RET: A Multi-Faceted Gene in Human Cancer

Receptor tyrosine kinases (RTK) are transmembrane (TM) proteins featuring an intracellular domain containing the tyrosine kinase (TK) enzyme. RTKs are often involved in cancer formation [13]. Notable examples are epidermal growth factor receptor (EGFR/ HER1) and anaplastic lymphoma kinase (ALK) in non-small cell lung carcinoma (NSCLC) [4], KIT in gastrointestinal stromal tumors (GIST) [5], FLT3 in acute myeloid leukemia (AML) [6], and HER2/ ERBB2/neu in breast cancer [7]. In some cases, cancer cells up-regulate expression of the RTK (as an example HER2 in breast cancer), its cognate growth factor or both, in other cases, structural alterations such as chromosomal rearrangements leading to the RTK recombination to heterologous genes (as an example EML4-ALK in lung adenocarcinoma) or point mutations (as EGFR, KIT or FLT3 mutations in NSCLC, GIST, or AML, respectively), lead to unchecked kinase and oncogenic activity [1-3]. This notion has stimulated the search for agents, such as monoclonal antibodies against the RTK extracellular domain (like trastuzumab for HER2 or cetuximab for EGFR) or ATP-competitive small molecule protein kinase inhibitors (PKIs) (like gefitinib and erlotinib for EGFR or crizotinib for ALK), to combat cancers driven by oncogenic RTKs [1-3]. The RET RTK was originally identified as an oncogene activated by a rearrangement occurred in vitro during transfection of NIH3T3 cells with human lymphoma DNA [8]. RET protein belongs to a cell-surface complex able to bind glial-derived neurotrophic factor (GDNF) ligands (GDNF, neurturin, artemin, and persephin) in conjunction with co-receptors of the GDNF receptor α family, designated GFRα 1-4 [9]. Binding to the ligand-co-receptor complex leads to RET dimerization and kinase activation. RET expression is tightly regulated during development and in the adulthood is limited to specific tissues, including neural crest-derived cells. RET is essential for the development of the enteric neurvous system and kidney, and germline loss-of-function mutations in RET cause Hirschsprung disease (aganglionic megacolon) and congenital anomalies of the kidney or lower urinary tract [10,11]. RET gene maps to chromosome 10q11.2. Fig. 1 shows that it is splitted in 21 coding exons. Exons 1-10 code for the extracellular region; exon 11 codes for the COOH-terminal part of the extracellular region, the TM domain, and the intracellular juxtamembrane domain. Finally, exons 12-21 code for the intracellular domain. An alternative splicing at exon 19 determine the synthesis of three RET protein isoforms with different C-terminal tails. In RET9 (1072 aa), exon 19 is unspliced; in RET51 (1114 aa), exon 19 is spliced to exon 20; in RET43 (1106 aa), exon 19 is spliced to to exon 21 [12-15]. RET9 and RET51 are the most abundant and well characterized isoforms (Fig. 1). RET protein features an extracellular portion (RET-EC) tha

Differential diagnosis of thyroid nodules using fine-needle aspiration cytology and oncogene mutation screening: are we ready?

Thyroid nodules are a very common clinical finding, and although the majority of them are benign, thyroid carcinoma accounts for about 5-15% of nodules. Fine-needle aspiration cytology (FNAC) is actually used for the differential diagnosis of these lesions. Although in most cases this examination clearly distinguishes benign from malignant lesions, some fine-needle aspiration (FNA) samples fall into undetermined thyroid cytology categories, which according to the most recent classification of thyroid FNAC consist of ‘suspicious for malignancy’, ‘suspicious for follicular or Hurtle cell neoplasm’, and ‘follicular lesion of undetermined significance/atypia of undetermined significance’. Moreover, some samples are insufficient for diagnosis. Taken together, these categories account for almost 20-30% of nodules. Owing to the high risk of papillary thyroid carcinoma, patients with lesions that are ‘suspicious for malignancy’ are currently subjected to lobectomy or total thyroidectomy. On the other hand, patients with ‘atypia of undetermined significance’ undergo repeated FNAs, and patients with ‘suspicious for follicular or Hurtle cell neoplasm’ are subjected to diagnostic lobectomy and subsequently, in the case of histological diagnosis of carcinoma, total thyroidectomy. Recent studies clearly indicate that molecular analysis of thyroid nodules can significantly improve the diagnostic power of cytology and drive the appropriate clinical management of these patients

