Concurrent or sequential letrozole with adjuvant breast radiotherapy: final results of the CO-HO-RT phase II randomized trial.

BACKGROUND: We present here final clinical results of the COHORT trial and both translational sub-studies aiming at identifying patients at risk of radiation-induced subcutaneous fibrosis (RISF): (i) radiation-induced lymphocyte apoptosis (RILA) and (ii) candidates of certain single-nucleotide polymorphisms (SNPs). PATIENTS AND METHODS: Post-menopausal patients with stage I-II breast cancer (n = 150) were enrolled and assigned to either concurrent (arm A) or sequential radiotherapy (RT)-letrozole (arm B). Among them, 121 were eligible for RILA and SNP assays. Grade ≥2 RISF were the primary end point. Secondary end points were lung and heart events and carcinologic outcome. RILA was performed to predict differences in RISF between individuals. A genome-wide association study was performed to identify SNPs associated with RILA and RISF. Analyses were done by intention to treat. RESULTS: After a median follow-up of 74 months, 5 patients developed a grade ≥2 RISF. No significant difference was observed between arms A and B. Neither grade ≥2 lung nor symptomatic cardiac toxicity was observed. Median RILA value of the five patients who had grade ≥2 RISF was significantly lower compared with those who developed grade ≤1 RISF (6.9% versus 13%, P = 0.02). Two SNPs were identified as being significantly associated with RILA: rs1182531 (P = 4.2 × 10(-9)) and rs1182532 (P = 3.6 × 10(-8)); both located within the PHACTR3 gene on chromosome 20q13.33. CONCLUSIONS: With long-term follow-up, letrozole can safely be delivered concomitantly with adjuvant breast RT. Translational sub-studies showed that high RILA values were correlated with patients who did not develop RISF. REGISTERED CLINICAL TRIAL: NCT00208273.

Chiral anomaly and strength of the electron-electron interaction in graphene.

The long-standing controversy concerning the effect of electron-electron interaction on the electrical conductivity of an ideal graphene sheet is settled. Performing the calculation directly in the tight binding approach without the usual prior reduction to the massless Dirac (Weyl) theory, it is found that, to leading order in the interaction strength α=e(2)/hv(0), the dc conductivity σ/σ(0)=1+Cα+O(α(2)) is significantly enhanced with respect to the independent-electron result σ(0), i.e., with the value C=0.26. The ambiguity characterizing the various existing approaches is nontrivial and related to the chiral anomaly in the system. In order to separate the energy scales in a model with massless fermions, contributions from regions of the Brillouin zone away from the Dirac points have to be accounted for. Experimental consequences of the relatively strong interaction effect are briefly discussed.

[Radiation-induced sequelae: toward an individual profile]. / Séquelles radio-induites et tests prédictifs.

The impact of curative radiotherapy depends mainly on the total dose delivered homogenously in the targeted volume. Nevertheless, the dose delivery is limited by the tolerated dose of the surrounding healthy tissues. Two different side effects (acute and late) can occur during and after radiotherapy. Of particular interest are the radiation-induced sequelae due to their irreversibility and the potential impact on daily quality of life. In a population treated in one center with the same technique, it appears that individual radiosensitivity clearly exists. In the hypothesis that genetic is involved in this area of research, lymphocytes seem to be the tissue of choice due to easy accessibility. Recently, low percentage of CD4 and CD8 lymphocyte apoptosis were shown to be correlated with high grade of sequelae. In addition, recent data suggest that patients with severe radiation-induced late side effects possess four or more SNP in candidate genes (ATM, SOD2, TGFB1, XRCC1 et XRCC3) and low radiation-induced CD8 lymphocyte apoptosis in vitro.

Severe deficiency of cystic fibrosis transmembrane conductance regulator messenger RNA carrying nonsense mutations R553X and W1316X in respiratory epithelial cells of patients with cystic fibrosis.

