Radiation-induced Adaptive Response Research Articles

BSBM-15 SYSTEMIC AND LOCAL IMMUNE RESPONSES FOLLOWING STEREOTACTIC RADIOSURGERY TO BRAIN METASTASES FROM HER2-AMPLIFIED BREAST CANCER

Abstract BACKGROUND Brain metastases (BMs) afflict 30-50% of HER2-amplified breast cancer (HER2-BC) patients. Stereotactic radiosurgery (SRS) is a highly effective focal treatment for BMs. Extracranial radiotherapy can promote anti-tumor immune responses that synergize with immunotherapy, but whether this applies to the brain microenvironment remains unclear. Here, we examined blood and BM samples from HER2-BC patients in the TROG 16.02 translational sub-study for immunological effects of SRS (ACTRN12616001265460). METHODS Blood samples from 10 patients taken pre- and 7-14 days post-SRS to intact HER2-BC BMs or post-resection BM cavities were analyzed by mass and flow cytometry for immune cell and cytokine modulation. One patient received pre-operative SRS for a BM that recurred 6 months after resection, followed by re-resection of the BM 7 days post-SRS. Tumors from pre- and post-SRS timepoints in this patient were analyzed by bulk RNAseq and immunohistochemistry. RESULTS Monocytes, CD8+ T effector memory and regulatory T cells were enriched in blood post-SRS, while conventional dendritic cells, CD4+ T early and CD4+ TEMRA cells were diminished. Stem cell factor (SCF) concentration, a growth factor important for monocyte production, was elevated in plasma post-SRS. In the tumor, SRS upregulated gene signatures for monocyte/macrophage processes (including SCF gene transcript levels), antigen presentation, and T cell activation. Cell type deconvolution from RNAseq suggested an SRS-induced loss of metastatic tumor cells and enrichment of macrophages and CD4+ T cells. Immunohistochemistry corroborated the influx of CD68+ macrophages and CD3+ T cells into tumor and brain regions post-SRS, with spatial co-localization evident between the cell types. Furthermore, the pre-SRS immune-excluded phenotype in tumor regions was no longer observed post-SRS. CONCLUSION Systemic and local immunological changes in this homogenous patient cohort receiving SRS to HER2-BC BMs suggest a radiation-induced adaptive immune response intracranially, involving the monocyte-macrophage lineage as antigen presenting cells, that should be further explored.

Immune system modulation by low-dose ionizing radiation-induced adaptive response.

Hormesis or low-dose ionizing radiation is known to induce various biological responses, a subcategory of which is the adaptive response, which has been reported to protect against higher radiation doses via multiple mechanisms. This study investigated the role of the cell-mediated immunological component of low-dose ionizing radiation-induced adaptive response. Herein, male albino rats were exposed to whole-body gamma radiation, using a Cs137 source with low-dose ionizing radiation doses of 0.25 and 0.5Gray (Gy); 14 days later, another irradiation session at a dose level of 5Gy was carried on. Four days post-irradiation at 5Gy, rats were sacrificed. The low-dose ionizing radiation-induced immuno-radiological response has been assessed through the T-cell receptor (TCR) gene expression quantification. Also, the serum levels of each of interleukins-2 and -10 (IL-2, IL-10), transforming growth factor-beta (TGF-β), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were quantified. Results indicated that priming low irradiation doses resulted in significant decrements in TCR gene expression and the serum levels of IL-2, TGF-β, and 8-OHdG with an increment in IL-10 expression compared to the irradiated group, which did not receive low priming doses. The observed low-dose ionizing radiation-induced radio-adaptive response significantly protected against high irradiation dose injuries, through immune suppression, representing a promising pre-clinical protocol that would be applied to minimize radiotherapy side effects on normal but not against the tumor cells.

Blockade of USP14 potentiates type I interferon signaling and radiation-induced antitumor immunity via preventing IRF3 deubiquitination.

