Gab2-Mediated Signaling Promotes Melanoma Metastasis

Metastatic melanoma is a disease with a poor prognosis that currently lacks effective treatments. Critical biological features of metastasis include acquisition of migratory competence, growth factor independence, and invasive potential. In an attempt to identify genes that contribute to melanoma pathogenesis, a genome-wide search using bacterial artificial chromosome array comparative genomic hybridization and single nucleotide polymorphism arrays in a series of 64 metastatic melanoma samples and 20 melanoma cell lines identified increased copy numbers of Gab2 located on 11q14.1. Gab2 is an adaptor protein that potentiates the activation of the Ras-Erk and PI3K-Akt pathways and has recently been implicated in human cancer; however, its role in melanoma has not been explored. In this study, we found that Gab2 was either amplified (∼11%) and/or overexpressed (∼50%) in melanoma. Gab2 protein expression correlated with clinical melanoma progression, and higher levels of expression were seen in metastatic melanomas compared with primary melanoma and melanocytic nevi. We found that overexpression of Gab2 potentiates, whereas silencing of Gab2 reduces, migration and invasion of melanoma cells. Gab2 mediated the hyperactivation of Akt signaling in the absence of growth factors, whereas inhibition of the PI3K-Akt pathway decreased Gab2-mediated tumor cell migration and invasive potential. Gab2 overexpression resulted in enhanced tumor growth and metastatic potential in vivo. These studies demonstrate a previously undefined role for Gab2 in melanoma tumor progression and metastasis.Melanoma is the fifth most common cancer in the US, accounting for more than 60,000 new cases each year.¹ If diagnosed in the early stages, melanoma can be cured by surgery; however metastatic disease has a poor prognosis with a median survival of 6 to 9 months.² There is no therapy for thicker or metastatic melanomas proven to have a significant impact on survival. Therefore, gaining mechanistic insight into melanoma metastasis and identifying therapeutic targets are critical for improved patient care.The gab genes, encoding mammalian Gab1, Gab2, and Gab3, represent a family of scaffolding or docking adaptor proteins.³ Gab proteins are recruited to activated receptors by direct or indirect mechanisms, mostly indirectly via Grb2. They contain several functional motifs that mediate interactions with multiple signal relay molecules and can assemble multimeric signaling complexes. On stimulation, Gab2 (Grb2-associated binding protein 2) undergoes tyrosine phosphorylation, creating a number of docking sites to mediate interactions with SH2 domain-containing proteins such as the tyrosine phosphatase Shp2 and the p85 subunit of PI3K. The interaction of Gab2 with Shp2 activates Ras-Erk signaling, whereas its association with the p85 subunit of PI3K is crucial in mediating the PI3K-Akt signaling.^3,4Recent studies provide evidence that Gab2 plays a critical role in human cancer. Gab2 is overexpressed in a subset of breast cancers.⁵ Its overexpression increases the proliferative capacity of mammary epithelial cells and alters growth factor dependence.⁶ Gab2 cooperates with receptor tyrosine kinases such as erbB2 or the Src family and promotes an invasive phenotype in breast tumorigenesis.^6,7 In the Her2/Neu-induced Gab2 knockout mouse model, Gab2-deficient cells exhibit decreased migration and mice show reduced lung metastasis, suggesting its role in promoting mammary tumor metastasis.⁸ Gab2 maps to a region commonly amplified in several human malignancies and is amplified in a subset of Gab2-overexpressing breast tumors. In addition to breast tumorigenesis, Gab2-mediated signaling has been implicated in hematological malignancies. The Grb2-Gab2 pathway is critical for leukemic transformation by Bcr-Abl.⁹ Gab2 can be activated downstream of tyrosine kinases in hematopoietic cells and propagates signals for the transforming activity of those kinases. Although these studies suggest the importance of Gab2-mediated signaling in breast tumorigenesis and leukemia, its role in melanoma is unexplored.In this study, we identified increased copy numbers of Gab2 in metastatic melanomas through a genome-wide search using bacterial artificial chromosome (BAC) array comparative genomic hybridization (CGH) and single nucleotide polymorphism (SNP) arrays that led us to analyze its role in melanoma. We found that metastatic melanomas express significantly higher levels of Gab2 than primary melanomas and melanocytic nevi, identifying Gab2 as a molecular marker for neoplastic progression. Moreover, we show that Gab2 promotes tumor cell migration and invasion by activating Akt signaling, and enhances tumor growth and metastasis in vivo, suggesting a role for Gab2-mediated signaling in promoting metastatic capability in melanoma.     