Cystic fibrosis (CF) is the most common, lethal inherited disorder in the Caucasian population. We have recently reported two African-American patients with nonsense mutations in each CF gene and severe pancreatic disease, but mild pulmonary disease. In order to examine the effect of these nonsense mutations on CF gene expression, bronchial and nasal epithelial cells were obtained from one of these patients (no. 246), a compound heterozygote for nonsense mutations R553X and W1316X; a healthy normal individual; a patient (no. 528) homozygous for the common CF mutation (delta F508); and a CF patient (no. 272) who carries the R553X mutation and a missense mutation, S549N. When mRNA from bronchial cells of the normal individual, the delta F508 homozygote, and the S549N/R553X compound heterozygote was reverse transcribed and amplified by polymerase chain reaction using primers derived from the CF gene, DNA fragments of the predicted size were observed. However, patient no. 246 with nonsense mutations in each CF gene has no detectable cystic fibrosis transmembrane conductance regulator (CFTR) messenger RNA, and therefore should have severely diminished, and possibly absent, CFTR protein. Furthermore, less than 2% of the CFTR transcripts in nasal epithelial cells from patient no. 272 (S549N/R553X) were derived from the gene with the nonsense mutation. We conclude that severe reduction in CFTR mRNA causes CF, but can have different consequences in the lung and pancreas.

TIP49b, a regulator of activating transcription factor 2 response to stress and DNA damage.

Activating transcription factor 2 (ATF2/CRE-BP1) is implicated in transcriptional control of stress-responsive genes. A yeast two-hybrid screen identified TBP-interacting protein 49b (TIP49b), a component of the INO80 chromatin-remodeling complex, as a novel ATF2-interacting protein. TIP49b's association with ATF2 is phosphorylation dependent and requires amino acids 150 to 248 of ATF2 (ATF2(150-248)), which are implicated in intramolecular inhibition of ATF2 transcriptional activities. Forced expression of TIP49b efficiently attenuated ATF2 transcriptional activities under normal growth conditions as well as after UV treatment, ionizing irradiation, or activation of p38 kinase, all of which induced ATF2 phosphorylation and increased TIP49b-ATF2 association. Constitutive expression of ATF2(150-248) peptide outcompeted TIP49b interaction with ATF2 and alleviated the suppression of ATF2 transcriptional activities. Expression of ATF2(150-248) in fibroblasts or melanoma but not in ATF2-null cells caused a profound G(2)M arrest and increased degree of apoptosis following irradiation. The interaction between ATF2 and TIP49b constitutes a novel mechanism that serves to limit ATF2 transcriptional activities and highlights the central role of ATF2 in the control of the cell cycle and apoptosis in response to stress and DNA damage.

Use of a highly sensitive assay to analyze the excision repair of dimer and nondimer DNA damages induced in human skin fibroblasts by 254-nm and solar ultraviolet radiation.

The excision repair of nondimer DNA damages induced in normal human skin fibroblasts exposed to the Mylar-filtered UV produced by a fluorescent sunlamp was investigated. This work was accomplished through the development of a modification of the bromodeoxyuridine photolysis assay that greatly increases the sensitivity of this assay. This enhancement in sensitivity was achieved through use of alkaline elution to measure the DNA strand breakage produced by the photolysis of bromodeoxyuridine incorporated into the DNA through excision repair. Using this modified bromodeoxyuridine photolysis assay, it was found that the solar UV-induced nondimer DNA damages appear to have been repaired by a short patch repair mechanism in which a small number of nucleotides (two to four) were inserted into the repaired site. This is in contrast to the long patch repair process involved in the excision of cyclobutane pyrimidine dimers in which approximately 40 nucleotides were inserted into each repaired region.

Ultraviolet-induced DNA damage stimulates topoisomerase I-DNA complex formation in vivo: possible relationship with DNA repair.

