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Natural background ionizing radiation is present on the earth's surface; however, the biological role of this chronic low-dose-rate exposure remains unknown. The Researching the Effects of the Presence and Absence of Ionizing Radiation (REPAIR) project is examining the impacts of sub-natural background radiation exposure through experiments conducted 2 km underground in SNOLAB. The rock overburden combined with experiment-specific shielding provides a background radiation dose rate 30 times lower than on the surface. We hypothesize that natural background radiation is essential for life and maintains genomic stability and that prolonged exposure to sub-background environments will be detrimental to biological systems. To evaluate this, human hybrid CGL1 cells were continuously cultured in SNOLAB and our surface control laboratory for 16 weeks. Cells were assayed every 4 weeks for growth rate, alkaline phosphatase (ALP) activity (a marker of cellular transformation in the CGL1 system), and the expression of genes related to DNA damage and cell cycle regulation. A subset of cells was also exposed to a challenge radiation dose (0.1 to 8 Gy of X rays) and assayed for clonogenic survival and DNA double-strand break induction to examine if prolonged sub-background exposure alters the cellular response to high-dose irradiation. At each 4-week time point, sub-background radiation exposure did not significantly alter cell growth rates, survival, DNA damage, or gene expression. However, cells cultured in SNOLAB showed significantly higher ALP activity, a marker of carcinogenesis in these cells, which increased with longer exposure to the sub-background environment, indicative of neoplastic progression. Overall, these data suggest that sub-background radiation exposure does not impact growth, survival, or DNA damage in CGL1 cells but may lead to increased rates of neoplastic transformation, highlighting a potentially important role for natural background radiation in maintaining normal cellular function and genomic stability.
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The aim of this paper is to review the history surrounding the discovery of lethal mutations, later described as delayed reproductive death. Lethal mutations were suggested very early on, to be due to a generalised instability in a cell population and are considered now to be one of the first demonstrations of "radiation-induced genomic instability" which led later to the establishment of the field of "non-targeted effects." The phenomenon was first described by Seymour et al. in 1986 and was confirmed by Trott's group in Europe and by Little and colleagues in the United States before being extended by Mendonca et al. in 1989, who showed conclusively that the distinguishing feature of lethal mutation occurrence was that it happened suddenly after about 9-10 population doublings in progeny which had survived the original dose of ionizing radiation. However, many authors then suggested that in fact, lethal mutations were implicit in the original experiments by Puck and Marcus in 1956 and were described in the extensive work by Sinclair in 1964, who followed clonal progeny for up to a year after irradiation and described "small colony formation" as a persistent consequence of ionizing radiation exposure. In this paper, we examine the history from 1956 to the present using the period from 1986-1989 as an anchor point to reach into the past and to go forward through the evolution of the field of low dose radiobiology where non-targeted effects predominate.
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Mutação , Humanos , História do Século XX , Instabilidade Genômica/efeitos da radiação , Animais , Genes Letais , História do Século XXIRESUMO
FRA1 (FOSL1) is a transcription factor and a member of the activator protein-1 superfamily. FRA1 is expressed in most tissues at low levels, and its expression is robustly induced in response to extracellular signals, leading to downstream cellular processes. However, abnormal FRA1 overexpression has been reported in various pathological states, including tumor progression and inflammation. To date, the molecular effects of FRA1 overexpression are still not understood. Therefore, the aim of this study was to investigate the transcriptional and functional effects of FRA1 overexpression using the CGL1 human hybrid cell line. FRA1-overexpressing CGL1 cells were generated using stably integrated CRISPR-mediated transcriptional activation, resulting in a 2-3 fold increase in FRA1 mRNA and protein levels. RNA-sequencing identified 298 differentially expressed genes with FRA1 overexpression. Gene ontology analysis showed numerous molecular networks enriched with FRA1 overexpression, including transcription-factor binding, regulation of the extracellular matrix and adhesion, and a variety of signaling processes, including protein kinase activity and chemokine signaling. In addition, cell functional assays demonstrated reduced cell adherence to fibronectin and collagen with FRA1 overexpression and altered cell cycle progression. Taken together, this study unravels the transcriptional response mediated by FRA1 overexpression and establishes the role of FRA1 in adhesion and cell cycle progression.
