Genetics and epigenetics of direct and indirect radiation responses in normal mammary and breast cancer cells

The successful approach for decreasing breast cancer fatalities depends upon reliable diagnostic screening and optimal treatment modalities. Ionizing radiation is widely used for both screening and therapeutic procedures. The main aim of this study was to analyze the effect of low (diagnostic) and high (treatment) doses of ionizing radiation on healthy breast cells, breast cancer cells, and cancer cells resistant to common drug therapies. The results presented here show that ionizing radiation initiates immune and apoptotic response in normal cells, and causes epigenetic alterations that may lead to genomic instability. In addition, our results demonstrate differential dose response to radiation in MCF-7 cells, and decreased sensitivity to radiation in tamoxifen-resistant MCF-7 cells. Our results may serve as foundation for the future analysis of the mechanisms of radiation responses of mammary gland tissues, and as an additional step for future analysis of effectiveness of combination therapy

High and low dose radiation effects on mammary adenocarcinoma cells -an epigenetic connection

ABSTRACT The successful treatment of cancer, including breast cancer, depends largely on radiation therapy and proper diagnostics. The effect of ionizing radiation on cells and tissues depends on the radiation dose and energy level, but there is insufficient evidence concerning how tumor cells respond to the low and high doses of radiation that are often used in medical diagnostic and treatment modalities. The purpose of this study was to investigate radiation-induced gene expression changes in the MCF-7 breast adenocarcinoma cell line. Using microarray technology tools, we were able to screen the differential gene expressions profiles between various radiation doses applied to MCF-7 cells. Here, we report the substantial alteration in the expression level of genes after high-dose treatment. In contrast, no dramatic gene expression alterations were noticed after the application of low and medium doses of radiation. In response to a high radiation dose, MCF-7 cells exhibited down-regulation of biological pathways such as cell cycle, DNA replication, and DNA repair and activation of the p53 pathway. Similar dose-dependent responses were seen on the epigenetic level, which was tested by a microRNA expression analysis. MicroRNA analysis showed dose-dependent radiation-induced microRNA expression alterations that were associated with cell cycle arrest and cell death. An increased rate of apoptosis was determined by an Annexin V assay. The results of this study showed that high doses of radiation affect gene expression genetically and epigenetically, leading to alterations in cell cycle, DNA replication, and apoptosis

Mutant p53 establishes targetable tumor dependency by promoting unscheduled replication

Gain-of-function (GOF) p53 mutations are observed frequently in most intractable human cancers and establish dependency for tumor maintenance and progression. While some of the genes induced by GOF p53 have been implicated in more rapid cell proliferation compared with p53-null cancer cells, the mechanism for dependency of tumor growth on mutant p53 is unknown. This report reveals a therapeutically targetable mechanism for GOF p53 dependency. We have shown that GOF p53 increases DNA replication origin firing, stabilizes replication forks, and promotes micronuclei formation, thus facilitating the proliferation of cells with genomic abnormalities. In contrast, absence or depletion of GOF p53 leads to decreased origin firing and a higher frequency of fork collapse in isogenic cells, explaining their poorer proliferation rate. Following genome-wide analyses utilizing ChIP-Seq and RNA-Seq, GOF p53–induced origin firing, micronuclei formation, and fork protection were traced to the ability of GOF p53 to transactivate cyclin A and CHK1. Highlighting the therapeutic potential of CHK1’s role in GOF p53 dependency, experiments in cell culture and mouse xenografts demonstrated that inhibition of CHK1 selectively blocked proliferation of cells and tumors expressing GOF p53. Our data suggest the possibility that checkpoint inhibitors could efficiently and selectively target cancers expressing GOF p53 alleles

Altered radiation responses of breast cancer cells resistant to hormonal therapy

Sherpa Romeo blue journal. Open access article. Creative Commons Attribution 3.0 License (CC BY 3.0) applies.Endocrine therapy agents (the selective estrogen receptor (ER) modulators such as tamoxifen or the selective ER down-regulators such as ICI 182,780) are key treatment regimens for hormone receptor-positive breast cancers. While these drugs are very effective in controlling ER-positive breast cancer, many tumors that initially respond well to treatment often acquire drug resistance, which is a major clinical problem. In clinical practice, hormonal therapy agents are commonly used in combination or sequence with radiation therapy. Tamoxifen treatment and radiotherapy improve both local tumor control and patient survival. However, tamoxifen treatment may render cancer cells less responsive to radiation therapy. Only a handful of data exist on the effects of radiation on cells resistant to hormonal therapy agents. These scarce data show that cells that were resistant to tamoxifen were also resistant to radiation. Yet, the existence and mechanisms of cross-resistance to endocrine therapy and radiation therapy need to be established. Here, we for the first time examined and compared radiation responses of MCF-7 breast adenocarcinoma cells (MCF-7/S0.5) and two antiestrogen resistant cell lines derived from MCF-7/S0.5: the tamoxifen resistant MCF-7/TAMR-1 and ICI 182,780 resistant MCF-7/182R-6 cell lines. Specifically, we analyzed the radiation-induced changes in the expression of genes involved in DNA damage, apoptosis, and cell cycle regulation. We found that the tamoxifen-resistant cell line in contrast to the parental and ICI 182,780-resistant cell lines displayed a significantly less radiationinduced decrease in the expression of genes involved in DNA repair. Furthermore, we show that MCF-7/TAMR-1 and MCF-7/182R-6 cells were less susceptible to radiation-induced apoptosis as compared to the parental line. These data indicate that tamoxifen-resistant breast cancer cells have a reduced sensitivity to radiation treatment. The current study may therefore serve as a roadmap to the future analysis of the mechanisms of cross-resistance between hormonal therapy and radiation.Ye

