Martin Hauer-Jensen

The radiotherapeutic injury--a complex 'wound'.

Radiotherapeutic normal tissue injury can be viewed as two simultaneously ongoing and interacting processes. The first has many features in common with the healing of traumatic wounds. The second is a set of transient or permanent alterations of cellular and extracellular components within the irradiated volume. In contrast to physical trauma, fractionated radiation therapy produces a series of repeated insults to tissues that undergo significant changes during the course of radiotherapy. Normal tissue responses are also influenced by rate of dose accumulation and other factors that relate to the radiation therapy schedule. This article reviews the principles of organised normal tissue responses during and after radiation therapy, the effect of radiation therapy on these responses, as well as some of the mechanisms underlying the development of recognisable injury. Important clinical implications relevant to these processes are also discussed.

Animal Models for Medical Countermeasures to Radiation Exposure

Abstract Since September 11, 2001, there has been the recognition of a plausible threat from acts of terrorism, including radiological or nuclear attacks. A network of Centers for Medical Countermeasures against Radiation (CMCRs) has been established across the U.S.; one of the missions of this network is to identify and develop mitigating agents that can be used to treat the civilian population after a radiological event. The development of such agents requires comparison of data from many sources and accumulation of information consistent with the “Animal Rule” from the Food and Drug Administration (FDA). Given the necessity for a consensus on appropriate animal model use across the network to allow for comparative studies to be performed across institutions, and to identify pivotal studies and facilitate FDA approval, in early 2008, investigators from each of the CMCRs organized and met for an Animal Models Workshop. Working groups deliberated and discussed the wide range of animal models available for assessing agent efficacy in a number of relevant tissues and organs, including the immune and hematopoietic systems, gastrointestinal tract, lung, kidney and skin. Discussions covered the most appropriate species and strains available as well as other factors that may affect differential findings between groups and institutions. This report provides the workshop findings.

Models for evaluating agents intended for the prophylaxis, mitigation and treatment of radiation injuries. Report of an NCI Workshop, December 3-4, 2003

Abstract Stone, H. B., Moulder, J. E., Coleman, C. N., Ang, K. K., Anscher, M. S., Barcellos-Hoff, M. H., Dynan, W. S., Fike, J. R., Grdina, D. J., Greenberger, J. S., Hauer-Jensen, M., Hill, R. P., Kolesnick, R. N., MacVittie, T. J., Marks, C., McBride, W. H., Metting, N., Pellmar, T., Purucker, M., Robbins, M. E., Schiestl, R. H., Seed, T. M., Tomaszewski, J., Travis, E. L., Wallner, P. E., Wolpert, M. and Zaharevitz, D. Models for Evaluating Agents Intended for the Prophylaxis, Mitigation and Treatment of Radiation Injuries. Report of an NCI Workshop, December 3–4, 2003. Radiat. Res. 162, 711–728 (2004). To develop approaches to prophylaxis/protection, mitigation and treatment of radiation injuries, appropriate models are needed that integrate the complex events that occur in the radiation-exposed organism. While the spectrum of agents in clinical use or preclinical development is limited, new research findings promise improvements in survival after whole-body irradiation and reductions in the risk of adverse effects of radiotherapy. Approaches include agents that act on the initial radiochemical events, agents that prevent or reduce progression of radiation damage, and agents that facilitate recovery from radiation injuries. While the mechanisms of action for most of the agents with known efficacy are yet to be fully determined, many seem to be operating at the tissue, organ or whole animal level as well as the cellular level. Thus research on prophylaxis/protection, mitigation and treatment of radiation injuries will require studies in whole animal models. Discovery, development and delivery of effective radiation modulators will also require collaboration among researchers in diverse fields such as radiation biology, inflammation, physiology, toxicology, immunology, tissue injury, drug development and radiation oncology. Additional investment in training more scientists in radiation biology and in the research portfolio addressing radiological and nuclear terrorism would benefit the general population in case of a radiological terrorism event or a large-scale accidental event as well as benefit patients treated with radiation.

Deficiency of microvascular thrombomodulin and up-regulation of protease-activated receptor-1 in irradiated rat intestine: possible link between endothelial dysfunction and chronic radiation fibrosis.

