Micronuclei frequency in peripheral blood lymphocytes of cancer patients: a meta-analysis

Micronuclei (MN) frequency is a biomarker of chromosomal damage, genome instability, and cancer risk that integrates acquired mutations and genetic susceptibility. To evaluate and summarize the evidence reporting association between cancer and MN formation, we performed a meta-analysis assessing the frequency of this biomarker in cancer patients. Findings from 37 publications were retrieved through an extensive search of the MedLine/PubMed database. Given the heterogeneity of the study design, all studies were re-classified into three groups: (i) baseline MN frequency of untreated cancer patients (25 studies), (ii) induced MN frequency in thyroid cancer patients undergoing radioiodine treatment (9 studies), and (iii) radiosensitivity of lymphocytes (12 studies) in untreated cancer patients. A meta-estimate of the frequency ratio (meta-FR) was computed in each group. A significant increase of MN frequency was found in untreated cancer patients (meta-FR=1.45; 95% Confidence Interval (95% CI): 1.28-1.64) and in thyroid cancer patients after radioiodine treatment (meta-FR=2.26; 95% CI: 1.90-2.68). The third meta-analysis showed a negative trend of meta-FR's when plotted vs. the dose used to study patients' radiosensitivity, possibly associated to a high rate of apoptosis. The results of this review substantiate the existing evidence about a role of MN in various steps of carcinogenesis. The relatively small numbers of papers suitable for the meta-analysis call for new and larger studies, possibly based on high-throughput techniques, to further understand the role of MN formation in the occurrence of genetic instability and cancer.     

Genetic polymorphisms and micronucleus formation: a review of the literature

The formation of micronuclei (MN) is extensively used in molecular epidemiology as a biomarker of chromosomal damage, genome instability, and eventually of cancer risk. The occurrence of MN represents an integrated response to chromosome-instability phenotypes and altered cellular viabilities caused by genetic defects and/or exogenous exposures to genotoxic agents. The present article reviews human population studies addressing the relationship between genetic polymorphisms and MN formation, and provides insight into how genetic variants could modulate the effect of environmental exposures to genotoxic agents, host factors (gender, age), lifestyle characteristics (smoking, alcohol, folate), and diseases (coronary artery disease, cancer). Seventy-two studies measuring MN frequency either in peripheral blood lymphocytes or exfoliated cells were retrieved after an extensive search of the MedLine/PubMed database. The effect of genetic polymorphisms on MN formation is complex, influenced to a different extent by several polymorphisms of proteins or enzymes involved in xenobiotic metabolism, DNA repair proteins, and folate-metabolism enzymes. This heterogeneity reflects the presence of multiple external and internal exposures, and the large number of chromosomal alterations eventually resulting in MN formation. Polymorphisms of EPHX, GSTT1, and GSTM1 are of special importance in modulating the frequency of chromosomal damage in individuals exposed to genotoxic agents and in unexposed populations. Variants of ALDH2 genes are consistently associated with MN formation induced by alcohol drinking. Carriers of BRCA1 and BRCA2 mutations (with or without breast cancer) show enhanced sensitivity to clastogens. Some evidence further suggests that DNA repair (XRCC1 and XRCC3) and folate-metabolism genes (MTHFR) also influence MN formation. As some of the findings are based on relatively small numbers of subjects, larger scale studies are required that include scoring of additional endpoints (e.g., MN in combination with fluorescent in situ hybridization, analysis of nucleoplasmic bridges and nuclear buds), and address gene-gene interactions.     

