European Thyroid Association: 2006 in Naples.
Explore the source record for details and available documents.
Humans↗
Biomedical subjects
Giancarlo Vecchio
Publications and source records attributed to Giancarlo Vecchio.
Minireview: RET: normal and abnormal functions.
The RET gene encodes a single-pass transmembrane receptor tyrosine kinase. RET is the oncogene that causes papillary thyroid carcinoma and medullary thyroid carcinoma. The latter may arise as a component of multiple endocrine neoplasia type 2 syndromes; germline mutations in RET are responsible for multiple endocrine neoplasia type 2 inheritance. In this report we review data on the mechanisms leading to RET oncogenic conversion and on RET targeting as a strategy in thyroid cancer treatment.
Gene Expression Regulation, Neoplastic↗
Disease associated mutations at valine 804 in the RET receptor tyrosine kinase confer resistance to selective kinase inhibitors.
We have recently demonstrated that the pyrazolopyrimidines PP1 and PP2 and the 4-anilinoquinazoline ZD6474 display a strong inhibitory activity (IC(50)< or =100 nM) towards constitutively active oncogenic RET kinases. Here, we show that most oncogenic MEN2-associated RET kinase mutants are highly susceptible to PP1, PP2 and ZD6474 inhibition. In contrast, MEN2-associated swap of bulky hydrophobic leucine or methionine residues for valine 804 in the RET kinase domain causes resistance to the three compounds. Substitution of valine 804 with the small amino- acid glycine renders the RET kinase even more susceptible to inhibition (ZD6474 IC(50): 20 nM) than the wild-type kinase. Our data identify valine 804 of RET as a structural determinant mediating resistance to pyrazolopyrimidines and 4-anilinoquinazolines.
Carcinoma, Medullary↗
H4(D10S170), a gene frequently rearranged with RET in papillary thyroid carcinomas: functional characterization.
Human thyroid papillary carcinomas are characterized by rearrangements of the RET protooncogene with a number of heterologous genes, which generate the RET/papillary thyroid carcinoma (PTC) oncogenes. One of the most frequent variants of these recombination events is the fusion of the intracellular kinase-encoding domain of RET to the first 101 amino acids of a gene named H4(D10S170). We have characterized the H4(D10S170) gene product, showing that it is a ubiquitously expressed 55 KDa nuclear and cytosolic protein that is phosphorylated following serum stimulation. This phosphorylation was found to depend on mitogen-activated protein kinase (MAPK) Erk1/2 activity and to be associated to the relocation of H4(D10S170) from the nucleus to the cytosol. Overexpression of the H4(D10S170) gene was able to induce apoptosis of thyroid follicular epithelial cells; conversely a carboxy-terminal truncated H4(D10S170) mutant H4(1-101), corresponding to the portion included in the RET/PTC1 oncoprotein, behaved as dominant negative on the proapoptotic function and nuclear localization of H4(D10S170). Furthermore, conditional expression of the H4(D10S170)-dominant negative truncated mutant protected cells from stress-induced apoptosis. The substitution of serine 244 with alanine abrogated the apoptotic function of H4(D10S170). These data suggest that loss of the H4(D10S170) gene function might have a role in thyroid carcinogenesis by impairing apoptosis.
Animals↗
Antineoplastic ribonucleases selectively kill thyroid carcinoma cells via caspase-mediated induction of apoptosis.
Bovine seminal ribonuclease (BS-RNase), a natural dimeric homolog of bovine pancreatic RNase (RNase A), and HHP2-RNase, an engineered dimeric form of human pancreatic RNase (HP-RNase), are endowed with powerful antitumor effects. Here we show that BS- and HHP2-RNases, but not monomeric RNase A, induce apoptosis of human thyroid carcinoma cell lines. RNase-induced apoptosis was associated with activation of initiation caspase-8 and -9. This was followed by activation of executioner caspase-3, leading to the proteolytic cleavage of poly(ADP-ribose) polymerase. The caspase inhibitor Z-Val-Ala-Asp-(OMe)-fluoromethylketone protected thyroid cancer cells from BS-RNase-induced apoptosis. RNase-triggered apoptosis and caspase activation were accompanied by reduced phosphorylation of Akt/protein kinase B (PKB), a serine-threonine kinase that when phosphorylated is able to deliver survival signals to cancer cells. BS-RNase antitumor effects in nude mice were accompanied by caspase activation and apoptosis. Because of the high selectivity of apoptotic effects for malignant cells, BS- and HHP2-RNase are promising tools for the treatment of aggressive thyroid cancer.
Amino Acid Chloromethyl Ketones↗
ONYX-015 enhances radiation-induced death of human anaplastic thyroid carcinoma cells.