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Proteínas Proto-Oncogênicas c-fos , Fator de Transcrição AP-1 , Humanos , Divisão Celular , Linhagem Celular , Regulação da Expressão Gênica , Proteínas Proto-Oncogênicas c-fos/genética , Proteínas Proto-Oncogênicas c-fos/metabolismo , Fator de Transcrição AP-1/genética , Fator de Transcrição AP-1/metabolismoRESUMO
The CGL1 human hybrid cell system has been utilized for many decades as an excellent cellular tool for investigating neoplastic transformation. Substantial work has been done previously implicating genetic factors related to chromosome 11 to the alteration of tumorigenic phenotype in CGL1 cells. This includes candidate tumor suppressor gene FOSL1, a member of the AP-1 transcription factor complex which encodes for protein FRA1. Here we present novel evidence supporting the role of FOSL1 in the suppression of tumorigenicity in segregants of the CGL1 system. Gamma-induced mutant (GIM) and control (CON) cells were isolated from 7 Gy gamma-irradiated CGL1s. Western, Southern and Northern blot analysis were utilized to assess FOSL1/FRA1 expression as well as methylation studies. GIMs were transfected to re-express FRA1 and in vivo tumorigenicity studies were conducted. Global transcriptomic microarray and RT-qPCR analysis were used to further characterize these unique cell segregants. GIMs were found to be tumorigenic in vivo when injected into nude mice whereas CON cells were not. GIMs show loss of Fosl/FRA1 expression as confirmed by Western blot. Southern and Northern blot analysis further reveals that FRA1 reduction in tumorigenic CGL1 segregants is likely due to transcriptional suppression. Results suggest that radiation-induced neoplastic transformation of CGL1 is in part due to silencing of the FOSL1 tumor suppressor gene promoter by methylation. The radiation-induced tumorigenic GIMs transfected to re-express FRA1 resulted in suppression of subcutaneous tumor growth in nude mice in vivo. Global microarray analysis and RT-qPCR validation elucidated several hundred differentially expressed genes. Downstream analysis reveals a significant number of altered pathways and enriched Gene Ontology terms genes related to cellular adhesion, proliferation, and migration. Together these findings provide strong evidence that FRA1 is a tumor suppressor gene deleted and epigenetically silenced after ionizing radiation-induced neoplastic transformation in the CGL1 human hybrid cell system.
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Transformação Celular Neoplásica , Neoplasias Induzidas por Radiação , Animais , Camundongos , Humanos , Camundongos Nus , Transformação Celular Neoplásica/genética , Células HeLa , Genes Supressores de Tumor , Carcinogênese/genética , Neoplasias Induzidas por Radiação/patologia , Fenótipo , Genômica , Epigênese Genética , Regulação Neoplásica da Expressão GênicaRESUMO
In 2017, a special edition of Radiation Research was published [Oct; Vol. 188 4.2 (https://bioone.org/journals/radiation-research/volume-188/issue-4.2)] which focused on a recently established radiobiology project within SNOLAB, a unique deep-underground research facility. This special edition included original articles, reviews and commentaries relevant to the research goals of this new project which was titled Researching the Effects of the Presence and Absence of Ionizing Radiation (REPAIR). These research goals were founded in understanding the biological effects of terrestrial and cosmic natural background radiation (NBR). Since 2017, REPAIR has evolved into a sub-NBR radiobiology research program which investigates these effects using multiple model systems and various biological endpoints. This paper summarizes the evolution of the REPAIR project over the first 6-years including its experimental scope and capabilities as well as research accomplishments.
