Oncogenic transformation of C3H 10T1/2 cells exposed to alpha particles: sensitivity through the cell cycle.
Oncogenic transformation of synchronized C3H 10T1/2 cells was determined after exposure to 4.3 MeV alpha particles (LET = 101 keV/microns). Two synchronization techniques were tested using basic and modified protocols: one based on the release of cells from contact inhibition and the second on the mitotic shake-off method. Progression of cells through the cycle was followed as a function of time by flow cytometric analysis, DNA labeling for passage through S phase, the growth curve for the cell number and mitotic index measurements. The conclusion is that, although the release of cells from confluence provides higher yields of synchronized cells, mitotic shake-off proved to be the best way of collecting a synchronized population of minimally perturbed cells. Cells synchronized by mitotic shake-off were irradiated with 0.30 Gy in the interval between 2 and 10 h corresponding to G1 and early S phases. For comparison asynchronous populations were irradiated in parallel. Oncogenic transformation frequency, corrected for background, in mid-G1 phase was (18 +/- 4) x 10(-5) (average values of frequencies at 4 and 6 h) compared with the value of (8 +/- 4) x 10(-5) for the asynchronous population. While these data are suggestive of a trend toward a slightly increased sensitivity in mid-G1 phase, it is not statistically significant. The surviving fraction is constant in G1 phase.
Bettega
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Dipartimento di Fisica dell'Università degli Studi, Milan, Italy.
Calzolari
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P
Costa
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A
Chiorda
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GN
Tallone
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L
D016475:3T3 Cells; D000512:Alpha Particles; D000818:Animals; D002453:Cell Cycle / Q000528:radiation effects*; D002470:Cell Survival / Q000528:radiation effects; D002471:Cell Transformation, Neoplastic; D005434:Flow Cytometry; D007700:Kinetics; D051379:Mice; D008809:Mice, Inbred C3H; D008938:Mitosis / Q000528:radiation effects; D008940:Mitotic Index / Q000528:radiation effects; D013997:Time Factors