Relevant gender differences in epidemiological profile, exposure to first antiretroviral regimen and survival in the Spanish AIDS Research Network Cohort.

BACKGROUND The possible differences in the disease spectrum and prognosis of HIV infection in women and men is a major point of concern. Women are under-represented in randomized clinical trials and in some cohorts. Discordant results have often been obtained depending on the setting. METHODS We assessed gender differences in clinical and epidemiological features, antiretroviral treatment (ART) exposure and survival in two multicentre cohorts of HIV-positive subjects in Spain: CoRIS-MD and CoRIS. Competing risk regression models were used to assess gender effect on time to start ART and time to first ART change, and a Cox regression model to estimate gender effect on time to death. RESULTS Between January 1996 and December 2008, 1,953 women and 6,072 men naive to ART at study entry were included. The trend analysis over time showed the percentage of women in the younger (<20 years) and older (>50 years) strata increased significantly (P<0.001) from 0.5% and 1.8% in 1996 to 4.9% and 4.2% in 2008, respectively. By competing risk analysis women started ART earlier than men (adjusted subhazard ratio [ASHR] 1.21, 95% CI 1.11, 1.31) in CoRIS cohort, while in CoRIS-MD none of these differences were observed. In both cohorts women showed a shorter time to the first ART change (ASHR 1.10, 95% CI 1.01, 1.19). Pregnancy and patient's/physician's decisions as reasons for changing were more frequent in women than in men in CoRIS. In the Cox regression model, gender was not associated with differences in survival. CONCLUSIONS In two large cohorts in Spain, we observed relevant gender differences in epidemiological characteristics and antiretroviral exposure outcomes, while survival differences were not attributable to gender.

In vitro heat exposure induces a redistribution of nuclear matrix proteins in human K562 erythroleukemia cells.

By using both conventional and confocal laser scanning microscopy with three monoclonal antibodies recognizing nuclear matrix proteins we have investigated by means of indirect fluorescence whether an incubation of isolated nuclei at the physiological temperature of 37 degrees C induces a redistribution of nuclear components in human K562 erythroleukemia cells. Upon incubation of isolated nuclei for 45 min at 37 degrees C, we have found that two of the antibodies, directed against proteins of the inner matrix network (M(r) 125 and 160 kDa), gave a fluorescent pattern different from that observed in permeabilized cells. By contrast, the fluorescent pattern did not change if nuclei were kept at 0 degrees C. The difference was more marked in case of the 160-kDa polypeptide. The fluorescent pattern detected by the third antibody, which recognizes the 180-kDa nucleolar isoform of DNA topoisomerase II, was unaffected by heat exposure of isolated nuclei. When isolated nuclear matrices prepared from heat-stabilized nuclei were stained by means of the same three antibodies, it was possible to see that the distribution of the 160-kDa matrix protein no longer corresponded to that observable in permeabilized cells, whereas the fluorescent pattern given by the antibody to the 125-kDa polypeptide resembled that detectable in permeabilized cells. The 180-kDa isoform of topoisomerase II was still present in the matrix nucleolar remnants. We conclude that a 37 degrees C incubation of isolated nuclei induces a redistribution of some nuclear matrix antigens and cannot prevent the rearrangement in the spatial organization of one of these antigens that takes place during matrix isolation in human erythroleukemia cells. The practical relevance of these findings is discussed.

Net increase of lactate and glutamate concentration in activated human visual cortex detected with magnetic resonance spectroscopy at 7 tesla.

After the landmark studies reporting changes in the cerebral metabolic rate of glucose (CMRGlc ) in excess of those in oxygen (CMRO2 ) during physiological stimulation, several studies have examined the fate of the extra carbon taken up by the brain, reporting a wide range of changes in brain lactate from 20% to 250%. The present study reports functional magnetic resonance spectroscopy measurements at 7 Tesla using the enhanced sensitivity to study a small cohort (n = 6). Small increases in lactate (19% ± 4%, P < 0.05) and glutamate (4% ± 1%, P < 0.001) were seen within the first 2 min of activation. With the exception of glucose (12% ± 5%, P < 0.001), no other metabolite concentration changes beyond experimental error were significantly observed. Therefore, the present study confirms that lactate and glutamate changes during physiological stimulation are small (i.e. below 20%) and shows that the increased sensitivity allows reproduction of previous results with fewer subjects. In addition, the initial rate of glutamate and lactate concentration increases implies an increase in CMRO2 that is slightly below that of CMRGlc during the first 1-2 min of activation.