An antibody-based method was used to examine genomic DNA cleavage by endogenous topoisomerases in living cells. The method quantifies cleavable (covalent) complex formation in vivo after exposure to topoisomerase poisons, as reported previously (D. Subramanian et al., Cancer Res., 55: 2097-2103, 1995). Unexpectedly, exposing cells to UVB irradiation stimulated endogenous topoisomerase I-DNA covalent complex formation by as much as 8-fold, even in the absence of drugs that stabilize the cleavable complex. Covalent complexes are not a result of nonspecific UV protein-DNA cross-linking; rather, they result from the enzymatic activity of topoisomerase I on genomic DNA. Because the action of topoisomerase II on genomic DNA was not affected by UVB exposure, the observation appears to be specific for type I. Topoisomerase I is rapidly mobilized onto the genome (within 12 min after UVB exposure); however, topoisomerase I polypeptide levels did not show a corresponding increase, suggesting that preexisting enzyme is being recruited to sites of DNA damage. Complexes persist up to 5 h post-UV exposure (concurrent with the period of active DNA repair), and their formation is independent of S phase. These findings can be partially explained by the fact that in vitro topoisomerase I activity on UV-damaged DNA tends to favor formation of cleavage complexes; thus, a higher yield of covalent complexes are detected at or near cyclopyrimidine dimer lesions. Because repair-deficient cells are additionally compromised in their ability to recruit topoisomerase I, a direct role for the enzyme in DNA excision repair process in vivo is proposed that may be related to the activity of the xeroderma pigmentosum complementation group D helicase. Finally, these results collectively demonstrate that topoisomerase I is a repair-proficient topoisomerase in vivo.

DNA excision repair in human cells treated with ultraviolet radiation and 7,12-dimethylbenz[a]anthracene 5,6-oxide.

Excision repair was measured in normal human and xeroderma pigmentosum group C cells treated with 7,12-dimethylbenz[a]-anthracene 5,6-oxide and with ultraviolet radiation by the techniques of unscheduled DNA synthesis, repair replication, a modification of bromodeoxyuridine photolysis employing the dye Hoechst 33258 and 365 nm radiation, and endonuclease-sensitive sites assay. Radioautography and repair replication showed that in normal cells the magnitude of repair after a saturation dose of epoxide (approx. 10 microM) to be 0.1-0.2 that after a saturating ultraviolet dose (20 J/m2 at 254), though survival data showed that both doses gave nearly similar killings. Repair was of the long-patch type and repair kinetics after the epoxide treatment were similar to ultraviolet. After a combined treatment with both agents, unscheduled synthesis in normal cells was more than additive, although, considering the experimental errors, these data and those of repair replication are consistent with additivity. The epoxide did not inhibit loss of sites sensitive to the ultraviolet endonuclease. However, after a combined treatment to xeroderma pigmentosum cells there was appreciably less unscheduled synthesis than for the sum of both treatments and the epoxide inhibited the loss of nuclease-sensitive sites. We interpret the data to indicate that there are different rate-limiting steps in the removal of the ultraviolet and the epoxide damages, and that the residual repair activity in xeroderma pigmentosum cells is accomplished by different, not just fewer, enzymes than in normal cells.

Repair of DNA damage induced in systemic lupus erythematosus skin fibroblasts by simulated sunlight.

Skin fibroblasts derived from three normal individuals and three patients exhibiting the disease systemic lupus erythematosus (SLE) were exposed to the simulated sunlight produced by a solar simulator. The induction and repair of DNA damage induced by this treatment were examined. The total number of lesions repaired by excision, as well as the removal of pyrimidine dimers and E. coli endonuclease III--sensitive sites did not differ significantly in the three SLE cell strains compared with normal cells. However, abnormalities in the formation and maintenance of DNA-protein crosslinks (DPC) and DNA single-strand breaks (SSB) were found in SLE-4 and SLE-5 following simulated sunlight exposure. In contrast, SLE-3 cells exhibited responses similar to normal cells in reference to SSB and DPC formation. These findings correlate well with the previously determined UV sensitivity of these SLE cell strains.

Differential regulation of P53 and Bcl-2 expression by ultraviolet A and B.

