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R Piva

Publications and source records attributed to R Piva.

At least 73 records · Page 4Linked to original sources
PubMed1991

Transgenic mice mimic the methylation pattern of the human HLA-DR alpha gene.

The methylation pattern of the human HLA-DR alpha gene has been studied in different tissues of transgenic mice. Offspring from two transgenic lines was selected for this analysis, carrying the integrated HLA-DR alpha gene in either single or multiple (8-10) copies per diploid genome. In transgenic animals two distinct methylation patterns of the HLA-DR alpha gene are generated, due to a complete methylation of all the GCGC and CCGG sites the former, and to unmethylation restricted to one or both the GCGC sites located in the 5' portion of the HLA-DR alpha gene, the latter. Unmethylation restricted to the 5' portion of the HLA-DR alpha gene is a highly conserved feature in human tissues and in vitro cultured cell lines; therefore, it is concluded that the methylation pattern of the human HLA-DR alpha transgene may be faithfully reconstituted in transgenic animals. Northern blotting analysis of the RNA isolated from tissues of the transgenic mouse carrying single-copy HLA-DR alpha transgene demonstrates its tissue specific expression, suggesting that transgenic mice may represent an "in vivo" experimental system to study the relationship between methylation state and transcriptional activation.

Animals↗
PubMed1991

Somatostatin reduces 3H-thymidine incorporation and c-myc, but not thyroglobulin ribonucleic acid levels in human thyroid follicular cells in vitro.

The action of somatostatin (SRIH) on 3H-thymidine (thy) incorporation and on c-myc and thyroglobulin RNA levels in a suspension of follicles from normal and goitrous human thyroid was examined. SRIH, at 10(-7) M concentration, inhibited basal thy incorporation (maximally by 4 h lasting for up 24 h), which effect was greater in goiter than in normal thyroid and was also detected in growing adherent epithelial cells. Moreover, in a follicle suspension SRIH prevented TSH-stimulated thy incorporation, both in normal and in goitrous thyroid. Basal expression of c-myc RNA was not affected by SRIH in either tissue, whereas the TSH-stimulated c-myc RNA level was significantly reduced in goiter. No effect of SRIH was observed on basal or TSH-stimulated thyroglobulin RNA levels. SRIH did not alter basal cAMP concentrations in normal or goitrous follicles, but it significantly reduced TSH-stimulated cAMP accumulation both in normal thyroid and in goiter. Overall, our data indicate a direct inhibitory action of SRIH on growth, but not on differentiation, of human thyroid, probably by a mechanism not entirely cAMP dependent.

Cells, Cultured↗
PubMed1991

A c-myc gene variant without exon 1 and with an abnormal methylation pattern inherited in a woman with no evidence of malignancy.

A c-myc DNA with a deletion which includes 5' flanking, exon 1 and intron I sequences has been found in normal white blood cells of a mother and one daughter in a Northern Italian family. In addition, the degree of methylation of specific CCGG sites in the truncated DNA is lower in both mother and daughter than that found in normal DNA. It is of interest that deletions of the first exon and hypomethylation of the c-myc gene have usually been observed only in some neoplasias. However, our results demonstrate that the c-myc truncated DNA with the abnormal methylation pattern here reported is a genomic variant which by itself is not related to neoplastic transformation.

Chromosome Deletion↗
PubMed1990

Different methylation of oestrogen receptor DNA in human breast carcinomas with and without oestrogen receptor.

The methylation of the human oestrogen receptor (ER) gene was analysed by restriction enzymes in normal and neoplastic human breast tissues and cell lines. CCGG sequences in regions inside the gene, which are methylated both in normal breast and in tissues that are not the target of the oestrogen, are hypomethylated in 30% of tumours, both ER+ and ER- carcinomas. Moreover, 5' sequences of the gene, which are hypomethylated in normal breast and not in tissues not the target of oestrogen, are methylated to a lower degree in ER+ carcinomas, whereas they are methylated to a greater degree in ER- carcinomas. However, the same region is equally hypomethylated in both ER+ and ER- cancer cell lines. Our results indicate that in breast carcinomas ER DNA methylation is deranged, and in cancer cell lines is different from that observed in primary tumours. Furthermore, the abnormal methylation in the 5' end seems to be related to abnormal expression, namely diffuse hypomethylation in carcinomas with high ER content and hypermethylation in carcinomas without ER. These findings support our previous hypothesis that DNA methylation could be involved in the control of ER gene expression and demonstrate that abnormal ER gene methylation is a typical feature of breast cancers.

