Administration of ON 01210.Na after exposure to ionizing radiation protects bone marrow cells by attenuating DNA damage response

<p>Abstract</p> <p>Background</p> <p>Ionizing radiation-induced hematopoietic injury could occur either due to accidental exposure or due to diagnostic and therapeutic interventions. Currently there is no approved drug to mitigate radiation toxicity in hematopoietic cells. This study investigates the potential of ON 01210.Na, a chlorobenzylsulfone derivative, in ameliorating radiation-induced hematopoietic toxicity when administered after exposure to radiation. We also investigate the molecular mechanisms underlying this activity.</p> <p>Methods</p> <p>Male C3H/HeN mice (n = 5 mice per group; 6-8 weeks old) were exposed to a sub-lethal dose (5 Gy) of γ radiation using a ¹³⁷Cs source at a dose rate of 0.77 Gy/min. Two doses of ON 01210.Na (500 mg/kg body weight) were administered subcutaneously at 24 h and 36 h after radiation exposure. Mitigation of hematopoietic toxicity by ON 01210.Na was investigated by peripheral white blood cell (WBC) and platelet counts at 3, 7, 21, and 28 d after radiation exposure. Granulocyte macrophage colony forming unit (GM-CFU) assay was done using isolated bone marrow cells, and terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) was performed on bone marrow sections at 7 d post-exposure. The DNA damage response pathway involving ataxia telangiectasia mutated (ATM) and p53 was investigated by Western blot in bone marrow cells at 7 d post-exposure.</p> <p>Results</p> <p>Compared to the vehicle, ON 01210.Na treated mice showed accelerated recovery of peripheral WBC and platelet counts. Post-irradiation treatment of mice with ON 01210.Na also resulted in higher GM-CFU counts. The mitigation effects were accompanied by attenuation of ATM-p53-dependent DNA damage response in the bone marrow cells of ON 01210.Na treated mice. Both phospho-ATM and phospho-p53 were significantly lower in the bone marrow cells of ON 01210.Na treated than in vehicle treated mice. Furthermore, the Bcl2:Bax ratio was higher in the drug treated mice than the vehicle treated groups.</p> <p>Conclusions</p> <p>ON 01210.Na treatment significantly mitigated the hematopoietic toxicity induced by a sub-lethal radiation dose. Mechanistically, attenuation of ATM-p53 mediated DNA damage response by ON 01210.Na is contributing to the mitigation of radiation-induced hematopoietic toxicity.</p

Small molecule receptor tyrosine kinase inhibitor of platelet-derived growth factor signaling (SU9518) modifies radiation response in fibroblasts and endothelial cells

BACKGROUND: Several small receptor tyrosine kinase inhibitors (RTKI) have entered clinical cancer trials alone and in combination with radiotherapy or chemotherapy. The inhibitory spectrum of these compounds is often not restricted to a single target. For example Imatinib/Gleevec (primarily a bcr/abl kinase inhibitor) or SU11248 (mainly a VEGFR inhibitor) are also potent inhibitors of PDGFR and other kinases. We showed previously that PDGF signaling inhibition attenuates radiation-induced lung fibrosis in a mouse model. Here we investigate effects of SU9518, a PDGFR inhibitor combined with ionizing radiation in human primary fibroblasts and endothelial cells in vitro, with a view on utilizing RTKI for antifibrotic therapy. METHODS: Protein levels of PDGFR-α/-β and phosphorylated PDGFR in fibroblasts were analyzed using western and immunocytochemistry assays. Functional proliferation and clonogenic assays were performed (i) to assess PDGFR-mediated survival and proliferation in fibroblasts and endothelial cells after SU9518 (small molecule inhibitor of PDGF receptor tyrosine kinase); (ii) to test the potency und selectivity of the PDGF RTK inhibitor after stimulation with PDGF isoforms (-AB, -AA, -BB) and VEGF+bFGF. In order to simulate in vivo conditions and to understand the role of radiation-induced paracrine PDGF secretion, co-culture models consisting of fibroblasts and endothelial cells were employed. RESULTS: In fibroblasts, radiation markedly activated PDGF signaling as detected by enhanced PDGFR phosphorylation which was potently inhibited by SU9518. In fibroblast clonogenic assay, SU9518 reduced PDGF stimulated fibroblast survival by 57%. Likewise, SU9518 potently inhibited fibroblast and endothelial cell proliferation. In the co-culture model, radiation of endothelial cells and fibroblast cells substantially stimulated proliferation of non irradiated fibroblasts and vice versa. Importantly, the RTK inhibitor significantly inhibited this paracrine radiation-induced fibroblast and endothelial cell activation. CONCLUSION: Radiation-induced autocrine and paracrine PDGF signaling plays an important role in fibroblast and endothelial cell proliferation. SU9518, a PDGFR tyrosine kinase inhibitor, reduces radiation-induced fibroblast and endothelial cell activation. This may explain therapeutic anticancer effects of Imatinib/Gleevec, and at the same time it could open a way of attenuating radiation-induced fibrosis

