Common genomic signaling among initial DNA damage and radiation-induced apoptosis in peripheral blood lymphocytes from locally advanced breast cancer patients

Reactive oxygen species induce Cys106-mediated anti-parallel HMGB1 dimerization that protects against DNA damage

Oxidative stress can induce covalent disulfide bond formation between protein-protein thiol groups and generate hydroxyl free radicals that damage DNA. HMGB1 is a DNA chaperone and damage-associated molecular pattern molecule. As a redox-sensitive protein, HMGB1 contains three cysteine residues: Cys23, Cys45, and Cys106. In this study, we focused on the relationship between HMGB1 dimerization and DNA stabilization under oxidative stress conditions. HMGB1 dimerization was positively modulated by CuCl₂ and H₂O₂. Mutation of the Cys106 residue blocked dimer formation. Treatment of HEK293T cells with CuCl₂ and H₂O₂ enhanced the oxidative self-dimerization of HMGB1, whereas this dimerization was inhibited in mutant HMGB1^C106A cells. Furthermore, we performed a bimolecular fluorescence complementation assay to visualize Cys106 oxidation-induced HMGB1 dimerization in live cells exposed to oxidative stress and were able to reproduce the dimerization effect of HMGB1 in fluorescence resonance energy transfer analysis. Interestingly, dimerized HMGB1 bound to DNA with higher affinity than monomeric HMGB1. Dimerized HMGB1 protected DNA from damage due to hydroxyl free radicals and prevented cell death. In conclusion, dimerized HMGB1 may play a regulatory role in DNA stabilization under oxidative stress.

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Accumulation of excessive ROS induces DNA damage, causing cell death.

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HMGB1 dimerizes in the presence of excessive ROS and binds DNA with high affinity.

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Binding of dimerized HMGB1 (Di-HMGB1) protects DNA from ROS action.

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We prepared an in vitro HMGB1 dimerization due to excessive ROS.

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Di-HMGB1 protected against DNA damage induced by radiation exposure.

Absence of correlation between radiation-induced CD8 T-lymphocyte apoptosis and sequelae in patients with prostate cancer accidentally overexposed to radiation

Purpose

454 patients with prostate adenocarcinoma were accidentally overexposed to radiation in Epinal hospital, France, between August 1999 and January 2007. We aimed toevaluate whether radiation-induced CD4 or CD8 T-lymphocyte apoptosis (RILA) correlates with the severity of radiation toxicity.

Methods

Between 2007 and 2013, all patients who received more than 108% of the prescribed radiation dose, after correction of the treatment plan, were convened, and blood was sampled at 6-months follow-up. Maximal Digestive toxicity (MDT) and maximal urinary toxicity (MUT) were graded using the Common Terminology Criteria for Adverse Events (NCI-CTCAE) v3.0 scale. RILA was assessed using flow cytometry.

Results

245 patients were included in our study. After a median follow-up of 4.8 years, the MDT and MUT reached grade 3-4 in 37 patients and 56 patients, respectively. Patients with prostatectomy exhibited a statistically higher grade of MUT compared with those treated with definitive radiotherapy (p=0.03). The median RILA values were 11.8% and 15.3% for CD4 and CD8 T-lymphocytes, respectively. We found no significant correlation between CD4 or CD8 RILA and either MDT or MUT.

Conclusion

RILA does not correlate with the inter-individual variation in MDT or MUT in the largest cohort of patients overexposed to radiation. The magnitude of the overdosage probably overrides biological predictors of toxicity, including individual radiosensitivity.

A multicenter study of biological effects assessment of pharmacy workers occupationally exposed to antineoplastic drugs in Pharmacy Intravenous Admixture Services

This multi-centered study was designed to evaluate the biological effects of exposure to antineoplastic drugs (ADs) at PIVAS (Pharmacy Intravenous Admixture Service) across ten Chinese hospitals. 8-hydroxy-2-deoxyguanosine (8-OHdG) was used as a biomarker of DNA oxidative damage and lymphocyte apoptosis assays using peripheral lymphocyte cells were used to detect primary DNA damage. The mutagenicity activity was estimated with the Ames fluctuation test. 158 exposed and 143 unexposed workers participated in this study. The urinary 8-OHdG/Cr concentrations of the exposed group was 22.05±17.89ng/mg Cr, which was significantly higher than controls of 17.36±13.50ng/mg Cr (P<0.05). The rate of early lymphocyte apoptosis was slightly increased in exposed group than that of the control group (P=0.087). The mutagenic activity was significantly higher in the exposed group relative to the control group (P<0.05). Moreover, while no statistically significant difference was observed, higher concentrations of 8-OHdG/Cr in urine and an early lymphocyte apoptosis rate were found in exposed group II as compared to exposed group I. In addition, a significant correlation between early lymphocyte apoptosis and exposure time to ADs was also observed (P<0.05). In conclusion, our study identified elevated biomarkers in PIVAS workers exposed to ADs. However whether these findings could lead to increased incidence of genotoxic responses remains to be further investigated.

Apoptosis for prediction of radiotherapy late toxicity: lymphocyte subset sensitivity and potential effect of TP53 Arg72Pro polymorphism

We tested apoptosis levels in in vitro irradiated T-lymphocytes from breast cancer (BC) patients with radiotherapy-induced late effects. Previous results reported in the literature were revised. We also examined the effect of TP53 Arg72Pro polymorphism on irradiation-induced apoptosis (IA). Twenty BC patients, ten with fibrosis and/or telangiectasias and ten matched controls with no late reactions, were selected from those receiving radiotherapy between 1993 and 2007. All patients were followed-up at least 6 years after radiotherapy. Using the combination of both CD3 and CD8 antibodies the in vitro IA was measured in CD3, CD8 and CD4 T-lymphocytes, and CD8 natural killer lymphocytes (CD8 NK) by flow cytometry. The TP53 Arg72Pro genotype was determined by sequencing. Patients with late radiotherapy toxicity showed less IA for all T-lymphocytes except for the CD8 NK. CD8 NK showed the highest spontaneous apoptosis and the lowest IA. IA in patients with toxicity appears to be lower than the control patients only in TP53 Arg/Arg patients (P = 0.077). This difference was not present in patients carrying at least one Pro allele (P = 0.8266). Our data indicate that late side effects induced by radiotherapy of BC are associated to low levels of IA. CD8 NK cells have a different response to in vitro irradiation compared to CD8 T-lymphocytes. It would be advisable to distinguish the CD8 NK lymphocytes from the pool of CD8+ lymphocytes in IA assays using CD8+ cells. Our data suggest that the 72Pro TP53 allele may influence the IA of patients with radiotherapy toxicity.

New biological markers in the decision of treatment of head and neck cancer patients

Head and neck squamous cell carcinoma is the sixth most common cancer type worldwide. Also the 5-year survival rate of less than 50 % seems to be lower than other cancer types. There are some reasons behind this high mortality rate; one of them is the lack of knowledge about the biology and genomic instability behind the carcinogenic processes. These biological features could condition the failure of frontline treatment, in which case rescue treatment should be used, representing an overtreatment for the patients. For years many biological factors have been tested as prognostic and predictive factors in relation to treatment with a modest success. To find appropriate tests which could be used in the context of the individualized treatment decision, we have reviewed new biological markers, not only in tumor tissue, but also in normal tissue from head and neck carcinoma patients.