Microvascular injury is believed to be mechanistically involved in radiation fibrosis, but direct molecular links between endothelial dysfunction and radiation fibrosis have not been established in vivo. We examined radiation-induced changes in endothelial thrombomodulin (TM) and protease-activated receptor-1 (PAR-1) in irradiated intestine, and their relationship to structural, cellular, and molecular aspects of radiation injury. Rat small intestine was locally exposed to fractionated X-radiation. Structural injury was assessed 24 hours and 2, 6, and 26 weeks after the last radiation fraction using quantitative histology and morphometry. TM, neutrophils, transforming growth factor-beta, and collagens I and III were assessed by quantitative immunohistochemistry. PAR-1 protein was localized immunohistochemically, and cells expressing TM or PAR-1 transcript were identified by in situ hybridization. Steady-state PAR-1 mRNA levels in intestinal smooth muscle were determined using laser capture microdissection and competitive reverse transcriptase-polymerase chain reaction. Radiation caused a sustained, dose-dependent decrease in microvascular TM. The number of TM-positive vessels correlated with all parameters of radiation enteropathy and, after adjusting for radiation dose and observation time in a statistical model, remained independently associated with neutrophil infiltration, intestinal wall thickening, and collagen I accumulation. PAR-1 immunoreactivity and transcript increased in vascular and intestinal smooth muscle cells in irradiated intestine. PAR-1 mRNA increased twofold in irradiated intestinal smooth muscle. Intestinal irradiation up-regulates PAR-1 and causes a dose-dependent, sustained deficiency of microvascular TM that is independently associated with the severity of radiation toxicity. Interventions aimed at preserving or restoring endothelial TM or blocking PAR-1 should be explored as strategies to increase the therapeutic ratio in clinical radiation therapy.

Acute radiation proctitis : A sequential clinicopathologic study during pelvic radiotherapy

PURPOSE Rectal toxicity is often dose limiting during pelvic radiation therapy. This prospective study examined the sequential development and associations of clinical, endoscopic, and histopathologic rectal toxicity during ongoing radiation therapy. METHODS AND MATERIALS Thirty-three patients with nongastrointestinal pelvic carcinomas underwent proctoscopy with biopsy before radiation therapy, after 2 weeks treatment, and toward the end of the treatment course (6 weeks). Symptoms of acute toxicity were recorded, and endoscopic changes were graded. Histologic changes in the surface epithelium, glandular layer, and lamina propria were assessed using an ad hoc scoring system. Macrophage accumulation was evaluated in anti-CD68 stained sections. RESULTS Pretreatment endoscopy and biopsies were unremarkable. Clinical symptoms progressed toward the end of the treatment course. In contrast, endoscopic pathology was maximal at 2 weeks. Biopsies obtained during treatment exhibited atrophy of the surface epithelium, acute cryptitis, crypt abscesses, crypt distortion and atrophy, and stromal inflammation. Histologic changes, particularly those in the surface epithelium, were consistently more pronounced at 2 weeks than they were at 6 weeks. CONCLUSION In contrast to clinical symptoms, endoscopic changes stabilize and histologic changes regress from the 2nd to the 6th week of treatment. These results may have implications for the design and timing of prophylactic and therapeutic interventions to reduce radiation proctitis.

Expression of fibrogenic cytokines in rat small intestine after fractionated irradiation

The molecular and cellular mechanisms that regulate the radiation-induced fibrotic response in the intestine are not known. In addition to increased amounts of connective tissue, inflammatory cell aggregates are often found, especially in conjunction with acute or chronic mucosal ulcerations. These inflammatory cells are a major source of cytokines that influence connective tissue metabolism. Hence, a possible link may exist between the cellular inflammatory response and fibrosis. This preclinical study examined the influence of fractionated irradiation on the expression of three inflammatory/fibrogenic cytokines in rat small intestine. A rat intestinal transposition model was used for localized fractionated irradiation of a 3-4-cm segment of small bowel. Fifty-nine male Sprague-Dawley rats were irradiated or sham irradiated with 9 daily fractions of 5.2 Gy. Expression of Interleukin 1 alpha (IL-1 alpha), Transforming growth factor beta 1 (TGF-beta 1), and Platelet derived growth factor-AA (PDGF-AA) was assessed by immunohistochemistry. Irradiated and unirradiated intestine was examined 24 h, 14 days, and 26 weeks after completion of irradiation. Unirradiated intestine exhibited immunohistochemical expression of IL-1 alpha, TGF-beta 1 and PDGF-AA that conformed to known staining patterns in normal tissue. Irradiated intestine showed increased expression of all three cytokines at all assessment times. The increased cytokine expression correlated with fibrosis and inflammatory cell infiltrates in irradiated intestine. This was particularly evident in areas with mucosal ulcerations. Fractionated irradiation of small intestine elicits increased expression of IL-1 alpha, TGF-beta 1, and PDGF-AA in areas of acute and chronic radiation injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Normal tissue effects: reporting and analysis.

