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- Original Article A study of the effect of radiation on chromosome number and tumorigenicity in a mouse tumor cell line
- Hai Won Chung, Joung Soon Kim, Won Young Lee
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Epidemiol Health 1982;4(1):175-188
DOI: https://doi.org/
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Abstract
The effects of radiation on the distribution of chromosome number in mouse Sarcoma 180 Y.S. cells were studied in respect to heterogeneity of their chromosome number and their tumorigenicity. The results summarized are as follows: 1. Modal chromosome number were shifted from 111-120 to 101-110 when the tumor cells were irradiated with 300 rad - 700 rad of γ-rays, which is in the range within the sublethal irradiation dose (700 rad). The overall distribution of chromosome number, however, was not much different from that of control ceils. Frequency distribution of hypofcetraploid cells decreased gradually by increased radiation dose, for example in control the proportion of hypotetraploid cells was 22.3% whereas the proportion decreased to 16.4% in 100 rad irradiation group, 14.5% in 200 rad, 14.8% in 300 rad, 12.9% in 500 rad, and 5.9% in 700 rad irradiation group. 2. The tumorigenicity measured by the fifty percent survival day of inoculated mice, was also reduced according to the increased radiation dose; fifty percent survival days of mice inoculated with irradiated tumor cells (104 cells/mouse) in vivo by probit analysis were 25.2, 27.2 and 30.8 days with rariation dose of 0, 300 and 700 rad respectively on day 1 after irradiation. Similar results were obtained on day 6 after irradiation and fifty percent survival days were 23.0, 27.3 and 29.8 days at 0, 300 and 700 rad respectively. Tumorigenicity of the cells was proportional to the dose of cells inoculated, but it was proportionally decreased to the radiation dose. Moreover these results were consistent with Sarcoma producing ability in syngenic mice and the DNA synthetic ability in irradiated tumor cells. Considering these findings in relation to the chromosome number of the tumor cells, the reduction of tumorigenicity by γ-radiation seems to be correlated with reduction of hypotetraploid cells. Meanwhile when tumor cells were cultured in vitro, the proportions of cells with more than 200 chromosomes were increased in accordance as the radiation dose increased; 14.3% in control, 18.4% in 500 rad and 23.6% in 700 rad irradiation group. 3. Proportions of hypotetraploid tumor cells cultured in vivo after in vivo irradiation with 700 rad were 5.4% and 6% on day 1 and 6 after irradiation respectively, and 12.7%, 10% and 9% according to serial vivo passage thereafter. On the other hand the proportions of cells with more than 200 chromosomes in in vitro cultures after in vitro irradiation with 700 rad were increased to 23.6% from 14.3% on day 2, which was then decreased to 11% on day 20 after irradiation. 4. It may be concluded that repeated sampling of tumor cells and follow-up studies are necessary during the entire clinical course from early stage of the disease in the same patient because cytogenetic feature of tumor ceil population varied all the time according to their varying culture conditions and irradiation. Furthermore the tumor cell study may be of great help in determination of the subsequent treatment method after radiotherapy and/or chemotherapy for an effective and efficient management of cancer patient.
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