Biology Contributions
Radiosensitivity of human normal and tumoral thyroid cells using fluorescence in situ hybridization and clonogenic survival assay

https://doi.org/10.1016/S0360-3016(99)00059-0Get rights and content

Abstract

Purpose: By using cell survival as a reference, we evaluated the radiosensitivity of human normal and tumoral thyroid cells using of radiation-induced translocations.

Methods and Materials: Tissue samples were obtained from patients undergoing thyroidectomy. Cell cultures were established, irradiated with 60Co, and metaphases painted using commercial whole-chromosome 4 hybridization probe and pancentromeric probe. The clonogenic survival was assessed by conventional colony forming assay.

Results: After irradiation, normal cultured thyroid cells yielded a higher number of translocations than cultures derived from adenomas or thyroid carcinoma. The colony forming assay demonstrated, by way of the mean inactivation dose, a higher survival of thyroid carcinoma and adenoma cells than of normal thyroid cells. This difference between tumoral and nontumoral cells is significant in each method (p = 0.0001), and cannot be explained by apoptosis in irradiated malignant cells. Correlation of the results obtained by both methods is shown by comparing the survival fraction at 2 Gy (SF2) and the percentage of chromosome 4 translocations at 2 Gy.

Conclusion: These results indicate that the yield of radiation-induced translocations serves as a good and rapid prediction of the intrinsic radiosensitivity of thyroid cells, and that this test could be applied to other tumors.

Introduction

The aim of this study was to evaluate rapidly and precisely the radiosensitivity of human thyroid cells using of fluorescence in situ hybridization (FISH) and to compare the results to the well-established, but cumbersome technique of cell survival. At the Gustave Roussy Institute, differentiated thyroid carcinomas are treated by surgery followed by one or more 131I ingestions of 3.7 GBq (100 mCi) to eradicate thyroid remnants or metastases 1, 2. A dose of 3.7 GBq of iodine delivers a nonnegligible whole-body dose of 0.5 Gy, as estimated by FISH, based on the yield of stable anomalies 3, 4. Thus, assessing radiation-induced damages in thyroid tissue before treatment may be helpful in managing treatment by radioiodine. Challeton et al.(5) have shown that the radiosensitivity of different, cultured thyroid tumor tissue can be measured by clonogenic assay. Some studies based on double strand breaks and their reparation have indicated that low clonogenic survival can be linked to a misrepair of these breaks 6, 7, 8, 9. Because this lack of repair after ionizing radiation can lead to anomalies such as dicentrics and translocations, we chose to compare two methods: the clonogenic assay and the FISH technique. The clonogenic assay is, at present, the only way to estimate the radiosensitivity of a cell population. However, this technique is very time consuming. In 1986, Pinkel established a new technique based on cytogenetics that evaluates directly the radiation impact on chromosomes by measuring reciprocal translocations 10, 11. Some authors have concluded that a high level of radiation-induced reciprocal translocations in permanent cell lines is linked to a higher radiosensitivity. Nevertheless, this technique is not yet used as a predictive test because a clear correlation between the clonogenic assay and FISH technique has not been established 12, 13, 14, 15, 16, 17, 18, 19, 20, 21. If reciprocal translocations could be shown to correspond to clonogenic survival, we would be able to estimate rapidly and reliably, after surgery, the radiosensitivity of thyroid tumors, and evaluate more precisely the iodine activity to be administered to a given patient for a given pathology.

Section snippets

Cells

Normal and tumoral thyroid cells were obtained from patients with thyroid tumor followed at the Gustave Roussy Institute. During surgery (after thyroidectomy), the thyroid or the lobo-isthmectomy was evaluated extemporaneously by the histology department. Following this, a piece of tumoral and peritumoral normal thyroid tissue was sent to the laboratory, where the tissue samples were immediately cut into small pieces and agitated in a 0.05% trypsin/0.029% EDTA solution for 2 h at 37°C.

Results

The immunohistochemistry tests confirmed the follicular epithelial origin for each cell type and patient. Only a few fibroblasts remained in our thyroid cells due to the low subculture and the special culture medium without proline (23). Nevertheless, if in a clonogenic assay, a fibroblast clone was present, it could be clearly identified and was discounted 25, 40. The ploidy of our cells for chromosome 4 was 2, and not modified in higher subcultures. Figure 1 shows the results of our FISH test

Discussion

Until now, the clonogenic assay has been regarded as a reference in the evaluation of radiosensitivity. We submitted primary cultures of normal and tumoral thyroid cells to 60Co irradiation, and employed the FISH technique to estimate the yield of reciprocal translocations in order to compare it to the clonogenic assay done at the same time. The results obtained by clonogenic assay indicated three different groups of cellular survival (depending on the pathology). Normal cells appeared to be

Acknowledgements

The authors are indebted to Ms. Ingrid Küchenthal for linguistic revision of the manuscript, and wish to thank the nurses, secretaries, and everyone who lent a helping hand in this study.

References (48)

  • L. Lehmann et al.

    Cytogenetic and molecular genetic characterization of a chromosome 2 rearrangement in a case of human papillary thyroid carcinoma with radiation therapy

    Cancer Genet Cytogenet

    (1997)
  • B. Fertil et al.

    Intrinsic radiosensitivity of human cell lines is correlated with radioresponsiveness of human tumorsAnalysis of 101 published survival curves

    Int J Radiat Oncol Biol Phys

    (1985)
  • A.M. Gillenwater et al.

    Thyroid carcinoma

    Cancer Treat Res

    (1997)
  • M. Schlumberger et al.

    Tumeurs de la Thyroı̈de

    (1997)
  • R. M’kacher et al.

    Sequential biological dosimetry after a single treatment with iodine-131 for differentiated thyroid carcinoma

    J Nucl Med

    (1997)
  • R. M’kacher et al.

    Biological dosimetry in patients treated with Iodine-131 for differentiated thyroid carcinoma

    J Nucl Med

    (1996)
  • P.E. Bryant

    DNA damage, repair and chromosomal damage

    Int J Radiat Biol

    (1997)
  • J. Bussink et al.

    Repair of chromosome and DNA breaks versus cell survival in Chinese hamster cells

    Int J Radiat Biol

    (1996)
  • E. Dikomey et al.

    Correlation between cellular radiosensitivity and non-repaired double-strand breaks studied in nine mammalian cell lines

    Int J Radiat Biol

    (1998)
  • R. Greinert et al.

    Comparative study of the repair kinetics of chromosomal aberrations and DNA strand breaks in proliferating and quiescent CHO cells

    Int J Radiat Biol

    (1996)
  • D. Pinkel et al.

    Cytogenetic analysis using quantitative, high-sensitivity, fluorescence hybridization

    Proc Natl Acad Sci USA

    (1986)
  • D. Pinkel et al.

    Fluorescence in situ hybridization with human chromosome-specific librariesDetection of trisomy 21 and translocation of chromosome 4

    Proc Natl Acad Sci USA

    (1988)
  • J.M. Coco-Martin et al.

    Use of fluorescence in situ hybridization to measure chromosome aberrations as a predictor of radiosensitivity in human tumour cells

    Int J Radiat Biol

    (1994)
  • M.S. Kovacs et al.

    Stable translocation detected by fluorescence in situ hybridizationA rapid surrogate end point to evaluate the efficacy of a potentiator of tumor response to radiotherapy

    Cancer Res

    (1997)
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    This work was supported by a grant from Electricité de France.

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