title: Neuroinflammatory and cognitive consequences of combined radiation and immunotherapy in a novel preclinical model.
abstract: BACKGROUND
  Cancer patients often report behavioral and cognitive changes following cancer treatment. These effects can be seen in patients who have not yet received treatment or have received only peripheral (non-brain) irradiation. Novel treatments combining radiotherapy (RT) and immunotherapy (IT) demonstrate remarkable efficacy with respect to tumor outcomes by enhancing the proinflammatory environment in the tumor. However, a proinflammatory environment in the brain mediates cognitive impairments in other neurological disorders and may affect brain function in cancer patients receiving these novel treatments. Currently, gaps exist as to whether these treatments impact the brain in individuals with or without tumors and with regard to the underlying mechanisms.
  
  
  RESULTS
  Combined treatment with precision RT and checkpoint inhibitor IT achieved control of tumor growth. However, BALB/c mice receiving combined treatment demonstrated changes in measures of anxiety levels, regardless of tumor status. C57BL/6J mice with tumors demonstrated increased anxiety, except following combined treatment. Object recognition memory was impaired in C57BL/6J mice without tumors following combined treatment. All mice with tumors showed impaired object recognition, except those treated with RT alone. Mice with tumors demonstrated impaired amygdala-dependent cued fear memory, while maintaining hippocampus-dependent context fear memory. These behavioral alterations and cognitive impairments were accompanied by increased microglial activation in mice receiving immunotherapy alone or combined with RT. Finally, based on tumor status, there were significant changes in proinflammatory cytokines (IFN-γ, IL-6, IL-5, IL-2, IL-10) and a growth factor (FGF-basic).
  
  
  METHODS
  Here we test the hypothesis that IT combined with peripheral RT have detrimental behavioral and cognitive effects as a result of an enhanced proinflammatory environment in the brain. BALB/c mice with or without injected hind flank CT26 colorectal carcinoma or C57BL/6J mice with or without Lewis Lung carcinoma were used for all experiments. Checkpoint inhibitor IT, using an anti-CTLA-4 antibody, and precision CT-guided peripheral RT alone and combined were used to closely model clinical treatment. We assessed behavioral and cognitive performance and investigated the immune environment using immunohistochemistry and multiplex assays to analyze proinflammatory mediators.
  
  
  CONCLUSIONS
  Although combined treatment achieved tumor growth control, it affected the brain and induced changes in measures of anxiety, cognitive impairments, and neuroinflammation.
authors.affiliation: Howard Hughes Medical Institute, Oregon Health and Science University, Portland, OR.|Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR.|Department of Radiation Medicine, Oregon Health and Science University, Portland, OR.
authors.forename: Gwendolyn J
authors.initials: GJ
authors.lastname: McGinnis
authors.affiliation: Earle A. Chiles Research Institute, Providence Cancer Center, Portland, OR.
authors.forename: David
authors.initials: D
authors.lastname: Friedman
authors.affiliation: Earle A. Chiles Research Institute, Providence Cancer Center, Portland, OR.
authors.forename: Kristina H
authors.initials: KH
authors.lastname: Young
authors.affiliation: Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR.
authors.forename: Eileen Ruth S
authors.initials: ER
authors.lastname: Torres
authors.affiliation: Department of Radiation Medicine, Oregon Health and Science University, Portland, OR.
authors.forename: Charles R
authors.initials: CR
authors.lastname: Thomas
authors.affiliation: Department of Radiation Medicine, Oregon Health and Science University, Portland, OR.|Earle A. Chiles Research Institute, Providence Cancer Center, Portland, OR.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gough
authors.affiliation: Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR.|Department of Radiation Medicine, Oregon Health and Science University, Portland, OR.|Department of Neurology, Oregon Health and Science University, Portland, OR.|Division of Neuroscience, Oregon National Primate Research Center, Portland, OR.
authors.forename: Jacob
authors.initials: J
authors.lastname: Raber
mesh_terms: D000818:Animals; D000074322:Antineoplastic Agents, Immunological / Q000633:toxicity*; D001007:Anxiety / Q000209:etiology / Q000523:psychology; D001245:Association Learning; D001522:Behavior, Animal / Q000187:drug effects / Q000528:radiation effects; D001921:Brain / Q000276:immunology / Q000473:pathology / Q000503:physiopathology / Q000528:radiation effects; D060908:CTLA-4 Antigen / Q000037:antagonists & inhibitors / Q000276:immunology; D018827:Carcinoma, Lewis Lung / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D003071:Cognition / Q000187:drug effects / Q000528:radiation effects; D003072:Cognition Disorders / Q000209:etiology* / Q000276:immunology / Q000503:physiopathology / Q000523:psychology; D015179:Colorectal Neoplasms / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D003863:Depression / Q000209:etiology / Q000523:psychology; D004660:Encephalitis / Q000209:etiology* / Q000276:immunology / Q000503:physiopathology / Q000523:psychology; D005106:Exploratory Behavior; D005260:Female; D008568:Memory; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009043:Motor Activity; D009425:Nesting Behavior; D011832:Radiation Injuries / Q000209:etiology* / Q000276:immunology / Q000503:physiopathology / Q000523:psychology; D016499:Radioimmunotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D021641:Recognition, Psychology; D013997:Time Factors
chemical_list: D000074322:Antineoplastic Agents, Immunological; D060908:CTLA-4 Antigen; C556707:Ctla4 protein, mouse; D016207:Cytokines
keywords: cancer-related neurological dysfunction; immunotherapy; microglia; neuroinflammation; radiotherapy