Development Of Normal Tissue Damage Research Articles

Proton scanning and X-ray beam irradiation induce distinct regulation of inflammatory cytokines in a preclinical mouse model

Purpose Conventional X-ray radiotherapy induces a pro-inflammatory response mediated by altered expression of inflammation-regulating cytokines. Proton scanning and X-ray irradiation produce distinct changes to cytokine gene expression in vitro suggesting that proton beam therapy may induce an inflammatory response dissimilar to that of X-ray radiation. The purpose of the present study was to determine whether proton scanning beam radiation and conventional X-ray photon radiation would induce differential regulation of circulating cytokines in vivo. Materials and methods Female CDF1 mice were irradiated locally at the right hind leg using proton pencil beam scanning or X-ray photons. Blood samples were obtained from two separate mice groups. Samples from one group were drawn by retro-orbital puncture 16 months post irradiation, while samples from the other group were drawn 5 and 30 days post irradiation. Concentration of the cytokines IL-6, IL-1β, IL-10, IL-17A, IFN-γ, and TNFα was measured in plasma using bead-based immunoassays. Results The cytokines IL-6, IL-1β, IL-10, IFN-γ, and TNFα were expressed at lower levels in plasma samples from proton-irradiated mice compared with X-ray-irradiated mice 16 months post irradiation. The same cytokines were downregulated in proton-irradiated mice 5 days post irradiation when compared to controls, while at day 30 expression had increased to the same level or higher. X-ray radiation did not markedly change expression levels at days 5 and 30. Conclusions The inflammatory response to proton and X-ray irradiation seem to be distinct as the principal pro-inflammatory cytokines are differentially regulated short- and long-term following irradiation. Both the development of normal tissue damage and efficacy of immunotherapy could be influenced by an altered inflammatory response to irradiation.

Differential gene expression in primary fibroblasts induced by proton and cobalt-60 beam irradiation

Introduction: Proton beam therapy delivers a more conformal dose distribution than conventional radiotherapy, thus improving normal tissue sparring. Increasing linear energy transfer (LET) along the proton track increases the relative biological effectiveness (RBE) near the distal edge of the Spread-out Bragg peak (SOBP). The severity of normal tissue side effects following photon beam radiotherapy vary considerably between patients.Aim: The dual study aim was to identify gene expression patterns specific to radiation type and proton beam position, and to assess whether individual radiation sensitivity influences gene expression levels in fibroblast cultures irradiated in vitro.Methods: The study includes 30 primary fibroblast cell cultures from patients previously classified as either radiosensitive or radioresistant. Cells were irradiated at three different positions in the proton beam profile: entrance, mid-SOBP and at the SOBP distal edge. Dose was delivered in three fractions × 3.5 Gy(RBE) (RBE 1.1). Cobalt-60 (Co-60) irradiation was used as reference. Real-time qPCR was performed to determine gene expression levels for 17 genes associated with inflammation response, fibrosis and angiogenesis.Results: Differences in median gene expression levels were observed for multiple genes such as IL6, IL8 and CXCL12. Median IL6 expression was 30%, 24% and 47% lower in entrance, mid-SOBP and SOBP distal edge groups than in Co-60 irradiated cells. No genes were found to be oppositely regulated by different radiation qualities. Radiosensitive patient samples had the strongest regulation of gene expression; irrespective of radiation type.Conclusions: Our findings indicate that the increased LET at the SOBP distal edge position did not generally lead to increased transcriptive response in primary fibroblast cultures. Inflammatory factors were generally less extensively upregulated by proton irradiation compared with Co-60 photon irradiation. These effects may possibly influence the development of normal tissue damage in patients treated with proton beam therapy.

