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J Fernández-Piqueras

Publications and source records attributed to J Fernández-Piqueras.

At least 19 recordsLinked to original sources
PubMed2006

Functional Fas (Cd95/Apo-1) promoter polymorphisms in inbred mouse strains exhibiting different susceptibility to gamma-radiation-induced thymic lymphoma.

The Fas death receptor is a cell surface molecule involved in apoptosis as well as in proliferative or activating signals of many cells types, including T lymphocytes. Using quantitative real-time reverse transcription-PCR analysis, we confirm that expression of this gene is scarcely perceptible in thymic lymphomas induced by gamma-irradiation in C57BL/6J mice. Notably, we also demonstrate for the first time that Fas expression is significantly upregulated in vivo both after single high dose of radiation and in thymic lymphoma-free mice. In addition, we determined its levels of expression in five mouse strains exhibiting different degrees of susceptibility (SPRET/Ei, SEG/Pas, BALB/cJ, C57BL/6J and RF/J). Interestingly, we found the highest levels of expression in SPRET/Ei and SEG/Pas strains (both derived from the Mus spretus species), which are known to have the most resistant phenotype, and the lowest levels in the most susceptible strains C57BL/6J and RF/J. DNA sequencing of the Fas promoter in all five strains showed many polymorphisms that can be classified into three functional haplotypes by using luciferase assays: (1) C57BL/6J and RF/J, (2) BALB/cJ and (3) SPRET/Ei and SEG/Pas. Promoter activities in response to single high doses of radiation correlated well with the levels of Fas expression and are consistent with the degree of strain susceptibility.

Animals↗
PubMed2006

Tumorigenic activity of p21Waf1/Cip1 in thymic lymphoma.

The cell cycle inhibitor p21Waf1/Cip1 is among the most important mediators of the tumor suppressor p53. However, there is increasing evidence indicating that p21 could favor tumorigenesis in specific cell types. In particular, the absence of p21 delays the development of thymic lymphomas induced either by ataxia-telangiectasia mutated deficiency or by ionizing irradiation. Here, we extend these observations to the context of p53-deficient mice. The absence of p21 results in a significant extension of the lifespan of p53-null and p53-haploinsufficient mice, and this effect can be attributed exclusively to a decrease in the incidence of spontaneous thymic lymphomas. Specifically, despite the occurrence of a variety of tumor types in the context of p53 deficiency, the only tumors that were significantly impaired by the absence of p21 were thymic lymphomas. Moreover, the absence of p21 also delays the incidence of radiation-induced thymic lymphomas in p53-deficient mice. Interestingly, p21-deficient lymphomas have a higher apoptotic rate than p21-proficient lymphomas, and this could be on the basis of the delayed incidence of thymic lymphomas in the absence of p21. Together, our results indicate that p21 plays an oncogenic role restricted to thymic lymphomas that is mechanistically independent of p53 and associated to a lower tumor apoptotic rate.

Animals↗
PubMed2006

Lack of correlation between DNA copy number and mRNA expression levels of c-myc in gamma-radiation-induced mouse thymic lymphomas by using quantitative real-time PCR.

BACKGROUND: It is well documented that over-expression of the c-myc proto-oncogene occurs in the vast majority of mouse thymic lymphomas induced by gamma-irradiation, evidencing the importance of this gene in T-cell lymphomagenesis. However, it remains unknown whether elevated levels of c-myc expression are driven by extra c-myc copy numbers. MATERIALS AND METHODS: Here we use a quantitative test on the basis of real-time PCR to determine the cellular copy number of c-myc in a set of 14 g-radiation- induced thymic lymphomas obtained from (C57BL/6J x BALB/cJ) F1 hybrid mice with increased mRNA c-myc expression. RESULTS: Since 5 out of 14 (35.7%) cases had no extra copy numbers of c-myc, gene amplification was obviously not the cause of c-myc over-expression in these tumours. In the remaining 9 tumours, c-myc over-expression was also accompanied with extra DNA copy numbers. Therefore, c-myc amplification might be a consequence of the genomic instability subsequent to the up-regulation of c-myc. However, linear regression analysis showed a lack of correlation between increasing DNA copy numbers and mRNA over expression of c-myc in these tumours (r = 0.029, p = 0.94). CONCLUSION: De-regulation of c-myc does not necessarily imply amplification of this gene in these tumours. This report is, to our knowledge, the first one comparing c-myc amplification with expression in lymphomas of the T-cell lineage.

Animals↗
PubMed2005

Epigenetic silencing of E- and N-cadherins in the stroma of mouse thymic lymphomas.

