairing its normal complex assembly with LTalpha. These observations provide new insights into the molecular heterogeneity and biological function of LTbeta within the tumor necrosis factor and LT ligand-receptor system.

Contribution of 4-methylthio-2-oxobutanoate and its transaminase to the growth of methionine-dependent cells in culture. Effect of transaminase inhibitors.

The growth in culture of methionine-dependent transformed cells of human, rat and mouse origin was arrested in the absence of L-methionine (Met) but took place in the presence of 4-methylthio-2-oxobutanoic acid (MTOB), the keto acid of Met. From 24 hr after seeding, cells grew in 0.1 mM MTOB medium at a rate comparable to that in 0.1 mM Met medium. Using [35S]MTOB, it was found that the Met synthesized was used in normal MRC-5 cells and in transformed HeLa cells to the same extent for protein, adenosylmethionine and adenosylhomocysteine syntheses. However, when the free Met content was examined, it was found to be 3-fold greater in HeLa than in MRC-5 cells. To examine the importance of this free Met for the growth of transformed cells, the transaminase responsible for converting MTOB to Met was chosen as a target enzyme for the synthesis of compounds with potential inhibitory activity. Since this is a multisubstrate enzyme, reduced Schiff bases were prepared containing both pyridoxal or other aromatic groups, as one constituent, and L-Met or other amino-acids in the free acid or ester or amide form, as the other constituent. Only esters containing the pyridoxal moiety and Met or certain of its structural analogues exhibited good selective growth inhibitory activity in that there was little (20%) or no effect on the growth of normal MRC-5 and derm cells, respectively, while that of transformed HeLa, HEp-2 and L1210 cells was strongly inhibited (80%). This inhibition was accompanied by a concomitant decrease in the activity of the MTOB transaminase in both HeLa and MRC-5 cells treated with 3c the most potent inhibitor. However, using [35S]MTOB it was found that MTOB itself accumulated 48% in HeLa but only 12% in MRC-5 cells treated with 3c. On the contrary [35S]Met formed from [35S]MTOB increased 3.7-fold in MRC-5 inhibitor-treated cells showing 20% growth inhibition whereas it decreased 38% in HeLa-treated cells showing 80% growth inhibition. This decrease in cellular Met in HeLa is not responsible for growth arrest. Indeed the growth of HeLa cells could not be restored by adding a 10-fold excess of Met. Since MTOB can alleviate Met-dependence, the intracellular homeostasis of this metabolite may play a hitherto unsuspected role in controlling cell growth.

Differential expression of isopeptide bonds N epsilon (gamma-glutamyl) lysine in benign and malignant human breast lesions: an immunohistochemical study.

N epsilon (gamma-glutamyl) lysine isopeptide bonds were detected in situ in histological sections from benign and malignant human breast tissue using the monoclonal antibody (MAb) 81D1c2. On cryostat sections of fresh-frozen mammary tissue post-fixed in acetone, or on paraffin sections also from mammary tissue fixed in Bouin's solution, the MAb reacted preferentially with glandular epithelial cells and staining was restricted to the nuclei. In 41 out of 44 benign lesions examined, staining was strong or moderate, while in 25 out of 33 malignant lesions no staining was observed. In the 8 remaining lesions of this group, staining was positive but weak. The difference in reactivity of this MAb with the 2 types of lesions is highly significant (p less than 0.0005) according to the chi 2 test.