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Non-targeted effects of low dose ionizing radiation act via TGFβ to promote mammary carcinogenesis

ABSTRACT: It is widely believed that the carcinogenic action of ionizing radiation is due to targeted DNA damage and resulting mutations, but there is also substantial evidence that non-targeted radiation effects alter epithelial phenotype and the stromal microenvironment. Activation of transforming growth factor β1 (TGFβ) is a non-targeted radiation effect that mediates cell fate decisions following DNA damage and regulates microenvironment composition; it could either suppress or promote cancer. We asked if such non-targeted radiation effects contribute to carcinogenesis by using a novel radiation chimera model. Unirradiated Trp53 null mammary epithelium was transplanted to the mammary stroma, previously divested of endogenous epithelia, of mice previously exposed to a single low (10 -100 cGy) radiation dose. By 300 days, 100% of transplants in irradiated hosts at either 10 or 100 cGy had developed Trp53 null breast carcinomas compared to 54% in unirradiated hosts. Tumor growth rate was also increased by high, but not low, dose host irradiation. In contrast, irradiation of Tgfb1 heterozygote mice prior to transplantation failed to decrease tumor latency, or increase growth rate at any dose. Host irradiation significantly reduced the latency of invasive ductal carcinoma compared to spindle cell carcinoma. However, irradiation of either host genotype significantly increased the frequency of estrogen receptor negative tumors. These data demonstrate two concepts critical to understanding radiation risks. First, non-targeted radiation effects can significantly promote the frequency and alter the features of epithelial cancer. Second, radiation-induced TGFβ activity is a key mechanism of tumor promotion. Keywords: Differential gene expression after low dose irradiation

ORGANISM(S): Mus musculus

PROVIDER: GSE18216 | GEO | 2010/03/01

SECONDARY ACCESSION(S): PRJNA119587

REPOSITORIES: GEO

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Project description:This is a genome-wide approach to identifying genes persistently induced in the mouse mammary gland by acute whole body low dose ionizing radiation (10cGy), 1 and 4 weeks after exposure. Gene expression that is modified under these parameters were compared between Tgfb1 wild type and heterozygote littermates in order to determine which genes induced or repressed by radiation were mediated via Tgfb1 status. Differential gene expression was analyzed in Tgfb1 heterozygote and wild type littermate 4th mammary glands, after whole body exposure to an acute dose of 10cGy ionizing radiation. Estrus cycle was normalized in all mice two days prior to irradiation by injection with an estrogen and progesterone mixture. It is widely believed that the carcinogenic action of ionizing radiation is due to targeted DNA damage and resulting mutations, but there is also substantial evidence that non-targeted radiation effects alter epithelial phenotype and the stromal microenvironment. Activation of transforming growth factor beta 1 (TGFbeta) is a non-targeted radiation effect that mediates cell fate decisions following DNA damage and regulates microenvironment composition; it could either suppress or promote cancer. Gene expression profiling shown herein demonstrates that low dose radiation (10 cGy) elicits persistent changes in Tgfb1 wild type and heterozygote murine mammary gland that are highly modulated by TGFbeta. We asked if such non-targeted radiation effects contribute to carcinogenesis by using a novel radiation chimera model. Unirradiated Trp53 null mammary epithelium was transplanted to the mammary stroma of mice previously exposed to a single low (10 -100 cGy) radiation dose. By 300 days, 100% of transplants in irradiated hosts at either 10 or 100 cGy had developed Trp53 null breast carcinomas compared to 54% in unirradiated hosts. Tumor growth rate was also increased by high, but not low, dose host irradiation. In contrast, irradiation of Tgfb1 heterozygote mice prior to transplantation failed to decrease tumor latency, or increase growth rate at any dose. Host irradiation significantly reduced the latency of invasive ductal carcinoma compared to spindle cell carcinoma, as well as those tumors negative for smooth muscle actin in wild type but not Tgfb1 heterozygote mice. However, irradiation of either host genotype significantly increased the frequency of estrogen receptor negative tumors. These data demonstrate two concepts critical to understanding radiation risks. First, non-targeted radiation effects can significantly promote the frequency and alter the features of epithelial cancer. Second, radiation-induced TGFbeta activity is a key mechanism of tumor promotion. Keywords: Differential gene expression after low dose irradiation Two genotypes: TGBbeta1 heterozygote and wildtype mouse mammary glands. Two time points post-10cGy-irradiation per genotype (1 week, 4 weeks); control time point was 1 week post-sham-irradiation. Two or three replicates per time point.