Freedom Trial First-Year Extension: Results from 4 Years of Denosumab Exposure in Women with Postmenopausal Osteoporosis

Aims: To investigate the long-term efficacy and safety of denosumab (DMAb) for the treatment of postmenopausal women with osteoporosis in an open-label extension to the 3-year FREEDOM study.1Methods: All women who completed the FREEDOM study were eligible to enter a long-term open-label extension (up to 10 years). After providing informed consent, participants received 6-monthly subcutaneous injections of DMAb (60 mg). Here we report data from the first year of followup. For women randomized to DMAb in the FREEDOM study ('long-term group'), this represents up to 48 months of DMAb exposure (eight 6-monthly injections). For those randomized to placebo ('de novo group') the data are from up to 12 months of exposure (two injections). All participants continued to take calcium (1 g) and vitamin D (≥400 IU) supplements daily. Changes in bone mineral density (BMD) and bone turnover markers (BTM) are reported for subjects enrolled in the extension. No formal statistical testing was planned for this interim report. P-values are descriptive.Results: Overall, 4,550 eligible women (70.2%) who completed the FREEDOM study entered the open-label extension study (long-term, n=2,343; de novo, n=2,207). During the first year of the extension, lumbar spine (LS) BMD in the long-term group further increased by 2.0% (12.1% increase vs. FREEDOM baseline at 48 months), and total hip (TH) BMD further increased by 0.8% (6.5% increase at 48 months) (p<0.0001 for both BMD gains during year 4; Fig. 1). During the first year of the extension, LS and TH BMD increased by 5.4% and 3.0%, respectively in the de novo group (both p<0.0001). After DMAb initiation, serum C-telopeptide (CTX) in the de novo group decreased rapidly and similarly to the long-term group (Fig. 2). Reductions in BTMs continue to attenuate at the end of the dosing interval as previously reported. Adverse event (AE) rates were similar (70.4% of women in the longterm group and 67.9% in the de novo group). Serious Aes were also similar (9.8% and 11.2% of women, respectively). During year 4, osteoporotic nonvertebral fractures were reported in 31 women in the long-term group and 51 in the denovo group.Fig. 1. Percentage change in BMD with denosumab for4 years (long-term) or 1 year (de novo)Fig. 2. Percentage change in sCTX over timeConclusions: These interim results suggest that continuation of DMAb treatment through 48 months is associated with further significant increases in spine and hip BMD with sustained reduction of bone turnover. The de-novo treatment group results confirm the first year active treatment findings previously reported1.Acknowledgements: Amgen Inc. sponsored this study. Figure ©2010, American Society for Bone and Mineral Research, used by permission, all rights reserved. Disclosure of Interest: H. Bone Grant/Research Support from: Amgen, Eli Lilly, Merck, Nordic Bioscience, Novartis, Takeda Pharmaceuticals, Consultant/Speaker's bureau/ Advisory activities with: Amgen, Merck, Takeda Pharmaceuticals, Zelos, S. Papapoulos Consultant/Speaker's bureau/ Advisory activities with: Amgen, Merck, Novartis, Lilly, Procter and Gamble, GSK, M.-L. Brandi Grant/Research Support from: MSD, GSK, Nycomed, NPS, Amgen, J. Brown Grant/Research Support from: Abbott, Amgen, Bristol Myers Squibb, Eli Lilly, Pfizer, Roche, Consultant/ Speaker's bureau/Advisory activities with: Abbott, Amgen, Eli Lilly, Novartis, Merck, Warner Chilcott,, R. Chapurlat Grant/Research Support from: Servier, Sanofi-Aventis, Warner-Chilcott, Novartis, Merck, Consultant/Speaker's bureau/Advisory activities with: Servier, Novartis, Amgen, E. Czerwinski: None Declared, N. Daizadeh Employee of: Amgen Inc., Stock ownership or royalties of: Amgen Inc., A. Grauer Employee of: Amgen Inc., Stock ownership or royalties of: Amgen Inc., C. Haller Employee of: Amgen Inc., Stock ownership or royalties of: Amgen Inc., M.-A. Krieg: None Declared, C. Libanati Employee of: Amgen Inc., Stock ownership or royalties of: Amgen Inc., Z. Man Grant/Research Support from: Amgen, D. Mellström: None Declared, S. Radominski Grant/Research Support from: Amgen, Pfizer, Roche, BMS, J.-Y. Reginster Grant/Research Support from: Bristol Myers Squibb, Merck Sharp & Dohme, Rottapharm, Teva, Lilly, Novartis, Roche, GlaxoSmithKline, Amgen, Servier, Consultant/Speaker's bureau/ Advisory activities with: Servier, Novartis, Negma, Lilly,Wyeth, Amgen, GlaxoSmithKline, Roche, Merckle, Nycomed, NPS, Theramex, UCB, Merck, Sharpe & Dohme, Rottapharm, IBSA, Genvrier, Teijin, Teva, Ebewee Pharma, Zodiac, Analis, Theramex, Novo-Nordisk, H. Resch: None Declared, J. A. Román Grant/Research Support from: Roche, Pharma, C. Roux Grant/Research Support from: Amgen, MSD, Novartis, Servier, Roche, Consultant/ Speaker's bureau/Advisory activities with: Amgen, MSD, Novartis, Servier, Roche, S. Cummings Grant/ Research Support from: Amgen, Lilly, Consultant/Speaker's bureau/Advisory activities with: Amgen, Lilly, Novartis, Merck