Radiation responses of chemoresistant adenocarcinoma cells : from molecular mechanisms to new reversal strategies

xi, 98 leaves : ill. (some col.) ; 29 cmBreast cancer is a major cause of cancer-related death among women throughout the world. Treatment of breast cancer often fails due to the development of resistance to both chemo- and radiotherapy. The aim of this study was to analyze and compare the response to radiation of MCF-7 breast adenocarcinoma cells and MCF-7 cells that are resistant to doxorubicin (MCF-7/DOX). The results presented in this thesis show that drug-resistant MCF-7/DOX cells survive high doses of radiation exposure better than MCF-7 cells. Moreover, the chemo- and radioresistance of MCF-7/DOX cells share common molecular mechanisms and loss of sensitivity to radiation in chemo-resistant cells may be explained by alterations in their DNA methylation profile. The results of experiments presented in this thesis may, therefore, serve as a first step for future analysis of tumour resistance to radio- and chemotherapy and for the development of novel epigenetic strategies for reversal of breast cancer resistance to cytotoxic treatment regimens

The methylation status of the embryonic limb skeletal progenitors determines their cell fate in chicken

Digits shape is sculpted by interdigital programmed cell death during limb development. Here, we show that DNA breakage in the periphery of 5-methylcytosine nuclei foci of interdigital precursors precedes cell death. These cells showed higher genome instability than the digit-forming precursors when exposed to X-ray irradiation or local bone morphogenetic protein (BMP) treatments. Regional but not global DNA methylation differences were found between both progenitors. DNA-Methyl-Transferases (DNMTs) including DNMT1, DNMT3B and, to a lesser extent, DNMT3A, exhibited well-defined expression patterns in regions destined to degenerate, as the interdigital tissue and the prospective joint regions. Dnmt3b functional experiments revealed an inverse regulation of cell death and cartilage differentiation, by transcriptional regulation of key genes including Sox9, Scleraxis, p21 and Bak1, via differential methylation of CpG islands across their promoters. Our findings point to a regulation of cell death versus chondrogenesis of limb skeletal precursors based on epigenetic mechanisms.We thank Prof. Miguel Lafarga for helpful comments and advice. We thank Dr Jose E Gomez-Arozamena for helping us with the irradiation experiments. We are grateful to Montse Fernandez Calderon, Susana Dawalibi, and Sonia Perez Mantecon, for excellent technical assistance. This work was supported by a Grant (BFU2017–84046-P) from the Spanish Science and Innovation Ministry to JAM. C.S.F is recipient of a FPI grant (BES-2015–074267)

Smoking‐induced genetic and epigenetic alterations in infertile men

Male fertility rates have shown a progressive decrease in both developing and industrialised countries in the past 50 years. Clinical and epidemiological studies have demonstrated controversial results about the harmful effects of cigarette smoking on seminal parameters. Some studies could not establish a negative effect by tobacco smoking on sperm quality and function, whereas others have found a significant reduction in sperm quality and function. This study reviews the components in cigarette smoke and discusses the effects of smoking on male fertility by focusing extensively on smoking‐induced genetic and epigenetic alterations in infertile men. Chromosomal aneuploidies, sperm DNA fragmentation and gene mutations are discussed in the first section, while changes in DNA methylation, chromatin remodelling and noncoding RNAs are discussed in the second section as part of epigenetic alterations