The antimicrobial activity of lactoferrin: Current status and perspectives

Lactoferrin (Lf) is a multifunctional iron glycoprotein which is known to exert a broad-spectrum primary defense activity against bacteria, fungi, protozoa and viruses. Its iron sequestering property is at the basis of the bacteriostatic effect, which can be counteracted by bacterial pathogens by two mechanisms: the production of siderophores which bind ferric ion with high affinity and transport it into cells, or the expression of specific receptors capable of removing the iron directly from lactoferrin at the bacterial surface. A particular aspect of the problem of iron supply occurs in bacteria (e.g. Legionella) which behave as intracellular pathogens, multiplying in professional and non professional macrophages of the host. Besides this bacteriostatic action, Lf can show a direct bactericidal activity due to its binding to the lipid A part of bacterial LPS, with an associated increase in membrane permeability. This action is due to lactoferricin (Lfc), a peptide obtained from Lf by enzymatic cleavage, which is active not only against bacteria, but even against fungi, protozoa and viruses. Additional antibacterial activities of Lf have also been described. They concern specific effects on the biofilm development, the bacterial adhesion and colonization, the intracellular invasion, the apoptosis of infected cells and the bactericidal activity of PMN. The antifungal activity of Lf and Lfc has been mainly studied towards Candida, with direct action on Candida cell membranes. Even the sensitivity of the genus tricophyton has been studied, indicating a potential usefulness of this molecule. Among protozoa, Toxoplasma gondii is sensitive to Lf, both in vitro and in vivo tests, while Trichomonads can use lactoferrin for iron requirements. As to the antiviral activity, it is exerted against several enveloped and naked viruses, with an inhibition which takes place in the early phases of viral invection, as a consequence of binding to the viral particle or to the cell receptors for virus. The antiviral activity of Lf has also been demonstrated in in vivo model invections and proposed for a selective delivery of antiviral drugs. The new perspectives in the studies on the antimicrobial activity of Lf appear to be linked to its potential prophylactic and therapeutical use in a considerable spectrum of medical conditions, taking advantage of the availability of the recombinant human Lf. But the historical evolution of our knowledge on Lf indicates that its antimicrobial activity must be considered in a general picture of all the biological properties of this multifunctional protein.     

The normalization of gene expression data in melanoma: investigating the use of glyceraldehyde 3-phosphate dehydrogenase and 18S ribosomal RNA as internal reference genes for quantitative real-time PCR

We examined a panel of 26 melanoma and fibroblast samples (tissues and cultured cells) to evaluate the suitability of two commonly used housekeeping genes, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and 18S ribosomal RNA (rRNA), for quantitative real-time PCR. Both genes showed significant variations within the individual cell line and tissue groups. Although no overall trends were observed in the expression of the 18S rRNA, GAPDH was up-regulated in melanoma tissue and cultured cells compared with the corresponding normal samples. In melanoma and fibroblast cell lines and tissues, absolute quantification appears to be more appropriate than normalizing messenger RNA (mRNA) expression via GAPDH or 18S rRNA housekeeping genes.     

Metal regulation of siderophore synthesis in Pseudomonas aeruginosa and functional effects of siderophore-metal complexes.

Pseudomonas aeruginosa synthesizes two siderophores, pyochelin and pyoverdin, characterized by widely different structures, physicochemical properties, and affinities for Fe(III). Titration experiments showed that pyochelin, which is endowed with a relatively low affinity for Fe(III), binds other transition metals, such as Cu(II), Co(II), Mo(VI), and Ni(II), with appreciable affinity. In line with these observations, Fe(III) and Co(II) at 10 microM or Mo(VI), Ni(II), and Cu(II) at 100 microM repressed pyochelin synthesis and reduced expression of iron-regulated outer membrane proteins of 75, 68, and 14 kDa. In contrast, pyoverdin synthesis and expression of the 80-kDa receptor protein were affected only by Fe(III). All of the metals tested, except Mo(VI), significantly promoted P. aeruginosa growth in metal-poor medium; Mo(VI), Ni(II), and Co(II) were more efficient as pyochelin complexes than the free metal ions and the siderophore. The observed correlation between the affinity of pyochelin for Fe(III), Co(II), and Mo(VI) and the functional effects of these metals indicates that pyochelin may play a role in their delivery to P. aeruginosa.     

Influence of transmucosal height in abutments of single and multiple implant-supported prostheses: a non-linear three-dimensional finite element analysis

The aim of this study was to analyze the influence of three different transmucosal heights of the abutments in single and multiple implant-supported prostheses through the finite element method. External hexagon implants, MicroUnit, and EsthetiCone abutments were scanned and placed in an edentulous maxillary model obtained from a tomography database. The simulations were divided into two groups: (1) one implant with 3.75 × 10 mm placed in the upper central incisor, simulating a single implant-supported fixed prosthesis with an EsthetiCone abutment; and (2) two implants with 3.75 × 10 mm placed in the upper lateral incisors with MicroUnit abutments, simulating a multiple implant-supported prosthesis. Subsequently, each group was subdivided into three models according to the transmucosal height (1, 2, and 3 mm). A static oblique load at an angle of 45 degrees to the long axis of the implant in palatal-buccal direction of 150 and 75 N was applied for multiple and single implant-supported prosthesis, respectively. The implants and abutments were assessed according to the equivalent Von Mises stress analyses while the bone and ceramics were analyzed through maximum and minimum principal stresses. The total deformation values increased in all models, while the transmucosal height was augmented. The transmucosal height of the abutments influences the stress values at the bone, ceramics, implants, and abutments of both the single and multiple implant-supported prostheses, with the transmucosal height of 1 mm showing the lowest stress values.