The effect of the physicochemical properties of a drug on its release from chitosonium malate matrix tablets

The effect of the physico-chemical properties of an active compound (such as solubility and molecular size) on its release characteristics from chitosonium malate matrix tablets has been investigated. For this purpose, the release of 11 drugs of various solubilities (1 in < 1 to 1 in 10000) and molecular weights (138–375) through chitosonium malate matrix tablets was studied. It may be concluded that, in addition to the solubility, the molecular size of drug is of importance in the drug release characteristics from the chitosonium malate matrix. When the release data (< 60%) were fitted to the simple power law equation, the mode of drug release from the chitosonium malate matrix was generally non-Fickian and Super Case II type. These drugs (timolol maleate, ephedrine, propranolol hydrochloride, acetylsalicylic acid, naproxen, sulphadiazine, indomethacin and pindolol) can be released at a nearly zero-order rate through the matrix.     

The reliability of digital cameras for color selection

PURPOSE: This study evaluated the validity of the color selection results obtained from digital cameras. MATERIALS AND METHODS: Four observers matched the colors of 30 extracted maxillary incisors under daylight conditions. Two different digital cameras, with 1.5- and 5.0-megapixel resolutions, were used to select the color of the standardized circular area with 3 reference points on the same teeth; a spectrophotometer was also used, and the results were compared with the human and camera observations. RESULTS: The highest significant agreement (60% agreement with the spectrophotometric values) was found with the 5.0-megapixel camera. CONCLUSION: It appears that the resolution capacity of a digital camera can increase the reliability of color selection.     

Role of cd56 and e-cadherin expression in the differential diagnosis of papillary thyroid carcinoma and suspected follicular-patterned lesions of the thyroid: the prognostic importance of e-cadherin

Introduction: The pathological diagnosis of papillary thyroid carcinoma (PTC) is generally easy on routine sections stained with hematoxylin and eosin (H&E). However, the differentiation of the follicular variant of PTC (FVPTC) from other suspected follicular-patterned lesions of the thyroid is highly difficult. Among these, the lesions for which FVPTC cannot be excluded are classified as well-differentiated tumors of uncertain malignant potential (WDT-UMP). The most common immunohistochemical (IHC) markers used in the differential diagnosis include HBME-1, galectin-3, and CK19. However, none of these markers provide a 100% differential diagnosis. Objective: The present study compared the diagnostic value of CD56 and E-cadherin for the differentiation of FVPTC from the other benign follicular-patterned lesions, with HBME-1, galectin-3, and CK19. Using these markers, the controversial cases within the WDT-UMP group were reclassified. Additionally, the relationship between the reductions in E-cadherin expression with poor prognostic factors was investigated. Materials and methods: The IHC expressions of CD56, E-cadherin, HBME-1, galectin-3, and CK19 were evaluated in 181 thyroid lesions, including 101 PTCs (45 classical variant PTCs and 56 FVPTCs), 20 WDT-UMPs, 20 follicular adenomas (FAs), 20 hyperplastic nodules (HN), and 20 hyperplastic foci of lymphocytic thyroiditis. The results were statistically compared via SPSS. Results: The expressions of all of the markers were statistically significantly different in PTC and follicular-patterned lesions (P<0.05). It was found that the only marker with both sensitivity and specificity above 90% was CD56 negativity (sensitivity 91.1%, specificity 91.7%). The most sensitive and also the most specific double panel was CD56 negativity and galectin-3 positivity (sensitivity 96%, specificity 85%), and the most sensitive and specific triple panel was CD56 negativity, HBME-1 positivity, and galectin-3 positivity (97% and 70%, respectively).     

Comparison of serum thiol–disulphide homeostasis and total antioxidant–oxidant levels between exudative age-related macular degeneration patients and healthy subjects

Purpose

The purpose of the study was to calculate serum total oxidant status (TOS), total antioxidant status (TAS), and dynamic thiol–disulphide (T-D) homeostasis in patients with age-related macular degeneration (AMD), and compare the results with healthy individuals.