The adaptive immune responses induced by radiotherapy has been demonstrated to largely rely on STING-dependent type I interferons (IFNs) production. However, irradiated tumor cells often fail to induce dendritic cells (DCs) to produce type I IFNs. Hence, we aim to uncover the limitation of STING-mediated innate immune sensing following radiation, and identify efficient reagents capable to rescue the failure of type I IFNs induction for facilitating radiotherapy. A targeted cell-based phenotypic screening was performed to search for active molecules that could elevate the production of type I IFNs. USP14 knockout or inhibition was assayed for IFN production and the activation of STING signaling in vitro. The mechanisms of USP14 were investigated by western blot and co-immunoprecipitation in vitro. Additionally, combinational treatments with PT33 and radiation in vivo and in vitro models were performed to evaluate type I IFNs responses to radiation. PT33 was identified as an enhancer of STING agonist elicited type I IFNs production to generate an elevated and durable STING activation profile in vitro. Mechanistically, USP14 inhibition or deletion impairs the deubiquitylation of K63-linked IRF3. Furthermore, blockade of USP14 with PT33 enhances DC sensing of irradiated-tumor cells in vitro, and synergizes with radiation to promote systemic antitumor immunity in vivo. Our findings reveal that USP14 is one of the major IFN production suppressors and impairs the activation of IRF3 by removing the K63-linked ubiquitination of IRF3. Therefore, blockage of USP14 results in the gain of STING signaling activation and radiation-induced adaptive immune responses.

Biological and cellular responses of humans to high-level natural radiation: A clarion call for a fresh perspective on the linear no-threshold paradigm

There remains considerable uncertainty in obtaining risk estimates of adverse health outcomes of chronic low-dose radiation. In the absence of reliable direct data, extrapolation through the linear no-threshold (LNT) hypothesis forms the cardinal tenet of all risk assessments for low doses (≤ 100 mGy) and for the radiation protection principle of As Low As Reasonably Achievable (ALARA). However, as recent evidences demonstrate, LNT assumptions do not appropriately reflect the biology of the cell at the low-dose end of the dose-response curve. In this regard, human populations living in high-level natural radiation areas (HLNRA) of the world can provide valuable insights into the biological and cellular effects of chronic radiation to facilitate improved precision of the dose-response relationship at low doses. Here, data obtained over decades of epidemiological and radiobiological studies on HLNRA populations is summarized. These studies do not show any evidence of unfavourable health effects or adverse cellular effects that can be correlated with high-level natural radiation. Contrary to the assumptions of LNT, no excess cancer risks or untoward pregnancy outcomes have been found to be associated with cumulative radiation dose or in-utero exposures. Molecular biology-driven studies demonstrate that chronic low-dose activates several cellular defence mechanisms that help cells to sense, recover, survive, and adapt to radiation stress. These mechanisms include stress-response signaling, DNA repair, immune alterations and most importantly, the radiation-induced adaptive response. The HLNRA data is consistent with the new evolving paradigms of low-dose radiobiology and can help develop the theoretical framework of an alternate dose-response model. A rational integration of radiobiology with epidemiology data is imperative to reduce uncertainties in predicting the potential health risks of chronic low doses of radiation.

