Chiara Gerini

A PPAR-gamma agonist attenuates pulmonary injury induced by irradiation in a murine model.

PURPOSE/OBJECTIVE(S) Due to its anti-inflammatory, antifibrotic and antineoplastic properties, the PPAR-γ agonist rosiglitazone is of interest in the prevention and therapy of radiation-induced pulmonary injury. We evaluated the radioprotective effects of rosiglitazone in a murine model of pulmonary damage to determine whether radioprotection was selective for normal and tumor tissues. METHODS Lungs in C57BL/6J mice were irradiated (19 Gy) with or without rosiglitazone (RGZ, 5mg/kg/day for 16 weeks, oral gavage). Computed tomography (CT) was performed and Hounsfield Units (HU) were determined during the observation period. Histological analysis and evaluation of fibrosis/inflammatory markers by western blot were performed at 16 weeks. A549 tumor-bearing CD1 mice were irradiated (16 Gy) with or without RGZ, and tumor volumes were measured at 35 days. RESULTS Rosiglitazone reduced radiologic and histologic signs of fibrosis, inflammatory infiltrate, alterations to alveolar structures, and HU lung density that was increased due to irradiation. RGZ treatment also significantly decreased Col1, NF-kB and TGF-β expression and increased Bcl-2 protein expression compared to the irradiation group and reduced A549 clonogenic survival and xenograft tumor growth. CONCLUSIONS Rosiglitazone exerted a protective effect on normal tissues in radiation-induced pulmonary injury, while irradiated lung cancer cells were not protected in vivo and in vitro. Thus, rosiglitazone could be proposed as a radioprotective agent in the treatment of lung cancer.

A PPAR-gamma agonist protects from radiation-induced intestinal toxicity

Objective Because of its anti-inflammatory, anti-fibrotic, anti-apoptotic and anti-neoplastic properties, the PPAR-γ agonist rosiglitazone is an interesting drug for investigating for use in the prevention and treatment of radiation-induced intestinal damage. We aimed to evaluate the radioprotective effect of rosiglitazone in a murine model of acute intestinal damage, assessing whether radioprotection is selective for normal tissues or also occurs in tumour cells. Methods Mice were total-body irradiated (12 Gy), with or without rosiglitazone (5 mg/kg/day). After 24 and 72 hours, mice were sacrificed and the jejunum was collected. HT-29 human colon cancer cells were irradiated with a single dose of 2 (1000 cells), 4 (1500 cells) or 6 (2000 cells) Gy, with or without adding rosiglitazone (20 µM) 1 hour before irradiation. HT-29-xenografted CD1 mice were irradiated (16 Gy) with or without rosiglitazone; tumour volumes were measured for 33 days. Results Rosiglitazone markedly reduced histological signs of altered bowel structures, that is, villi shortening, submucosal thickening, necrotic changes in crypts, oedema, apoptosis, and inflammatory infiltrate induced by irradiation. Rosiglitazone significantly decreased p-NF-kB p65 phosphorylation and TGFβ protein expression at 24 and 72 hours post-irradiation and significantly decreased gene expression of Collagen1, Mmp13, Tnfα and Bax at 24 hours and p53 at 72 hours post-irradiation. Rosiglitazone reduced HT-29 clonogenic survival, but only produced a slight reduction of xenograft tumour growth. Conclusion Rosiglitazone exerts a protective effect on normal tissues and reduces alterations in bowel structures and inflammation in a radiation-induced bowel toxicity model, without interfering with the radiation effect on HT-29 cancer cells. PPAR-γ agonists should be further investigated for their application in abdominal and pelvic irradiation.

A PPAR gamma agonist protects against oral mucositis induced by irradiation in a murine model