Methods

Thirty-three exudative AMD patients and 33 healthy controls were included in this case–control study. Participants’ serum TAS and TOS levels were measured. In addition, total thiol (TT), native thiol (NT), and disulphide (DS) concentrations were assessed using a novel automated method of measurement.

Results

In comparison with the control group, serum TAS, TT, and NT levels were found to be significantly lower (p < 0.0001, p = 0.004, p = 0.003, respectively) and TOS levels were detected higher (p = 0.032) in AMD patients. Serum DS levels were elevated in the AMD patient group, but the difference was not statistically significant (p = 0.219). DS/TT and DS/NT ratios were significantly higher (p = 0.012, p = 0.013, respectively) in AMD patients. A positive correlation was found between TT and NT (p < 0.0001) in AMD group.

Conclusions

Serum TOS levels are higher, TAS levels are lower, and the T-D balance is shifted to the DS bond side in AMD patients. These results suggest that increased oxidative stress and decreased antioxidant levels may play a role in AMD progression. Further studies are needed to confirm the pathophysiologic role of T-D homeostasis in AMD.

     

Comparison of cervical spine motion during intubation with a C‑MAC D‑Blade® and an LMA Fastrach®

Die Anaesthesiologie - This prospective randomized study compared cervical motion during intubation with a C‑MAC D‑Blade® and with a laryngeal mask airway LMA Fastrach®. The...     

Saddle pulmonary embolism visualized by real time three-dimensional echocardiography

Saddle pulmonary embolism is defined as a visible thromboembolus straddling the bifurcation of the main pulmonary artery. It is very unusual to visualize a pulmonary artery thrombus on transthoracic echocardiography. We describe a case of a saddle embolus of the main pulmonary artery visualized by real time three-dimensional echocardiography and successfully treated with intravenous unfractionated heparin, followed by oral anticoagulation achieving a complete dissolution of the thrombus. (Echocardiography 2012;29:E8-E9).     

Effect of varying core thicknesses and artificial aging on the color difference of different all-ceramic materials

Objective. Clinicians should reserve all-ceramics with high translucency for clinical applications in which high-level esthetics are required. Furthermore, it is unclear whether a correlation exists between core thickness and color change. The aim of this study was to examine the effects of different core thicknesses and artificial aging on the color stability of three all-ceramic systems. Materials and methods. Ninety disc-shaped cores with different thicknesses (0.5 mm, 0.8 mm and 1.0 mm) were prepared from three all-ceramic systems, In-Ceram Alumina (IC), IPS e.max Press (EM) and Katana (K). The colors of the samples were measured with a spectrophotometer and the color parameters (L*, a*, b*, ΔE) were calculated according to the CIE L*a*b* (Commission Internationale de L'Eclairage) color system before and after aging. Results. The effects of aging on color parameters were statistically significant (p < 0.001), regardless of core thickness. For all systems, the CIE a* values increased as the thickness of the core increased. Conversely, such increases in core porcelain thickness were correlated with decreasing CIE L* and b* values. Core thickness had a statistically significant effect on color change among the groups. Conclusions. Different core thicknesses (from 1.0–0.5 mm) and artificial aging affected color stability of the all-ceramic materials tested.     

Factor V Leiden mutation in cerebrovascular disease.

Several studies indicate a high prevalence of factor V Leiden mutation as the most frequent coagulation defect found in patients with venous thrombosis. The relationship between this mutation and cerebrovascular disease has not been established in adults. In this investigation, we studied 29 patients with ischemic stroke and 20 with intracerebral hemorrhage, all of whom were compared with 20 controls. A region of the factor V gene containing the Leiden mutation site was amplified with polymerase chain reaction and the presence of mutation was determined with restriction enzyme digestion. We found no evidence of an association between factor V Leiden mutation and ischemic stroke or intracerebral hemorrhage. There was no evidence of association in subgroup the analysis by age, smoking status, myocardial infarction, hypertension, diabetes mellitus, or coronary disease. Factor V Leiden mutation doesn't seem to be associated with a risk of cerebrovascular disease.