Modeling of Molecular Mechanisms of Radiation Adaptive Response Formation

The phenomenon of adaptive response is expressed in the increase of resistance of a biological object to high doses of mutagens under the conditions of previous exposure to these (or other) mutagens in low doses. Low doses of mutagen activate a number of protective mechanisms in a living object, which are called hormetic. Thus, the adaptive response and hormesis are links in the same chain. Radiation hormesis refers to the generally positive effect of low doses of low LET radiation on biological objects. The phenomenology of radiation-induced adaptive response and radiation hormesis for biological objects of different levels of organization is considered; the review of existing theories describing the dose-effect relationship has been reviewed. The hypothesis proposing one of the mechanisms of formation of radiation adaptive response of cells taking into account the conformational structure of chromatin has been submitted. The analysis of modern concepts of the phenomenon of hormesis on the basis of modeling of molecular mechanisms of formation of hormetic reactions to low-dose low LET radiation has been carried out. The parameters that can be used for quantitative and graphical evaluation of the phenomenon of hormesis was considered, and a formula for calculating the coefficient of radiation-induced adaptive response has been proposed. A review of mathematical models describing the radiation relative risk of gene mutations and neoplastic transformations at low-dose irradiation of cohorts has been performed. The following conclusions have been made: radiation hormesis and adaptive response are generally recognized as real and reproducible biological phenomena, which should be considered as very important phenomena of evolutionarily formed biological protection of living organisms from ionizing radiation. The hormesis model of dose-response relationship makes much more accurate predictions of a living object's response to radiation (or other stressors) in the low-dose range than the linear threshold (LNT) model does. The LNT model can adequately describe reactions only in the region of high doses of radiation, and, therefore, extrapolation modeling of biological object’s reactions from the zone of high doses to low doses is not correct.

Radiation-induced Adaptive Response: New Potential for Cancer Treatment.

Radiotherapy is highly effective due to its ability to physically focus the treatment to target the tumor while sparing normal tissue and its ability to be combined with systemic therapy. This systemic therapy can be utilized before radiotherapy as an adjuvant or induction treatment, during radiotherapy as a radiation "sensitizer," or following radiotherapy as a part of combined modality therapy. As part of a unique concept of using radiation as "focused biology," we investigated how tumors and normal tissues adapt to clinically relevant multifraction (MF) and single-dose (SD) radiation to observe whether the adaptations can induce susceptibility to cell killing by available drugs or by immune enhancement. We identified an adaptation occurring after MF (3 × 2 Gy) that induced cell killing when AKT-mTOR inhibitors were delivered following cessation of radiotherapy. In addition, we identified inducible changes in integrin expression 2 months following cessation of radiotherapy that differ between MF (1 Gy × 10) and SD (10 Gy) that remain targetable compared with preradiotherapy. Adaptation is reflected across different "omics" studies, and thus the range of possible molecular targets is not only broad but also time, dose, and schedule dependent. While much remains to be studied about the radiation adaptive response, radiation should be characterized by its molecular perturbations in addition to physical dose. Consideration of the adaptive effects should result in the design of a tailored radiotherapy treatment plan that accounts for specific molecular changes to be targeted as part of precision multimodality cancer treatment.

First person profile: C. Norman Coleman, MD: A leading radiation and medical oncologist, Dr. Coleman has worked to improve cancer prevention, treatment, and quality of life on a global level.

First person profile: C. Norman Coleman, MD: A leading radiation and medical oncologist, Dr. Coleman has worked to improve cancer prevention, treatment, and quality of life on a global level.

The role of DNA repair genes in radiation-induced adaptive response in Drosophila melanogaster is differential and conditional.

Studies in human and mammalian cell cultures have shown that induction of DNA repair mechanisms is required for the formation of stimulation effects of low doses of ionizing radiation, named "hormesis". Nevertheless, the role of cellular defense mechanisms in the formation of radiation-induced hormesis at the level of whole organism remains poorly studied. The aim of this work was to investigate the role of genes involved in different mechanisms and stages of DNA repair in radioadaptive response and radiation hormesis by lifespan parameters in Drosophila melanogaster. We studied genes that control DNA damage sensing (D-Gadd45, Hus1, mnk), nucleotide excision repair (mei-9, mus210, Mus209), base excision repair (Rrp1), DNA double-stranded break repair by homologous recombination (Brca2, spn-B, okr) and non-homologous end joining (Ku80, WRNexo), and the Mus309 gene that participates in several mechanisms of DNA repair. The obtained results demonstrate that in flies with mutations in studied genes radioadaptive response and radiation hormesis are absent or appear to a lesser extent than in wild-type Canton-S flies. Chronic exposure of γ-radiation in a low dose during pre-imaginal stages of development leads to an increase in expression of the studied DNA repair genes, which is maintained throughout the lifespan of flies. However, the activation of conditional ubiquitous overexpression of DNA repair genes does not induce resistance to an acute exposure to γ-radiation and reinforces its negative impact.

