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Biomedical subjects

M Santoro

Publications and source records attributed to M Santoro.

At least 145 records · Page 8Linked to original sources
PubMed1995

Activated RET oncogene products induce maturation of xenopus oocytes.

The RET proto-oncogene encodes a transmembrane receptor of the tyrosine kinase family, recently found to be the gene responsible for the multiple endocrine neoplasia type 2A and 2B syndromes. RET was found specifically activated, by gene rearrangement, in human thyroid carcinomas of the papillary subtype. In most cases the activation consisted of an in frame fusion of the RET tyrosine-kinase domain, at the carboxy-terminus, with heterologous genes at the amino-terminus. These chimeric oncogenes are collectively named RET/PTC. Two forms of these gene products, RET/PTC1 and RET/PTC3, have been tested for their ability to induce meiotic maturation in Xenopus oocytes. Injection of RET/PTC mRNAs into immature oocytes induced maturation-promoting-factor (MPF) activation and germinal vesicle breakdown (GVBD). The injected oocytes expressed polypeptides recognized by an anti-RET gene product antibody as well as by an antiphosphotyrosine antibody, indicating activation of the tyrosine-kinase domain. The RET/PTC induced maturation was dependent on endogenous ras; in fact, the coinjection of RET/PTC mRNA with a neutralizing anti-ras antibody blocked oocytes maturation without interfering with the accumulation and tyrosine-phosphorylation of the RET/PTC protein.

Animals↗
PubMed1995

The expression of the high mobility group HMGI (Y) proteins correlates with the malignant phenotype of human thyroid neoplasias.

High Mobility Group I (HMGI) proteins are nuclear proteins involved in the regulation of chromatin structure and function. Elevated expression of the HMGI proteins (HMGI, HMGY and HMGI-C) has been correlated with the presence of a highly malignant phenotype in epithelial and fibroblastic rat thyroid cells, and in several experimental carcinomas. Here, we demonstrate that HMGI and HMGY proteins are expressed in human thyroid carcinomas and thyroid carcinoma cell lines, but not in adenomas, goiters, normal thyroid tissues and cells. These results indicate a correlation between HMGI and HMGY expression and the malignant phenotype of thyroid neoplasias, suggesting that these proteins may be used as markers in thyroid cancer.

Adenoma↗
PubMed1995

Point mutation of the RET proto-oncogene in the TT human medullary thyroid carcinoma cell line.

The RET proto-oncogene encodes a tyrosine-kinase receptor specifically expressed in tissues of neuroectodermal origin. Recently specific point mutations of RET have been demonstrated to be responsible for the Multiple Endocrine Neoplasia type 2A and 2B and Familial Medullary Thyroid Carcinoma syndromes, characterized by the occurrence of medullary thyroid carcinomas. Here we report that a human medullary thyroid carcinoma cell line, the TT cell line, harbours a MEN2A-type mutation, specifically a cysteine to triptophan substitution at the level of the RET codon 634. This mutation is heterozygous and both normal and mutated alleles are expressed. We suggest that the TT cell line could be a useful cell system to investigate the role played by the RET oncogene in the transformation and differentiation of human thyroid C-cells.

Base Sequence↗
PubMed1995

Activation of RET as a dominant transforming gene by germline mutations of MEN2A and MEN2B.

Multiple endocrine neoplasia types 2A and 2B (MEN2A and MEN2B) and familial medullary thyroid carcinoma are dominantly inherited cancer syndromes. All three syndromes are associated with mutations in RET, which encodes a receptor-like tyrosine kinase. The altered RET alleles were shown to be transforming genes in NIH 3T3 cells as a consequence of constitutive activation of the RET kinase. The MEN2A mutation resulted in RET dimerization at steady state, whereas the MEN2B mutation altered RET catalytic properties both quantitatively and qualitatively. Oncogenic conversion of RET in these neoplastic syndromes establishes germline transmission of dominant transforming genes in human cancer.

3T3 Cells↗
PubMed1995

Inhibition of HMGI-C protein synthesis suppresses retrovirally induced neoplastic transformation of rat thyroid cells.

