A genomic copy number signature predicts radiation exposure in post-Chernobyl breast cancer.

Breast cancer is the second leading cause of cancer death among women worldwide and besides life style, age and genetic risk factors, exposure to ionizing radiation is known to increase the risk for breast cancer. Further, DNA copy number alterations (CNAs), which can result from radiation-induced double-strand breaks, are frequently occurring in breast cancer cells. We set out to identify a signature of CNAs discriminating breast cancers from radiation-exposed and non-exposed female patients. We analyzed resected breast cancer tissues from 68 exposed female Chernobyl clean-up workers and evacuees and 68 matched non-exposed control patients for CNAs by array comparative genomic hybridization analysis (aCGH). Using a stepwise forward-backward selection approach a non-complex CNA signature, that is, less than ten features, was identified in the training data set, which could be subsequently validated in the validation data set (p value < 0.05). The signature consisted of nine copy number regions located on chromosomal bands 7q11.22-11.23, 7q21.3, 16q24.3, 17q21.31, 20p11.23-11.21, 1p21.1, 2q35, 2q35, 6p22.2. The signature was independent of any clinical characteristics of the patients. In all, we identified a CNA signature that has the potential to allow identification of radiation-associated breast cancer at the individual level.

Doses of Ukrainian female clean-up workers with diagnosed breast cancer.

The Chernobyl reactor accident in 1986 has caused significant exposure to ionizing radiation of the Ukrainian population, in particular clean-up workers and evacuees from the exclusion zones. A study aiming at the discovery of radiation markers of the breast cancer was conducted from 2008 to 2015 within a collaborative project by HZM, LMU, and NRCRM. In this study, post-Chernobyl breast cancer cases both in radiation-exposed female patients diagnosed at age less than 60 from 1992 to 2014 and in non-exposed controls matched for residency, tumor type, age at diagnosis, TNM classification as well as tumor grading were investigated for molecular changes with special emphasis to copy number alterations and miRNA profiles. Cancer registry and clinical archive data were used to identify 435 breast cancer patients among female clean-up workers and 14 among evacuees from highly contaminated territories as candidates for the study. Of these, 129 breast cancer patients fit study inclusion criteria and were traced for individual reconstruction of the target organ (breast) doses. The doses were estimated for 71 exposed cases (clean-up workers and evacuees from which biomaterial was available for molecular studies and who agreed to participate in a dosimetric interview) by the use of the well-established RADRUE method, which was adjusted specifically for the assessment of breast doses. The results of 58 female clean-up workers showed a large inter-individual variability of doses in a range of about five orders of magnitude: from 0.03 to 929 mGy, with median of 5.8 mGy. The study provides the first quantitative estimate of exposures received by female clean-up workers, which represent a limited but very important group of population affected by the Chernobyl accident. The doses of 13 women evacuated after the accident who did not take part in the clean-up activities (from 4 to 45 mGy with median of 19 mGy) are in line with the previous estimates for the evacuees from Pripyat and the 30-km zone.

Expression of miRNA-26b-5p and its target TRPS1 is associated with radiation exposure in post-Chernobyl breast cancer.

Ionizing radiation is a well-recognized risk factor for the development of breast cancer. However, it is unknown whether radiation-specific molecular oncogenic mechanisms exist. We investigated post-Chernobyl breast cancers from radiation-exposed female clean-up workers and nonexposed controls for molecular changes. Radiation-associated alterations identified in the discovery cohort (n = 38) were subsequently validated in a second cohort (n = 39). Increased expression of hsa-miR-26b-5p was associated with radiation exposure in both of the cohorts. Moreover, downregulation of the TRPS1 protein, which is a transcriptional target of hsa-miR-26b-5p, was associated with radiation exposure. As TRPS1 overexpression is common in sporadic breast cancer, its observed downregulation in radiation-associated breast cancer warrants clarification of the specific functional role of TRPS1 in the radiation context. For this purpose, the impact of TRPS1 on the transcriptome was characterized in two radiation-transformed breast cell culture models after siRNA-knockdown. Deregulated genes upon TRPS1 knockdown were associated with DNA-repair, cell cycle, mitosis, cell migration, angiogenesis and EMT pathways. Furthermore, we identified the interaction partners of TRPS1 from the transcriptomic correlation networks derived from gene expression data on radiation-transformed breast cell culture models and sporadic breast cancer tissues provided by the TCGA database. The genes correlating with TRPS1 in the radiation-transformed breast cell lines were primarily linked to DNA damage response and chromosome segregation, while the transcriptional interaction partners in the sporadic breast cancers were mostly associated with apoptosis. Thus, upregulation of hsa-miR-26b-5p and downregulation of TRPS1 in radiation-associated breast cancer tissue samples suggests these molecules representing radiation markers in breast cancer.

Systematic review and meta-analysis of circulatory disease from exposure to low-level ionizing radiation and estimates of potential population mortality risks.