Oseltamivir in seasonal, avian H5N1 and pandemic 2009 A/H1N1 influenza: pharmacokinetic and pharmacodynamic characteristics.

Oseltamivir is the ester-type prodrug of the neuraminidase inhibitor oseltamivir carboxylate. It has been shown to be an effective treatment for both seasonal influenza and the recent pandemic 2009 A/H1N1 influenza, reducing both the duration and severity of the illness. It is also effective when used preventively. This review aims to describe the current knowledge of the pharmacokinetic and pharmacodynamic characteristics of this agent, and to address the issue of possible therapeutic drug monitoring. According to the currently available literature, the pharmacokinetics of oseltamivir carboxylate after oral administration of oseltamivir are characterized by mean ± SD bioavailability of 79 ± 12%, apparent clearance of 25.3 ± 7.0 L/h, an elimination half-life of 7.4 ± 2.5 hours and an apparent terminal volume of distribution of 267 ± 122 L. A maximum plasma concentration of 342 ± 83 μg/L, a time to reach the maximum plasma concentration of 4.2 ± 1.1 hours, a trough plasma concentration of 168 ± 32 μg/L and an area under the plasma concentration-time curve from 0 to 24 hours of 6110 ± 1330 μg · h/L for a 75 mg twice-daily regimen were derived from literature data. The apparent clearance is highly correlated with renal function, hence the dosage needs to be adjusted in proportion to the glomerular filtration rate. Interpatient variability is moderate (28% in apparent clearance and 46% in the apparent central volume of distribution); there is no indication of significant erratic or limited absorption in given patient subgroups. The in vitro pharmacodynamics of oseltamivir carboxylate reveal wide variation in the concentration producing 50% inhibition of influenza A and B strains (range 0.17-44 μg/L). A formal correlation between systemic exposure to oseltamivir carboxylate and clinical antiviral activity or tolerance in influenza patients has not yet been demonstrated; thus no formal therapeutic or toxic range can be proposed. The pharmacokinetic parameters of oseltamivir carboxylate after oseltamivir administration (bioavailability, apparent clearance and the volume of distribution) are fairly predictable in healthy subjects, with little interpatient variability outside the effect of renal function in all patients and bodyweight in children. Thus oseltamivir carboxylate exposure can probably be controlled with sufficient accuracy by thorough dosage adjustment according to patient characteristics. However, there is a lack of clinical study data on naturally infected patients. In addition, the therapeutic margin of oseltamivir carboxylate is poorly defined. The usefulness of systematic therapeutic drug monitoring in patients therefore appears to be questionable; however, studies are still needed to extend the knowledge to particular subgroups of patients or dosage regimens.

Inferring ultraviolet anatomical exposure patterns while distinguishing the relative contribution of radiation components

Exposure to solar ultraviolet (UV) radiation is the main causative factor for skin cancer. UV exposure depends on environmental and individual factors, but individual exposure data remain scarce. While ground UV irradiance is monitored via different techniques, it is difficult to translate such observations into human UV exposure or dose because of confounding factors. A multi-disciplinary collaboration developed a model predicting the dose and distribution of UV exposure on the basis of ground irradiation and morphological data. Standard 3D computer graphics techniques were adapted to develop a simulation tool that estimates solar exposure of a virtual manikin depicted as a triangle mesh surface. The amount of solar energy received by various body locations is computed for direct, diffuse and reflected radiation separately. Dosimetric measurements obtained in field conditions were used to assess the model performance. The model predicted exposure to solar UV adequately with a symmetric mean absolute percentage error of 13% and half of the predictions within 17% range of the measurements. Using this tool, solar UV exposure patterns were investigated with respect to the relative contribution of the direct, diffuse and reflected radiation. Exposure doses for various body parts and exposure scenarios of a standing individual were assessed using erythemally-weighted UV ground irradiance data measured in 2009 at Payerne, Switzerland as input. For most anatomical sites, mean daily doses were high (typically 6.2-14.6 Standard Erythemal Dose, SED) and exceeded recommended exposure values. Direct exposure was important during specific periods (e. g. midday during summer), but contributed moderately to the annual dose, ranging from 15 to 24% for vertical and horizontal body parts, respectively. Diffuse irradiation explained about 80% of the cumulative annual exposure dose.

