Unknown,Transcriptomics,Genomics,Proteomics

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

ABSTRACT: 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.

ORGANISM(S): Mus musculus

SUBMITTER: Mary Barcellos-Hoff

PROVIDER: E-GEOD-18216 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Radiation acts on the microenvironment to affect breast carcinogenesis by distinct mechanisms that decrease cancer latency and affect tumor type.

Nguyen David H DH Oketch-Rabah Hellen A HA Illa-Bochaca Irineu I Geyer Felipe C FC Reis-Filho Jorge S JS Mao Jian-Hua JH Ravani Shraddha A SA Zavadil Jiri J Borowsky Alexander D AD Jerry D Joseph DJ Dunphy Karen A KA Seo Jae Hong JH Haslam Sandra S Medina Daniel D Barcellos-Hoff Mary Helen MH

Cancer cell 20110501 5

Tissue microenvironment is an important determinant of carcinogenesis. We demonstrate that ionizing radiation, a known carcinogen, affects cancer frequency and characteristics by acting on the microenvironment. Using a mammary chimera model in which an irradiated host is transplanted with oncogenic Trp53 null epithelium, we show accelerated development of aggressive tumors whose molecular signatures were distinct from tumors arising in nonirradiated hosts. Molecular and genetic approaches show t ...[more]

PMID: 21575864

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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.

Dataset Information

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

Publications

Radiation acts on the microenvironment to affect breast carcinogenesis by distinct mechanisms that decrease cancer latency and affect tumor type.

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