Analysis of radiation-induced changes to human melanoma cultures using a mathematical model.
OBJECTIVE
Tumour cells respond to ionizing radiation by cycle arrest, cell death or repair and possible regrowth. We have developed a dynamic mathematical model of the cell cycle to incorporate transition probabilities for entry into DNA replication and mitosis. In this study, we used the model to analyse effects of radiation on cultures of five human melanoma cell lines.


METHODS
Cell lines were irradiated (9 Gy) prior to further culture and harvesting at multiple points up to 96 h later. Cells were fixed, stained with propidium iodide and analysed for G(1)-, S- and G(2)/M-phase cells by flow cytometry. Data for all time points were fitted to a mathematical model. To provide unique solutions, cultures were grown in the presence and absence of the mitotic poison paclitaxel, added to prevent cell division.


RESULTS
The model demonstrated that irradiation at 9 Gy induced G(2)-phase arrest in all lines for at least 96 h. Two cell lines with wild-type p53 status additionally exhibited G(1)-phase arrest with recovery over 15 h, as well as evidence of cell loss. Resumption of cycling of surviving cells, as indicated by increases in G(1)/S and G(2)/M-phase transitions, was broadly comparable with results of clonogenic assays.


CONCLUSIONS
The results, combined with existing data from clonogenic survival assays, support the hypothesis that a dominant effect of radiation in these melanoma lines is the induction of long-term cell cycle arrest.
Basse
B
B
Auckland Cancer Society Research Centre, The University of Auckland, Auckland, New Zealand.
Joseph
W R
WR
Marshall
E S
ES
Baguley
B C
BC
D002453:Cell Cycle / Q000528:radiation effects*; D045744:Cell Line, Tumor; D004261:DNA Replication / Q000528:radiation effects; D004273:DNA, Neoplasm / Q000737:chemistry; D005434:Flow Cytometry; D006801:Humans; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D008962:Models, Theoretical; D011839:Radiation, Ionizing; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D004273:DNA, Neoplasm; D016159:Tumor Suppressor Protein p53
Cytometry. 1991;12(2):119-26
1710959
Oncol Res. 1993;5(8):301-9
8012062
Radiat Res. 2001 Jan;155(1 Pt 2):248-253
11121242
Science. 2003 Jun 6;300(5625):1542-8
12791985
Eur J Cancer. 1995;31A(2):230-7
7718330
EMBO J. 2003 Oct 15;22(20):5612-21
14532133
Cancer Res. 1996 Feb 15;56(4):840-7
8631022
Cancer Cell Int. 2001 Nov 23;1(1):1
11983025
Eur J Cancer. 1994;30A(9):1370-6
7999427
Oncol Res. 2000;12(3):149-55
11216673
Radiat Res. 2005 Jan;163(1):53-62
15606307
J Math Biol. 2004 Oct;49(4):329-57
15657794
Biochem Cell Biol. 2003 Jun;81(3):123-9
12897845
Cell Cycle. 2007 Apr 15;6(8):943-50
17387280
Math Biosci. 2008 May;213(1):40-9
18433802
J Math Biol. 2003 Oct;47(4):295-312
14523574
Bull Math Biol. 2005 Jul;67(4):815-30
15893554
Bull Math Biol. 2007 Jul;69(5):1673-90
17361361
Int J Radiat Oncol Biol Phys. 2004 Jul 15;59(4):928-42
15234026
Cytometry. 1989 Nov;10(6):695-705
2582959
Prog Biophys Mol Biol. 2004 Jun-Jul;85(2-3):353-68
15142752
Cancer Res. 1996 Feb 15;56(4):816-25
8631019