Adenofibroma↗
PubMed1990

[Effects of somatostatin on human thyroid folliculi in vitro].

Somatostatin (SRIF) inhibits calcitonin and T3-T4 secretion in thyroid. We have investigated the in vitro effect of SRIF on the basal and TSH induced [3H]thy incorporation, thyroglobulin (tgb) RNA and cAMP level in follicular cells, isolated from normal and adenomatous human thyroids. [3H]thy uptake has been evaluated as TCA-precipitable material in 2, 4, 8, 24 h incubated follicles and 24 h incubated adherent cells. Tgb RNA has been quantified with cytoplasmic dot blot hybridization and cAMP level with RIA method. SRIF reduces basal and TSH-induced [3H]thy in both suspension follicles and epithelial adherent cells. However it does not modify tgb RNA nor cAMP levels in incubated follicles. These data suggest a direct antiproliferative effect of SRIF on human thyroid.

Humans↗
PubMed1989

Methylation state of cellular genes and oncogenes as a marker of malignancy in human carcinomas.

The methylation pattern of the human HLA-DR alpha gene was analyzed in primary tumors and lymph node metastases isolated from patients with a variety of tumors, including thyroid, pancreas, breast and gastric carcinomas and melanomas. In normal tissues (including breast, muscle, brain, sperm, T-and B-lymphocytes) the HLA-DR alpha gene is hypermethylated at CCGG and GCGC sites. In all tissues studied, the only constantly unmethylated region was located in the 5' portion of the gene. Our results indicate that the HLA-DR alpha gene is hypomethylated in metastatic lymph nodes, as well as in the carcinomas and melanomas studied. These findings lend support to the hypothesis that DNA hypomethylation of the human HLA-DR alpha gene may represent a molecular marker of malignant tumors.

DNA↗
PubMed1989

Abnormal methylation of estrogen receptor gene and reduced estrogen receptor RNA levels in human endometrial carcinomas.

Demethylation of specific sites or restricted genomic regions has been reported to correlate with gene activation and also with carcinogenesis. As abnormal expression of Estrogen Receptor (ER) could be involved in the genesis or progression of tumors in estrogen target tissues, the methylation of ER gene has been compared in 8 endometrial carcinomas and 29 normal endometria. In order to look for a correlation between methylation and expression, levels of ER RNA were also measured. While the 5' region of ER gene was found to be demethylated in both normal and carcinomatous tissues, there was demethylation of some specific sites in the internal part of the gene only in the carcinomas examined. In addition, in the carcinomatous tissues the levels of ER RNA were low, indicating that an increase of ER gene hypomethylation does not raise, and even may reduce, the ER expression in endometrium. The abnormal undermethylation observed in ER gene appears to be unrelated to general DNA hypomethylation which is frequently present in neoplastic tissues; nor has it been found in ER DNA isolated from breast carcinomas. These data strongly support the hypothesis that such a methylation is specifically related to endometrial transformation and therefore it can be considered an additional marker of this disease.

Blotting, Southern↗
PubMed1989

In vitro effects of estrogen on tgb and c-myc gene expression in normal and neoplastic human thyroids.

The authors investigated the effects of 17 beta-estradiol (E) and thyroid-stimulating hormone (TSH) on tgb (coding for thyroglobulin), c-myc RNA levels, and [3H]thymidine (thy) incorporation in suspension cultures of normal, adenomatous and carcinomatous human thyroid follicles. The cultured follicles showed decreased tgb RNA and enhanced c-myc RNA levels. In the culture of normal and adenomatous samples E caused a significant increase of [3H]thy incorporation and tgb RNA levels, with no effect on c-myc RNA levels. No effect of E was observed in the carcinomatous thyroid culture. TSH induced a significant increase of [3H]thy incorporation and c-myc expression only in adenoma cultures and a significant increase of tgb RNA levels in both normal and adenomatous samples. TSH had no effect on the carcinoma. The results show that E, like TSH, stimulates in vitro the expression of the tgb gene in differentiated cells, without stimulating the expression of the c-myc proto-oncogene, suggesting a possible action of E on normal thyroid function and perhaps growth, even if not associated with increased c-myc expression.