BACKGROUND: Although high doses of ionizing radiation have long been linked to circulatory disease, evidence for an association at lower exposures remains controversial. However, recent analyses suggest excess relative risks at occupational exposure levels. OBJECTIVES: We performed a systematic review and meta-analysis to summarize information on circulatory disease risks associated with moderate- and low-level whole-body ionizing radiation exposures. METHODS: We conducted PubMed/ISI Thomson searches of peer-reviewed papers published since 1990 using the terms "radiation" AND "heart" AND "disease," OR "radiation" AND "stroke," OR "radiation" AND "circulatory" AND "disease." Radiation exposures had to be whole-body, with a cumulative mean dose of < 0.5 Sv, or at a low dose rate (< 10 mSv/day). We estimated population risks of circulatory disease from low-level radiation exposure using excess relative risk estimates from this meta-analysis and current mortality rates for nine major developed countries. RESULTS: Estimated excess population risks for all circulatory diseases combined ranged from 2.5%/Sv [95% confidence interval (CI): 0.8, 4.2] for France to 8.5%/Sv (95% CI: 4.0, 13.0) for Russia. CONCLUSIONS: Our review supports an association between circulatory disease mortality and low and moderate doses of ionizing radiation. Our analysis was limited by heterogeneity among studies (particularly for noncardiac end points), the possibility of uncontrolled confounding in some occupational groups by lifestyle factors, and higher dose groups (> 0.5 Sv) generally driving the observed trends. If confirmed, our findings suggest that overall radiation-related mortality is about twice that currently estimated based on estimates for cancer end points alone (which range from 4.2% to 5.6%/Sv for these populations).

Hematopoietic cell infusion for the treatment of nuclear disaster victims: new data from the Chernobyl accident.

PURPOSE: To present previously unavailable data on the use of stem cell administration to aid recovery of victims of the Chernobyl disaster. On 26 April 1986, an accident at Unit 4 of the Chernobyl Nuclear Power Plant took place during the planned test of one of the safety systems. The diagnosis of acute radiation syndrome (ARS) was confirmed in 134 individuals exposed to high levels of radiation. There were nine patients heretofore unreported in the scientific literature who underwent intraosseous injections of allogeneic bone marrow cells in Kyiv. CONCLUSIONS: Transplantation was associated with significantly shortened time to recovery of granulocyte and platelet counts in these patients. While current guidelines would certainly include the use of cytokines, these data provide an indication of the effectiveness of stem cell transplant to treat victims of radiation exposure.

Allelic imbalances in radiation-associated acute myeloid leukemia.

Acute myeloid leukemia (AML) can develop as a secondary malignancy following radiotherapy, but also following low-dose environmental or occupational radiation exposure. Therapy-related AML frequently carries deletions of chromosome 5q and/or 7, but for low-dose exposure associated AML this has not been described. For the present study we performed genome-wide screens for loss-of-heterozygosity (LOH) in a set of 19 AML cases that developed after radiation-exposure following the Chernobyl accident. Using Affymetrix SNP arrays we found large regions of LOH in 16 of the cases. Eight cases (42%) demonstrated LOH at 5q and/or 7, which is a known marker of complex karyotypic changes and poor prognosis. In accordance with literature data, the overall survival for these patients was significantly shorter as compared to patients without this alteration (P=0,014). We could show here for the first time that exposure to low-dose ionizing radiation induces AML with molecular alterations similar to those seen in therapy-related cases.

Membrane transport and apoptosis-related proteins in radiation-associated acute myeloid leukemia following the Chornobyl accident.

We report on the results of multidrug-resistance transporters (P-glycoprotein, LRP, and MDR1), and apoptosis-related proteins (Fas, Bcl-2, Bax, p53, and Bcl-X(L)) expression analysis of 56 acute myeloid leukemia (AML) patients by flow cytometry. Of these, there were 21 persons exposed to ionizing radiation due to the Chornobyl accident with radiation-associated and 35 patients with spontaneous AML. Leukemic cells in patients with radiation-associated AML more often overexpressed antiapoptotic protein Bcl-2 (12/21 vs. 6/35, p < 0.005) and less often demonstrated expression of Fas receptor (12/21 vs. 30/35, p < 0.05). Moreover, leukemic cells were simultaneously Fas negative and Bcl-2 positive in 4 out of 21 patients exposed to ionizing radiation but none of spontaneous cases had similar phenotype (p < 0.05). Patients with radiation-associated AML compared to spontaneous cases more often were P-glycoprotein positive (12/20 vs. 9/31, p < 0.05). P-glycoprotein overexpression significantly correlated with the resistance of the disease to chemotherapy in patients with radiation-associated AML (p < 0.05).

MLL gene alterations in radiation-associated acute myeloid leukemia.

AIM: Although acute myelogenous leukemia (AML) arising after radiation exposure is considered to be secondary, little is known about the molecular mechanisms by which the radiation induces the leukemogenic phenotype. The aim of the study was to analyze whether the MLL translocations are as frequent in radiation-associated AML as in spontaneous AML cases. METHODS: Sixty one AML samples obtained at diagnosis were analyzed for the presence of MLL abnormalities using fluorescent in situ hybridization and/or reverse transcription polymerase chain reaction. Of these patients, 27 had experienced radiation exposure due to the Chernobyl accident, 32 were non-irradiated (spontaneous AML), and 2 developed therapy-related AML after chemotherapy with topoisomerase II inhibitors. RESULTS: MLL gene translocations were detected in both groups of spontaneous and therapy-related AML (1/32 and 1/2 cases respectively). The sole MLL rearrangement found in the group of radiation-associated AML patients was a duplication of the gene. CONCLUSION: Our data preclude the involvement of MLL gene translocations in radiation-induced leukemogenesis, but support the assumption that loss and gain of chromosomal material could be crucial in the leukemogenesis of AML patients with the history of radiation exposure due to the Chernobyl accident.