Aberrant expression of some tumour suppressor genes and oncogenes by thymocytes had been involved in the development of primary thymic lymphomas induced by gamma-irradiation, but genetic alterations affecting critical genes expressed by stromal cells have not been yet explored. This paper analyzes a series of such tumours induced in C57BL/6J and in F1 hybrids of BALB/c and C57BL/6J mouse strains. As expected, hystopathological analyses revealed profound disorganizations within the thymus with a poor demarcation of the cortical and medullar areas. Immunological and quantitative on-line RT-PCR analyses confirm that E-cadherin (Cdh1) is essentially expressed by stromal cells of the thymus, while evidencing that the expression of this gene is significantly reduced in all tumours. In addition, and contrary to what one would expect, N-cadherin (Cdh2) that is exclusively expressed by stromal cells is likewise down-regulated in most of the thymic lymphomas. Although hypermethylation of the promoter region appears to be involved in the inactivation of Cdh2 in all tumours, additional epigenetic mechanisms mediated by repressors such as Snai1 may also play a role in Cdh1 silencing. These results represent the first reported case for tumour-associated gene alterations occurring not in the tumour cells per se, but in the stromal cells of primary thymic lymphomas. Additionally, since the expression of both genes is significantly up-regulated after a single high dose of gamma-radiation, but remained unchanged in treated thymic-lymphoma-free-mice, epigenetic down-regulation of E- and N-cadherin appears to occur concomitantly with the progression towards the most advanced stages of gamma-radiation-induced thymic lymphomas.

Animals↗
PubMed2004

Defective expression of Notch1 and Notch2 in connection to alterations of c-Myc and Ikaros in gamma-radiation-induced mouse thymic lymphomas.

Gamma-radiation-induced thymic lymphomas constitute a heterogeneous group of T-cell lymphomas. Some tumour suppressor genes and oncogenes have been shown to be defective in a fraction of such lymphomas, yet a considerable number of these remain elusive in terms of gene alterations. In the present work we present evidence that gamma-radiation-induced thymic lymphomas in (C57BL/6 J x BALB/c) F1 hybrid mice often exhibit increased levels of Notch1 expression, but, contrary to what was expected, they also exhibit a clearly reduced Notch2 mRNA expression, suggesting a cooperative antagonism of these genes. These results represent the first reported instance for the involvement of Notch2 inactivation in the development of thymic primary tumours while confirming the role of Notch1 as an activated oncogene. Additional analyses revealed that c-Myc over-expression and partial inactivation of Znfn1a1/Ikaros appear to be relevant events some how coupled to alterations in Notch genes inducing these kinds of tumours.

Animals↗
PubMed2001

Evidence of a possible epigenetic inactivation mechanism operating on a region of mouse chromosome 19 in gamma-radiation-induced thymic lymphomas.

Loss of heterozygosity (LOH) analysis, performed in 68 gamma-radiation-induced primary thymic lymphomas of F1 hybrid mice, provided evidence of significant LOH on chromosome 19 in a region defined by the D19Mit106 (22 cM) and D19Mit100 (27 cM) markers (Thymic Lymphoma Suppressor Region 8, TLSR8). Cd95 and Pten, two genes mapped at this region, were inactivated in a vast majority of these tumors (85.3% for Cd95 and 61.8% for Pten). Moreover, altered expression of Cd95 and Pten occurred concomitantly in 34 of 68 (50%) thymic lymphomas suggesting a coordinated mechanism of inactivation of these genes. Surprisingly, we also found that Jak2, a proto-oncogene located between Cd95 and Pten, was simultaneously inactivated in a significant fraction of the tumors analysed (24 of 34, 70.6%). Taken together these findings and the lack of mutations in the coding sequences of the mentioned genes clearly suggest a possible regional epigenetic inactivation mechanism on mouse chromosome 19 operating during the development of these tumors.

Animals↗
PubMed2001

Psychiatric comorbidity in pathological gamblers seeking treatment.

OBJECTIVE: The authors' goal was to determine the frequency of psychiatric comorbidity among treatment-seeking pathological gamblers, compare the severity of gambling and psychological problems in gamblers with and without comorbid disorders, and investigate differences between gamblers with and without comorbid disorders in the dopamine D(2) receptor gene (DRD(2)). METHOD: Sixty-nine pathological gamblers who consecutively applied to a specialized outpatient treatment program were evaluated with structured interviews, self-report questionnaires, and psychological scales and were genotyped for a DRD(2) polymorphism. RESULTS: A comorbid psychiatric disorder was present in 43 (62.3%) of the gamblers. The most frequent diagnoses were personality disorders (N=29 [42.0%]), alcohol abuse or dependence (N=23 [33.3%]), and adjustment disorders (N=12 [17.4%]). Gamblers with comorbid psychiatric disorders had gambling scores and psychological scale scores indicating greater severity of gambling and psychopathology. Significant differences in DRD(2) allele distribution were found in gamblers with and without comorbid disorders. CONCLUSIONS: Psychiatric comorbidity is common among pathological gamblers and is associated with greater severity of clinical problems. The DRD(2) gene could be a liability genetic factor for psychiatric comorbidity in pathological gambling.