Increased Hematopoietic Stem Cells/Hematopoietic Progenitor Cells Measured as Endogenous Spleen Colonies in Radiation-Induced Adaptive Response in Mice (Yonezawa Effect).

The existence of radiation-induced adaptive response (AR) was reported in varied biosystems. In mice, the first in vivo AR model was established using X-rays as both the priming and the challenge doses and rescue of bone marrow death as the end point. The underlying mechanism was due to the priming radiation-induced resistance in the blood-forming tissues. In a series of investigations, we further demonstrated the existence of AR using different types of ionizing radiation (IR) including low linear energy transfer (LET) X-rays and high LET heavy ion. In this article, we validated hematopoietic stem cells/hematopoietic progenitor cells (HSCs/HPCs) measured as endogenous colony-forming units-spleen (CFU-S) under AR inducible and uninducible conditions using combination of different types of IR. We confirmed the consistency of increased CFU-S number change with the AR inducible condition. These findings suggest that AR in mice induced by different types of IR would share at least in part a common underlying mechanism, the priming IR-induced resistance in the blood-forming tissues, which would lead to a protective effect on the HSCs/HPCs and play an important role in rescuing the animals from bone marrow death. These findings provide a new insight into the mechanistic study on AR in vivo.

Early antioxidant responses via the concerted activation of NF-κB and Nrf2 characterize the gamma-radiation-induced adaptive response in quiescent human peripheral blood mononuclear cells

The radiation-induced adaptive response (RI-AR) is a non-targeted effect which is outside the scope of the classical Linear-No-Threshold (LNT) dose-response paradigm. However, the mechanisms of the RI-AR are not well understood. We have studied the RI-AR in quiescent human peripheral blood mononuclear cells (PBMCs). PBMCs in G0 phase were ‘primed’ with a low dose (100 mGy gamma radiation) and then, after an ‘adaptive window’ of 4 h, ‘challenged’ with a high dose (2 Gy). A small (5.7%) increase in viability and a decrease in DNA strand breaks were seen in primed cells, compared to non-primed cells. This was consistent with lower levels of reactive oxygen species, higher mitochondrial membrane potential, and increased activity of antioxidant enzymes such as catalase, superoxide dismutase, thioredoxin reductase, and glutathione peroxidase, in the primed cells. Reduced oxidative stress in primed PBMCs correlated with greater nuclear translocation of the redox-sensitive transcription factors Nuclear factor kappa B (NF-κB) and Nuclear factor E2-related factor 2 (Nrf2). Distinct differences in responses were seen in PBMCs irradiated with low dose (100 mGy) and high dose (2 Gy). These findings provide insight into the mechanisms of radioadaptation in human cells.

Effect of modeled microgravity on radiation-induced adaptive response of root growth in Arabidopsis thaliana

Space particles have an inevitable impact on organisms during space missions; radio-adaptive response (RAR) is a critical radiation effect due to both low-dose background and sudden high-dose radiation exposure during solar storms. Although it is relevant to consider RAR within the context of microgravity, another major space environmental factor, there is no existing evidence as to its effects on RAR. In the present study, we established an experimental method for detecting the effects of gamma-irradiation on the primary root growth of Arabidopsis thaliana, in which RAR of root growth was significantly induced by several dose combinations. Microgravity was simulated using a two-dimensional rotation clinostat. It was shown that RAR of root growth was significantly inhibited under the modeled microgravity condition, and was absent in pgm-1 plants that had impaired gravity sensing in root tips. These results suggest that RAR could be modulated in microgravity. Time course analysis showed that microgravity affected either the development of radio-resistance induced by priming irradiation, or the responses of plants to challenging irradiation. After treatment with the modeled microgravity, attenuation in priming irradiation-induced expressions of DNA repair genes (AtKu70 and AtRAD54), and reduced DNA repair efficiency in response to challenging irradiation were observed. In plant roots, the polar transportation of the phytohormone auxin is regulated by gravity, and treatment with an exogenous auxin (indole-3-acetic acid) prevented the induction of RAR of root growth, suggesting that auxin might play a regulatory role in the interaction between microgravity and RAR of root growth.

