ICAR: endoscopic skull‐base surgery

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Nω -linked arginine peptides

From Nα-trityl-L-arginine benzyl ester, Nω-glycyl-, Nω-L-valyl-, and Nω-L-arginyl-L-arginine have been prepared. These non-typical arginine peptides were transformed, especially in alkaline solution, into ornithine and the corresponding 2-iminoimidazolidin-4-one (glycocyamidine) derivatives. In this way the suggestion of Zervas and Bergmann that a non-typical Nω-L-arginyl-L-arginine is formed as an intermediate in the disproportionation of arginine methyl ester was confirmed. When arginine derivatives are used in peptide synthesis, the formation of non-typical arginine peptides can occur. This could lead to the final incorporation of ornithine instead of arginine into the peptide chain. © Royal Society of Chemistry

Diagnostic and prognostic significance of human kallikrein 11 (KLK11) mRNA expression levels in patients with laryngeal cancer

Objectives: Human kallikrein 11 gene (KLK11) encodes a secreted serine protease. In view of its diagnostic and prognostic strength in many malignancies, we investigated the mRNA expression levels of KLK11 in laryngeal tissues in order to unveil its clinical usefulness in laryngeal cancer. Design and methods: KLK11 expression was quantified in 163 tissue samples from 105 laryngeal cancer patients with the development of a highly sensitive real-time PCR methodology, using SYBR Green® chemistry. Results: KLK11 expression in laryngeal cancer specimens of primary or recurrent nature was significantly inferior compared with their non-malignant counterparts (P< 0.001 and P= 0.026, respectively), a finding of immense diagnostic value as illustrated in the ROC curve analyses (P< 0.001). Survival analysis showed that patients harboring KLK11-positive tumors had a significantly decreased risk of death (HR = 0.26, P= 0.042). Conclusions: Our data recommend KLK11 mRNA expression as a novel and independent biomarker in laryngeal cancer for diagnostic and prognostic purposes. © 2012 The Canadian Society of Clinical Chemists

Continuation of smoking after treatment of laryngeal cancer: An independent prognostic factor?

Aim: The aim of the study is to examine if continuation of smoking after treatment is an independent factor affecting the prognosis of laryngeal cancer. Materials and Methods: A total of 153 patients met the inclusion criteria for this prospective study, and they were followed up for 12-60 months. Smoking cessation/continuation rates were recorded and associated with disease recurrence and overall patient survival. Results: The recurrence rate was 35.29%. Twenty-five percent of the patients continued smoking after treatment, 75% stopped. Of the patients who quit smoking, 28.69% died during the follow-up period, compared to 52.63% of those who continued (p = 0.0047). The respective recurrence rates were 28.7 and 55.26% (p = 0.0022). A stepwise multivariate Cox regression analysis eliminated potential confounders regarding the overall survival rate and confirmed that time between symptom onset and diagnosis, T and N stage and continuation of smoking after treatment are statistically significant factors. Among them, continuation of smoking was found to have the strongest correlation to the overall survival rate. Conclusion: Continuation of smoking after treatment of laryngeal cancer is an independent negative prognostic factor. From a clinical standpoint, all patients with known laryngeal cancer should be strongly encouraged to quit smoking. Copyright © 2012 S. Karger AG, Basel

Accounting for conformational variability in NMR structure of cyclopeptides: Ensemble averaging of interproton distance and coupling constant restraints

The application of an ensemble-averaging (EA) protocol to highlight conformational variability and to determine the interconverting conformations in NMR structure of cyclopeptides is described. Most of the NMR-based conformational studies of cyclopeptides reported in the literature rely on protocols that basically assume the existence of a single structure. This is sometimes referred as the one NOE (or ROE)/one distance hypothesis. In contrast, the EA protocol used in this work relies on a model that explicitly takes into account the averaging in NMR data and tests the significancy of the results which is very often disregarded in structure determination by NMR. This EA method was applied to the conformational analysis of the peptide cyclo(Gly-Pro-Phe-Gly-Pro-Nle) in DMSO by NMR. Qualitative analysis of the ROEs observed for this peptide indicates that it adopts the well-known double reverse turn structure. However, certain interproton distances derived from a set of ROESY experiments, as well as some coupling constants, are not compatible with the existence of a unique conformation but reflect the presence of several conformers in fast exchange on the NMR time scale. Therefore, structures consistent as ensemble with the NMR-derived restraints were determined using a restrained molecular-dynamics-based ensemble- averaging protocol which explicitly takes multiconformers into account and treats the restraints as ensemble-averaged quantities. The NMR-derived data used as input restraints in this EA protocol include the distance restraints (DR), the homonuclear coupling constants (J), and a large set of unambiguous antidistance restraints (ADR) that are generally disregarded in conformational analysis of cyclopeptides. The number of interconverting conformers was determined from the significance of the fit of the DR and ADR using the complete cross-validation method. The results shows that pairs of conformers give a satisfactory and significant fit of all NMR data. The conformational analysis of the interconverting partners reveals that the hexapeptide cyclo(Gly-Pro-Phe-Gly-Pro-Nle) exists in solution either as a βVIII-βII/iγ-βI or a βII-βII/βI-β-I equilibrium

