Chemoprevention of prostate cancer with selenium: an update on current clinical trials and preclinical findings

Prostate cancer is the most common cancer diagnosed and the second leading cause of cancer-related deaths in men in the United States. The etiological factors that give rise to prostate cancer are not known. Therefore, it is not possible to develop primary intervention strategies to remove the causative agents from the environment. However, secondary intervention strategies with selenium (Se) compounds and other agents represent a viable option to reduce the morbidity and mortality of prostate cancer. In this review, we discuss ongoing clinical trials. In addition, we discuss preclinical mechanistic studies that provide insights into the biochemical and molecular basis for the anti-carcinogenic activity of both inorganic and organic forms of Se.     

Analysis of human cytochrome P450 2C8 substrate specificity using a substrate pharmacophore and site-directed mutants

The structural determinants of substrate specificity of human liver cytochrome P450 2C8 (CYP2C8) were investigated using site-directed mutants chosen on the basis of a preliminary substrate pharmacophore and a three-dimensional (3D) model. Analysis of the structural features common to CYP2C8 substrates exhibiting a micromolar K(m) led to a substrate pharmacophore in which the site of oxidation by CYP2C8 is 12.9, 8.6, 4.4, and 3.9 A from features that could establish ionic or hydrogen bonds, and hydrophobic interactions with protein amino acid residues. Comparison of this pharmacophore with a 3D model of CYP2C8 constructed using the X-ray structure of CYP2C5 suggested potential CYP2C8 amino acid residues that could be involved in substrate recognition. Twenty CYP2C8 site-directed mutants were constructed and expressed in yeast to compare their catalytic activities using five CYP2C8 substrates that exhibit different structures and sizes [paclitaxel, fluvastatin, retinoic acid, a sulfaphenazole derivative (DMZ), and diclofenac]. Mutation of arginine 241 had marked effects on the hydroxylation of anionic substrates of CYP2C8 such as retinoic acid and fluvastatin. Serine 100 appears to be involved in hydrogen bonding interactions with a polar site of the CYP2C8 substrate pharmacophore, as shown by the 3-4-fold increase in the K(m) of paclitaxel and DMZ hydroxylation after the S100A mutation. Residues 114, 201, and 205 are predicted to be in close contact with substrates, and their mutations lead either to favorable hydrophobic interactions or to steric clashes with substrates. For instance, the S114F mutant was unable to catalyze the 6alpha-hydroxylation of paclitaxel. The S114F and F205A mutants were the best catalysts for retinoic acid and paclitaxel (or fluvastatin) hydroxylation, respectively, with k(cat)/K(m) values 5 and 2.1 (or 2.4) times higher, respectively, than those found for CYP2C8. Preliminary experiments of docking of the substrate into the experimentally determined X-ray structure of substrate-free CYP2C8, which became available quite recently [Schoch, G. A., et al. (2004) J. Biol. Chem. 279, 9497], were consistent with key roles for S100, S114, and F205 residues in substrate binding. The results suggest that the effects of mutation of arginine 241 on anionic substrate hydroxylation could be indirect and result from alterations of the packing of helix G with helix B'.     

The human mitochondrial ADP/ATP carriers: kinetic properties and biogenesis of wild-type and mutant proteins in the yeast S. cerevisiae

The mitochondrial adenine nucleotide carrier, or Ancp, plays a key role in the maintenance of the energetic fluxes in eukaryotic cells. Human disorders have been found associated to unusual human ANC gene (HANC) expression but also to direct inactivation of the protein, either by autoantibody binding or by mutation. However, the individual biochemical properties of the three HAncp isoforms have not yet been deciphered. To do so, the three HANC ORF were expressed in yeast under the control of the regulatory sequences of ScANC2. Each of the three HANC was able to restore growth on a nonfermentable carbon source of a yeast mutant strain lacking its three endogenous ANC. Their ADP/ATP exchange properties could then be measured for the first time in isolated mitochondria. HANC3 was the most efficient to restore yeast growth, and HAnc3p presented the highest V(M) (80 nmol ADP min(-1) mg protein(-1)) and K(ADP)(M)(8.4 microM). HAnc1p and HAnc2p presented similar kinetic constants (V(M) approximately 30-40 nmol ADP min(-(1) mg protein(-1) and K(ADP)(M) approximately 2.5-3.7 microM), whose values were consistent with HANC1's and HANC2's lower capacity to restore yeast growth. However, the HANC genes restored growth at a lower level than ScANC2, indicating that HAncp amount may be limiting in vivo. To optimize the HAncp production, we investigated their biogenesis into mitochondria by mutagenesis of two charged amino acids in the N-terminus of HAnc1p. Severe effects were observed with the D3A and D3K mutations that precluded yeast growth. On the contrary, the K10A mutation increased yeast growth complementation and nucleotide exchange rate as compared to the wild type. These results point to the importance of the N-terminal region of HAnc1p for its biogenesis and transport activity in yeast mitochondria.     

Serological identification of fast progressors of structural damage with rheumatoid arthritis

Introduction

Rheumatoid arthritis (RA) patients with structural progression are in most need of immediate treatment to maintain tissue integrity. The serum protein fingerprint, type I collagen degradation mediated by matrix metalloproteinases (MMP)-cleavage (C1M), is a biomarker of tissue destruction. We investigated whether baseline serum C1M levels could identify structural progressors and if the biomarker levels changed during anti-inflammatory treatment with tocilizumab (TCZ).