The induction of apoptosis by ultraviolet (UV) radiation and other DNA damaging agents plays a critical role in monitoring the accumulation of genetic damage and the suppression of tumor development. We hypothesize that UVA and UVB induce apoptosis by modulating balances between p53 and/or bcl-2 genes. Using MCF-7 cells that express both wild-type P53 and Bcl-2 proteins, we demonstrated that UVA and UVB induced apoptosis through regulating expression of apoptosis promoting or inhibiting genes. UVA induced immediate apoptosis and downregulated bcl-2 expression. Bcl-2 expression was reduced by approximately 40% at 4 h post-150 kJ UVA irradiation per m2 with a maximum downregulation (over 70%) at 24 h. The dose-response studies revealed that significant reduction of bcl-2 expression was observed at UVA doses ranging from 50 to 200 kJ per m2; however, p53 levels were not affected by UVA. In contrast, UVB exhibited a entirely different action than UVA in that UVB substantially induced p53 expression, but had no effect on bcl-2 expression. The induction of P53 by UVB was dose and time dependent with the maximum expression at 24 h post-2 and post-4 kJ UVB irradiation per m2. Down-regulation of bcl-2 and fragmentation of DNA induced by UVA occurred earlier (approximately at 4 h) than upregulation of p53 and DNA fragmentation by UVB (12-24 h). These results suggest that UVA and UVB cause cell damage through different mechanisms and that the balances between the expression of p53 and bcl-2 may play an important role in regulating the apoptosis induced by UV irradiation.

Identification of possible reactive oxygen species involved in ultraviolet radiation-induced oxidative DNA damage.

We have previously demonstrated that each region of the ultraviolet (UV) spectrum (UVA, UVB, and UVC) induces the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in purified calf thymus DNA and HeLa cells in a fluence-dependent manner. In the present study, we further characterize the possible reactive oxygen species (ROS) that are involved in the induction of 8-oxodGuo by UV radiation. Sodium azide, a singlet oxygen (1O2) scavenger though its quenching effect on HO. was also reported, inhibited 8-oxodGuo production in calf thymus DNA exposed to UVA, UVB, or UVC in a concentration-dependent fashion with maximal quenching effect of over 90% at a concentration of 10 mM. Catalase, at a concentration of 50 U/ml, reduced the yields of UVA- and UVB-induced 8-oxodGuo formation by approximately 50%, but had little effect on UVC-induced 8-oxodGuo production. In contrast, 50 U/ml of superoxide dismutase (SOD) did not affect induction of 8-oxodGuo by any portion of the UV spectrum. Hydroxyl radical (HO.) scavengers mannitol and dimethylsulfoxide (DMSO) moderately reduced the levels of 8-oxodGuo induced by UVA and UVB, but not those by UVC. Instead, mannitol and DMSO enhanced the formation of 8-oxodGuo induced by UVC. These results suggest that certain types of ROS are involved in UV-induced 8-oxodGuo formation with 1O2 playing the predominant role throughout the UV spectrum. Except for UVC, other ROS such as hydrogen peroxide (H2O2) and HO. may also be involved in UVA- and UVB-induced oxidative DNA damage. Superoxide anion appears not to participate in UV-induced oxidation of guanosine in calf thymus DNA, as SOD did not display any quenching effects.

Infant health care utilization predicted by pattern of prenatal care.

STUDY OBJECTIVE: The objective of this study was to examine the relationship between patterns of prenatal care and subsequent infant health care use in a sample of inner-city women and their infants. In testing this relationship we controlled for several sociodemographic, economic, and psychological factors. DESIGN: This case-control study examined medical records of 148 infants born to mothers previously enrolled in a 9-month study of prenatal care and use or nonuse of illicit drugs. Cases (N = 62) were defined as infants born to women who first registered for prenatal care after 28 weeks' gestation or completed fewer than four prenatal visits. Controls (N = 86) were all other infants matched by date of birth. Data on maternal health and sociodemographic factors were obtained from a maternal interview and medical record review. Maternal drug use was defined as the use of illicit drugs at any time during the pregnancy based on maternal interview and/or a positive maternal or neonatal urine toxicology screen obtained within 48 hours of delivery. RESULTS: Infants of case mothers had significantly lower birth weight and gestational age, increased number of protective service referrals, and lower completion rate of three or more health supervision visits by 9 months of age. Multiple logistic regression analysis revealed that adequate prenatal care was significantly associated with adequate use of infant health care independent of maternal drug use, educational level, marital status, and number of previous living children. CONCLUSIONS: Patterns of infant health care use can be predicted before birth based on the mother's pattern of prenatal care use.