Project description:The development of a biodosimetric assay based on the combined gene expression analysis of ex vivo-irradiated human peripheral blood (PB) and humans treated with total body irradiation has been developed. Gene expression profile signature of human radiation injury into a rapid and high-throughput chemical ligation-dependent probe amplification assay (CLPA) has been shown to discriminate 6 radiation dose levels in human PB. Candidate gene lists were first developed assaying human ex vivo and human TBI samples on the Affymetrix platform. For the Ex Vivo samples, healthy consented adult donor was randomly assigned to a radiation group and labeled with the target dose of 0 cGy, 150 cGy, 300 cGy, or 600 cGy. In addition to the radiation exposures, the samples were also treated with either no treatment, GCSF, or LPS at time points 6 hours and 24 hours. Radiation expire times from the Cs137 irradiator were calculated to achieve target doses specific for tubes filled with blood and inserted in the roaring test tube holder. The dose rate was 480 cGy/min for the duration of the study. The healthy donors were enrolled to participate in this study following a protocol to collect PB samples that was previously approved by the Duke University Institutional Review Board. For the TBI samples, adult patients, ages 21 to 66, were evaluated at the Duke University Adult Bone Marrow Transplantation Program enrolled in a Duke IRB-approved protocol to collect PB prior to and post TBI conditioning. With approval from the Duke University Institutional Review Board (IRB), between 5-12 mL of peripheral blood was collected from consented patients prior to and 6 hours following TBI with 150-200 cGy as part of their pre-transplantation conditioning. All patients receiving non-myeloablative conditioning were treated with 200 cGy of TBI from a linear accelerator at a dose rate of 20 cGy/min. All patients who underwent TBI-based myeloablative allogeneic or autologous stem-cell transplantation received radiation fractionated at 150 cGy per fraction at 20 cGy/min. All patients had PB collected (50 ml) prior to and 6 hours following exposure to either 200 cGy or 150 cGy radiation treatment. The dose exposure for TBI patients used in this study were 0 cGy, 150 cGy, 450 cGy and 1050 cGy at 0, 6, 30 and 78 hours post irradiation. Total RNA was extracted and assayed on the Affymetrix platform.

Project description:Densely ionizing radiation is a major component of the space radiation environment and has potentially greater carcinogenic effect compared to sparsely ionizing radiation that is prevalent in the terrestrial environment. It is unknown to what extent the irradiated microenvironment contributes to the differential carcinogenic potential of densely ionizing radiation. To address this gap, 10-week old BALB/c mice were irradiated with 100 cGy sparsely ionizing g-radiation or 10, 30, or 80 cGy of densely ionizing, 350 MeV/amu Si particles and transplanted 3 days later with syngeneic Trp53 null mammary fragments. Tumor appearance was monitored for 600 days. Tumors arising in Si-particle irradiated mice had a shorter median time to appearance, grew faster and were more likely to metastasize. Most tumors arising in sham-irradiated mice were ER-positive, pseudo-glandular and contained both basal keratin 14 and luminal keratin 8/18 cells (designated K14/18), while most tumors arising in irradiated hosts were K8/18 positive (designated K18) and ER negative. Comparison of K18 vs K14/18 tumor expression profiles showed that genes increased in K18 tumors were associated with ERBB2 and KRAS while decreased genes overlapped with those down regulated in metastasis and by loss of E-cadherin. Consistent with this, K18 tumors grew faster than K14/18 tumors and more mice with K18 tumors developed lung metastases compared to mice with K14/18 tumors. However, K18 tumors arising in Si-particle irradiated mice grew even faster and were more metastatic compared to control mice. A K18 Si-irradiated host profile was enriched in genes involved in mammary stem cells, stroma, and Notch signaling. Thus systemic responses to densely ionizing radiation enriches for a ER-negative, K18-positive tumor, whose biology is more aggressive compared to similar tumors arising in non-irradiated hosts. Key Words: ionizing radiation; breast cancer; heavy ion radiation;initiation; promotion 3 different dose of Si were used. Total RNA was extracted from mammary tumors derived from transplantations of non-irradiated p53null mammary fragments into irradiated hosts. We analyzed a total of 45 Trp53-null tumors: 18 from sham-irradiated hosts, 9 from 10 cGy Si-irradiated hosts, 10 from 30 cGy Si-irradiated hosts, and 8 from irradiated hosts.

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Non-targeted effects of low dose ionizing radiation act via TGFβ to promote mammary carcinogenesis

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