Methods

The LITHE-biomarker study ({"type":"clinical-trial","attrs":{"text":"NCT00106535","term_id":"NCT00106535"}}NCT00106535, n = 585) was a one-year phase III, double-blind, placebo (PBO)-controlled, parallel group study of TCZ 4 or 8 mg/kg every four weeks, in RA patients on stable doses of methotrexate (MTX). Spearman''s ranked correlation was used to assess the correlation between baseline C1M levels and structural progression at baseline and at weeks 24 and 52. Multivariate regression was performed for delta structural progression. Change in C1M levels were studied as a function of time and treatment.

Results

At baseline, C1M was significantly correlated to C-reactive protein (P <0.0001), visual analog scale pain (P <0.0001), disease activity score28-erythrocyte sedimentation rate (DAS28-ESR) (P <0.0001), joint space narrowing (JSN) (P = 0.0056) and modified total Sharp score (mTSS) (P = 0.0006). Baseline C1M was significantly correlated with delta-JSN at Week 24 (R² = 0.09, P = 0.0001) and at Week 52 (R² = 0.27, P <0.0001), and with delta-mTSS at 24 weeks (R² = 0.006, P = 0.0015) and strongly at 52 weeks (R² = 0.013, P <0.0001) in the PBO group. C1M levels were dose-dependently reduced in the TCZ + MTX group.

Conclusions

Baseline C1M levels correlated with worsening joint structure over one year. Serum C1M levels may enable identification of those RA patients that are in most need of aggressive treatment

Trial registration

ClinicalTrials.gov: {"type":"clinical-trial","attrs":{"text":"NCT00106535","term_id":"NCT00106535"}}NCT00106535     

Social rationality and scales of action: inter-ethnic relations in cockfighting and game-fishing,Raiatea, French Polynesia

This article challenges the notion of economic rationality as a criterion for explaining ethnic boundary maintenance. It offers an ethnographic analysis of inter-ethnic relations in the context of games (cockfights and game-fishing contests) in the island of Raiatea (French Polynesia). Although all players engage in the same basic gambling practices, money is differentially scaled and mobilized by the Tahitian and Chinese participants. Building on recent pragmatic approaches to rationality, it is shown that the players' rationalities differ not from the point of view of economic maximization, but only in so far as they participate in social relations at different scales.     

Circulating Protein Fragments of Cartilage and Connective Tissue Degradation Are Diagnostic and Prognostic Markers of Rheumatoid Arthritis and Ankylosing Spondylitis

Inflammation driven connective tissue turnover is key in rheumatic diseases, such as ankylosing spondylitis (AS). Few biomarkers are available for measuring disease prognosis or the efficacy of interventions applied in these tissue-related conditions. Type II collagen is the primary structural protein of cartilage and type III collagen of connective tissues, and obvious targets for the collagenalytic, which increase during tissue inflammation. The objective of the study was to investigate the diagnostic and prognostic utility of cartilage, C2M, and synovial, C3M, turnover biomarkers in AS. Serum samples were retrieved from patients suffering from AS (n = 103), RA (n = 47) and healthy controls (n = 56). AS progressors were defined as having new vertebral syndesmophytes or more that 3 unit change in mSASSS over a two-year period. Type II collagen degradation markers in serum were measured by the C2M ELISA, and type III collagen degradation by the C3M ELISA. Logistic regression and dichotomized decision tree were used to analyze the prognostic value of the markers individually or in combination. Both C2M and C3M levels were significantly higher in RA patients than in healthy controls (p<0.0001). Diagnostic utility was analyzed by ROC and areas under the curve (AUCs) were 72% and 89% for C2M and C3M, respectively. Both C2M and C3M, were significantly higher in serum samples from AS patient than from healthy controls (p<0.0001). The AUCs of C2M and C3M, respectively, were 70% and 81% for AS. A combination of C2M and C3M, dichotomized according to best cut-offs for individual markers, could correctly identify 80% of the progressors and 61% of the non-progressors. The present study is the first to show that specific biomarkers of cartilage and connective tissue degradation facilitate both diagnosis and prediction of progression of RA and AS.     

Glucocorticoids exert context-dependent effects on cells of the joint in vitro

Introduction

Glucocorticoids are known to attenuate bone formation in vivo leading to decreased bone volume and increased risk of fractures, whereas effects on the joint tissue are less characterized. However, glucocorticoids appear to have a reducing effect on inflammation and pain in osteoarthritis. This study aimed at characterizing the effect of glucocorticoids on chondrocytes, osteoclasts, and osteoblasts.

Experimental

We used four model systems to investigate how glucocorticoids affect the cells of the joint; two intact tissues (femoral head- and cartilage-explants), and two separate cell cultures of osteoblasts (2T3-pre-osteoblasts) and osteoclasts (CD14⁺-monocytes). The model systems were cultured in the presence of two glucocorticoids; prednisolone or dexamethasone. To induce anabolic and catabolic conditions, cultures were activated by insulin-like growth factor I/bone morphogenetic protein 2 and oncostatin M/tumor necrosis factor-α, respectively. Histology and markers of bone- and cartilage-turnover were used to evaluate effects of glucocorticoid treatment.

Results

Prednisolone treatment decreased collagen type-II degradation in immature cartilage, whereas glucocorticoids did not affect collagen type-II in mature cartilage. Glucocorticoids had an anti-catabolic effect on catabolic-activated cartilage from a bovine stifle joint and murine femoral heads. Glucocorticoids decreased viability of all bone cells, leading to a reduction in osteoclastogenesis and bone resorption; however, bone morphogenetic protein 2-stimulated osteoblasts increased bone formation, as opposed to non-stimulated osteoblasts.

Conclusions

Using highly robust in vitro models of bone and cartilage turnover, we suggest that effects of glucocorticoids highly depend on the activation and differential stage of the cell targeted in the joint. Present data indicated that glucocorticoid treatment may be beneficial for articular cartilage, although detrimental effects on bone should be taken into account.