ONYX-015 is a genetically modified adenovirus with a deletion of the E1B early gene and therefore is designed to replicate preferentially in p53-mutated cells causing their death. We previously demonstrated that the ONYX-015 virus kills anaplastic thyroid carcinoma (ATC) cells and enhances the antineoplastic effects of doxorubicin and paclitaxel. Here we report that ONYX-015 increased the cytopathic effect of radiotherapy in three ATC cell lines. In fact, ONYX-015 and radiation induced a significant cytopathic effect on ATC cells. DNA fragmentation analysis showed that ATC ONYX-015-treated cells were very sensitive to radiation-induced apoptosis. In addition, low doses of ONYX-015 associated with a single radiation dose of 10 Gy delayed the growth of a xenograft tumor induced by ARO cells in athymic mice. Our results suggest that the combination of ONYX-015 and radiotherapy should be considered for experimental trials in patients with anaplastic thyroid carcinoma.
Adenoviridae↗
ZD6474, an orally available inhibitor of KDR tyrosine kinase activity, efficiently blocks oncogenic RET kinases.
RET/papillary thyroid carcinoma (PTC) oncogenes, generated by recombination of the tyrosine kinase-encoding domain of RET with different heterologous genes, are prevalent in papillary carcinomas of the thyroid. Point mutations of RET cause multiple endocrine neoplasia type 2 (MEN2) familial cancer syndrome and are found in sporadic medullary thyroid carcinomas. Here, we show that ZD6474, a low molecular weight tyrosine kinase inhibitor, blocks the enzymatic activity of RET-derived oncoproteins at a one-half maximal inhibitory concentration of 100 nM. ZD6474 blocked in vivo phosphorylation and signaling of the RET/PTC3 and RET/MEN2B oncoproteins and of an epidermal growth factor (EGF)-activated EGF-receptor/RET chimeric receptor. RET/PTC3-transformed cells-treated ZD6474 lost proliferative autonomy and showed morphological reversion. ZD6474 prevented the growth of two human PTC cell lines that carry spontaneous RET/PTC1 rearrangements. Finally, it blocked anchorage-independent growth of RET/PTC3-transformed NIH3T3 fibroblasts and the formation of tumors after injection of NIH-RET/PTC3 cells into nude mice. Thus, targeting RET oncogenes with ZD6474 might offer a potential treatment strategy for carcinomas sustaining oncogenic activation of RET.
3T3 Cells↗
Generation and characterization of novel monoclonal antibodies to the Ret receptor tyrosine kinase.
Ret is a tyrosine kinase receptor involved in several human diseases germ-line mutations are responsible for multiple endocrine neoplasia type 2 syndromes while somatic mutations of Ret are found in sporadic medullary thyroid carcinomas. In the present work, we describe the generation and characterization of a panel of novel monoclonal antibodies to Ret obtained by immunizing mice with a Ret-FC fusion protein. Fifty-five independent monoclonal antibodies recognize Ret-FC by enzyme linked immunosorbent assay but not a non-related FC fusion protein. Twenty antibodies further characterized recognize Ret expressing cells by flow cytometry. Finally, immunoprecipitation analysis showed that these antibodies recognize Ret mature glycosylated and immature forms. Thus, these monoclonal antibodies could be used as diagnostic tools to detect Ret expression, as well as therapeutic tools to downmodulate Ret or to deliver cytotoxic drugs to malignancies that overexpress Ret as neuroblastomas, medullary and papillary thyroid carcinomas, seminomas, and leukemia.
Animals↗
The kinase inhibitor PP1 blocks tumorigenesis induced by RET oncogenes.
Oncogenic activation of the RET receptor tyrosine kinase is common in different human cancers. We found that the pyrazolo-pyrimidine PP1 inhibited RET-derived oncoproteins with a half maximal inhibitor concentration of 80 nM. Furthermore, RET/PTC3-transformed cells treated with 5 microM of PP1 lost proliferative autonomy and showed morphological reversion. PP1 prevented the growth of two human papillary thyroid carcinoma cell lines that carry spontaneous RET/PTC1 rearrangements and blocked anchorage-independent growth and tumorigenicity in nude mice of NIH3T3 fibroblasts expressing the RET/PTC3 oncogene. These findings suggest targeting RET oncogenes with PP1 or related compounds as a novel treatment strategy for RET-associated neoplasms.
3T3 Cells↗
Molecular mechanisms of RET activation in human cancer.
