Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C1326912 (tumorigenesis)
 57,481 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The catalytic activities of Ret tyrosine kinases as the products of oncogene RET with multiple endocrine neoplasia type 2A (Ret-MEN2A) or 2B (Ret-MEN2B) mutations and the hybrid gene from c-RET and RFP (Rfp-Ret) were higher than those of c-Ret. We demonstrated that ultraviolet light (UV) irradiation induced activation of c-Ret and superactivation of genetically mutated, and thereby constitutively activated, Ret-MEN2A, Ret-MEN2B, and Rfp-Ret. We found that small proportions of c-Ret and Ret-MEN2B and a large proportion of MEN2A were dimerized due to disulfide bonds and that high kinase activity resided in these fractions. The UV-induced activation of c-Ret and superactivation of Ret-MEN2A and Ret-MEN2B were then shown to be closely associated with promotion of the disulfide bond-mediated dimerization of the Ret proteins. Furthermore, we showed that a large proportion of Rfp-Ret was dimerized or polymerized and that almost all kinase activities resided in the highly polymerized but not dimerized fraction. The UV-induced superactivation of Rfp-Ret was also found to be closely associated with promotion of polymerization but not with dimerization of Rfp-Ret. Further experiments revealed that UV induced intracellular dimerization and activation of the extracellular domain-deleted mutant Ret (Ret-PTC-1). Most importantly, the levels of basal kinase activity and dimerization of Ret-TPC-1-C376A, in which cysteine 376 in the tyrosine kinase domain of Ret-TPC-1 was replaced with alanine, were low and were not increased by UV irradiation. These results suggest that the cysteine at this position works as the primary target of dimerization of Ret proteins inside the cell for both the maintenance of the basal kinase activity and its promotion by UV, possibly in co-operation with the cysteine(s) in the extracellular domain of Ret-MEN2A and Rfp-Ret, which is the target of dimerization and polymerization outside the cell. The potential biological significance of the UV-mediated superactivation of mutant Ret through the newly proposed mechanism in oncogenesis is discussed.
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PMID:Molecular mechanism of activation and superactivation of Ret tyrosine kinases by ultraviolet light irradiation. 1121 88

The RET proto-oncogene encodes a cell membrane tyrosine-kinase receptor protein whose ligands belong to the glial cell line-derived neurotrophic factor. RET functions as a multicompetent receptor complex that includes alphaGFRs and RET. Somatic rearrangements of RET designated as RET/PTC (from papillary thyroid carcinoma) were identified in papillary thyroid carcinoma before RET was recognized as the susceptibility gene for MEN2. There are now at least at least 15 types of RET/PTC rearrangements involving RET and 10 different genes. RET/PTC1 and RET/PTC3 are by far the most common rearrangements. All of the rearrangements are due to DNA damage and result in the fusion of the RET tyrosine-kinase (RET-TK) domain to the 5'-terminal region of heterologous genes. RET/PTC rearrangements are very common in radiation-induced tumors but have been detected in variable proportions of sporadic (i.e., non-radiation associated) papillary carcinomas. It is estimated that up to approximately half the papillary thyroid carcinomas in the United States and Canada harbor RET/PTC rearrangements, most commonly RET/PTC-1, followed by RET/PTC-3 and occasionally RET/PTC-2. The cause of these rearrangements in sporadic papillary carcinomas is not known, but the close association between their presence and the papillary carcinoma phenotype indicates that they play a causative role in tumor development. The proposed mechanisms of RET/PTC-induced tumorigenesis and the clinical and pathologic implications of RET/PTC activation are discussed.
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PMID:RET oncogene activation in papillary thyroid carcinoma. 1170 26

Expression of the wild-type RET proto-oncogene has been observed in non-medullary, follicular cell-derived tumors (FCDT), but the relation with the histopathological features has not been fully demonstrated. To assess the expression of RET and protein products in relation to morphological types of FCDT, including follicular adenoma (FA), papillary carcinoma (PTC), follicular carcinoma (FTC) and anaplastic carcinoma (AnC), 58 non-neoplastic and neoplastic samples using pathological paraffin sections by immunohistochemistry (IHC), reverse transcriptase-polymerase chain reaction (RT-PCR) and laser capture microdissection (LCM) methods were analyzed. Expression of RET proto-oncogene was detected in 27.3% of FCDT by IHC and 25.5% by RT-PCR using a primer set at a regular break point. The present study also found higher expression ratios of RET in FA (50.0%) and the follicular variant of PTC (50.0%), in contrast to FTC (20.0%), ordinary PTC (20.0%) and poorly differentiated or AnC (14.3%) by RT-PCR. One patient with PTC showed a discrepancy in the results by RT-PCR using a different primer set at the C-terminus of RET. The study found that the RET proto-oncogene is often stimulated in FCDT, not only in PTC but also in follicular tumors (FA and FTC), and may contribute to tumorigenesis of these tumors.
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PMID:Expression of RET in follicular cell-derived tumors of the thyroid gland: prevalence and implication of morphological type. 1260 95