BACKGROUND Due to its anti-inflammatory, antifibrotic and antineoplastic properties, the PPAR gamma agonist rosiglitazone is of interest in prevention and therapy of radiation-induced toxicities. We aimed to evaluate the radioprotective effect of rosiglitazone in a mouse model of radiation-induced oral mucositis. MATERIAL AND METHODS Oral mucositis was obtained by irradiation of the oral region of C57BL/6J mice, pretreated or not with rosiglitazone. Mucositis was assessed by macroscopic scoring, histology and molecular analysis. Tumor xenograft was obtained by s.c. injection of Hep-2 cells in CD1 mice. Tumor volume was measured twice a week to evaluate effect of rosiglitazone alone and combined with radiotherapy. RESULTS Irradiated mice showed typical features of oral mucositis, such as oedema and reddening, reaching the peak of damage after 12-15days. Rosiglitazone markedly reduced visible signs of mucositis and significantly reduced the peak. Histological analysis showed the presence of an inflammatory cell infiltrate after irradiation; the association with rosiglitazone noticeably reduced infiltration. Rosiglitazone significantly inhibited radiation-induced tnfα, Il-6 and Il-1β gene expression. Rosiglitazone controlled the increase of TGF-β and NF-kB p65 subunit proteins induced by irradiation, and enhanced the expression of catalase. Irradiation and rosiglitazone significantly reduced tumor volume as compared to control. Rosiglitazone did not protect tumor from the therapeutic effect of radiation. CONCLUSION Rosiglitazone exerted a protective action on normal tissues in radiation-induced mucositis. Moreover, it showed antineoplastic properties on head-neck carcinoma xenograft model and selective protection of normal tissues. Thus, PPAR gamma agonists should be further investigated as radioprotective agents in head and neck cancer.

High resolution melting analysis of deletion/insertion polymorphisms: A new method for the detection and quantification of mixed chimerism in allogeneic stem cell transplantation

Increasing mixed chimerism after allogeneic stem cell transplantation has been associated with a high risk of relapse and probable graft failure in patient with hematological malignancies as well as non-malignant conditions. We evaluated a new method for chimerism detection, based on the quantitative High Resolution Melting Analysis (HRMA) of deletion/insertion polymorphisms (DIPs). The study consisted in the selection of a panel of DIPs, all generating genotype-specific melting curves, and in the use of samples containing opposite molecular species (homozygous INS/INS and DEL/DEL) mixed in different percentages to create a standard curve for each polymorphism. The detection of mixed chimerism with the HRMA attained a sensitivity of <1%, as well as good accuracy and precision with Percent Errors and Coefficients of Variation not exceeding 30% in reconstruction experiments with DNA mixtures. The present approach provides accurate and precise estimates of mixed chimerism and makes the method open to evaluation for its use in clinical practice.

Peroxisome proliferator activated receptor-gamma stimulation for prevention of 5-fluorouracil-induced oral mucositis in mice

Oral mucositis is a side effect of treatment regimens containing 5‐fluorouracil (5‐FU). The purpose of this study was to present our evaluation to see if rosiglitazone (RGZ) protected normal tissues from chemotherapy‐induced oral mucositis.

Tumor Microenvironment, Hypoxia, and Stem Cell-Related Radiation Resistance

Resistance to therapy of glioblastoma is attributable to cellular and phenotypical heterogeneity. Increasing evidence supports the hypothesis that the intratumoral heterogeneity derives from a combination of genetic/epigenetic events and of a cellular hierarchy dominated by a subpopulation of cells exhibiting stem cell properties, named glioblastoma stem cells (GSCs). Growing body of data accounts for GSCs role in initiation, progression, and radioresistance of glioblastoma.

Basic Knowledge of Glioblastoma Radiobiology

Glioblastoma (GBM) is radioresistant tumors with an infaust prognosis. Local disease control is the main intent of treatment because of the high incidence of recurrence. Radiotherapy post surgical resection is the mainstay of the management of GBM; however, high dose treatments fail to improve survival. Major determinants of radioresistance are here reviewed. GBM is characterized by genomic heterogeneity intra- and intertumors. GBM cells can present dysregulation of genes involved in main sensors and effectors of DNA damage, DNA repair, cell cycle regulation, apoptosis, and signaling pathways. High expression of growth factor can affect response to radiation, as well as angiogenesis, hypoxia and presence of cancer stem cells can increase radioresistance. High expression of extracellular matrix degrading enzymes and of transcription factors master regulators of epithelial mesenchymal transition support invasiveness and diffuse infiltration. A good knowledge of basic radiobiology of GBM can help in finding new therapeutic targets.

Cancer Stem Cells: Biology and Potential Therapeutic Applications

Cancer stem cells (CSCs) have been postulated since the emergence of experimental evidences supporting the existence of a subset of cancer cells capable of self-renewal, multiple-lineage differentiation, and chemoresistance–radioresistance. Nonetheless, their precise identification, effective role as a driving force in tumor progression and metastatic spread, and even their existence are widely debated. Comprehension of pathophysiological features, biology, and microenvironmental interactions of CSCs would provide innovative tools to refine diagnostic workup and to overcome resistance to conventional cancer treatments. In the following chapter, the development of the CSCs’ hierarchical model and identification of the hallmark of the presence of stem cells in cancer are described; an overview of the major clinical applications and future challenges in research is outlined.