title: Proton irradiation augments the suppression of tumor progression observed with advanced age.
abstract: Proton radiation is touted for improved tumor targeting, over standard gamma radiation, due to the physical advantages of ion beams for radiotherapy. Recent studies from our laboratory demonstrate that in addition to these targeting advantages, proton irradiation can inhibit angiogenic and immune factors critical to "hallmark" processes that impact cancer progression, thereby modulating tumor development. Outside the therapeutic utilization of protons, high-energy protons constitute a principal component of galactic cosmic rays and thus are a consideration in carcinogenesis risk for space flight. Given that proton irradiation modulates fundamental biological processes known to decrease with aging (e.g. angiogenesis and immunogenicity), we investigated how proton irradiation impacts tumor advancement as a function of host age, a question with both therapeutic and carcinogenesis implications. Tumor lag time and growth dynamics were tracked, after injection of murine Lewis lung carcinoma (LLC) cells into syngeneic adolescent (68 day) vs. old (736 day) C57BL/6 mice with or without coincident irradiation. Tumor growth was suppressed in old compared to adolescent mice. These differences were further modulated by proton irradiation (1 GeV), with increased inhibition and a significant radiation-altered molecular fingerprint evident in tumors grown in old mice. Through global transcriptome analysis, TGFβ1 and TGFβ2 were determined to be key players that contributed to the tumor dynamics observed. These findings suggest that old hosts exhibit a reduced capacity to support tumor advancement, which can be further reduced by proton irradiation.
authors.affiliation: Center of Cancer Systems Biology, GRI, Tufts University School of Medicine, Boston, Massachusetts 02135.
authors.forename: Afshin
authors.initials: A
authors.lastname: Beheshti
authors.forename: Michael
authors.initials: M
authors.lastname: Peluso
authors.forename: Clare
authors.initials: C
authors.lastname: Lamont
authors.forename: Philip
authors.initials: P
authors.lastname: Hahnfeldt
authors.forename: Lynn
authors.initials: L
authors.lastname: Hlatky
mesh_terms: D000375:Aging / Q000528:radiation effects; D000818:Animals; D018827:Carcinoma, Lewis Lung / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology* / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000528:radiation effects; D018450:Disease Progression; D020869:Gene Expression Profiling; D051379:Mice; D061766:Proton Therapy; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D053781:Transforming Growth Factor beta2 / Q000378:metabolism; D047368:Tumor Burden / Q000528:radiation effects
chemical_list: D053773:Transforming Growth Factor beta1; D053781:Transforming Growth Factor beta2