Any effective cancer therapy developed to date is associated with a spectrum of normal tissue effects of varying incidence and severity. With an increasing number of novel therapeutic approaches undergoing clinical testing and an increased effort to optimize the established treatment modalities, methods for reliable quantification of normal tissue effects have become a key element in advancing cancer care. Here, we present a review of many of the issues involved in reporting and analyzing clinical normal tissue effect data. A distinction is introduced between explorative (science-driven) and pragmatic (patient-centered) studies. The desirable properties of criteria for reporting and grading toxicity are discussed from a biological and clinical perspective. Validation of toxicity criteria and the statistical issues involved in analyzing this type of data are presented with special emphasis on descriptors of the time evolution of toxicity. Finally, we discuss surrogate markers for late effects, mechanistic studies, and the design of clinical studies with normal tissue endpoints as a primary outcome. It is concluded that a consensus is required on guidelines for the reporting of normal tissue effects to improve the comparability of published reports on treatment outcome.

Statins increase thrombomodulin expression and function in human endothelial cells by a nitric oxide-dependent mechanism and counteract tumor necrosis factor alpha-induced thrombomodulin downregulation.

Expression of functionally active thrombomodulin (TM) on the luminal surface of endothelial cells is critical for vascular thromboresistance. TM maintains thrombohemorrhagic homeostasis by forming a complex with thrombin, which subsequently loses its procoagulant properties and instead activates protein C. Acquired deficiency of endothelial TM is of particular pathophysiological significance in sepsis and related disorders. We show here that two different 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), atorvastatin and simvastatin, strongly increase the expression and functional activity of TM in human umbilical vein endothelial cells, human coronary artery endothelial cells, and EA.hy926 endothelial cells. The increase in endothelial TM conferred by statin was prevented by the addition of mevalonic acid, geranylgeranyl-pyrophosphate, and nitric oxide scavenger, and was mimicked by the addition of a specific inhibitor of geranylgeranyl transferase, as well as by nitric oxide donors. Moreover, statin counteracted tumor necrosis factor alpha-induced downregulation of endothelial cell TM. The increase in endothelial cell TM activity in response to statin constitutes a novel pleiotropic (non-lipid-related) effect of these commonly used compounds, and may be of clinical significance in disorders where deficient endothelial TM and protein C activation play a pathophysiological role.

Bowel injury: current and evolving management strategies

The intestine is often dose limiting during abdominal and pelvic radiation therapy. Delayed bowel toxicity is difficult to manage and adversely impacts the quality of life of long-term cancer survivors. Of the 8 to 9 million cancer survivors currently living in the United States, more than half have had abdominal or pelvic tumors, and about 60% of these patients have undergone or will undergo radiation therapy. Therefore, interventions that limit postradiation intestinal dysfunction would significantly improve outcomes in a large number of patients. Worthwhile steps toward reducing toxicity of treatments have been taken recently by introducing dose-sculpting treatment techniques. However, prophylactic or therapeutic approaches derived from an improved understanding of the pathophysiology of bowel injury will result in further advances. This article reviews current principles in the diagnosis and management of intestinal radiation injury. It also provides an overview of investigational strategies aimed at reducing radiation-induced bowel toxicity. These strategies include free radical scavengers, antioxidants, cytoprotective agents, cytokines, and enterotrophic interventions, as well as modulators of intraluminal factors, endothelial dysfunction, and neuroimmune interactions. Preclinical testing in clinically relevant animal models will facilitate translation of these strategies into the clinic and contribute to improving cancer cure rates and quality of life in cancer survivors.

Gamma-tocotrienol, a tocol antioxidant as a potent radioprotector

Purpose: To assess the radioprotective potential of gamma-tocotrienol. Materials and methods: To optimise its dose and time regimen, gamma-tocotrienol (GT3) was injected subcutaneously (SC) at different doses into male CD2F1 mice [LD50/30 (lethal radiation dose that results in the mortality of 50% mice in 30 days) radiation dose of 8.6 Gy with vehicle]. The mice were given 10.5, 11 and 11.5 Gy cobalt-60 radiation, and 30-day survival-protection was determined. Time optimisation was done by SC administration of GT3 at different intervals before irradiation. Dose reduction factor (DRF) was determined by probit analysis using mortality as the end point at six radiation doses. Protection from radiation induced pancytopenia was determined by enumerating peripheral blood cells from mice given GT3 and irradiated at 7 Gy. Results: At an optimal dose of 200 mg/kg given SC 24 h before irradiation, GT3 had a DRF of 1.29. GT3 accelerated the recovery of total white blood cells, neutrophils, monocytes, platelets, and reticulocytes in irradiated mice, compared to vehicle-injected, irradiated controls. Conclusion: GT3 is a radioprotectant having a higher DRF than any other tocols. The protection it provides close to the gastro-intestinal range indicate that GT3 can be considered as an ideal radioprotectant meriting further drug development stages for the ultimate use in humans.