Spatial analysis of the relationship between mortality from cardiovascular and cerebrovascular disease and drinking water hardness.

Previously published scientific papers have reported a negative correlation between drinking water hardness and cardiovascular mortality. Some ecologic and case-control studies suggest the protective effect of calcium and magnesium concentration in drinking water. In this article we present an analysis of this protective relationship in 538 municipalities of Comunidad Valenciana (Spain) from 1991-1998. We used the Spanish version of the Rapid Inquiry Facility (RIF) developed under the European Environment and Health Information System (EUROHEIS) research project. The strategy of analysis used in our study conforms to the exploratory nature of the RIF that is used as a tool to obtain quick and flexible insight into epidemiologic surveillance problems. This article describes the use of the RIF to explore possible associations between disease indicators and environmental factors. We used exposure analysis to assess the effect of both protective factors--calcium and magnesium--on mortality from cerebrovascular (ICD-9 430-438) and ischemic heart (ICD-9 410-414) diseases. This study provides statistical evidence of the relationship between mortality from cardiovascular diseases and hardness of drinking water. This relationship is stronger in cerebrovascular disease than in ischemic heart disease, is more pronounced for women than for men, and is more apparent with magnesium than with calcium concentration levels. Nevertheless, the protective nature of these two factors is not clearly established. Our results suggest the possibility of protectiveness but cannot be claimed as conclusive. The weak effects of these covariates make it difficult to separate them from the influence of socioeconomic and environmental factors. We have also performed disease mapping of standardized mortality ratios to detect clusters of municipalities with high risk. Further standardization by levels of calcium and magnesium in drinking water shows changes in the maps when we remove the effect of these covariates.

Ganciclovir exposure under a 450mg daily dosage of valganciclovir for cytomegalovirus prevention in kidney transplantation: a prospective study.

Manuel O, Pascual M, Perrottet N, Lamoth F, Venetz J-P, Decosterd LA, Buclin T, Meylan PR. Ganciclovir exposure under a 450 mg daily dosage of valganciclovir for cytomegalovirus prevention in kidney transplantation: a prospective study. 
Clin Transplant 2010: 24: 794-800. Abstract:  This prospective study aimed at determining the ganciclovir exposure observed under a daily dosage of 450 mg valganciclovir routinely applied to kidney transplant recipients with a GFR above 25 mL/min at risk for cytomegalovirus (CMV) disease. Ganciclovir levels at trough (C(trough) ) and at peak (C(3 h) ) were measured monthly. Ganciclovir exposure (area under the curve [AUC(0-24) ]) was estimated using Bayesian non-linear mixed-effect modeling (NONMEM). Thirty-six patients received 450 mg of valganciclovir daily for three months. Median ganciclovir C(3 h) was 3.9 mg/L (range: 1.3-7.1), and C(trough) was 0.4 mg/L (range 0.1-2.7). Median AUC(0-24) of ganciclovir was 59.3 mg h/L (39.0-85.3) in patients with GFR(MDRD) 26-39 mL/min, 35.8 mg h/L (24.9-55.8) in patients with GFR(MDRD) 40-59 mL/min, and 29.6 mg h/L (22.0-43.2) in patients with GFR(MDRD)  ≥ 60 mL/min. No major differences in adverse events according to ganciclovir exposure were observed. CMV viremia was not detected during prophylaxis. After discontinuing prophylaxis, CMV viremia was seen in 8/36 patients (22%), and 4/36 patients (11%) developed CMV disease. Ganciclovir exposure after administration of valganciclovir 450 mg daily in recipients with GFR ≥60 mL/min was comparable to those previously reported with oral ganciclovir. A routine daily dose of 450 mg valganciclovir appears to be acceptable for CMV prophylaxis in most kidney transplant recipients.