Quantitative expression analysis of the apoptosis-related gene, BCL2L12, in head and neck squamous cell carcinoma

Background: BCL2L12 is a recently identified gene belonging to the BCL2 family, members of which are implicated in head and neck squamous cell carcinoma (HNSCC). We have recently shown that BCL2L12 mRNA expression is an unfavorable prognostic indicator in nasopharyngeal carcinoma (NPC) and that BCL2L12 can be regarded as a novel, useful tissue biomarker for the prediction of NPC patients' short-term relapse. The aim of this study was to analyze the mRNA expression of the novel apoptosis-related gene BCL2L12 in patients with HNSCC. Methods: Total RNA was isolated from 53 malignant tumors originating in larynx, pharynx, tongue, buccal mucosa, parotid glands, and nasal cavity, as well as from 34 adjacent non-cancerous tissue specimens, resected from patients with HNSCC. A highly sensitive real-time PCR method for BCL2L12 mRNA quantification in head and neck tissues was developed using the SYBR® Green chemistry. After preparing cDNA by reverse transcription, relative quantification was performed using the comparative CT () method. Results: BCL2L12 mRNA levels were lower in laryngeal tumors of advanced tumor, node, metastasis (TNM) stage or bigger size and in well-differentiated malignant tongue neoplasms, compared with early-stage laryngeal tumors or poorly differentiated tongue tumors. Interestingly, the BCL2L12 expression showed significant discriminatory value, distinguishing efficiently patients with tongue squamous cell carcinoma (SCC) from non-cancerous population. Conclusions: This is the first study examining the BCL2L12 mRNA expression in HNSCC. Our results suggest that BCL2L12 mRNA expression may serve as a potential prognostic biomarker in tongue and/or larynx SCC, which principally constitute the great majority of HNSCC cases worldwide. © 2012 John Wiley & Sons A/S

L-DOPA decarboxylase (DDC) expression status as a novel molecular tumor marker for diagnostic and prognostic purposes in laryngeal cancer

L-DOPA decarboxylase (DDC) plays an essential role in the enzymatic synthesis of dopamine and alterations in its gene expression have been reported in several malignancies. Our objective was to analyze DDC messenger RNA (mRNA) and protein expression in laryngeal tissues and to evaluate the clinical implication of this molecule in laryngeal cancer. In this study, total RNA was isolated from 157 tissue samples surgically removed from 100 laryngeal cancer patients. A highly sensitive real-time polymerase chain reaction methodology based on SYBR Green I fluorescent dye was developed for the quantification of DDC mRNA levels. In addition, Western blot analysis was performed for the detection of DDC protein. DDC mRNA expression was revealed to be significantly downregulated in primary laryngeal cancer samples compared with their nonmalignant counterparts (P=001). A significant negative association was also disclosed between DDC mRNA levels and TNM staging (P=034). Univariate analysis showed that patients bearing DDC-positive tumors had a significantly decreased risk of death (hazard ratio = 0.23, P=012) and local recurrence (hazard ratio = 0.32, P=.006), whereas DDC expression retained its favorable prognostic significance in the multi-variate analysis. Kaplan-Meier curves further demonstrated that DDC-positive patients experienced longer overall and disease-free survival periods (P=006 and P=004, respectively). Moreover, DDC protein was detected in both neoplastic and noncancerous tissues. Therefore, our results suggest that DDC expression status could qualify as a promising biomarker for the future clinical management of laryngeal cancer patients. © 2012 Neoplasia Press, Inc. All rights reserved

Three-Dimensional Structure of Cyclohexapeptides Containing a Phosphinic Bond in Aqueous Solution: A Template for Zinc Metalloprotease Inhibitors. A NMR and Restrained Molecular Dynamics Study

The 3D structures of two phosphinic cyclic hexapeptide inhibitors of bacterial collagenase, cyclo-(Gly1-Pro2-Phe3ψ[PO2-CH2]Gly4-Pro5-Nle6) (compound I) and cyclo(Gly1-Pro2-D-Phe3ψ [PO2-CH2]-Gly4-Pro5-Nle6) (compound II), in aqueous solution, as derived from NMR spectroscopy and molecular dynamics simulations, are described. The general structures of these cyclic hexapeptides closely resemble the “canonic” two-reverse-turn structure, with the proline occupying the (i + 1) position of the turns and the glycine the connecting positions. The phosphinic bond is located between the (i + 2) and (i + 3) positions of one of these turns. However, a striking feature of the backbone structure of these peptides is the presence of double type VIII-turns in compound I, and in compound II of type VIII- and tentatively named type IX-turns. The comparison of the 3D structures of these two cyclic hexapeptides shows that the stereochemistry of the phenylalanylphosphinyl residue influences not only the local conformation but also the global topology of the peptide macrocycle. The differences in the 3D structure of these compounds are discussed in relation to their inhibitory potencies and with the view of using these constrained cyclic peptides as a scaffold for the development of rigid metalloproteases inhibitors. © 1995, American Chemical Society. All rights reserved