Room: Exhibit Hall
Purpose: The fusion reaction (p + Â¹Â¹B ->3Î±) has been suggested as a means to convert stopping protons into low-energy and high linear energy transfer (LET) Î±-particles, which can potentially cause more damage to DNA. The idea is to load the target with Â¹Â¹B using sodium borocaptate (BSH), a drug developed for Boron Neutron Capture Therapy (BNCT). Our goal is to investigate the extent of the cell kill enhancement in-vitro, at Â¹Â¹B concentrations achievable in BNCT.
Methods: CHO (Chinese hamster ovary) cells were loaded with Â¹Â¹B by dissolving BSH in F12k culture media. Cells were incubated overnight, plated the next morning and irradiated in the media containing BSH (with Â¹Â¹B concentrations of 0, 40 and 80 ppm), which were removed after irradiation. Cells were placed at the Bragg peak of a 71 MeV proton beam with a dose-averaged LET of 4.35 keV/micron. Cell survival was determined using clonogenic assays and survival curves fitted using the linear-quadratic model. Plating efficiency was studied to assess potential cytotoxic effects of BSH on the cells.
Results: Plating efficiencies at the three concentrations investigated were in agreement, suggesting that the cytotoxicity of BSH was low. Analysis of clonogenic survival curves showed no evidence for increased CHO cell kill with the addition of BSH. A preliminary estimate of the Î±-particle yield suggests that this should be expected, since the number of alphas was ~1x10â?µ lower than the number of incident protons.
Conclusion: A previous study reported a twofold increase in cell kill when DU145 cells were irradiated with protons in the presence of 40 and 80 ppm of Â¹Â¹B. Our result, although obtained with a different cell line, contradicts these findings. Future work will include repeating this study using a human cancer cell line and performing Monte Carlo simulations to evaluate the yield of Î±-particles.