Effect of a change in reactor power on response of murine solid tumors in vivo, referring to impact on quiescent tumor cell population

• Published in: International journal of radiation biology 2019-05, Vol.95 (5), p.635-645
• Main Authors: Masunaga, Shin-ichiro, Sakurai, Yoshinori, Tanaka, Hiroki, Takata, Takushi, Suzuki, Minoru, Sanada, Yu, Tano, Keizo, Maruhashi, Akira, Ono, Koji
• Format: Article
• Language: English
• Subjects: Boron neutron capture therapy; compound biological effectiveness factor; dose rate effect; quiescent tumor cell; reactor power; Space life sciences
• ISSN: 0955-3002; 1362-3095
• DOI: 10.1080/09553002.2019.1558300

Purpose: To examine the effect of a change in reactor power on the response of solid tumors, referring to impact on quiescent (Q) tumor cell population. Materials and methods: Tumor-bearing mice received 5-bromo-2′-deoxyuridine (BrdU) to label all proliferating (P) tumor cells, and were treated with boronophenylalanine- 10 B (BPA) or sodium mercaptododecaborate- 10 B (BSH). After reactor neutron beam irradiation at a power of 1 or 5 MW with an identical beam spectrum, cells from tumors were isolated and incubated with a cytokinesis blocker. The responses of BrdU-unlabeled Q and total (P + Q) tumor cells were assessed based on the frequencies of micronucleation using immunofluorescence staining for BrdU. Results: After neutron irradiation with or without 10 B-carrier, radio-sensitivity was reduced by decreasing reactor power in both cells, especially in Q cells and after irradiation with BPA. The values of relative and compound biological effectiveness were larger at a power of 5 MW and in Q cells than at a power of 1 MW and in total cells, respectively. The sensitivity difference between total and Q cells was widened when combined with 10 B-carrier, especially with BPA, and through decreasing reactor power. Conclusion: 5 MW is more advantageous than 1 MW for boron neutron capture therapy.