Alpha-particle-induced neoplastic transformation in synchronized hybrid cells of HeLa and human skin fibroblasts.
Survival and oncogenic transformation frequencies were determined through the cell cycle in hybrid cells (HeLa x human skin fibroblasts), exposed to 0.30 and 0.15 Gy 4.3 MeV (LET= 101 keV/microm) alpha-particles. The cells were synchronized by mitotic collection and irradiated at times ranging from 2 to 10 h after collection, corresponding to G1 and early S. At 0.30 Gy the highest value in the transformation frequency (1.6 +/- 0.3) x 10(-4) transformants/survivor, occurred 4 h after mitotic collection, corresponding to mid-G1 and was about twice as high as that for the asynchronous population (0.7 +/- 0.1) x 10(-4) transformants/survivor. A similar pattern was seen at 0.15 Gy albeit less marked. The results are similar to previous findings with C3H10T1/2 exposed to 0.30 Gy where (1.8 +/- 0.4) x 10(-4) and (0.8 +/- 0.4) x 10(-4) transformants/survivor were found in mid-G1 and in the asynchronous population respectively. The results of both these studies with 101 keV/microm alpha particles indicate that mid-G1 cells may be more sensitive than asynchronous cells by up to a factor of two. However, it is unlikely that such a factor is sufficient to represent the cell cycle 'hot spot' for transformation postulated to explain the inverse dose-rate effect.
Bettega
D
D
Physics Department, University of Milan and I.N.F.N., Italy.
Calzolari
P
P
Piazzolla
A
A
Tallone
L
L
Redpath
J L
JL
D000512:Alpha Particles; D002452:Cell Count; D002453:Cell Cycle; D002470:Cell Survival / Q000528:radiation effects; D002471:Cell Transformation, Neoplastic / Q000528:radiation effects*; D005347:Fibroblasts / Q000528:radiation effects; D006367:HeLa Cells; D006801:Humans; D006822:Hybrid Cells; D011836:Radiation Tolerance