Purpose: This study examined the feasibility, efficacy (abscopal effect), and immune effects of TGFβ blockade during radiotherapy in metastatic breast cancer patients.Experimental Design: Prospective randomized trial comparing two doses of TGFβ blocking antibody fresolimumab. Metastatic breast cancer patients with at least three distinct metastatic sites whose tumor had progressed after at least one line of therapy were randomized to receive 1 or 10 mg/kg of fresolimumab, every 3 weeks for five cycles, with focal radiotherapy to a metastatic site at week 1 (three doses of 7.5 Gy), that could be repeated to a second lesion at week 7. Research bloods were drawn at baseline, week 2, 5, and 15 to isolate PBMCs, plasma, and serum.Results: Twenty-three patients were randomized, median age 57 (range 35–77). Seven grade 3/4 adverse events occurred in 5 of 11 patients in the 1 mg/kg arm and in 2 of 12 patients in the 10 mg/kg arm, respectively. Response was limited to three stable disease. At a median follow up of 12 months, 20 of 23 patients are deceased. Patients receiving the 10 mg/kg had a significantly higher median overall survival than those receiving 1 mg/kg fresolimumab dose [hazard ratio: 2.73 with 95% confidence interval (CI), 1.02–7.30; P = 0.039]. The higher dose correlated with improved peripheral blood mononuclear cell counts and a striking boost in the CD8 central memory pool.Conclusions: TGFβ blockade during radiotherapy was feasible and well tolerated. Patients receiving the higher fresolimumab dose had a favorable systemic immune response and experienced longer median overall survival than the lower dose group. Clin Cancer Res; 24(11); 2493–504. ©2018 AACR.

The transcription factor NF-E2-related factor 2 (Nrf2) binds the antioxidant DNA response element (ARE) to activate important cellular cytoprotective defense systems. Recently several types of cancers have been shown to overexpress Nrf2, but its role in the cellular response to radiation therapy has yet to be fully determined. In this study, we report that single doses of ionizing radiation from 2 to 8 Gy activate ARE-dependent transcription in breast cancer cells in a dose-dependent manner, but only after a delay of five days. Clinically relevant daily dose fractions of radiation also increased ARE-dependent transcription, but again only after five days. Downstream activation of Nrf2-ARE-dependent gene and protein markers, such as heme oxygenase-1, occurred, whereas Nrf2-deficient fibroblasts were incapable of these responses. Compared with wild-type fibroblasts, Nrf2-deficient fibroblasts had relatively high basal levels of reactive oxygen species that increased greatly five days after radiation exposure. Further, in vitro clonogenic survival assays and in vivo sublethal whole body irradiation tests showed that Nrf2 deletion increased radiation sensitivity, whereas Nrf2-inducing drugs did not increase radioresistance. Our results indicate that the Nrf2-ARE pathway is important to maintain resistance to irradiation, but that it operates as a second-tier antioxidant adaptive response system activated by radiation only under specific circumstances, including those that may be highly relevant to tumor response during standard clinical dose-fractionated radiation therapy. Cancer Res; 70(21); 8886–95. ©2010 AACR.

Normal tissue responses to ionizing radiation have been a major subject for study since the discovery of X‐rays at the end of the 19th century. Shortly thereafter, time–dose relationships were established for some normal tissue endpoints that led to investigations into how the size of dose per fraction and the quality of radiation affected outcome. The assessment of the radiosensitivity of bone marrow stem cells using colony‐forming assays by Till and McCulloch prompted the establishment of in situ clonogenic assays for other tissues that added to the radiobiology toolbox. These clonogenic and functional endpoints enabled mathematical modeling to be performed that elucidated how tissue structure, and in particular turnover time, impacted clinically relevant fractionated radiation schedules. More recently, lineage tracing technology, advanced imaging and single cell sequencing have shed further light on the behavior of cells within stem, and other, cellular compartments, both in homeostasis and after radiation damage. The discovery of heterogeneity within the stem cell compartment and plasticity in response to injury have added new dimensions to the consideration of radiation‐induced tissue damage. Clinically, radiobiology of the 20th century garnered wisdom relevant to photon treatments delivered to a fairly wide field at around 2 Gy per fraction, 5 days per week, for 5–7 weeks. Recently, the scope of radiobiology has been extended by advances in technology, imaging and computing, as well as by the use of charged particles. These allow radiation to be delivered more precisely to tumors while minimizing the amount of normal tissue receiving high doses. One result has been an increase in the use of schedules with higher doses per fraction given in a shorter time frame (hypofractionation). We are unable to cover these new technologies in detail in this review, just as we must omit low‐dose stochastic effects, and many aspects of dose, dose rate and radiation quality. We argue that structural diversity and plasticity within tissue compartments provides a general context for discussion of most radiation responses, while acknowledging many omissions. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

The body senses “danger” from “damaged self” molecules through members of the same receptor superfamily it uses for microbial “non-self”, triggering canonical signaling pathways that lead to the generation of acute inflammatory responses. For this reason, the biology of normal tissue responses to moderate and clinically relevant doses of radiation is inextricably connected to innate immunity. The complex sequence of inflammatory events that ensues causes further cell and tissue damage to eliminate potential invaders but also leads to cytoprotective responses that limit the spread of damage and to wound healing through tissue regeneration or replacement. These sequential processes are orchestrated through multiple feedback control mechanisms involving cyclical production of free radicals and cytokines that are common to both radiation and immune signaling. This requires a concerted effort by resident tissue and inflammatory cell types, with macrophages apparently leading the way. The initial response to moderate doses of radiation therefore feeds into a pro-inflammatory paradigm whose eventual outcome is critically dependent upon the properties of the immune cells that are involved in tissue damage, regeneration and repair and that are in part under genetic influence. Importantly, these canonical pathways provide targets for interventions aimed at modifying normal tissue radiation responses. In this review, we examine areas of intersection between innate immunity and normal tissue radiobiology.