Expression of NF-κB p50 in Tumor Stroma Limits the Control of Tumors by Radiation Therapy

Radiation therapy aims to kill cancer cells with a minimum of normal tissue toxicity. Dying cancer cells have been proposed to be a source of tumor antigens and may release endogenous immune adjuvants into the tumor environment. For these reasons, radiation therapy may be an effective modality to initiate new anti-tumor adaptive immune responses that can target residual disease and distant metastases. However, tumors engender an environment dominated by M2 differentiated tumor macrophages that support tumor invasion, metastases and escape from immune control. In this study, we demonstrate that following radiation therapy of tumors in mice, there is an influx of tumor macrophages that ultimately polarize towards immune suppression. We demonstrate using in vitro models that this polarization is mediated by transcriptional regulation by NFκB p50, and that in mice lacking NFκB p50, radiation therapy is more effective. We propose that despite the opportunity for increased antigen-specific adaptive immune responses, the intrinsic processes of repair following radiation therapy may limit the ability to control residual disease

Determination of Selenium in Biological Materials by Stable Isotope Dilution Gas Chromatography-Mass Spectrometry

Selenium can be determined quantitatively in biological samples after digestion using nitric acid, orthophosphoric acid, and hydrogen peroxide and the formation of 5-nitropiazselenol. Samples are spiked with enriched 82Se and lsotoplc ratio of 80Se to 82Se is measured by combined gas chromatographymass spectrometry using dual ion monitoring. Precise determination at the parts-per-billion level is possible. The accuracy of the method Is verlfied by using standard reference materials

IL-12 deficiency suppresses 12-O-tetradecanoylphorbol-13-acetate-induced skin tumor development in 7,12-dimethylbenz(a)anthracene-initiated mouse skin through inhibition of inflammation

Interleukin (IL)-12 deficiency exacerbates tumorigenesis in ultraviolet (UV) radiation-induced skin. Here, we assessed the effects of IL-12 deficiency on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion in 7,12-dimethylbenz(a)anthracene (DMBA)-initiated mouse skin. Using this two-stage chemical carcinogenesis protocol, we found that the development of DMBA/TPA-induced skin tumors was diminished in IL-12p40-knockout mice than in their wild-type counterparts. At the termination of the experiment (at 24 weeks), the skin tumor incidence and tumor multiplicity were significantly lower (P < 0.005) in interleukin-12-knockout (IL-12 KO) mice than in their wild-type counterparts, as was the malignant transformation of DMBA/TPA-induced papillomas to carcinomas (P < 0.01). Analysis of samples collected at the termination of the experiments for biomarkers of inflammation by immunohistochemical analysis, western blotting, enzyme-linked immunosorbent assay and real-time polymerase chain reaction revealed significantly lower levels of cyclooxygenase-2 (COX-2), prostaglandin (PG) E2, proliferating cell nuclear antigen, cyclin D1 and the proinflammatory cytokines (tumor necrosis factor-α, IL-1β and IL-6) in the DMBA/TPA-treated tumors and tumor-uninvolved skin of IL-12 KO mice than the skin and tumors of DMBA/TPA-treated wild-type mice. Analysis of the skin 6 h after TPA treatment showed that the TPA-induced promotion of skin edema, inflammatory leukocyte infiltration, COX-2 expression and PGE2 production was significantly lower in the skin of the IL-12-KO mice than their wild-type counterparts. These results indicate that DMBA/TPA-induced skin tumor development differs from UVB-induced skin tumor development in that endogenous IL-12 acts to inhibit UVB-induced skin tumor development and malignant progression of the skin tumors to carcinoma. In the case of DMBA/TPA-induced skin tumor development, the endogenous IL-12 modulates the tumor promoter stimulation of inflammatory responses