Mutations that produce oncogenes with dominant gain of function target receptor protein tyrosine kinases (PTKs) in cancer and confer uncontrolled proliferation, impaired differentiation, or unrestrained survival to the cancer cell. However, insufficient PTK signaling may be responsible for developmental diseases. Gain of function of the RET receptor PTK is associated with human cancer. At the germline level, point mutations of RET are responsible for multiple endocrine neoplasia type 2 (MEN2A, MEN2B, and FMTC). Mutations of extracellular cysteines are found in MEN2A patients, and a Met918Thr mutation is responsible for most MEN2B cases. At the somatic level, gene rearrangements juxtaposing the tyrosine kinase domain of RET to heterologous gene partners are found in papillary carcinomas of the thyroid. These rearrangements generate the chimeric RET/PTC oncogenes. Both MEN2 mutations and PTC gene rearrangements potentiate the intrinsic tyrosine kinase activity of RET and, ultimately, the RET downstream signaling events. A multidocking site of the C-tail of RET is essential for both mitogenic and survival RET signaling. Such a site is involved in the recruitment of several intracellular molecules, such as the Shc, FRS2, IRS1, Gab1/2, and Enigma. The different activating mutations not only potentiate the enzymatic activity of the RET kinase but also may alter qualitatively RET signaling properties by: (1) altering RET autophosphorylation (in the case of the MEN2B mutation), (2) modifying the subcellular distribution of the active kinase, and (3) providing the active kinase with a scaffold for novel protein-protein interactions (as in the case of RET/PTC oncoproteins). This review describes the molecular mechanisms by which the different genetic alterations cause the conversion of RET into a dominant transforming oncogene.
Carcinoma, Papillary↗
ONYX-015, an E1B gene-defective adenovirus, induces cell death in human anaplastic thyroid carcinoma cell lines.
Being one of the most lethal human neoplasms and refractory to such conventional treatment as chemo- and radiotherapy, anaplastic thyroid carcinoma is a prime target for innovative therapy. p53 gene inactivation is a constant feature of this neoplasia. Therefore, we evaluated a therapeutic approach based on an E1B 55-kDa gene-defective adenovirus (ONYX-015) that replicates only in cells with impaired p53 function and leads to cell death. Here we report that the ONYX-015 virus induces cell death in three human thyroid anaplastic carcinoma cell lines (ARO, FRO, and KAT-4). In addition, we found that the growth of xenograft tumors induced in athymic mice by the injection of ARO cells was drastically reduced by ONYX-015 treatment. The ONYX-015 virus worked synergistically with two antineoplastic drugs (doxorubicin and paclitaxel) in inducing ARO and KAT-4 cell death. These results suggest that ONYX-015 may be a valid tool in the treatment of the human thyroid anaplastic carcinoma.
Adenocarcinoma, Follicular↗
Verapamil reverts resistance to drug-induced apoptosis in Ki-ras-transformed cells by altering the cell membrane and the mitochondrial transmembrane potentials.
We have previously shown that in vivo ras-transformed cell lines display natural doxorubicin resistance compared with the normal cells and that such resistance is accompanied by a plasma membrane depolarization. In this article we first extend the analysis of doxorubicin effect to other ras-transformed cell lines, which are characterized by an increasing degree of malignant phenotype. Rat thyroid ras-transformed cells are markedly resistant to doxorubicin and the degree of drug resistance correlates with the degree of cell malignancy. The lower amount of drug accumulated inside the malignant and resistant cells is a consequence of their constitutive depolarized membrane potential and may account for their lack of drug-induced apoptosis. Verapamil, a known modulator of drug resistance, is able to decrease the resistance of all the malignant cell lines, initially causing a higher incorporation of doxorubicin as a consequence of its ability to hyperpolarize the membrane potential. In resistant cells, verapamil is also able to alter the mitochondrial membrane potential allowing apoptosis. In conclusion, these studies demonstrate that ras transformation induces the natural resistance to doxorubicin of the malignant cells. We suggest that the most malignant and resistant cells, of metastatic origin, could be preferentially destroyed by manipulation of their membrane properties, and we confirm the possibility of overcoming drug resistance by the administration of verapamil also in P-gp170-nonexpressing cells.
Animals↗
45th annual meeting of the Italian Cancer Society. Bergamo, 9-12 November 2003.
The 45th Annual Meeting of the Italian Cancer Society (SIC), held at the Centro Congressi Giovanni XXIII in Bergamo, Italy on 9-12 November, 2003, attracted almost 400 participants. The Scientific Committee chaired by R Giavazzi (Mario Negri Institute, Bergamo) and the board of the Italian Cancer Society produced a packed and varied program. Plenary sessions with keynote speakers (24 lectures) were combined with oral proffered papers (20 selected presentations), providing a platform from laboratory science to clinical interventions. Two hundred and sixty-one abstracts were submitted to the conference and presented in poster and poster discussion sessions, providing a stimulating ground for discussion and a network of interactive collaboration among young investigators. The venue of Bergamo offered exceptional hospitality with social events in the beautiful old town and at the Modern Art Museum. We hope that the following report gives an idea of the event and will encourage the reader to attend the 46th meeting of the SIC, 24-26 October, 2004 in Pisa.
Anticarcinogenic Agents↗