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Radiação de Fundo , Radiação Cósmica , Radiobiologia , Radiação IonizanteRESUMO
Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) have exhibited great promise in the treatment of tumors with homologous recombination (HR) deficiency, however, PARPi resistance, which ultimately recovers DNA repair and cell progress, has become an enormous clinical challenge. Recently, KP372-1 was identified as a novel potential anticancer agent that targeted the redox enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1), to induce extensive reactive oxygen species (ROS) generation that amplified DNA damage, leading to cancer cell death. To overcome PARPi resistance and expand its therapeutic utility, we investigated whether a combination therapy of a sublethal dose of KP372-1 with a nontoxic dose of PARPi rucaparib would synergize and enhance lethality in NQO1 over-expressing cancers. We reported that the combination treatment of KP372-1 and rucaparib induced a transient and dramatic AKT hyperactivation that inhibited DNA repair by regulating FOXO3a/GADD45α pathway, which enhanced PARPi lethality and overcame PARPi resistance. We further found that PARP inhibition blocked KP372-1-induced PARP1 hyperactivation to reverse NAD+/ATP loss that promoted Ca2+-dependent autophagy and apoptosis. Moreover, pretreatment of cells with BAPTA-AM, a cytosolic Ca2+ chelator, dramatically rescued KP372-1- or combination treatment-induced lethality and significantly suppressed PAR formation and γH2AX activation. Finally, we demonstrated that this combination therapy enhanced accumulation of both agents in mouse tumor tissues and synergistically suppressed tumor growth in orthotopic pancreatic and non-small-cell lung cancer xenograft models. Together, our study provides novel preclinical evidence for new combination therapy in NQO1+ solid tumors that may broaden the clinical utility of PARPi.
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ß-Lapachone is a classic quinone-containing antitumor NQO1-bioactivatable drug that directly kills NQO1-overexpressing cancer cells. However, the clinical applications of ß-lapachone are primarily limited by its high toxicity and modest lethality. To overcome this side effect and expand the therapeutic utility of ß-lapachone, we demonstrate the effects of a novel combination therapy including ß-lapachone and the proliferating cell nuclear antigen (PCNA) inhibitor T2 amino alcohol (T2AA) on various NQO1+ cancer cells. PCNA has DNA clamp processivity activity mediated by encircling double-stranded DNA to recruit proteins involved in DNA replication and DNA repair. In this study, we found that compared to monotherapy, a nontoxic dose of the T2AA synergized with a sublethal dose of ß-lapachone in an NQO1-dependent manner and that combination therapy prevented DNA repair, increased double-strand break (DSB) formation and promoted programmed necrosis and G1 phase cell cycle arrest. We further determined that combination therapy enhanced antitumor efficacy and prolonged survival in Lewis lung carcinoma (LLC) xenografts model. Our findings show novel evidence for a new therapeutic approach that combines of ß-lapachone treatment with PCNA inhibition that is highly effective in treating NQO1+ solid tumor cells.
