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The role of radiation therapy in the treatment of patients with pancreatic ductal adenocarcinoma (PDA) is controversial. Randomized controlled trials investigating the efficacy of radiation therapy in patients with locally advanced unresectable PDA have reported mixed results, with effects ranging from modest benefit to worse outcomes compared with control therapies. We investigated whether radiation causes inflammatory cells to acquire an immune-suppressive phenotype that limits the therapeutic effects of radiation on invasive PDAs and accelerates progression of preinvasive foci.

Seifert L, Werba G, Tiwari S, Giao Ly NN, Nguy S, Alothman S, Alqunaibit D, Avanzi A, Daley D, Barilla R, Tippens D, Torres-Hernandez A, Hundeyin M, Mani VR, Hajdu C, Pellicciotta I, Oh P, Du K, Miller G.

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We proposed to exploit hypoxia-inducible factor (HIF)-1alpha overexpression in prostate tumours and use this transcriptional machinery to control the expression of the suicide gene cytosine deaminase (CD) through binding of HIF-1alpha to arrangements of hypoxia response elements. CD is a prodrug activation enzyme, which converts inactive 5-fluorocytosine to active 5-fluorouracil (5-FU), allowing selective killing of vector containing cells.

Laure Marignol, Ruth Foley, Thomas Southgate, Mary Coffey, Donal Hollywood and Mark Lawler

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To characterize the tumor microenvironment after standard radiation therapy (SRT) and pulsed radiation therapy (PRT) in Lewis lung carcinoma (LLC) allografts.

Jonathan L Kane, Sarah A Krueger, Alaa Hanna, Thomas R Raffel, George D Wilson, Gerard J Madlambayan and Brian Marples

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Radiation modulates both tumor cells and immune cells in the tumor microenvironment to exert its anti-tumor activity; however, the molecular connection between tumor cells and immune cells that mediates radiation-exerted tumor suppression activity in the tumor microenvironment is largely unknown. We report here that radiation induces rapid activation of the p65/p50 and p50/p50 NF-κB complexes in human soft tissue sarcoma (STS) cells. Radiation-activated p65/p50 and p50/p50 bind to the TNFα promoter to activate its transcription in STS cells. Radiation-induced TNFα induces tumor cell death in an autocrine manner. A sublethal dose of Smac mimetic BV6 induces cIAP1 and cIAP2 degradation to increase tumor cell sensitivity to radiation-induced cell death in vitro and to enhance radiation-mediated suppression of STS xenografts in vivo. Inhibition of caspases, RIP1, or RIP3 blocks radiation/TNFα-induced cell death, whereas inhibition of RIP1 blocks TNFα-induced caspase activation, suggesting that caspases and RIP1 act sequentially to mediate the non-compensatory cell death pathways. Furthermore, we determined in a syngeneic sarcoma mouse model that radiation up-regulates IRF3, IFNβ, and the T cell chemokines CCL2 and CCL5 in the tumor microenvironment, which are associated with activation and increased infiltration of Th1/Tc1 T cells in the tumor microenvironment. Moreover, tumor-infiltrating T cells are in their active form since both the perforin and FasL pathways are activated in irradiated tumor tissues. Consequently, combined BV6 and radiation completely suppressed tumor growth in vivo. Therefore, radiation-induced NF-κB functions as a molecular link between tumor cells and immune cells in the tumor microenvironment for radiation-mediated tumor suppression.

Priscilla S. Simon, Kankana Bardhan, May R. Chen, Amy V. Paschall, Chunwan Lu, Roni J. Bollag, Feng-Chong Kong, JianYue Jin, Feng-Ming Kong, Jennifer L. Waller, Raphael E. Pollock and Kebin Liu

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