Heavy rains triggering flash floods in urban environment: A case from Chiavari (Genoa metropolitan area, Italy)

Between 10th and 11th November, 2014, heavy rainfall over a short period fell on the eastern Genoa metropolitan area. The geohydrological event had important ground effects, among them the simultaneous flooding of Entella and Rupinaro streams, in Chiavari city. In lower Lavagna valley, the main tributary of the Entella, a landslide caused two casualties, while serious damage to buildings and infrastructures were registered in Chiavari\u2019s Old Town and in the nearby communities of Carasco and Cogorno. In the Entella basin, the rainfall peaked at 60 mm/hour and accumulated 220 mm in six hours. The levels of the streams rose instantly, showing concentration times of less than an hour. The Entella rose seven meters, flooding Carasco, Cogorno, and the Caperana neighborhood of Chiavari. Flash flooding of the Rupinaro stream caused water to rise to 1.5 m in Chiavari\u2019s historic core. Analyses were carried out of the weather conditions and the ground effects of the events; in addition, studies were made of the main causes of the geo-hydrological risk. In particular, variations in climate and uncontrolled urban development were the cause of increased geo-hydrological hazards and vulnerability of this area, historically subject to flooding. Such conditions of risk are unacceptable, and urgent measures are required to mitigate the effects of heavy rainfall events

Rainfall thresholds for possible landslide occurrence in Italy

Abstract The large physiographic variability and the abundance of landslide and rainfall data make Italy an ideal site to investigate variations in the rainfall conditions that can result in rainfall-induced landslides. We used landslide information obtained from multiple sources and rainfall data captured by 2228 rain gauges to build a catalogue of 2309 rainfall events with – mostly shallow – landslides in Italy between January 1996 and February 2014. For each rainfall event with landslides, we reconstructed the rainfall history that presumably caused the slope failure, and we determined the corresponding rainfall duration D (in hours) and cumulated event rainfall E (in mm). Adopting a power law threshold model, we determined cumulated event rainfall–rainfall duration (ED) thresholds, at 5% exceedance probability, and their uncertainty. We defined a new national threshold for Italy, and 26 regional thresholds for environmental subdivisions based on topography, lithology, land-use, land cover, climate, and meteorology, and we used the thresholds to study the variations of the rainfall conditions that can result in landslides in different environments, in Italy. We found that the national and the environmental thresholds cover a small part of the possible DE domain. The finding supports the use of empirical rainfall thresholds for landslide forecasting in Italy, but poses an empirical limitation to the possibility of defining thresholds for small geographical areas. We observed differences between some of the thresholds. With increasing mean annual precipitation (MAP), the thresholds become higher and steeper, indicating that more rainfall is needed to trigger landslides where the MAP is high than where it is low. This suggests that the landscape adjusts to the regional meteorological conditions. We also observed that the thresholds are higher for stronger rocks, and that forested areas require more rainfall than agricultural areas to initiate landslides. Finally, we observed that a 20% exceedance probability national threshold was capable of predicting all the rainfall-induced landslides with casualties between 1996 and 2014, and we suggest that this threshold can be used to forecast fatal rainfall-induced landslides in Italy. We expect the method proposed in this work to define and compare the thresholds to have an impact on the definition of new rainfall thresholds for possible landslide occurrence in Italy, and elsewhere

A tool for the automatic calculation of rainfall thresholds for landslide occurrence

Abstract Empirical rainfall thresholds are commonly used to forecast landslide occurrence in wide areas. Thresholds are affected by several uncertainties related to the rainfall and the landslide information accuracy, the reconstruction of the rainfall responsible for the failure, and the method to calculate the thresholds. This limits the use of the thresholds in landslide early warning systems. To face the problem, we developed a comprehensive tool, CTRL–T ( C alculation of T hresholds for R ainfall-induced L andslides− T ool) that automatically and objectively reconstructs rainfall events and the triggering conditions responsible for the failure, and calculates rainfall thresholds at different exceedance probabilities. CTRL−T uses a set of adjustable parameters to account for different morphological and climatic settings. We tested CTRL−T in Liguria region (Italy), which is highly prone to landslides. We expect CTRL−T has an impact on the definition of rainfall thresholds in Italy, and elsewhere, and on the reduction of the risk posed by rainfall-induced landslides

The receptor-type protein tyrosine phosphatase J antagonizes the biochemical and biological effects of RET-derived oncoproteins.