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Antineoplásicos/farmacologia , Dano ao DNA/efeitos dos fármacos , NAD(P)H Desidrogenase (Quinona)/metabolismo , Naftoquinonas/farmacologia , Neoplasias/tratamento farmacológico , Estresse Oxidativo/efeitos dos fármacos , Antígeno Nuclear de Célula em Proliferação/metabolismo , Animais , Apoptose/efeitos dos fármacos , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Reparo do DNA/efeitos dos fármacos , Feminino , Fase G1/efeitos dos fármacos , Humanos , Células MCF-7 , Camundongos , Camundongos Endogâmicos C57BL , Neoplasias/genética , Espécies Reativas de Oxigênio/metabolismoRESUMO
Cellular senescence is an essential tumor suppressive mechanism that prevents the propagation of oncogenically activated, genetically unstable, and/or damaged cells. Induction of tumor cell senescence is also one of the underlying mechanisms by which cancer therapies exert antitumor activity. However, an increasing body of evidence from preclinical studies demonstrates that radiation and chemotherapy cause accumulation of senescent cells (SnCs) both in tumor and normal tissue. SnCs in tumors can, paradoxically, promote tumor relapse, metastasis, and resistance to therapy, in part, through expression of the senescence-associated secretory phenotype. In addition, SnCs in normal tissue can contribute to certain radiation- and chemotherapy-induced side effects. Because of its multiple roles, cellular senescence could serve as an important target in the fight against cancer. This commentary provides a summary of the discussion at the National Cancer Institute Workshop on Radiation, Senescence, and Cancer (August 10-11, 2020, National Cancer Institute, Bethesda, MD) regarding the current status of senescence research, heterogeneity of therapy-induced senescence, current status of senotherapeutics and molecular biomarkers, a concept of "one-two punch" cancer therapy (consisting of therapeutics to induce tumor cell senescence followed by selective clearance of SnCs), and its integration with personalized adaptive tumor therapy. It also identifies key knowledge gaps and outlines future directions in this emerging field to improve treatment outcomes for cancer patients.
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Senescência Celular , Neoplasias , Biomarcadores , Humanos , Neoplasias/tratamento farmacológico , Neoplasias/patologia , Fenótipo Secretor Associado à SenescênciaRESUMO
Data indicate that ultrahigh dose rate (>106 Gy/second) FLASH radiotherapy (FLASH-RT) delivery of radiation reduces normal tissue damage without compromising tumor response. Orthotopic glioblastoma mouse studies now demonstrate that radiation fraction size, total dose, and number of fractions are critical parameters for FLASH-RT cognitive sparing without compromising tumor response.See related article by Montay-Gruel et al., p. 775.
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Glioblastoma , Radioterapia (Especialidade) , Animais , Cognição , Glioblastoma/radioterapia , Camundongos , Dosagem RadioterapêuticaRESUMO
Astronauts participating in prolonged space missions constitute a population of individuals who are at an increased risk for cataractogenesis due to exposure to densely ionizing charged particles. Using a rat model, we have previously shown that after irradiation of eyes with either low-linear energy transfer (LET) 60Co γ rays or high-LET 56Fe particles, the rate of progression of anterior and posterior subcapsular cataracts was significantly greater in ovariectomized females implanted with 17-ß-estradiol (E2) compared to ovariectomized or intact rats. However, our additional low-LET studies indicated that cataractogenesis may be a modifiable late effect, since we have shown that the modulation of cataractogenesis is dependent upon the timing of administration of E2. Interestingly, we found that E2 protected against cataractogenesis induced by low-LET radiation, but only if administered after the exposure; if administered prior to and after irradiation, for the entire period of observation, then E2 enhanced progression and incidence of cataracts. Since most radioprotectors tested to date are unsuccessful in protecting against the effects of high-LET radiation, we wished to determine whether the protection mediated by E2 against radiation cataractogenesis induced by low-LET radiation would also be observed after high-LET irradiation. Female 56-day-old Sprague-Dawley rats were treated with E2 at various times relative to the time of single-eye irradiation with 2 Gy of 56Fe ions. We found that administration of E2 before irradiation and throughout the lifetime of the rat enhanced cataractogenesis compared to ovariectomized animals. The enhancing effect was slightly reduced when estrogen was removed after irradiation. However, in contrast to what we observed after γ-ray irradiation, there was no inhibition of cataractogenesis if E2 was administered only after 56Fe-ion irradiation. We conclude that protection against cataractogenesis by estrogen is dependent upon the type and ionization density of radiation that the lens was exposed to. The lack of inhibition of radiation cataractogenesis in rats that receive E2 treatment after high-LET irradiation may be attributed to the qualitative differences in the types of DNA damage induced with high-LET radiation compared to low-LET radiation or how damage may be modified at the DNA or tissue level after irradiation.
