Mammalian cells repair DNA double-strand breaks (DSBs) via efficient pathways of direct, nonhomologous DNA end joining (NHEJ) and homologous recombination (HR). Prior work has identified a complex of two polypeptides, PSF and p54(nrb), as a stimulatory factor in a reconstituted in vitro NHEJ system. PSF also stimulates early steps of HR in vitro. PSF and p54(nrb) are RNA recognition motif-containing proteins with well-established functions in RNA processing and transport, and their apparent involvement in DSB repair was unexpected. Here we investigate the requirement for p54(nrb) in DSB repair in vivo. Cells treated with siRNA to attenuate p54(nrb) expression exhibited a delay in DSB repair in a γ-H2AX focus assay. Stable knockdown cell lines derived by p54(nrb) miRNA transfection showed a significant increase in ionizing radiation-induced chromosomal aberrations. They also showed increased radiosensitivity in a clonogenic survival assay. Together, results indicate that p54(nrb) contributes to rapid and accurate repair of DSBs in vivo in human cells and that the PSF·p54(nrb) complex may thus be a potential target for radiosensitizer development.

Objectives: MiR-34b is a tumour suppressor in different kinds of carcinomas. This study investigated the role of miR-34b in proliferation and apoptosis of cervical cancer. Materials and methods: The expression of miR-34b in 60 cervical cancer patients were quantified by RT-PCR and correlated with their clinicopathological parameters. Besides, there is a significant reverse relationship between miR-43b and TGF-β1 expression in tumour tissues. Cell proliferation and apoptosis was detected by CCK-8 assays and flow cytometry in cell lines transfected with miR-34b mimics. Western blotting, quantitative reverse transcription-PCR (RT-PCR) and luciferase assays were conducted to analyze the regulation of TGF-β1 by miR-34b in cell lines. Results: Here, we found expression of miR-34b to be downregulated in cervical cancer in comparison with the adjacent normal tissues. Expression levels of miR-34b were associated with enhanced malignant potential, such as tumour stage and stromal invasion. The overexpression of miR-34b potently suppressed cell proliferation and induced the apoptosis of cell lines. Conclusions: MiR-34b and TGF-β1 contribute to cervical cancer cell proliferation and apoptosis and are potential targets for cervical cancer therapeutics.

Radiotherapy of thoracic cancer often causes pulmonary inflammation leading to pneumonitis and fibrosis. We favor the hypothesis that cytokine-mediated multicellular interactions may result in the overexpression of proinflammatory cytokines such as TNF-α and TGF-β1, which promotes progressive radiation-induced lung injury. The root of Angelica sinensis, known as ‘Danggui’ in Chinese medicine, is widely used to treat radiation-induced pneumonitis in humans and shows clinical efficacy and low/no toxicity with an unclear mechanism. Using quantitative RT-PCR and immunohistochemistry (IHC) methods, we investigated radiation-induced lung injury in a mouse model. C57BL/6 mice were assigned to 4 groups: no treatment (NT), Angelica Sinensis treatment only (AS), X-ray irradiation only (XRT, single fraction of 12 Gy irradiation to the thoraces) and AS treatment plus XRT (AS/XRT). Mice in NT and AS groups exhibited low TNF-α and TGF-β1 mRNA levels and few positive cell counts for TNF-α (8-17 cells per field, x400 magnification) and TGF-β1 (9-31 cells per field), respectively. In XRT mice, there were increased inflammatory cells positive for TNF-α and TGF-β1 in lung tissue compared with NT mice (P<0.01). However, when XRT mice received AS treatment (AS/XRT), the number of inflammatory cells in lung tissue positive for both TNF-α and TGF-β1 was decreased compared with XRT-only mice (P<0.01) accompanied by moderately decreased mRNA levels of TNF-α and TGF-β1. We conclude that radiation induces expression of TNF-α and TGF-β1 in the inflammatory cells of irradiated lung tissue during the pneumonic phase. The predominant localization of TNF-α and TGF-β1 in inflammatory cell infiltrates suggests these cytokines' involvement in the process of radiation-induced pneumonitis. Moreover, effective down-regulation of TNF-α and TGF-β1 in irradiated lung tissue by Angelica Sinensis is, at least in part, indicative of its clinical efficacy in treating radiation-induced pneumonitis.

Eukaryotic cells begin to assemble discrete, nucleoplasmic repair foci within seconds after the onset of exposure to ionizing radiation. Real-time imaging of this assembly has the potential to further our understanding of the effects of medical and environmental radiation exposure. Here, we describe a microirradiation system for targeted delivery of ionizing radiation to individual cells without the need for specialized facilities. The system consists of a 25-micron diameter electroplated Nickel-63 electrode, enveloped in a glass capillary and mounted in a micromanipulator. Because of the low energy of the beta radiation and the minute total amount of isotope present on the tip, the device can be safely handled with minimum precautions. We demonstrate the use of this system for tracking assembly of individual repair foci in real time in live U2OS human osteosarcoma cells. Results indicate that there is a subset of foci that appear and disappear rapidly, before a plateau level is reached approximately 30 min post-exposure. This subset of foci would not have been evident without real-time observation. The development of a microirradiation system that is compatible with a standard biomedical laboratory expands the potential for real-time investigation of the biological effects of ionizing radiation.