Oxidative Stress, a Bridge that Links Radioadaptive Responses Induced by Ionizing Radiation to Those Induced by Non-Ionizing Radiation

The disturbance in the balance between production of reactive oxygen species (ROS) and antioxidant defense mechanisms may cause oxidative stress. Some environmental stimuli such as exposure to ionizing radiation or non-ionizing radiations (e.g. radiofrequency electromagnetic fields emitted from mobile phones and other wireless technologies) can severely disturb this balance. Substantial evidence now indicates that not only exposure to ionizing radiation can start oxidizing events which change the atomic structure by direct interactions of radiation with target macromolecules or via water radiolysis-induced products, non-ionizing radiations may trigger the same events. Radioadaptive response or radiation-induced adaptive response can be defined as the acquisition of radiation resistance against exposure to high levels of radiation in cultured cells or organisms that had been pre-exposed to a priming low dose radiation. The induction of adaptive responses by pre-exposure to ionizing and non-ionizing radiations is well documented by different researchers as well as our team. The induction of adaptive response by non-ionizing radiations, like ionizing radiations, requires a minimum level of damage to trigger this phenomenon. Therefore, ROS play a key role in producing the minimum level of damage that is required for triggering the induction of adaptive response. Current data support this hypothesis that there are similar patterns for induction of adaptive response by ionizing and non-ionizing radiations, and oxidative stress is a bridge that links radioadaptive responses induced by ionizing radiation to those induced by non-ionizing radiation.

Abstract SY39-03: Radiation-mediated DNA sensing pathway for immunity and tumor regression

Abstract It is thought that ablative radiotherapy (RT), used for rapid control tumor growth, induces genotoxic stress and mitosis crisis leading to prolonged dormancy of irradiated tumor at local and distal site in most patients. We have unexpectedly observed that initial reduction of tumor burden following ablative RT also depends largely on type I IFN for CTL. Targeting tumor with IFN can control tumor growth through initiating a coordinated innate and adaptive immune attack against tumor cells. However, the mechanism for radiation-mediated type I IFN induction remains unclear. Here, we demonstrated that STING, but not MYD88, was required for type I IFN-dependent antitumor effects of radiation. STING in dendritic cells (DCs) controlled radiation-mediated IFN-β induction and was activated by irradiated-tumor cells. The cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) mediated DCs sensing of irradiated-tumor cells. Moreover, STING was essential for radiation-induced adaptive immune responses, which relied on type I IFN signaling on DCs. Exogenous IFN-β treatment rescued cGAS/STING-deficient immune responses. Accordingly, enhancing STING signaling by cGAMP administration promoted antitumor efficacy of radiation. Our results reveal that the molecular mechanism of radiation-mediated antitumor immunity depends on a proper cytosolic DNA-sensing pathway, pointing towards a new understanding of radiation and host interactions. Furthermore, we uncover a new strategy to improve radiotherapy by cGAMP treatment. RT induced IFN can also upregulate PD-L1 that suppress T cell-mediated damage and develop radiation resistance for relapse over time. Anti-PDL-1 antibody can greatly reduce radiation resistance leading to complete tumor regression. Furthermore, our study challenges the rationale for current radio/chemotherapy strategies and highlights the importance of immune activation in preventing tumor relapse. Citation Format: Yang-xin Fu. Radiation-mediated DNA sensing pathway for immunity and tumor regression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr SY39-03. doi:10.1158/1538-7445.AM2015-SY39-03

Ionizing radiation-induced adaptive response in fibroblasts under both monolayer and 3-dimensional conditions.

