title: A combination of high dose rate (10X FFF/2400 MU/min/10 MV X-rays) and total low dose (0.5 Gy) induces a higher rate of apoptosis in melanoma cells in vitro and superior preservation of normal melanocytes.
abstract: The aim of this study was to determine the apoptotic effects, toxicity, and radiosensitization of total low dose irradiation delivered at a high dose rate in vitro to melanoma cells, normal human epidermal melanocytes (HEM), or normal human dermal fibroblasts (HDF) and to study the effect of mitochondrial inhibition in combination with radiation to enhance apoptosis in melanoma cells. Cells irradiated using 10X flattening filter-free (FFF) 10 MV X-rays at a dose rate of 400 or 2400 MU/min and a total dose of 0.25-8 Gy were analyzed by cell/colony counting, MitoTracker, MTT, and DNA-damage assays, as well as by quantitative real-time reverse transcriptase PCR in the presence or absence of mitochondrial respiration inhibitors. A dose rate of 2400 MU/min killed on average five-fold more melanoma cells than a dose rate 400 MU/min at a total dose of 0.5 Gy and preserved 80% survival of HEM and 90% survival of HDF. Increased apoptosis at the 2400 MU/min dose rate is mediated by greater DNA damage, reduced cell proliferation, upregulation of apoptotic genes, and downregulation of cell cycle genes. HEM and HDF were relatively unharmed at 2400 MU/min. Radiation induced upregulation of mitochondrial respiration in both normal and cancer cells, and blocking the respiration with inhibitors enhanced apoptosis only in melanoma cells. A high dose rate with a low total dose (2400 MU/min, 0.5 Gy/10X FFF 10 MV X-rays) enhances radiosensitivity of melanoma cells while reducing radiotoxicity toward HEM and HDF. Selective cytotoxicity of melanoma cells is increased by blocking mitochondrial respiration.
authors.affiliation: aThe Genomics and Biomarkers Program, University Medical Center bClinical Division, Hackensack University Medical Center, The John Theurer Cancer Center, Hackensack, New Jersey, USA.
authors.forename: Sreeja
authors.initials: S
authors.lastname: Sarojini
authors.forename: Andrew
authors.initials: A
authors.lastname: Pecora
authors.forename: Natasha
authors.initials: N
authors.lastname: Milinovikj
authors.forename: Joseph
authors.initials: J
authors.lastname: Barbiere
authors.forename: Saakshi
authors.initials: S
authors.lastname: Gupta
authors.forename: Zeenathual M
authors.initials: ZM
authors.lastname: Hussain
authors.forename: Mehmet
authors.initials: M
authors.lastname: Tuna
authors.forename: Jennifer
authors.initials: J
authors.lastname: Jiang
authors.forename: Laura
authors.initials: L
authors.lastname: Adrianzen
authors.forename: Jaewook
authors.initials: J
authors.lastname: Jun
authors.forename: Laurice
authors.initials: L
authors.lastname: Catello
authors.forename: Diana
authors.initials: D
authors.lastname: Sanchez
authors.forename: Neha
authors.initials: N
authors.lastname: Agarwal
authors.forename: Stephanie
authors.initials: S
authors.lastname: Jeong
authors.forename: Youngjin
authors.initials: Y
authors.lastname: Jin
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Remache
authors.forename: Andre
authors.initials: A
authors.lastname: Goy
authors.forename: Alois
authors.initials: A
authors.lastname: Ndlovu
authors.forename: Anthony
authors.initials: A
authors.lastname: Ingenito
authors.forename: K Stephen
authors.initials: KS
authors.lastname: Suh
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D019610:Cytoprotection / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008544:Melanocytes / Q000502:physiology / Q000528:radiation effects*; D008545:Melanoma / Q000473:pathology*; D011829:Radiation Dosage; D014965:X-Rays