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Catarata/prevenção & controle , Radioisótopos de Cobalto , Estradiol/uso terapêutico , Raios gama/efeitos adversos , Íons Pesados/efeitos adversos , Ferro , Lesões Experimentais por Radiação/prevenção & controle , Medicina Aeroespacial , Animais , Catarata/etiologia , Esquema de Medicação , Implantes de Medicamento , Estradiol/administração & dosagem , Incidência , Transferência Linear de Energia , Ovariectomia , Ratos , Ratos Sprague-DawleyRESUMO
Ultrahigh dose-rate radiotherapy (RT), or 'FLASH' therapy, has gained significant momentum following various in vivo studies published since 2014 which have demonstrated a reduction in normal tissue toxicity and similar tumor control for FLASH-RT when compared with conventional dose-rate RT. Subsequent studies have sought to investigate the potential for FLASH normal tissue protection and the literature has been since been inundated with publications on FLASH therapies. Today, FLASH-RT is considered by some as having the potential to 'revolutionize radiotherapy'. FLASH-RT is considered by some as having the potential to 'revolutionize radiotherapy'. The goal of this review article is to present the current state of this intriguing RT technique and to review existing publications on FLASH-RT in terms of its physical and biological aspects. In the physics section, the current landscape of ultrahigh dose-rate radiation delivery and dosimetry is presented. Specifically, electron, photon and proton radiation sources capable of delivering ultrahigh dose-rates along with their beam delivery parameters are thoroughly discussed. Additionally, the benefits and drawbacks of radiation detectors suitable for dosimetry in FLASH-RT are presented. The biology section comprises a summary of pioneering in vitro ultrahigh dose-rate studies performed in the 1960s and early 1970s and continues with a summary of the recent literature investigating normal and tumor tissue responses in electron, photon and proton beams. The section is concluded with possible mechanistic explanations of the FLASH normal-tissue protection effect (FLASH effect). Finally, challenges associated with clinical translation of FLASH-RT and its future prospects are critically discussed; specifically, proposed treatment machines and publications on treatment planning for FLASH-RT are reviewed.
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Neoplasias/radioterapia , Radioterapia/métodos , Biologia , Humanos , Física , Dosagem RadioterapêuticaRESUMO
BACKGROUND: Somatic cell hybrid systems generated by combining cancerous with non-cancerous cells provide useful model systems to study neoplastic transformation. Combined with recent advances in omics-based technologies, novel molecular signatures that drive radiation-induced carcinogenesis can be analyzed at an exceptional global level. METHODS: Here, we present a complete whole-transcriptome analysis of gamma-induced mutants (GIM) and gamma irradiated control (CON) segregants isolated from the CGL1 (HeLa x normal fibroblast) human hybrid cell-system exposed to high doses of radiation. Using the Human Transcriptome Array 2.0 microarray technology and conservative discrimination parameters, we have elucidated 1067 differentially expressed genes (DEGs) between tumorigenic and non-tumorigenic cells. RESULTS: Gene ontology enrichment analysis revealed that tumorigenic cells demonstrated shifts in extracellular matrix (ECM) and cellular adhesion profiles, dysregulation of cyclic AMP (cAMP) signaling, and alterations in nutrient transport and cellular energetics. Furthermore, putative upstream master regulator analysis demonstrated that loss of TGFß1 signaling due to reduced SMAD3 expression is involved in radiation-induced carcinogenesis. CONCLUSIONS: Taken together, this study presents novel insights into specific gene expression and pathway level differences that contribute to radiation-induced carcinogenesis in a human cell-based model. This global transcriptomic analysis and our published tumor suppressor gene deletion loci analyses will allow us to identify and functionally test candidate nexus upstream tumor suppressor genes that are deleted or silenced after exposure to radiation.