To observe the adaptive response (AR) induced by ionizing radiation in human fibroblasts under monolayer and 3-dimensional (3-D) condition. Three kinds of fibroblasts were cultured under both monolayer and 3-D condition. Immunofluorescent staining was used to detect the γ-H2AX foci and the morphological texture. Trypan blue staining was used to detect the cell death. Western blot was used to detect the expressions of γ-H2AX, p53 and CDKN1A/p21 (p21). We found that DNA damage increased in a dose-dependent and time-dependent manner after high doses of radiation. When cells were pretreated with a priming low dose of radiation followed by high dose radiation, DNA damage was attenuated under both monolayer and 3-D condition, and the adaptive response (AR) was induced. Additionally, the morphology of cells under monolayer and 3-D conditions were different, and radiation also induced AR according to morphological texture analysis. Priming low dose radiation induced AR both under monolayer and 3-D condition. Interestingly, 3-D microenvironment made cells more sensitive to radiation. The expression of p53 and p21 was changed and indicated that they might participate in the regulation of AR.

STING-Dependent Cytosolic DNA Sensing Promotes Radiation-Induced Type I Interferon-Dependent Antitumor Immunity in Immunogenic Tumors

Ionizing radiation-mediated tumor regression depends on type I interferon (IFN) and the adaptive immune response, but several pathways control I IFN induction. Here, we demonstrate that adaptor protein STING, but not MyD88, is required for type I IFN-dependent antitumor effects of radiation. In dendritic cells (DCs), STING was required for IFN-? induction in response to irradiated-tumor cells. The cytosolic DNA sensor cyclic GMP-AMP (cGAMP) synthase (cGAS) mediated sensing of irradiated-tumor cells in DCs. Moreover, STING was essential for radiation-induced adaptive immune responses, which relied on type I IFN signaling on DCs. Exogenous IFN-? treatment rescued the cross-priming bycGAS or STING-deficient DCs. Accordingly, activation of STING by a second messenger cGAMP administration enhanced antitumor immunity induced by radiation. Thus radiation-mediated antitumor immunity in immunogenic tumors requires a functional cytosolic DNA-sensing pathway and suggests that cGAMP treatment might provide a new strategy to improve radiotherapy.

Mechanisms and biological importance of photon-induced bystander responses: do they have an impact on low-dose radiation responses.

Elucidating the biological effect of low linear energy transfer (LET), low-dose and/or low-dose-rate ionizing radiation is essential in ensuring radiation safety. Over the past two decades, non-targeted effects, which are not only a direct consequence of radiation-induced initial lesions produced in cellular DNA but also of intra- and inter-cellular communications involving both targeted and non-targeted cells, have been reported and are currently defining a new paradigm in radiation biology. These effects include radiation-induced adaptive response, low-dose hypersensitivity, genomic instability, and radiation-induced bystander response (RIBR). RIBR is generally defined as a cellular response that is induced in non-irradiated cells that receive bystander signals from directly irradiated cells. RIBR could thus play an important biological role in low-dose irradiation conditions. However, this suggestion was mainly based on findings obtained using high-LET charged-particle radiations. The human population (especially the Japanese, who are exposed to lower doses of radon than the world average) is more frequently exposed to low-LET photons (X-rays or γ-rays) than to high-LET charged-particle radiation on a daily basis. There are currently a growing number of reports describing a distinguishing feature between photon-induced bystander response and high-LET RIBR. In particular, photon-induced bystander response is strongly influenced by irradiation dose, the irradiated region of the targeted cells, and p53 status. The present review focuses on the photon-induced bystander response, and discusses its impact on the low-dose radiation effect.