Abstract Thyroid cancer is frequently associated with the oncogenic conversion of the RET receptor tyrosine kinase. RET gene rearrangements, which lead to the generation of chimeric RET/papillary thyroid carcinoma (PTC) oncogenes, occur in PTC, whereas RET point mutations occur in familial multiple endocrine neoplasia type 2 (MEN2) and sporadic medullary thyroid carcinomas (MTC). We showed previously that the expression of the receptor-type protein tyrosine phosphatase J (PTPRJ) is suppressed in neoplastically transformed follicular thyroid cells. We now report that PTPRJ coimmunoprecipitates with wild-type RET and with the MEN2A-associated RET(C634R) oncoprotein but not with the RET/PTC1 and RET-MEN2B isoforms. Using mutated forms of PTPRJ and RET-MEN2A, we show that the integrity of the respective catalytic domains is required for the PTPRJ/RET-MEN2A interaction. PTPRJ expression induces dephosphorylation of the RET(C634R) and, probably via an indirect mechanism, RET/PTC1 oncoproteins on two key RET autophosphorylation sites (Tyr1062 and Tyr905). This results in a significant decrease of RET-induced Shc and extracellular signal-regulated kinase 1/2 phosphorylation levels. In line with this finding, adoptive PTPRJ expression reduced the oncogenic activity of RET(C634R) in an in vitro focus formation assay of NIH3T3 cells. As expected from the coimmunoprecipitation results, the RET(M918T) oncoprotein, which is associated to MEN2B and sporadic MTC, was resistant to the dephosphorylating activity of PTPRJ. Taken together, these findings identify RET as a novel substrate of PTPRJ and suggest that PTPRJ expression levels may affect tumor phenotype associated with RET/PTC1 and RET(C634R) mutants. On the other hand, resistance to PTPRJ may be part of the mechanism of RET oncogenic conversion secondary to the M918T mutation. (Cancer Res 2006; 66(12): 6280-7

Activation of the Erk8 Mitogen-activated Protein (MAP) Kinase by RET/PTC3, a Constitutively Active Form of the RET Proto-oncogene

Mitogen-activated protein (MAP) kinases have a central role in several biological functions, including cell adhesion and spreading, chemotaxis, cell cycle progression, differentiation, and apoptosis. Extracellular signal-regulated kinase 8 (Erk8) is a large MAP kinase whose activity is controlled by serum and the c-Src non-receptor tyrosine kinase. Here, we show that RET/PTC3, an activated form of the RET proto-oncogene, was able to activate Erk8, and we demon- strate that such MAP kinase participated in RET/PTC3-dependent stimulation of the c-jun promoter. By using RET/PTC3 molecules mutated in specific tyrosine autophosphorylation sites, we charac- terized Tyr981, a known binding site for c-Src, as a major determi- nant of RET/PTC3-induced Erk8 activation, although, surprisingly, the underlying mechanism did not strictly depend on the activity of Src. In contrast, we present evidence that RET/PTC3 acts on Erk8 through Tyr981-mediated activation of c-Abl. Furthermore, we localized the region responsible for the modulation of Erk8 activity by the RET/PTC3 and Abl oncogenes in the Erk8 C-terminal domain. Altogether, these results support a role for Erk8 as a novel effector of RET/PTC3 and, therefore, RET biological functions

Deciphering seasonal effects of triggering and preparatory precipitation for improved shallow landslide prediction using generalized additive mixed models

The increasing availability of long-term observational data can lead to the development of innovative modelling approaches to determine landslide triggering conditions at regional scale, opening new avenues for landslide prediction and early warning. This research blends the strengths of existing approaches with the capabilities of generalized additive mixed models (GAMMs) to develop an interpretable approach that identifies seasonally dynamic precipitation conditions for shallow landslides. The model builds upon a 21-year record of landslides in South Tyrol (Italy) and separates precipitation that induced landslides from precipitation that did not. The model accounts for effects acting at four temporal scales: short-term &ldquo;triggering&rdquo; precipitation, medium-term &ldquo;preparatory&rdquo; precipitation, seasonal effects and across-year data variability. It provides relative landslide probability scores that were used to establish seasonally dynamic thresholds with optimal performance in terms of hit and false alarm rates, as well as additional thresholds related to user-defined performance scores. The GAMM shows a high predictive performance and indicates that more precipitation is required to induce a landslide in summer than in winter/spring, which can presumably be attributed mainly to vegetation and temperature effects. The discussion illustrates why the quality of input data, study design and model transparency are crucial for landslide prediction using advanced data-driven techniques.</p