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Carcinogênese/genética , Proteínas de Neoplasias/genética , Neoplasias Induzidas por Radiação/genética , Transcriptoma/efeitos da radiação , Carcinogênese/efeitos da radiação , Fibroblastos/metabolismo , Fibroblastos/efeitos da radiação , Raios gama/efeitos adversos , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica/efeitos da radiação , Células HeLa , Humanos , Células Híbridas/efeitos da radiação , Mutação/efeitos da radiação , Neoplasias Induzidas por Radiação/patologiaRESUMO
PURPOSE: Research in radiation oncology (RO) is imperative to support the discovery of new uses of radiation and improvement of current approaches to radiation delivery and to foster the continued evolution of our field. Therefore, in 2016, the American Society of Radiation Oncology performed an evaluation of research grant funding for RO. METHODS AND MATERIALS: Members of the Society of Chairs of Academic Radiation Oncology Programs (SCAROP) were asked about funded and unfunded grants that were submitted by their departments between the fiscal years 2014 and 2016. Grants were grouped according to broad categories defined by the 2017 American Society of Radiation Oncology Research Agenda. Additionally, active grants in the National Institutes of Health (NIH) Research Portfolio Online Reporting Tools database were collated using RO faculty names. RESULTS: Overall, there were 816 funded (44%) and 1031 unfunded (56%) SCAROP-reported grants. Total grant funding was over $196 million. The US government funded the plurality (42.2%; 345 of 816) of grants compared with nonprofit and industry funders. Investigators from 10 institutions accounted for >75% of funded grants. Of the funded grants, 43.5% were categorized as "genomic influences and targeted therapies." The proportion of funded to unfunded grants was highest within the category of "tumor microenvironment, normal tissue effects, and reducing toxicity" (53.4% funded). "New clinical trial design and big data" had the smallest share of SCAROP grant applications and the lowest percent funded (38.3% of grants). NIH grants to RO researchers in 2014 to 2016 accounted for $85 million in funding. From the 31 responding SCAROP institutions, there was a 28% average success rate for RO proposals submitted to the NIH during this period. CONCLUSIONS: Though RO researchers from responding institutions were relatively successful in obtaining funding, the overall amount awarded remains small. Continued advocacy on behalf of RO is needed, as well as investment to make research careers more attractive areas for emerging faculty.
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Pesquisa Biomédica/tendências , Radioterapia (Especialidade)/organização & administração , Sociedades Médicas/organização & administração , Distinções e Prêmios , Escolha da Profissão , Feminino , Humanos , Masculino , National Cancer Institute (U.S.) , Pesquisadores , Apoio à Pesquisa como Assunto , Estados UnidosAssuntos
Neoplasias da Próstata , Radioterapia (Especialidade) , Humanos , Masculino , Pesquisa , Estados UnidosRESUMO
Circulating tumor DNA (ctDNA) analysis has been shown to aid in both the detection of cancer and evaluation of somatic mutations in tumors. CtDNA concentration in plasma increases in proportion to tumor volume and/or metabolic activity and growth; however, this principle has yet to be applied to cell culture. We hypothesized that cell line-specific cell-free DNA (cfDNA) can be used to measure cell viability and cell survival in cell culture. Clonogenic assays on non-small cell lung cancer (NSCLC) cell lines H322, A549 and H322 were exposed to radiation doses of 0, 4 and 8 Gy. Prior to colony fixation and counting, cfDNA was extracted and quantified from cell culture media. The correlation between cell line-specific cfDNA and number of colonies grown on culture plates was examined. An H1299:A549 coculture model was used to evaluate the differential release of cell line-specific cfDNA. The results of this work indicate a strong correlation between CfDNA quantification from cell culture media and clonogenic survival at all radiation doses and in all cell lines tested (R2 range = 0.77-0.99). Cell survival curves derived from cfDNA were virtually indistinguishable from matched traditional clonogenic survival data ( P > 0.05; no significant difference exists between clonogenic curves). CfDNA quantification also accurately estimates colony count in a two-cell-line coculture model. In conclusion, cell-free DNA quantification from cell culture media can be used to measure cell survival, and appears suitable for development in a high-throughput clonogenic assay and radiosensitizer screening platform.