Cell Division↗
PubMed1989

Differential hypomethylation of the c-myc protooncogene in bladder cancers at different stages and grades.

The 5-methylcytosine content of c-myc proto-oncogene DNA obtained from samples of normal bladders and of bladders with transitional cell carcinoma of different stage and grade was analyzed. Five CCGG sites (from the third coding region to the 3' flanking region of the gene) which showed different methylation in normal and neoplastic samples were identified. The overall c-myc methylation levels were significantly reduced in carcinomas. Furthermore, a significant correlation between disease invasiveness and methylation level was found. Nevertheless, in each group of patients with the same histological grade, heterogeneity has been observed. This might be suggestive of different prognosis of the disease.

5-Methylcytosine↗
PubMed1989

The methylation pattern in the 5' end of the human estrogen receptor gene is tissue specific and related to the degree of gene expression.

Restriction enzyme mapping has been used to study the relationship between methylation at the 5' end of the human estrogen receptor gene (ER) and its various levels of expression in estrogen target tissues, like endometrium, placenta and breast. The methylation patterns were compared with that found in white blood cells. A cluster of CpG sites, including the transcription start site, was undermethylated in all examined tissues. In front and downstream of this area, a 1 Kb region was undermethylated in endometrium where the ER gene is highly expressed, methylated to some extent in placenta and breast, which express the gene to a low degree, and greatly methylated in white blood cells which are thought not to express this gene. These data provide evidence that in the 5' end of the human ER DNA, CpG methylation is tissue-specific, and related to the level of the ER gene expression.

Female↗
PubMed1988

Estrogen induced increase of estrogen receptor RNA in human breast cancer cells.

Estrogen Receptor (ER) RNA has been studied in ER positive and ER negative cells, grown in alpha medium and fetal calf serum (FCS), with and without estrogen addition. ER mRNA was detected only in ER positive cells. When cells were grown without estrogen addition, a progressive and transient increase of ER RNA levels was observed. When cells were cultured with estradiol, the ER RNA increase took place early and ER RNA levels remained 2 times higher than in untreated cells. Therefore, a down-regulation of ER RNA is not apparent in neoplastic breast cells. We hypothesize that the increase of ER expression is caused by stabilization of ER transcripts, due to the estrogen induced ER cytoplasmic depletion.

Breast Neoplasms↗
PubMed1988

Use of 3'HVR genomic probe for presymptomatic diagnosis of adult polycystic kidney disease in northern Italy: comparison of DNA analysis and renal ultrasonographic data.

A highly polymorphic DNA probe (3'HVR) with genetic linkage to the locus of autosomal dominant polycystic kidney disease was used for screening. Families with subjects at risk were from the Po river delta region (Northern Italy), where the disease accounts for 24% of the demands for dialysis. 3'HVR alleles were investigated in white blood cell DNA from 142 members of 18 families. The genomic marker was found informative in 88% of cases. Two recombinations between the marker and the disease locus were observed in 79 meioses. In 42 of the subjects at risk the results of DNA analysis and renal ultrasonography were compared. In 36 subjects the tests confirmed each other (18 were positive). In the other six subjects (all under 20 years of age and four under 10) only DNA analysis could diagnose the inheritance of cystic disease in the absence of demonstrable cysts. The findings indicate that in the population of the Po river delta the presymptomatic detection of adult polycystic kidney disease by 3'HVR linkage analysis is feasible in 88% of cases with approximately 95% reliability.

Adolescent↗
PubMed1987

Clustering of undermethylated CCGG and GCGC sequences in the 5' region of the Ha-ras-1 oncogene of human leukemic K562 cells.

The methylation state of the CCGG and GCGC sites of the Ha-ras-1 oncogene was analysed in the human leukemic K562 cell line, which was found to actively transcribe this gene. The results obtained demonstrate that the Ha-ras-1 oncogene is extensively methylated in both exonic, intronic, VTR and 3' untranslated portions, while undermethylations are present in a CG-rich island localized upstream of exon 1, near putative transcription initiation signals. Treatment of K562 cells with 5-azacytidine induces undermethylation of the Ha-ras-1 oncogene without major differences in the accumulation of Ha-ras-1 mRNA transcripts.

Base Sequence↗