Dose-dependent and independent temporal patterns of gene responses to ionizing radiation in normal and tumor cells and tumor xenografts - PubMed (original) (raw)

Dose-dependent and independent temporal patterns of gene responses to ionizing radiation in normal and tumor cells and tumor xenografts

N N Khodarev et al. Proc Natl Acad Sci U S A. 2001.

Abstract

U87 cells derived from human malignant gliomas and growtharrested human embryonic lung (HEL) fibroblasts were examined with respect to their response to ionizing radiation by profiling their RNAs. In the first series of experiments, cells grown in vitro were harvested and the RNAs were extracted 5 h after exposure to 1, 3, or 10 Gy. In the second series of experiments the U87 tumors were implanted in nude mice and subjected to the same doses of irradiation. The xenografts were harvested at 1, 5, or 24 h after irradiation and subjected to the same analyses. We observed and report on (i) cell-type common and cell-type specific responses, (ii) genes induced at low levels of irradiation but not at higher doses, (iii) temporal patterns of gene response in U87 xenografts that varied depending on radiation dose and temporal patterns of response that were similar at all doses tested, (iv) significantly higher up-regulation of cells in xenografts than in in vitro cultures, and (v) genes highly up-regulated by radiation. The responding genes could be grouped into nine functional clusters. The representation of the nine clusters was to some extent dependent on dose and time after irradiation. The results suggest that clinical outcome of ionizing radiation treatment may benefit significantly by taking into account both cell-type and radiation-dose specificity of cellular responses.

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Figures

Figure 1

Scatterplots of intensity values of independent GeneFilters GF211 arrays, hybridized with different samples of RNA. DNA arrays were hybridized and data were acquired with

imagequant

and normalized as described in Materials and Methods. Intensity values of one array plotted versus intensity values of the same genes on another array are shown. (Left) U87 in vitro. (Right) U87 in vivo. (Upper) Scatterplots of two arrays, hybridized with the same mock (un-irradiated) sample of RNA. Numbers at the left bottom corner of panels indicate the cutoff values for intensities (see Materials and Methods). (Lower Left) Intensity values of RNA from U87 cell cultures exposed to 1, 3, and 10 Gy, extracted from cells harvested 5 h after irradiation and plotted versus corresponding values RNA from in vitro mock-irradiated cells (see Top Left). (Lower Right) Intensity values of RNA from U87 xenografts exposed to 10 Gy, and extracted from tissues harvested at 1, 5, and 24 h after irradiation and plotted versus corresponding RNA from in vivo mock-irradiated cells (see Top Right).

Figure 2

Representation of temporal patterns of gene expression after IR of U87 xenografts in mice. The xenografts were exposed to 1, 3, and 10 Gy and collected at 1, 5, or 24 h after irradiation. U87 genes that responded both in irradiated xenografts and in culture (Table 3) were grouped in six clusters (A–F). (AG–FG). The distribution of functional groups in each cluster. In clusters A–D, the temporal response was dose independent, although the magnitude of the response was partially dose dependent. Green, blue, and red corresponds to 1, 3, and 10 Gy, respectively. The black line shows the mean value for the entire cluster. Mean values of induction for each cluster are presented by gray lines and colored lines present examples of individual responses for glutamate-cysteine ligase (A), protein phosphatase 2A (B), and phospholemman chloride channel (C). In clusters E and F, the temporal pattern of gene response was dose dependent. Colored lines correspond to mean values of entire cluster at each dose tested. The genes are identified in Table 3. (AG–FG) A more restricted distribution based on 68 genes.

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Dose-dependent and independent temporal patterns of gene responses to ionizing radiation in normal and tumor cells and tumor xenografts - PubMed (original) (raw)