Use of oral contraceptives in women with cystic fibrosis.

Oral contraceptive pills (OCP) represent the most common contraceptive method among teenagers and young adults. Because many women with cystic fibrosis (CF) are now surviving into childbearing age and are at risk for the complications of pregnancy in CF, oral contraceptive use may be indicated. However, it has been suggested that OCP use by CF patients may be associated with deterioration in pulmonary function. Ten adolescent and young adult women with CF and moderate-to-severe obstructive lung disease were studied while taking a combination oral contraceptive pill (Ovral 28). No significant deterioration was found in clinical status or pulmonary function. Careful follow-up should nevertheless be continued to monitor for other adverse effects of oral contraceptive use in CF, such as cholelithiasis.

Airway hyperreactivity in cystic fibrosis. Clinical correlates and possible effects on the course of the disease.

To evaluate whether increased airway reactivity affected the course of patients with cystic fibrosis (CF), we categorized 40 CF patients as to methacholine sensitivity and then evaluated their disease activity and natural history. Twenty methacholine reactors had more severe lung disease (lower S-K clinical scores and more impairment of pulmonary function) than did 16 nonreactive patients, and acute bronchodilator response was greater in the methacholine reactors. Thirty-four patients were followed prospectively over a 17- to 24-month period. Among 19 methacholine reactors, there were more pulmonary exacerbations and a more rapid decline in FEV1. In general, increased obstruction was associated with increased reactivity. Although the data are subject to differing interpretations, they are consistent with the hypothesis that in patients with CF, airway hyperreactivity occurs secondary to bronchial damage, age, is associated with more rapid pulmonary deterioration, and is an unfavorable prognostic finding.

Homogeneity of bronchopulmonary distribution of 99mTc aerosol in normal subjects and in cystic fibrosis patients.

We characterized the bronchopulmonary distribution of a 0.9 percent saline aerosol (1.12 microM) labelled with 99mTc sulfur colloid in nine normal subjects and five patients with CF. Homogeneity of distribution was quantified using indices derived from computerized analysis of Anger camera pulmonary images including skew (a measure of distribution asymmetry) and kurtosis (a measure of distribution range). Aerosol clearance in 97 minutes (a measure of large, central airway deposition) was also assessed. Values of skew and kurtosis were reproducible for the patients with CF and were significantly elevated compared to the normal subjects. Reproducibility of skew and kurtosis were not studied in the normal subjects. Clearance was not significantly different in the two groups. We conclude that the bronchopulmonary distribution of this radioaerosol is nonuniform in patients with CF, compared to normal subjects, and clearance may be impaired in patients with CF who are severely ill.

A controlled trial of long-term bronchodilator therapy in cystic fibrosis.

To evaluate the effect of long-term bronchodilator therapy in CF patients with demonstrated bronchial hyperresponsiveness, we first performed methacholine challenges to determine responsiveness, then entered 27 patients (16 methacholine responders and 11 nonresponders) into a two-month double-blind crossover trial of albuterol, 90 micrograms by inhalation four times a day vs placebo. Among the responders, daily PEFR measures improved significantly more during treatment with albuterol (12 +/- 32 L/min) than with placebo (-0.4 +/- 19 L/min; p less than 0.05). In addition, a clinically important level of improvement in PEFR (15 percent increase) was reached significantly more frequently in the responders. Methacholine nonresponders had no change in PEFR on either albuterol or placebo. Daily symptom scores as well as spirometry measurements at biweekly visits did not show significant changes. We conclude that long-term therapy with inhaled albuterol improves lung function in CF patients, but only in those with bronchial hyperresponsiveness as demonstrated by methacholine challenge.

Radioaerosol assessment of lung improvement in cystic fibrosis patients treated for acute pulmonary exacerbations.

