Neoplastic transformation in vitro induced by low doses of 232 MeV protons.
The aim was to define the dose--response curve for high-energy proton-induced neoplastic transformation in vitro. The HeLa x skin fibroblast human hybrid cell assay was used to determine the frequency of neoplastic transformation following doses of 232 MeV protons (mean linear energy transfer, LET=0.44 keV microm(-1)) in the range 5-600 mGy. Proton irradiations were carried out at the Loma Linda University Proton Treatment Facility, CA, USA. The data indicate no evidence for induction of transformation below a dose of 100 mGy. At doses of 5 and 50 mGy, there is evidence for a possible suppression of transformation frequencies below that for spontaneous transformation. The shape of the dose--response curve for high-energy proton-induced transformation of the human hybrid cell line CGL1 does not follow a linear no-threshold model and shows evidence for a threshold as well as for possible suppression of transformation at doses <100 mGy, similar to that seen for other low-LET radiations.
Elmore
E
E
Department of Radiation Oncology, University of California, Irvine, CA 92697, USA.
Lao
X-Y
XY
Ko
M
M
Rightnar
S
S
Nelson
G
G
Redpath
Jl
J
D002471:Cell Transformation, Neoplastic; D004307:Dose-Response Relationship, Radiation; D006367:HeLa Cells; D006801:Humans; D018499:Linear Energy Transfer; D011522:Protons
D011522:Protons