High and Low LET Radiation Differentially Induce Normal Tissue Damage Signals

Radiotherapy using high linear energy transfer (LET) radiation is aimed at efficiently killing tumor cells while minimizing dose (biological effective) to normal tissues to prevent toxicity. It is well established that high LET radiation results in lower cell survival per absorbed dose than low LET radiation. However, whether various mechanisms involved in the development of normal tissue damage may be regulated differentially is not known. Therefore the aim of this study was to investigate whether two actions related to normal tissue toxicity, p53-induced apoptosis and expression of the profibrotic gene PAI-1 (plasminogen activator inhibitor 1), are differentially induced by high and low LET radiation. Cells were irradiated with high LET carbon ions or low LET photons. Cell survival assays were performed, profibrotic PAI-1 expression was monitored by quantitative polymerase chain reaction, and apoptosis was assayed by annexin V staining. Activation of p53 by phosphorylation at serine 315 and serine 37 was monitored by Western blotting. Transfections of plasmids expressing p53 mutated at serines 315 and 37 were used to test the requirement of these residues for apoptosis and expression of PAI-1. As expected, cell survival was lower and induction of apoptosis was higher in high -LET irradiated cells. Interestingly, induction of the profibrotic PAI-1 gene was similar with high and low LET radiation. In agreement with this finding, phosphorylation of p53 at serine 315 involved in PAI-1 expression was similar with high and low LET radiation, whereas phosphorylation of p53 at serine 37, involved in apoptosis induction, was much higher after high LET irradiation. Our results indicate that diverse mechanisms involved in the development of normal tissue damage may be differentially affected by high and low LET radiation. This may have consequences for the development and manifestation of normal tissue damage.

Comparison of single, fractionated and hyperfractionated irradiation on the development of normal tissue damage in rat lung

The effect of fractionated thoracic irradiation on the development of normal tissue damage in rats was compared to that produced by single doses. Animals received a single dose of 15 Gy, 30 Gy in 10 daily fractions of 3 Gy each (fractionation), or 30 Gy in 30 fractions of 1 Gy each 3 times a day (hyperfractionation). The treatments produced minimal lethality since a total of only 6 animals died between days 273 and 475 after the initiation of treatment, with no difference in survival observed between the control and any of the 3 treated groups. Despite the lack of lethality, evidence of lung damage was obtained by histological examination. At times less than 180 days after treatment, the lungs of animals receiving a single dose of 15 Gy displayed more severe changes than did animals from either fractionation group. At longer times after treatment (days 261 and 475), the histological appearances within each group were changed, collagen deposits and fibrosis being the most significant observations. Animals that had received either single doses or fractionated doses had more of the pulmonary parenchyma involved than did animals that had received hyperfractionated doses. We conclude that, in the rat lung model, a total radiation dose of 30 Gy fractionated over 14 days produces no more acute lethality nor damage to lung tissue than does 15 Gy delivered as a single dose. However, long-term effects as evidenced by deposits of collagen and development of fibrosis are significantly reduced by hyperfractionation when compared to single doses and daily fractionation.

Development of normal tissue damage in the rat subsequent to thoracic irradiation and prior treatment with cancer chemotherapeutic agents.

The effect of combined modalities (radiotherapy-chemotherapy) on the development of long-term normal tissue damage was investigated in rats. Animals received single I.P. injections of Hank's balanced saline solution, adriamycin (ADR, 1.0 mg/kg), bleomycin (BLM, 10 units/kg), or dihydroxyanthraquinone (DHAQ, 3.0 mg/kg); and/or irradiation of the chest with 25 MV x-rays (12 Gy) at 0, 43, 93, or 199 days after drug treatment. Only animals treated with DHAQ displayed appreciable toxicity, with more animals dying at less than 200 days when radiation was added at 0 or 43 days. Although animals treated with BLM or radiation exhibited evidence of lung damage (histologically by 199 days and radiographically by 300 days), their survival was not compromised. The simultaneous administration of x-ray and BLM produced enhanced effects as compared to either agent alone. These results demonstrate an enhancement of normal tissue damage by combined treatment with radiation and chemotherapeutic agents, not only for acute toxicity but also for long-term effects. This damage was ultimately expressed as alteration of lung structure (histologically and radiographically) in the case of BLM, and as animal lethality in the case of DHAQ. In addition, there was a reduction in the degree of enhancement observed as a function of the separation in time between treatment with chemotherapeutic agents and subsequent irradiation. These factors should be considered when combined modality therapy is used for treatment of cancer in the thoracic region.

Development of normal tissue damage in rats subsequent to chest irradiation following treatment with drugs

Development of normal tissue damage in rats subsequent to chest irradiation following treatment with drugs