We compared bronchopulmonary distribution homogeneity of a radioaerosol before and after hospitalization in 20 patients with cystic fibrosis (CF) with pulmonary exacerbations in order to assess lung improvement. Deposition homogeneity was quantified in terms of skew (an index of distribution symmetry), derived from frequency distribution histograms generated from gamma camera images of the lungs following radioaerosol inhalation. Lower skew values indicate enhanced distribution homogeneity. Right lung skew (RLS) was significantly reduced following therapy (1.00 +/- 0.49 to 0.84 +/- 0.47), whereas skew in the left lung was unchanged (0.95 +/- 0.38 to 0.87 +/- 0.40). The reduction in RLS was significant in patients with Shwachman-Kulczycki (SK) clinical scores less than 50 (1.27 +/- 0.53 to 0.90 +/- 0.42), but not in patients with scores greater than 50 (0.81 +/- 0.38 to 0.80 +/- 0.52). These results indicate that treatment affected the right lung more than the left lung, particularly in patients with SK scores less than 50, and suggests that radioaerosol lung imaging may be valuable in identifying sites of impairment to be targeted during treatment. Statistically, skew was less sensitive an indicator of acute change than several other clinical indices that improved following hospital treatment.

The induction of DNA strand breaks in normal human skin fibroblasts exposed to solar ultraviolet radiation.

The levels of apparent DNA single-strand breaks (ssb) were measured, following a 0-20 h incubation of normal human skin fibroblasts exposed to the solar uv wavelengths produced by a fluorescent sunlamp. The ssb were determined using the alkaline elution assay, which was performed either without proteinase K (proK) or in its presence, so as to eliminate any DNA-protein crosslinks that may be present in the cells. Cells were irradiated with either 3 kJ/m2 of sunlamp uv greater than 295 nm, 150 kJ/m2 of sunlamp uv greater than 315 nm, or 150 kJ/m2 of sunlamp uv greater than 320 nm. These treatments resulted in the production of 5-10 ssb/10(10) Da. For the two shorter wavelength irradiations, the levels of ssb decreased rapidly upon incubation of the cells. However, when the elutions were performed using proK, the number of ssb increased about twofold following a 2-4 h incubation. In contrast, the levels of ssb decreased in the sunlamp uv greater than 320 nm irradiated cells for elutions performed with or without proK. These results suggest that under certain irradiation conditions, ssb are formed in cells upon incubation, which are hidden by the crosslinking of protein to DNA.

Inhibition of semiconservative DNA synthesis in ICR 2A frog cells by pyrimidine dimers and nondimer photoproducts induced by ultraviolet radiation.

DNA synthesis was examined in ultraviolet (uv)-irradiated ICR 2A frog cells in which either pyrimidine dimers or nondimer photoproducts represented the major class of DNA lesions. Dimers were induced by exposure of cells to 254 nm uv, while nondimer photoproducts were induced by irradiation of cells with uv produced by a fluorescent sunlamp (FSL) that was filtered through 48A Mylar (removes wavelengths less than 310 nm). The FSL-irradiated cultures were also treated with photoreactivating light (PRL) which removed most of the small number of dimers induced by the irradiation, leaving a relatively pure population of nondimer photoproducts. In addition, cells were exposed to 60Co gamma rays. The cultures were pulse-labeled and the size distribution of the DNA synthesized was estimated using both sucrose gradient sedimentation and alkaline step elution. Using either of these techniques, it was found that the presence of dimers resulted in a reduction principally in the synthesis of high molecular weight (MW) DNA. In contrast, nondimer photoproducts caused a strong inhibition in the synthesis of low MW DNA, as was also observed in gamma-irradiated cells. Hence the induction of pyrimidine dimers in DNA mainly affected the elongation of replicons, whereas nondimer lesions primarily caused an inhibition of replicon initiation.

The repair of DNA damages induced in normal human skin fibroblasts exposed to simulated sunlight.

The induction and repair of DNA damages produced by exposure of normal human skin fibroblasts to the simulated sunlight produced by a solar simulator were examined. The photoproducts measured were pyrimidine dimers, E. coli endonuclease III-sensitive sites, 6-4 photoproducts, Dewar isomers, DNA-protein crosslinks, and DNA single-strand breaks. The results of these experiments serve to form a basis for the quantitation of damages induced by exposure to sunlight.