Tumors of thyroid follicular cells provide a very interesting model to understand the development of human cancer. It is becoming apparent that distinct molecular events are associated with specific stages in a multistep tumorigenic process with good genotype/ phenotype correlation. For instance, mutations of the gsp and thyroid-stimulating hormone receptor genes are associated with benign hyperfunctioning thyroid nodules and adenomas while alterations of other specific genes, such as oncogenic tyrosine kinase alterations (RET/PTC, TRK) in papillary carcinoma and the newly discovered PAX8/peroxisome proliferator-activated receptor gamma rearrangement, are distinctive features of cancer. Although activating RAS mutations occur at all stages of thyroid tumorigenesis, evidence is accumulating that they may also play an important role in tumor progression, a role that is well documented for p53. Environmental factors (iodine deficiency, ionizing radiations) have been shown to play a crucial role in promoting the development of thyroid cancer, influencing both its genotypic and phenotypic features. It is possible that the follicular thyroid cell has unique ways to respond to DNA damage. Similarly to leukemia or sarcomas (and unlike most epithelial cancers), numerous specific rearrangements are being discovered in thyroid cancer suggesting preferential activation of DNA repair instead of cell death programs after environmentally induced genetic alterations.
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PMID:Molecular pathobiology of thyroid neoplasms. 1266 46

Thyroid papillary cancers (PTCs) are associated with activating mutations of genes coding for RET or TRK tyrosine kinase receptors, as well as of RAS genes. Activating mutations of BRAF were reported recently in most melanomas and a small proportion of colorectal tumors. Here we show that a somatic mutation of BRAF, V599E, is the most common genetic change in PTCs (28 of 78; 35.8%). BRAF(V599E) mutations were unique to PTCs, and not found in any of the other types of differentiated follicular neoplasms arising from the same cell type (0 of 46). Moreover, there was no overlap between PTC with RET/PTC, BRAF, or RAS mutations, which altogether were present in 66% of cases. The lack of concordance for these mutations was highly unlikely to be a chance occurrence. Because these signaling proteins function along the same pathway in thyroid cells, this represents a unique paradigm of human tumorigenesis through mutation of three signaling effectors lying in tandem.
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PMID:High prevalence of BRAF mutations in thyroid cancer: genetic evidence for constitutive activation of the RET/PTC-RAS-BRAF signaling pathway in papillary thyroid carcinoma. 1267 Aug 89

RET/PTC rearrangements are believed to be tumor-initiating events in papillary thyroid carcinomas. We identified microsomal prostaglandin E2 synthase-1 (mPGES-1) as a RET/PTC-inducible gene through subtraction hybridization cloning and expression profiling with custom microarrays. The inducible prostaglandin E2 (PGE2) biosynthetic enzymes cyclooxygenase-2 (COX-2) and mPGES-1 are up-regulated in many cancers. COX-2 is overexpressed in thyroid malignancies compared with benign nodules and normal thyroid tissues. Eicosanoids may promote tumorigenesis through effects on tumor cell growth, immune surveillance, and angiogenesis. Conditional RET/PTC1 or RET/PTC3 expression in PCCL3 thyroid cells markedly induced mPGES-1 and COX-2. PGE2 was the principal prostanoid and up-regulated (by approximately 60-fold), whereas hydroxyeicosatetraenoic acid metabolites were decreased, consistent with shunting of prostanoid biosynthesis toward PGE2 by coactivation of the two enzymes. RET/PTC activated mPGES-1 gene transcription. Based on experiments with kinase inhibitors, with PCCL3 cell lines with doxycycline-inducible expression of RET/PTC mutants with substitutions of critical tyrosine residues in the kinase domain, and lines with inducible expression of activated mutants of H-RAS and MEK1, RET/PTC was found to regulate mPGES-1 through Shc-RAS-MEK-ERK. These data show a direct relationship between activation of a tyrosine kinase receptor oncogene and regulation of PGE2 biosynthesis. As enzymes involved in prostanoid biosynthesis can be targeted with pharmacological inhibitors, these findings may have therapeutic implications.
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PMID:Microsomal prostaglandin E2 synthase-1 is induced by conditional expression of RET/PTC in thyroid PCCL3 cells through the activation of the MEK-ERK pathway. 1455 60