Comorbidity↗
PubMed2000

Characterization of the murine p19(ARF) promoter CpG island and its methylation pattern in primary lymphomas.

The INK4a/ARF locus encodes two different proteins involved in cell cycle control. Both molecules, p16(INK4a) and p19(ARF), inhibit cell cycle progression and have been shown to act as tumor suppressors in a variety of models. Their expression is controlled by separate promoters responding to different stimuli and they therefore show independent transcriptional regulation. We have cloned and characterized a 2.5 kb region upstream of the murine p19(ARF) gene to determine the role of DNA methylation in suppressing p19(ARF) transcription in a wide panel of murine primary T cell lymphomas. This region contains a DNA fragment with the characteristics of a CpG island similar to those described for the murine p16(INK4a) and p15(INK4b) genes. Expression of p19(ARF) is decreased in a significant number (20%) of the murine lymphomas analyzed. Overexpression of the p19(ARF) transcript is also frequent, suggesting alterations in molecules of the retinoblastoma or p53 pathways that are involved in p19(ARF) regulation. Although hypermethylation of the INK4a and INK4b promoters is frequently involved in murine lymphomas, the p19(ARF) CpG island is infrequently methylated in the murine primary lymphomas studied in this work. Since loss of p19(ARF) expression cannot be explained as the result of homozygous deletions or hypermethylation of the ARF gene, other regulatory mechanisms seem to be altered in these malignancies.

Animals↗
PubMed1999

Loss of heterozygosity at the proximal-mid part of mouse chromosome 4 defines two novel tumor suppressor gene loci in T-cell lymphomas.

Recent studies in our laboratory reported frequent loss of heterozygosity (LOH) on mouse chromosome 4 in T-cell lymphomas, identifying three candidate tumor suppressor regions (TLSR1-3). To determine the possible existence of other tumor suppressor gene loci on the proximal-mid part of chromosome 4 and to clarify whether the p16(INK4a) (alpha and beta) and p15(INK4b) genes are the inactivation targets of deletion at TLSR1, we have tested 73 gamma-radiation-induced T-cell lymphomas of F1 hybrid mice by LOH analysis. Frequent LOH was found at the INK4a and INK4b loci and the surrounding markers D4Mit77, D4Mit245 and D4Wsm1. In addition, we identified two distinct regions of significant allelic losses in the proximal-mid part of chromosome 4, defined by the markers D4Mit116 (TLSR4) and D4Mit21 (TLSR5). Taken together, this evidence and our previous data indicate the existence of at least five different candidate sites for tumor suppressor genes on chromosome 4, thus revealing a main role for this chromosome in the development of mouse T-cell lymphomas.

Alleles↗
PubMed1999

Mouse p73 gene maps to the distal part of chromosome 4 and might be involved in the progression of gamma-radiation-induced T-cell lymphomas.

We have isolated and sequenced a DNA fragment of about 12 kb that comprises exons 5-14 of the mouse p73 gene. We have identified four polymorphic markers, and one of them has been used to genetically map p73 to the distal part of chromosome 4. Previously, we have reported that gamma-radiation-induced T-cell lymphomas undergo frequent loss of heterozygosity around marker D4Mit205b at the distal part of chromosome 4. Based on this, we have performed loss of heterozygosity analysis in a set of T-cell lymphomas, and we have found allelic losses of p73 in 32.6% (16 of 49) of the tumors analyzed. Interestingly, allelic losses occur concurrently at both p73 and D4Mit205b, thus suggesting that p73 could be specifically inactivated in radiation-induced T-cell lymphomas.

Alleles↗
PubMed1999

Analysis of the INK4a/ARF locus in non-Hodgkin's lymphomas using two new internal microsatellite markers.

Inactivation of the INK4a/ARF locus is a frequent event in non-Hodgkin's lymphomas (NHLs), which may be attributed to deletion, point mutation, and 5' CpG methylation at its promoter region. In the present study we evaluated the occurrence of deletions and genetic instability of INK4a/ARF locus in 30 paired normal and tumor samples of B cell NHLs by conducting an allelotypic analysis with two new polymorphic markers, one located at the intron 1 of p16INK4a gene and the other one placed downstream exon 1beta of p19ARF. Comparison of these results with those obtained in a previous paper using flanking markers (D9S171, D9S942, D9S958 and IFNA) allowed us to detect two new cases of microsatellite instability (L-446 and L-442), and to confirm the occurrence of LOH at the INK4a/ARF locus in one tumor (M-3770). On the contrary, this locus is not affected in three different tumors (L-421, L-272 and L-159) which exhibited LOH at some of the flanking markers.