Elevated expression of the three high-mobility group I (HMGI) proteins (HMGI, HMGY, and HMGI-C) has previously been correlated with the presence of a highly malignant phenotype in epithelial and fibroblastic rat thyroid cells and in experimental thyroid, lung, mammary, and skin carcinomas. Northern (RNA) blot and run-on analyses demonstrated that the induction of HMGI genes in transformed thyroid cells occurs at the transcriptional level. An antisense methodology to block HMGI-C protein synthesis was then used to analyze the role of this protein in the process of thyroid cell transformation. Transfection of an antisense construct for the HMGI-C cDNA into normal thyroid cells, followed by infection with transforming myeloproliferative sarcoma virus or Kirsten murine sarcoma virus, generated cell lines that expressed significant levels of the retroviral transforming oncogenes v-mos or v-ras-Ki and removed the dependency on thyroid-stimulating hormones. However, in contrast with untransfected cells or cells transfected with the sense construct, those containing the antisense construct did not demonstrate the appearance of any malignant phenotypic markers (growth in soft agar and tumorigenicity in athymic mice). A great reduction of the HMGI-C protein levels and the absence of the HMGI(Y) proteins was observed in the HMGI-C antisense-transfected, virally infected cells. Therefore, the HMGI-C protein seems to play a key role in the transformation of these thyroid cells.

Animals↗
PubMed1995

Molecular defects in thyroid carcinomas: role of the RET oncogene in thyroid neoplastic transformation.

Tumors are believed to arise as a result of an accumulation of mutations in critical genes involved in the control of cell proliferation. Thyroid neoplasms represent a good model for studying the role of these mutations in epithelial cell multistep carcinogenesis because they comprise a broad spectrum of lesions with different degrees of malignancy. Recent reports have described the involvement of specific genetic alterations in different types of thyroid neoplasms. Papillary carcinomas are characterized by the activation of the receptor tyrosine kinases RET and TRK-A proto-oncogenes. Ras point mutations are frequently observed in tumors with follicular histology and a high prevalence of p53 point mutations have been found in anaplastic carcinomas. A definition of molecular defects characterizing thyroid tumors will be helpful in establishing sensitive and specific detection strategies and, in addition, to define genetic and environmental factors important for their pathogenesis.

Carcinoma↗
PubMed1995

Bacteriophage T4 gene 28.

The complete nucleotide sequence of bacteriophage T4D gene 28 has been determined. Gene 28 product is a structural component of the viral baseplate for which an enzymatic activity has also been proposed.

Amino Acid Sequence↗
PubMed1995

[Nephro-jejunal fistula associated with nephro-cutaneous fistula].

The development of a renal fistula is a rare event which results from an acute or chronic inflammatory process in the kidney. The authors report a very rare case of nephrojejunal and nephro-cutaneous fistulas due to acute and chronic pyelonephritis in a patient with staghorn stones of the left kidney.

Aged↗
PubMed1995

[Spontaneous nephro-cutaneous fistula].

The authors report a rare case of spontaneous nephrocutaneous fistula. The patient was asymptomatic and with a negative history for renal lithiasis, inflammation, trauma or tuberculosis. Radiological and echographical examinations permitted a complete study of the fistulous tract and the renal function; the staghorn calculi and pyelonephritis guided the decision to operate on the patient performing a nephrectomy and ureterectomy with a quick complete recovery. Biological test for micobacterium tuberculosis resulted positive after 60 days.

Cutaneous Fistula↗
PubMed1995

Expression of the RET oncogene induces differentiation of SK-N-BE neuroblastoma cells.

Expression of the RET proto-oncogene, a cell surface receptor for an as yet unknown ligand, is associated with tumors, tissues, and cell lines of neural crest origin. Accumulating evidence suggests that RET activity is involved in the process of neuronal differentiation. Moreover, induction of phenotypic differentiation of neuroblastoma cell lines is associated with the rapid accumulation of RET transcripts. To verify the role of RET in neuronal differentiation, we introduced into the human neuroblastoma cell line SK-N-BE four versions of the RET oncogene, activated by different mechanisms: RET/PTC1 and RET/PTC3, which are activated by rearrangement with heterologous genes; and two activated RET mutants, which carry the single amino acid substitution found associated to the inheritance of the multiple endocrine neoplasia type 2A (retMEN2A allele) and type2B (retMEN2B allele), respectively. We demonstrate that, after transfection with the RET oncogenes, SK-N-BE cells display a reduced growth rate and acquire a neurite-bearing phenotype accompanied by enhanced expression of the axonal growth-associated protein, GAP-43, and the high molecular weight neurofilament, NF200. These results indicate that, when activated, RET is able to cause growth inhibition and to promote neuronal differentiation of neuroblastoma cells.