Activated CD4+ T cells enhance radiation effect through the cooperation of interferon-γ and TNF-α

<p>Abstract</p> <p>Background</p> <p>Approaches that enhance radiation effect may lead to improved clinical outcome and decrease toxicity. Here we investigated whether activated CD4+ T cells (aCD4) can serve as an effective radiosensitizer.</p> <p>Methods</p> <p>CD4+ T cells were activated with anti-CD3 and anti-CD28 mAbs. Hela cells were presensitized with aCD4 or conditioned supernatant (aCD4S) or recombinant cytokines for 2 days, followed γ-irradiation. The treated cells were cultured for an additional 2 to 5 days for cell proliferation, cell cycle, and western blot assays. For confirmation, other cancer cell lines were also used.</p> <p>Results</p> <p>Presensitization of tumor cells with aCD4 greatly increased tumor cell growth inhibition. Soluble factors secreted from activated CD4⁺T cells were primarily responsible for the observed effect. IFN-γ seemed to play a major role. TNF-α, though inactive by itself, significantly augmented the radiosensitizing activity of IFN-γ. aCD4S, but not IFN-γ or IFN-γ/TNF-α combination, was found to enhance the γ-irradiation-induced G2/M phase arrest. Bax expression was highly upregulated in Hela cells presensitized with aCD4S followed by γ-irradiation. The radio-sensitizing activity of aCD4 is not uniquely observed with Hela cell line, but also seen with other cancer cell lines of various histology.</p> <p>Conclusions</p> <p>Our findings suggest possible molecular and cellular mechanisms that may help explain the radio-sensitization effect of activated lymphocytes, and may provide an improved strategy in the treatment of cancer with radiotherapy.</p

Non-steroidal anti-inflammatory drug-induced apoptosis in gastric cancer cells is blocked by protein kinase C activation through inhibition of c-myc

Apoptosis plays a major role in gastrointestinal epithelial cell turnover, ulcerogenesis and tumorigenesis. We have examined apoptosis induction by non-steroidal anti-inflammatory drugs (NSAIDs) in human gastric (AGS) cancer cells and the role of protein kinase C (PKC) and apoptosis-related oncogenes. After treatment with aspirin or indomethacin, cell growth was quantified by MTT assay, and apoptosis was determined by acridine orange staining, DNA fragmentation and flow cytometry. The mRNA and protein of p53, p21waf1/cip1 and c-myc was detected by Northern and Western blotting respectively. The influence of PKC on indomethacin-induced apoptosis was determined by co-incubation of 12-O-tetradecanoylphorbol 13-acetate (TPA). The role of c-myc was determined using its antisense oligonucleotides. The results showed that both aspirin and indomethacin inhibited cell growth and induced apoptosis of AGS cells in a dose- and time-dependent manner, without altering the cell cycle. Indomethacin increased c-myc mRNA and protein, whereas p53 and p21waf1/cip1 were unchanged. Down-regulation of c-myc by its antisense oligonucleotides reduced apoptosis induction by indomethacin. TPA could inhibit indomethacin-induced apoptosis and accumulate cells in G2/M. Overexpression of c-myc was inhibited by TPA and p21waf1/cip1 mRNA increased. In conclusion, NSAIDs induce apoptosis in gastric cancer cells which may be mediated by up-regulation of c-myc proto-oncogene. PKC activation can abrogate the effects of NSAIDs by decreasing c-myc expression. © 1999 Cancer Research Campaig

Effects of Long-Term Space Flight on Erythrocytes and Oxidative Stress of Rodents

Erythrocyte and hemoglobin losses have been frequently observed in humans during space missions; these observations have been designated as “space anemia”. Erythrocytes exposed to microgravity have a modified rheology and undergo hemolysis to a greater extent. Cell membrane composition plays an important role in determining erythrocyte resistance to mechanical stress and it is well known that membrane composition might be influenced by external events, such as hypothermia, hypoxia or gravitational strength variations. Moreover, an altered cell membrane composition, in particular in fatty acids, can cause a greater sensitivity to peroxidative stress, with increase in membrane fragility. Solar radiation or low wavelength electromagnetic radiations (such as gamma rays) from the Earth or the space environment can split water to generate the hydroxyl radical, very reactive at the site of its formation, which can initiate chain reactions leading to lipid peroxidation. These reactive free radicals can react with the non-radical molecules, leading to oxidative damage of lipids, proteins and DNA, etiologically associated with various diseases and morbidities such as cancer, cell degeneration, and inflammation. Indeed, radiation constitutes on of the most important hazard for humans during long-term space flights. With this background, we participated to the MDS tissue-sharing program performing analyses on mice erythrocytes flown on the ISS from August to November 2009. Our results indicate that space flight induced modifications in cell membrane composition and increase of lipid peroxidation products, in mouse erythrocytes. Moreover, antioxidant defenses in the flight erythrocytes were induced, with a significant increase of glutathione content as compared to both vivarium and ground control erythrocytes. Nonetheless, this induction was not sufficient to prevent damages caused by oxidative stress. Future experiments should provide information helpful to reduce the effects of oxidative stress exposure and space anemia, possibly by integrating appropriate dietary elements and natural compounds that could act as antioxidants