Chromosome Mapping↗
PubMed1999

Cooperative alterations of Rb pathway regulators in mouse primary T cell lymphomas.

Alterations in the Rb pathway have been described in many different tumors. In order to study this cell cycle regulatory mechanism in murine T cell lymphomas, we have analyzed the RNA and protein expression of the cyclin D1, cdk4 and retinoblastoma genes in primary tumor samples. We have detected overexpression of the cyclin D1 gene and deficient expression of the retinoblastoma gene in 42 and 28% of these tumors, respectively. The immunohistochemical analysis showed that these RT-PCR results are correlated with a significant increase in the number of positive cells for cyclin D1 and a moderate decrease in the expression of Rb protein, respectively. The analysis of cyclin D1, Rb, p15(INK4b) and p16(INK4a) showed that 75% of lymphomas had alterations in these genes and indicates that the Rb pathway is frequently altered in mouse primary T cell lymphomas. Moreover, 31% of lymphomas presented simultaneous alterations in at least two of these genes, suggesting the importance of concurrent alteration of different Rb pathway regulators. In addition, we have characterized these samples for mutational status of the N-ras and K-ras genes. We have only detected mutations in codon 12 of K-ras in six of 49 lymphomas (12%). Interestingly, five of these lymphomas also showed alterations in at least one of the Rb pathway regulators analyzed here. Taken together, these data suggest that deregulation of the Rb pathway regulators and/or oncogenic activation of K-ras may represent a common important clue in progression of murine T cell lymphomas.

Animals↗
PubMed1998

A new candidate site for a tumor suppressor gene involved in mouse thymic lymphomagenesis is located on the distal part of chromosome 4.

In a previous work we provided preliminary evidence of the existence of a putative tumor suppressor gene region on the distal part of chromosome 4 in gamma-radiation-induced T-cell lymphomas of (C57BL/6J x RF/J) F1 hybrid mice. This region, named as TLSR2 (Thymic Lymphoma Suppressor Region 2), was located centered at D4Mit54. A more detailed allelotype analysis in the mentioned tumors with new informative microsatellites on distal chromosome 4 region, as well as in thymic lymphomas induced with gamma-rays in F1 hybrids generated from reciprocal crosses between the strains C57BL/6J and BALB/cJ, and having in mind the new map position of D4Mit205b, allowed us to confirm the existence of TLSR2 and to define it more precisely as centered at D4Mit205b. In addition, we identified a new candidate region, named as TLSR3 (Thymic Lymphoma Suppressor Region 3), located between the Mom-1 locus and D4Mit68, as the site of another putative tumor suppressor region involved in thymic lymphomagenesis.

Animals↗
PubMed1998

An AC-repeat adjacent to mouse Cdkn2B allows the detection of specific allelic losses in the p15INK4b and p16INK4a tumor suppressor genes.

The cyclin-dependent kinase inhibitors p15INK4b and p16INK4a are involved in the development of a wide range of human and murine tumors. These tumor suppressor genes are inactivated by deletions frequently associated to point mutations in the coding regions or hypermethylation of their promoters. In this work, we describe a simple-sequence length polymorphism located in mouse Chromosome (Chr) 4, between the Cdkn2B (p15INK4b) and Cdkn2A (p16INK4a) genes, only 700 bp downstream of the Cdkn2B locus. This DNA region was analyzed in different inbred strains showing a variable AC-repetitive DNA sequence. We used this microsatellite to detect loss of heterozygosity of the Cdkn2A and Cdkn2B loci in gamma-irradiation-induced thymic lymphomas of C57BL/6J x RF/J F1 hybrids. Using this specific marker, we were able to locate additional allelic losses not detected by other microsatellites. Since the allelic losses can be detected by a simple PCR amplification, this AC-repetitive sequence is specially useful as a genetic marker for these Cdkn2 genes and specifically for the p15INK4b cell cycle inhibitor.

Alleles↗
PubMed1997

Frequent allelic losses of 9p21 markers and low incidence of mutations at p16(CDKN2) gene in non-Hodgkin lymphomas of B-cell lineage.

We present an allelotype analysis of 35 cases of non-Hodgkin lymphomas and normal pairs using four microsatellite markers that flank the region occupied by the CDKN2 gene locus at 9p21. Frequent allelic losses (LOH) were detected in B-cell lineage NHLs, including Burkitt lymphoma (33.3% of total, if we only consider high grade tumors). In five of these tumors LOH did not include the CDKN2 gene. Mutational analysis of exon 1 and 2 of CDKN2 (SSGP and sequencing of abnormal bands) revealed a nonsense mutation (Arg72Ter) in one tumor (case 10), where the second hit of the Knudson's model consisted of the elimination of the wild type allele. In view of these results, the hypothesis of two different candidate tumor suppressor gene regions around the CDKN2 locus remains an intriguing possibility.

Alleles↗