It is apparent that in the last decade carcinoma of the thyroid is becoming increasingly prevalent. The multistage complex theory of thyroid carcinogenesis is based on observations made on cohort patients studies and during animal experiments over a period of last fifty years. The process of thyroid oncogenesis is conceived to be a series of events induced by genetic and environmental factors which alter follicular cells division and growth control. These factors can be considered as initiators (chemical agents and ionising radiation) and promoters (some goitrogenes and drugs). The first class of factors induce incipient tumorigenesis while the second augments TSH secretion and radically increases tumour growth. Normally silent, intracellular proto-oncogenes (of which Ret/PTC series are the most conceived ones) can become activated by chromosomal translocations, deletions or mutations and can transform normal follicular cell into a condition of uncontrolled division and growth. The most significant known cause of thyroid carcinomas in men is exposure to external or internal ionising radiation. Beside that, long-term iodine deficiency, effects of certain chemical carcinogens, drugs and goitrogenes must be considered as significant risk factors. Possible role of sodium/iodide symporter is becoming an objective of the most recent investigations.
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PMID:[Current opinion on the etiology of differentiated thyroid carcinoma]. 1517 55

RET/PTC1 and RET/PTC3 are the markers for papillary thyroid carcinoma. Their reported prevalence varies broadly. Nonrearranged c-RET has also been detected in a variable proportion of papillary carcinomas. The published data suggest that a wide range in expression levels may contribute to the different frequency of c-RET and, particularly, of RET/PTC detection. However, quantitative expression analysis has never been systematically carried out. We have analyzed by real-time RT-PCR 25 papillary carcinoma and 12 normal thyroid samples for RET/PTC1, RET/PTC3 and for RET exons 10-11 and 12-13, which are adjacent to the rearrangement site. The variability in mRNA levels was marked and four carcinoma groups were identified: one lacking RET/PTC rearrangement with balanced RET exon levels similar to those of the normal samples (7/25 cases, 28%), the second (6/25 cases, 24%) with balanced RET expression and very low levels of RET/PTC1, the third with unbalanced RET exons 10-11 and 12-13 expression, high RET/PTC1 levels but no RET/PTC3 (7/25 cases, 28%), and the fourth with unbalanced RET expression, high RET/PTC1 levels and low levels of RET/PTC3 (5/25 cases, 20%). Papillary carcinomas with high RET/PTC1 expression showed an association trend for large tumor size (P=0.063). Our results indicate that the variability in c-RET and RET/PTC mRNA levels contributes to the apparent inconsistencies in their reported detection rates and should be taken into account not only for diagnostic purposes but also to better understand the role of c-RET activation in thyroid tumorigenesis.
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PMID:Real-time quantitative RT-PCR identifies distinct c-RET, RET/PTC1 and RET/PTC3 expression patterns in papillary thyroid carcinoma. 1550 56

We investigated the expression of annexin-1 (ANXA1) in thyroid carcinoma cell lines and in thyroid cancers with a different degree of differentiation. The highest level of ANXA1 expression examined by Western blotting was detected in the papillary carcinoma cells (NPA) and in the follicular cells (WRO). On the other hand, the most undifferentiated thyroid carcinoma cells (ARO and FRO) presented the lowest level of ANXA1 expression. In surgical tissue specimens from 32 patients with thyroid cancers, we found high immunoreactivity for ANXA1 in papillary (PTC) and follicular (FTC) thyroid cancers while in undifferentiated thyroid cancers (UTC) the expression of the protein was barely detectable. Control thyroid tissue resulted positive for ANXA1. In summary, 70% of UTC examined weakly expressed ANXA1, whereas 65% of PTC or FTC specimens tested showed high expression of the protein. Thus ANXA1 expression may correlate with the tumorigenesis suggesting that the protein may represent an effective differentiation marker in thyroid cancer.
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PMID:Annexin-1 downregulation in thyroid cancer correlates to the degree of tumor differentiation. 1662 80

A number of genetic abnormalities in oncogenes or anti-oncogenes have been identified in association with thyroid carcinogenesis. Especially, oncogenes such as ras mutation, ret/PTC and Braf mutation that constitutively activate MAP kinase pathway a refrequently found in papillary thyroid cancer. The p53 mutation aggravates differentiated thyroid cancers to anaplastic thyroid cancer. These gene alterations are studied not only to understand basically the mechanisms of oncogenesis but also to develop clinically genetic diagnosis or molecular target therapy. In this article, we review the genetic diagnostic methods and phenotype-genotype relationship of human thyroid cancers.
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PMID:[Gene abnormalities in thyroid cancer]. 1801 56


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