Abstract 861: Survivin-mediated adaptive response: a risk factor for IGRT

Abstract Exposure of cells to very low doses of ionizing radiation can induce an enhanced resistance or adaptive response to a subsequent larger radiation dose as demonstrated by an increase in cell survival. Expression of a radio-adaptive response has been attributed to pro-survival signaling processes induced by very low radiation doses in the range of 5 to 100 mGy. The radiation-induced adaptive response is gaining considerable attention due in part to the expanding use of imaging technologies such as computerized axial tomography and portal imaging to monitor tumor response and positioning during multi-dose standard radiation therapy protocols. The focus of this study was to investigate whether this process could occur when the very small imaging radiation dose was administered prior to or following the administration of the first of two typically used radiation therapy level doses. SA-NH mouse sarcoma cells and SA-NH cells stably transfected with mutated IκBα (SA-NH+mIκBα1) to inhibit the activation of NFκB were grown to confluence in vitro or as tumors in the right hind leg of C3H mice. Percentage of cell survival, apoptosis frequencies and survivin protein levels were determined as a function of radiation conditions and transfection of cells with survivin siRNA. A significant radio-adaptive response was observed in cells exposed to 5 mGy - 100 mGy 15 min to 6 h prior to or after irradiation with the first of two 2 Gy therapeutic radiation doses and was associated with a concomitant reduction in apoptosis frequencies and a rapid elevation in survivin protein levels. The very low dose radiation-induced elevation in survivin levels, the reduction in apoptosis frequencies and enhanced cell survival were not observed in SA-NH+mIκBα1 cells or SA-NH cells transfected with survivin siRNA. We have identified a very low radiation dose-induced survivin-mediated adaptive response that could compromise therapeutic outcomes associated with the increased usage of imaging procedures in radiation therapy. This work was supported by NIH/NCI grant R01 CA132998 and DOE Low Dose Program/Project Grant DE-SC0001271 (D.J.G.) Citation Format: David J. Grdina, Jeffrey S. Murley, Richard C. Miller, Gayle E. Woloschak, Jian Jian Li, Ralph R. Weichselbaum. Survivin-mediated adaptive response: a risk factor for IGRT. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 861. doi:10.1158/1538-7445.AM2014-861

Cell Cycle Regulators Guide Mitochondrial Activity in Radiation-Induced Adaptive Response

There are accruing concerns on potential genotoxic agents present in the environment including low-dose ionizing radiation (LDIR) that naturally exists on earth's surface and atmosphere and is frequently used in medical diagnosis and nuclear industry. Although its long-term health risk is being evaluated and remains controversial, LDIR is shown to induce temporary but significant adaptive responses in mammalian cells and animals. The mechanisms guiding the mitochondrial function in LDIR-induced adaptive response represent a unique communication between DNA damage and cellular metabolism. Elucidation of the LDIR-regulated mitochondrial activity may reveal new mechanisms adjusting cellular function to cope with hazardous environmental stress. Key cell cycle regulators, including Cyclin D1/CDK4 and Cyclin B1/cyclin-dependent kinase 1 (CDK1) complexes, are actively involved in the regulation of mitochondrial functions via phosphorylation of their mitochondrial targets. Accumulating new evidence supports a concept that the Cyclin B1/CDK1 complex acts as a mediator in the cross talk between radiation-induced DNA damage and mitochondrial functions to coordinate cellular responses to low-level genotoxic stresses. The LDIR-mediated mitochondrial activity via Cyclin B1/CDK1 regulation is an irreplaceable network that is able to harmonize vital cellular functions with adjusted mitochondrial metabolism to enhance cellular homeostasis. Further investigation of the coordinative mechanism that regulates mitochondrial activities in sublethal stress conditions, including LDIR, will reveal new insights of how cells cope with genotoxic injury and will be vital for future targeted therapeutic interventions that reduce environmental injury and cancer risk.