Blotting, Northern↗
PubMed1994

RON is a heterodimeric tyrosine kinase receptor activated by the HGF homologue MSP.

RON, a cDNA homologous to the hepatocyte growth factor (HGF) receptor gene (MET), encodes a putative tyrosine kinase. Here we show that the RON gene is expressed in several epithelial tissues as well as in granulocytes and monocytes. The major RON transcript is translated into a glycosylated single chain precursor, cleaved into a 185 kDa heterodimer (p185RON) of 35 (alpha) and 150 kDa (beta) disulfide-linked chains, before exposure at the cell surface. The Ron beta-chain displays intrinsic tyrosine kinase activity in vitro, after immunoprecipitation by specific antibodies. In vivo, tyrosine phosphorylation of p185RON is induced by stimulation with macrophage stimulating protein (MSP), a protease-like factor containing four 'kringle' domains, homologous to HGF. In epithelial cells, MSP-induced tyrosine phosphorylation of p185RON is followed by DNA synthesis. p185RON is not activated by HGF, nor is the HGF receptor activated by MSP in biochemical and biological assays. p185RON is also activated by a pure recombinant protein containing only the N-terminal two kringles of MSP. These data show that p185RON is a tyrosine kinase activated by MSP and that it is member of a family of growth factor receptors with distinct specificities for structurally related ligands.

Base Sequence↗
PubMed1994

Frequent activation of ret protooncogene by fusion with a new activating gene in papillary thyroid carcinomas.

Tumor specific rearrangements of ret gene are frequently detected in papillary thyroid carcinomas. These rearrangements result in the formation of chimeric genes showing the tyrosine kinase domain of ret fused with the 5' end sequences of different genes. We examined a series of 52 patients and identified 10 cases of ret fusion with D10S170 locus resulting in the generation of ret/PTC1 oncogene, 2 cases with the gene encoding the regulatory subunit RI alpha of PKA (ret/PTC2), and finally 6 cases, here described, with a newly discovered gene called ele1 localized on chromosome 10 and leading to the formation of ret/PTC3 oncogene. Our results show the expression of the ret/PTC3 hybrid gene in all the 6 cases and demonstrated its association with the synthesis of 2 constitutively phosphorylated isoforms of the oncoprotein (p75 and p80). The chromosome 10 localization of both ret and ele1 and the detection, in all cases, of a sequence reciprocal to that generating the oncogenic rearrangements, strongly suggest that ret/PTC3 formation is a consequence of an intrachromosomal inversion of chromosome 10.

3T3 Cells↗
PubMed1994

Description of a human papillary thyroid carcinoma cell line. Morphologic study and expression of tumoral markers.

BACKGROUND: The establishment of cell lines from thyroid carcinomas can provide an in vitro model of oncogenesis. B-CPAP is a new cell line that has been obtained from a differentiated papillary thyroid carcinoma. The data presented give a broader characterization and expression of tumoral markers of this cell line and identify the differentiated functions that are preserved. METHODS: An ultrastructural study was performed to confirm the thyroid nature of the new cell line. The cellular markers (thyroglobulin, S100, neuron-specific enolase [NSE]) and the oncogenes (mutated p53, H-ras, c-myc, PTC, trk) were studied by immunohistochemistry, Southern blot, or in situ hybridization. RESULTS: The cells were of a differentiated ultrastructural thyroid type. All of the cells proved immunoreactive with antibodies specific to thyroglobulin, S100 proteins, NSE, and mutant p53 protein. Mutations of H-ras, PTC, and trk were not observed. The c-myc gene was not amplified. CONCLUSIONS: The cell line described in these data provides a suitable model for the study of thyroid carcinogenesis, given that the cells present thyroid characteristics, and metabolic disorders not previously found in such cell lines. In addition, the coexpression of S100 proteins and mutant p53 proteins in the cells should permit the study of the interaction between these two proteins.

Aged↗
PubMed1994

Cloning of the rat tissue inhibitor of metalloproteinases type 2 (TIMP-2) gene: analysis of its expression in normal and transformed thyroid cells.