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Sobrevivência Celular/efeitos da radiação , Ácidos Nucleicos Livres/metabolismo , Técnicas Citológicas/métodos , Carcinoma Pulmonar de Células não Pequenas/patologia , Linhagem Celular Tumoral , Técnicas de Cocultura , Humanos , Neoplasias Pulmonares/patologiaRESUMO
Cellular transformation assays have been utilized for many years as powerful in vitro methods for examining neoplastic transformation potential/frequency and mechanisms of carcinogenesis for both chemical and radiological carcinogens. These mouse and human cell based assays are labor intensive but do provide quantitative information on the numbers of neoplastically transformed foci produced after carcinogenic exposure and potential molecular mechanisms involved. Several mouse and human cell systems have been generated to undertake these studies, and they vary in experimental length and endpoint assessment. The CGL1 human cell hybrid neoplastic model is a non-tumorigenic pre-neoplastic cell that was derived from the fusion of HeLa cervical cancer cells and a normal human skin fibroblast. It has been utilized for the several decades to study the carcinogenic/neoplastic transformation potential of a variety of ionizing radiation doses, dose rates and radiation types, including UV, X ray, gamma ray, neutrons, protons and alpha particles. It is unique in that the CGL1 assay has a relatively short assay time of 18-21 days, and rather than relying on morphological endpoints to detect neoplastic transformation utilizes a simple staining method that detects the tumorigenic marker alkaline phosphatase on the neoplastically transformed cells cell surface. In addition to being of human origin, the CGL1 assay is able to detect and quantify the carcinogenic potential of very low doses of ionizing radiation (in the mGy range), and utilizes a neoplastic endpoint (re-expression of alkaline phosphatase) that can be detected on both viable and paraformaldehyde fixed cells. In this article, we review the history of the CGL1 neoplastic transformation model system from its initial development through the wide variety of studies examining the effects of all types of ionizing radiation on neoplastic transformation. In addition, we discuss the potential of the CGL1 model system to investigate the effects of near zero background radiation levels available within the radiation biology lab we have established in SNOLAB.
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Transformação Celular Neoplásica/efeitos da radiação , Fibroblastos/citologia , Células Híbridas/patologia , Células Híbridas/efeitos da radiação , Neoplasias Induzidas por Radiação/patologia , Pele/citologia , Animais , Células HeLa , HumanosRESUMO
Constitutive activation of the pro-survival transcription factor NF-κB has been associated with resistance to both chemotherapy and radiation therapy in many human cancers, including prostate cancer. Our lab and others have demonstrated that the natural product parthenolide can inhibit NF-κB activity and sensitize PC-3 prostate cancers cells to X-rays in vitro; however, parthenolide has poor bioavailability in vivo and therefore has little clinical utility in this regard. We show here that treatment of PC-3 and DU145 human prostate cancer cells with dimethylaminoparthenolide (DMAPT), a parthenolide derivative with increased bioavailability, inhibits constitutive and radiation-induced NF-κB binding activity and slows prostate cancer cell growth. We also show that DMAPT increases single and fractionated X-ray-induced killing of prostate cancer cells through inhibition of DNA double strand break repair and also that DMAPT-induced radiosensitization is, at least partially, dependent upon the alteration of intracellular thiol reduction-oxidation chemistry. Finally, we demonstrate that the treatment of PC-3 prostate tumor xenografts with oral DMAPT in addition to radiation therapy significantly decreases tumor growth and results in significantly smaller tumor volumes compared to xenografts treated with either DMAPT or radiation therapy alone, suggesting that DMAPT might have a potential clinical role as a radiosensitizing agent in the treatment of prostate cancer.