MMP-2 siRNA Inhibits Radiation-Enhanced Invasiveness in Glioma Cells

Our previous work and that of others strongly suggests a relationship between the infiltrative phenotype of gliomas and the expression of MMP-2. Radiation therapy, which represents one of the mainstays of glioma treatment, is known to increase cell invasion by inducing MMP-2. Thus, inhibition of MMP-2 provides a potential means for improving the efficacy of radiotherapy for malignant glioma.We have tested the ability of a plasmid vector-mediated MMP-2 siRNA (p-MMP-2) to modulate ionizing radiation-induced invasive phenotype in the human glioma cell lines U251 and U87. Cells that were transfected with p-MMP-2 with and without radiation showed a marked reduction of MMP-2 compared to controls and pSV-transfected cells. A significant reduction of proliferation, migration, invasion and angiogenesis of cells transfected with p-MMP-2 and in combination with radiation was observed compared to controls. Western blot analysis revealed that radiation-enhanced levels of VEGF, VEGFR-2, pVEGFR-2, p-FAK, and p-p38 were inhibited with p-MMP-2-transfected cells. TUNEL staining showed that radiation did not induce apoptosis in U87 and U251 cells while a significant increase in TUNEL-positive cells was observed when irradiated cells were simultaneously transfected with p-MMP-2 as compared to controls. Intracranial tumor growth was predominantly inhibited in the animals treated with p-MMP-2 alone or in combination with radiation compared to controls.MMP-2 inhibition, mediated by p-MMP-2 and in combination with radiation, significantly reduced tumor cell migration, invasion, angiogenesis and tumor growth by modulating several important downstream signaling molecules and directing cells towards apoptosis. Taken together, our results demonstrate the efficacy of p-MMP-2 in inhibiting radiation-enhanced tumor invasion and progression and suggest that it may act as a potent adjuvant for radiotherapy in glioma patients

Efficient Elimination of Cancer Cells by Deoxyglucose-ABT-263/737 Combination Therapy

As single agents, ABT-263 and ABT-737 (ABT), molecular antagonists of the Bcl-2 family, bind tightly to Bcl-2, Bcl-xL and Bcl-w, but not to Mcl-1, and induce apoptosis only in limited cell types. The compound 2-deoxyglucose (2DG), in contrast, partially blocks glycolysis, slowing cell growth but rarely causing cell death. Injected into an animal, 2DG accumulates predominantly in tumors but does not harm other tissues. However, when cells that were highly resistant to ABT were pre-treated with 2DG for 3 hours, ABT became a potent inducer of apoptosis, rapidly releasing cytochrome c from the mitochondria and activating caspases at submicromolar concentrations in a Bak/Bax-dependent manner. Bak is normally sequestered in complexes with Mcl-1 and Bcl-xL. 2DG primes cells by interfering with Bak-Mcl-1 association, making it easier for ABT to dissociate Bak from Bcl-xL, freeing Bak to induce apoptosis. A highly active glucose transporter and Bid, as an agent of the mitochondrial apoptotic signal amplification loop, are necessary for efficient apoptosis induction in this system. This combination treatment of cancer-bearing mice was very effective against tumor xenograft from hormone-independent highly metastasized chemo-resistant human prostate cancer cells, suggesting that the combination treatment may provide a safe and effective alternative to genotoxin-based cancer therapies

Comparison of the clonogenic survival of A549 non-small cell lung adenocarcinoma cells after irradiation with low-dose-rate beta particles and high-dose-rate X-rays

Purpose: Lung cancer is the leading cause of cancer-related death. Among the new modalities to treat cancer, internal radiotherapy seems to be very promising. However, the achievable dose-rate is two orders of magnitude lower than the one used in conventional external radiotherapy, and data has to be collected to evaluate the cell response to highlight the potential effectiveness of low-dose-rate beta particles irradiation. This work investigates the phosphorus beta irradiation ( P) dose response on the clonogenicity of human A549 non-small cell lung adenocarcinoma cells and compares it to high-dose-rate X-irradiations results. Materials and methods: Cell survival was evaluated by a colony forming assay eight days after low-dose-rate P beta irradiations (0.8 Gy/h) and high-dose-rate X-ray irradiations (0.855 Gy/min). Results: Survival curves were obtained for both types of irradiations, and showed hyper-radiosensitivity at very low doses. Radiosensitivity parameters were obtained by using the linear-quadratic and induced-repair models. Conclusions: Comparison with high-dose-rate X-rays shows a similar surviving fraction, confirming the effectiveness of beta particles for tumor sterilization. © 2012 Informa UK, Ltd