Radiations and male fertility

During recent years, an increasing percentage of male infertility has to be attributed to an array of environmental, health and lifestyle factors. Male infertility is likely to be affected by the intense exposure to heat and extreme exposure to pesticides, radiations, radioactivity and other hazardous substances. We are surrounded by several types of ionizing and non-ionizing radiations and both have recognized causative effects on spermatogenesis. Since it is impossible to cover all types of radiation sources and their biological effects under a single title, this review is focusing on radiation deriving from cell phones, laptops, Wi-Fi and microwave ovens, as these are the most common sources of non-ionizing radiations, which may contribute to the cause of infertility by exploring the effect of exposure to radiofrequency radiations on the male fertility pattern. From currently available studies it is clear that radiofrequency electromagnetic fields (RF-EMF) have deleterious effects on sperm parameters (like sperm count, morphology, motility), affects the role of kinases in cellular metabolism and the endocrine system, and produces genotoxicity, genomic instability and oxidative stress. This is followed with protective measures for these radiations and future recommendations. The study concludes that the RF-EMF may induce oxidative stress with an increased level of reactive oxygen species, which may lead to infertility. This has been concluded based on available evidences from in vitro and in vivo studies suggesting that RF-EMF exposure negatively affects sperm quality

ОБҐРУНТУВАННЯ СТРАТЕГІЧНИХ НАПРЯМІВ ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ДЕРЖАВНОГО УПРАВЛІННЯ ФІНАНСАМИ РЕГІОНУ

The article substantiates the strategic directions of increasing the efficiency of state financial management of the region, proposes an economic-mathematical model for assessing the optimal scale of tax-budgetary decentralization in the conditions of interregional differentiation. The authors emphasize that the urgency of solving the problems of state financial management of the region is due to the impossibility at this stage of creating a certain universal model of regional development. This is primarily related to the unfinished process of forming a comprehensive assessment of the territorial level of development, analysis of socio-economic differentiation and typification of regions, use of state and regional financial policy tools. It is noted that the finances of the region, as the main tool for the implementation of the state socio-economic policy, are designed to promote the development of production, the growth of employment of the population, the attraction of investments in the economy, etc.Three options for the distribution of tax powers between the state and the regions were considered: 1) all tax powers belong to the regions, which independently determine the level of the tax burden and the volume of production of public goods; 2) all tax powers belong to the centre, which determines the level of the tax burden and distributes the received tax revenues between the regions, thus influencing the volume of production of public goods in each of the regions; 3) the distribution of tax powers between the centre and the regions, for which the volume of production of public goods in each of the regions depends both on the tax and budget policy of the centre and on the tax policy of each of the regions. Based on the application of economic-mathematical modelling methods, a conclusion was made about the dependence of the optimal level of decentralization on the level of interregional economic differentiation.Two groups of problems have been singled out, which directly affect the financial management of the region and the consideration of which requires the application of different methodological approaches and methods of state administration: external problems that do not depend on specific regions, are common to all regions of Ukraine, but affect each of them differently them; internal problems that were formed under the influence of internal factors of socio-economic development, which determine the characteristics of each specific region.The key factors of success for a specific region have been determined, provided that certain instruments of state regulation are applied.У статті обґрунтовано стратегічні напрями підвищення ефективності державного управління фінансами регіону, запропоновано економіко-математичну модель оцінки оптимальних масштабів податково-бюджетної децентралізації в умовах міжрегіональної диференціації. Автори акцентують, що актуальність вирішення проблем державного управління  фінансами регіону зумовлена неможливістю на цьому етапі створення певної універсальної моделі регіонального розвитку. Це передусім пов’язано з незавершеним процесом формування комплексної оцінки територіального рівня розвитку, аналізу соціально-економічної диференціації і типізації регіонів, використання інструментів державної та регіональної фінансової політики. Зазначено, що фінанси регіону як головний інструмент реалізації державної соціально-економічної політики, покликані сприяти розвиткові виробництва, зростанню зайнятості населення, залученню інвестицій в економіку тощо.Розглянуто три варіанти розподілу податкових повноважень між державою і регіонами: 1) усі податкові повноваження належать регіонам, які самостійно визначають рівень податкового навантаження і обсяг виробництва суспільних благ; 2) усі податкові повноваження належать центру, який визначає рівень податкового навантаження і розподіляє одержані податкові доходи між регіонами, впливаючи тим самим на обсяги виробництва суспільних благ у кожному з регіонів; 3) розподіл податкових повноважень між центром і регіонами, за якого обсяг виробництва суспільних благ у кожному з регіонів залежить як від податково-бюджетної політики центру, так і від податкової політики кожного з регіонів. На підставі застосування методів економіко-математичного моделювання зроблено висновок про залежність оптимального рівня децентралізації від рівня міжрегіональної економічної диференціації.Виділено дві групи проблем, які прямо впливають на управління фінансами регіону і врахування яких потребує застосування різних методичних підходів і способів державного управління: зовнішні проблеми, які не залежать від конкретних регіонів, є спільними для всіх регіонів України, але по-різному впливають на кожен із них; внутрішні проблеми, які сформувались під впливом внутрішніх факторів соціально-економічного розвитку, що визначають особливості кожного конкретного регіону.Визначено ключові фактори успіху для конкретного регіону за умови застосування тих чи інших інструментів державного регулювання