Exposition aux particules fines/ultrafines et effets sur la santé chez les mécaniciens

Une hypgothèse permettant d'expliquer l'effet néfaste des particules sur la santé serait que les particules agiraient par l'intermédiaire d'espèces oxydantes qui attaqueraient l'ADN ou les lipides constituant les membranes cellulaires. Les antioxydants présents dans les cellules/organes réduiraient ces effets. Une étude effectuée dans différents atteliers mécaniques a permis de constater un effet biologique chez les mécaniciens malgré le fait qu'ils étaient exposés à des concentrations inférieures aux VME. La concentration urinaire d'un composé mesurant les atteintes oxydantes sur l'ADN a augmenté durant deux journées consécutives de travail. Les niveaux d'antioxydants ont aussi augmenté, indiquant une activation des processus de défense individuels. Les résultats confirment aussi l'importance du fer, du cuivre et duNOx ainsi que des propriétés chimiques de surface des particules dans l'induction de réactions d'oxydation sur des constituants biologiques.

Development of a retrospective job exposure matrix for PCB-exposed workers in capacitor manufacturing

Objectives: Polychlorinated biphenyls (PCBs) are considered probable human carcinogens by the International Agency for Research on Cancer and one congener, PCB126, has been rated as a known human carcinogen. A period-specific job exposure matrix (JEM) was developed for former PCB-exposed capacitor manufacturing workers (n=12,605) (1938-1977). Methods: A detailed exposure assessment for this plant was based on a number of exposure determinants (proximity, degree of contact with PCBs, temperature, ventilation, process control, job mobility). The intensity and frequency of PCB exposures by job for both inhalation and dermal exposures, and additional chemical exposures were reviewed. The JEM was developed in nine steps: (1) all unique jobs (n=1,684) were assessed using (2) defined PCB exposure determinants; (3) the exposure determinants were used to develop exposure profiles; (4) similar exposure profiles were combined into categories having similar PCB exposures; (5) qualitative intensity (high-medium-low-baseline) and frequency (continuous-intermittent) ratings were developed, and (6) used to qualitatively rate inhalation and dermal exposure separately for each category; (7) quantitative intensity ratings based on available air concentrations were developed for inhalation and dermal exposures based on equal importance of both routes of exposure; (8) adjustments were made for overall exposure, and (9) for each category the product of intensity and frequency was calculated, and exposure in the earlier era was weighted. Results: A period-specific JEM modified for two eras of stable PCB exposure conditions. Conclusions: These exposure estimates, derived from a systematic and rigorous use of the exposure determinant data, lead to cumulative PCB exposure-response relationships in the epidemiological cancer mortality and incidence studies of this cohort. [Authors]

Exposition au VIH, à l'hépatite B et C au cabinet médical et à l'hôpital. Prévention et prophylaxie postexpositionnelle [Exposure to HIV, hepatitis B and C in office practice and hospital. Prevention and post-exposure prophylaxis]

Suite à un accident exposant à du sang (piqûre; coupure), provenant d'un patient infecté, le risque d'infection par VIH est d'environ 0,3% et par le virus de l'hépatite C (VHC) d'environ 0,5%. Chez les personnes vaccinées avec une réponse immunitaire adéquate (titre d'anticorps HBs >100 mUI/ml), aucune infection professionnelle par hépatite B n'a été reconnue en Suisse. La plupart des infections par VIH et VHB peuvent être prévenues par un traitement d'urgence et une prophylaxie postexpositionnelle (PEP). Il n'y a actuellement aucune prophylaxie postexpositionnelle pour le VHC. En cas de transmission de VHC, un traitement rapide par peginterféron et ribavirine est à envisager. Chaque hôpital et cabinet médical doivent mettre sur pied un système pour assurer une prise en charge optimale et en urgence des blessures par piqûres ou coupures. Lors de blessures accidentelles avec du sang de patients séropositifs pour le VIH et dans des situations complexes, il est recommandé de consulter un médecin du personnel ou un infectiologue expérimenté. The risk of infection after an occupational needle stick injury with blood from an infected source patient is approximately 0.3% for HIV and 0.5% for hepatitis C virus (HCV). In Switzerland no cases of occupational HBV infection have been recorded in fully vaccinated persons with a documented adequate vaccine response (HBsantibody titer >100 mIU/mL). Most occupational HIV und HBV infections can be prevented by appropriate emergency measures and post-exposure prophylaxis (PEP). No HCV-PEP is currently available. Early therapy with peginterferon and ribavirin should be considered in cases of occupational HCV seroconversion. Every hospital and office practice should establish a system for 24 h/24 h emergency management of occupational needle stick injuries. In the setting of an HIV-seropositive source patient and in complex situations, early consultation with a specialist in occupational medicine or infectious diseases should be considered.