Targeted therapy against EGFR and VEGFR using ZD6474 enhances the therapeutic potential of UV-B phototherapy in breast cancer cells

BackgroundThe hypoxic environment of tumor region stimulated the up regulation of growth factors responsible for angiogenesis and tumor proliferation. Thus, targeting the tumor vasculature along with the proliferation by dual tyrosine kinase inhibitor may be the efficient way of treating advanced breast cancers, which can be further enhanced by combining with radiotherapy. However, the effectiveness of radiotherapy may be severely compromised by toxicities and tumor resistance due to radiation-induced adaptive response contributing to recurrence and metastases of breast cancer. The rational of using ZD6474 is to evaluate the feasibility and efficacy of combined VEGFR2 and EGFR targeting with concurrent targeted and localized UV-B phototherapy in vitro breast cancer cells with the anticipation to cure skin lesions infiltrated with breast cancer cells.Materials and methodsBreast cancer cells were exposed to UV-B and ZD6474 and the cell viability, apoptosis, invasion and motility studies were conducted for the combinatorial effect. Graphs and statistical analyses were performed using Graph Pad Prism 5.0.ResultsZD6474 and UV-B decreased cell viability in breast cancers in combinatorial manner without affecting the normal human mammary epithelial cells. ZD6474 inhibited cyclin E expression and induced p53 expression when combined with UV-B. It activated stress induced mitochondrial pathway by inducing translocation of bax and cytochrome-c. The combination of ZD6474 with UV-B vs. either agent alone also more potently down-regulated the anti-apoptotic bcl-2 protein, up-regulated pro-apoptotic signaling events involving expression of bax, activation of caspase-3 and caspase-7 proteins, and induced poly (ADP-ribose) polymerase resulting in apoptosis. ZD6474 combined with UV-B inhibited invasion of breast cancer cells in vitro as compared to either single agent, indicating a potential involvement of pro-angiogenic growth factors in regulating the altered expression and reorganization of cytoskeletal proteins in combinatorial treated breast cancer cells. Involvement of combination therapy in reducing the expression of matrix metalloprotease was also observed.ConclusionsCollectively, our studies indicate that incorporating an anti-EGFR plus VEGFR strategy (ZD6474) with phototherapy (UV-B), an alternative approach to the ongoing conventional radiotherapy for the treatment of infiltrating metastatic breast cancer cells in the skin and for locally recurrence breast cancer than either approach alone.

Influence of low-dose-rate red and near-infrared radiations on the level of reactive oxygen species, the genetic apparatus and the tumor growth in mice in vivo

The effect of low-dose-rate red and near-infrared radiations from the matrix of light emitted diode (650 nm and 850 nm) and a He-Ne laser (633 nm) on activation of the reserve of a natural defense system in the mice exposed to radiation in vivo was studied by the level of reactive oxygen species (ROS) production in blood cells, the induction of cytogenetic adaptive response in bone marrow cells, thymus and spleen, and the rate of Ehrlich ascites carcinoma growth in a solid form. As a positive control animals were irradiated with X-rays by the scheme of the radiation-induced adaptive response (0.1 Gy + 1.5 Gy). The levels of ROS production was assessed in whole blood by luminol-dependent chemiluminescence, of cytogenetic damage--by the "micronucleus test" in the bone marrow, the weight of the thymus and spleen--by index of organ, and the rate of tumor growth--according to its size for 30 days after inoculation. Adaptogenic and anticarcinogenic effects of studied radiations were revealed. The values of these effects were not different from those in animals pre-irradiated with the X-rays. The relationship between the level of ROS production and adaptive response induction in the mice under the influence of non-ionizing radiation was first ascertained. The experimental data obtained may indicate a similar mechanism of induction of protective responses to ionizing and non-ionizing radiations in mice in vivo.