We have recently reported that the introduction of the E1A gene of the adenovirus 5 gene into the rat thyroid PC Cl 3 epithelial cell line causes loss of the differentiated thyroid phenotype without the appearance of the typical markers of neoplastic transformation. It is well known that the E1A gene is able either to induce or to repress the transcription of various endogenous cellular genes. In order to characterize the genes involved in the transformation of PC Cl 3 cells by the E1A gene, we have isolated several cDNA clones, whose expression was induced by E1A. One of these clones was found to be the rat homologue of the human tissue inhibitor of metalloproteinase type 2 (TIMP-2) gene. Here we show the complete sequence of the rat TIMP-2. Its homology to the human TIMP-2 is 98% at the amino acid level and, like its human counterpart, the rat TIMP-2 is transcribed in two different mRNAs of 1.0 and 3.5 kb. The expression of TIMP-2, in PC Cl 3 cells, was significantly induced by the E1A gene and also by other oncogenes. Finally TIMP-2 was shown to be significantly overexpressed in human thyroid neoplastic cell lines and some tumoral thyroid samples.

Adenovirus E1A Proteins↗
PubMed1994

An epidermal growth factor receptor/ret chimera generates mitogenic and transforming signals: evidence for a ret-specific signaling pathway.

A chimeric expression vector which encoded for a molecule encompassing the extracellular domain of the epidermal growth factor (EGF) receptor (EGFR) and the intracellular domain of the ret kinase (EGFR/ret chimera) was generated. Upon ectopic expression in mammalian cells, the EGFR/ret chimera was correctly synthesized and transported to the cell surface, where it was shown capable of binding EGF and transducing an EGF-dependent signal intracellularly. Thus, the EGFR/ret chimera allows us to study the biological effects and biochemical activities of the ret kinase under controlled conditions of activation. Comparative analysis of the growth-promoting activity of the EGFR/ret chimera expressed in fibroblastic or hematopoietic cells revealed a biological phenotype clearly distinguishable from that of the EGFR, indicating that the two kinases couple with mitogenic pathways which are different to some extent. Analysis of biochemical pathways implicated in the transduction of mitogenic signals also evidenced significant differences between the ret kinase and other receptor tyrosine kinases. Thus, the sum of our results indicates the existence of a ret-specific pathway of mitogenic signaling.

3T3 Cells↗
PubMed1994

The high transforming potency of erbB-2 and ret is associated with phosphorylation of paxillin and a 23 kDa protein.

Two-dimensional gel maps of proteins phosphorylated by the epidermal growth factor receptor (EGFR) and erbB-2 kinases were obtained, to investigate the molecular basis of the different biological properties of these two molecules. Several proteins were phosphorylated by EGFR or erbB-2 with different stoichiometry. Differences were either quantitative or qualitative. In NIH3T3 cells, erbB-2 is 100-fold more transforming than EGFR. In the same cell line several proteins were preferentially phosphorylated by erbB-2, as compared to EGFR. To identify which of these substrates might be directly involved in mitogenic signaling, we obtained two-dimensional maps of proteins phosphorylated on tyrosine by EGFR/ret and an EGFR/erbB-2TK chimeric receptors. Both these chimerae behaved indistinguishably from erbB-2 in a number of bioassays and potently transformed NIH3T3 cells. Paxillin and a 23 kDa substrate were invariably phosphorylated to higher stoichiometry whenever potent mitogenic and transforming signals were activated. We propose that paxillin and the 23 kDa substrate are important elements in the erbB-2 and ret-activated mitogenic and transforming signaling.

3T3 Cells↗
PubMed1994

[Ovarian pregnancy].

A case of ovarian pregnancy in a patient with intrauterine device is reporter. The patient was hemodynamically instable and immediate laparotomy was indicated. The treatment was left oophorectomy. Ovarian pregnancy is a rare form of ectopic pregnancy in which the gestational sac is implanted in the ovary. The incidence appears to be of 1 to 3 per cent of all ectopic gestations with a frequency of one in 7000 to 40000 deliveries and it is now believed to occur four times more frequently than previously thought. It has been suggested that the increasing incidence is caused by the use of IUD. In contrast to patients with tubal pregnancy traditional risk factors such as pelvic inflammatory disease, prior surgical procedure upon the pelvis may not apply. The clinical signs are similar to those found in tubal pregnancies and in hemorrhagic corpus luteum cysts. The treatment is emergency laparatomy followed by oophorectomy in many instances. When the patient is hemodynamically stable laparoscopy and the ovarian wedge resection should be the treatment of choice.

Adult↗