2

The pharmacokinetic profile of imatinib has been assessed in healthy subjects and in population studies among thousands of patients with CML or GIST. Imatinib is rapidly and extensively absorbed from the GI tract, reaching a peak plasma concentration (Cmax) within 1-4 h following administration. Imatinib bioavailability is high (98%) and independent of food intake. Imatinib undergoes rapid and extensive distribution into tissues, with minimal penetration into the central nervous system. In the circulation, it is approximately 95% bound to plasma proteins, principally α1-acid glycoprotein (AGP) and albumin. Imatinib undergoes metabolism in the liver via the cytochrome P450 enzyme system (CYP), with CYP3A4 being the main isoenzyme involved. The N-desmethyl metabolite CGP74588 is the major circulating active metabolite. The typical elimination half-life for imatinib is approximately 14-22 h. Imatinib is characterized by large inter-individual pharmacokinetic variability, which reflects in a wide spread of concentrations observed under standard dosage. Besides adherence, several factors have been shown to influence this variability, especially demographic characteristics (sex, age, body weight and disease diagnosis), blood count characteristics, enzyme activity (mainly CYP3A4), drug interactions, activity of efflux transporters and plasma levels of AGP. Additionally, recent retrospective studies have shown that drug exposure, reflected in either the area under the concentration-time curve (AUC) or more conveniently the trough level (Cmin), correlates with treatment outcomes. Increased toxicity has been associated with high plasma levels, and impaired clinical efficacy with low plasma levels. While no upper concentration limit has been formally established, a lower limit for imatinib Cmin of about 1000 ng/mL has been proposed repeatedly for improving outcomes in CML and GIST patients. Imatinib is licensed for use in chronic phase CML and GIST at a fixed dose of 400 mg once daily (600 mg in some other indications) despite substantial pharmacokinetic variability caused by both genetic and acquired factors. The dose can be modified on an individual basis in cases of insufficient response or substantial toxic effects. Imatinib would, however, meet traditional criteria for a therapeutic drug monitoring (TDM) program: long-term therapy, measurability, high inter-individual but restricted intra-individual variability, limited pharmacokinetic predictability, effect of drug interactions, consistent association between concentration and response, suggested therapeutic threshold, reversibility of effect and absence of early markers of efficacy and toxic effects. Large-scale, evidence-based assessments of drug concentration monitoring are therefore still warranted for the personalization of imatinib treatment.

Impact of genomic methylation on radiation sensitivity of colorectal carcinoma.

PURPOSE: To investigate the influence of demethylation with 5-aza-cytidine (AZA) on radiation sensitivity and to define the intrinsic radiation sensitivity of methylation deficient colorectal carcinoma cells. METHODS AND MATERIALS: Radiation sensitizing effects of AZA were investigated in four colorectal carcinoma cell lines (HCT116, SW480, L174 T, Co115), defining influence of AZA on proliferation, clonogenic survival, and cell cycling with or without ionizing radiation. The methylation status for cancer or DNA damage response-related genes silenced by promoter methylation was determined. The effect of deletion of the potential target genes (DNMT1, DNMT3b, and double mutants) on radiation sensitivity was analyzed. RESULTS: AZA showed radiation sensitizing properties at >or=1 micromol/l, a concentration that does not interfere with the cell cycle by itself, in all four tested cell lines with a sensitivity-enhancing ratio (SER) of 1.6 to 2.1 (confidence interval [CI] 0.9-3.3). AZA successfully demethylated promoters of p16 and hMLH1, genes associated with ionizing radiation response. Prolonged exposure to low-dose AZA resulted in sustained radiosensitivity if associated with persistent genomic hypomethylation after recovery from AZA. Compared with maternal HCT116 cells, DNMT3b-defcient deficient cells were more sensitive to radiation with a SER of 2.0 (CI 0.9-2.1; p = 0.03), and DNMT3b/DNMT1-/- double-deficient cells showed a SER of 1.6 (CI 0.5-2.7; p = 0.09). CONCLUSIONS: AZA-induced genomic hypomethylation results in enhanced radiation sensitivity in colorectal carcinoma. The mediators leading to sensitization remain unknown. Defining the specific factors associated with radiation sensitization after genomic demethylation may open the way to better targeting for the purpose of radiation sensitization.