ELSEVIER l Biology Contribution Int. J. Radiation Oncology Biol. Phys., Vol. 37. I\io. i. pp. 163-169, 1997 Copyright 0 1997 Elsevier Science Inc. Printed in the (JSA. Ail rights reserved 0360-3016/97 %I700 t .OO PII so360-3016(96)00449-x CHARACTERIZATION AND RADIOSENSITIVITY AT HIGH OR LOW DOSE RATE OF FOUR CELL LINES DERIVED FROM HUMAN THYROID TUMQRS CBCILE CHALLETON, M.D.,**+ FELICIA BRANEA, M.D.,**+ MARTIN SCHLUMBERGER, M.D.,*,+ NADINE GAILLARD, PH.D.,* FLORENT DE VATHAIRE, PH.D.,$ CHRISTOPHE BADIE, M.Sc.,” PATRICK ANTONINI, PH.D.” AND CLAUDE PARMENTIER, M.D.**+ *Service de Medecine Nucleaire, ‘INSERM U 66, *INSERM U 351, “INSERM U 247, “CNRS 1JRA I 158, Institut Gustave Roussy, Villejuif, France Purpose: This study attempted to establish cell lines derived from human differentiated thyroid tumors, and to characterize and evaluate the radiation dose-rate effect. Methods and l+Sateriais: Two cell lines (Kl and K2) were derived from papilhq carcinomas, one (K7) from a follicular less-dtfferentlated carcinoma and one (A14) radiition were established by the in vitro colony meth Gy/h) or low doserate (0.6 Gy/h) by a “Co source. T and multltarget modelof radiation action. Results:Doubling times were around 24 h. All cell lines were positive for httracelhdar adenosine monophosphate (CAMP) response to thyrotropm (TSH) was fortheceIllhmsdori~from the follbmlar adenoma and follicular carchmma. The two cell lines derived from -Were tumorigenic after ino&ation into nude mice. (SF2) wasnot signigcantly different for the thr 0.42. For the adenoma cell line A14, we found parameter.After low-dose-rate irradiation, only onecell line (K2) showed a signiiant low-dose-rate sparhtg with a dose reduction factor of 1.35. Conclusion:The major result of our study is the weak effect of the doserate on the survival of thyroid cell lines. Copyright 0 1997 Elsevier Science Inc. Human thyroid tumoral cell lines,Intrinsic radiosensitivity, Low-dose-rate irradiation. INTRODUCTION The effects of ionizing radiation on thyroid tissue are of particular interest, because 13’1 and external radiotherapy are used as therapy after incomplete surgery or for distant metastases in patients with differentiated thyroid carci- noma (16). However, these two modalities have different dose rates. We thought that better knowledge of the effect of the dose and dose rate on the survival of thyroid cells should contribute to a better understanding of the effec- tiveness of radiation therapy in thyroid cancer patients. Permanent cultures of thyroid tumor cells permit de- tailed analyses of radiation-induced effects. Indeed, this technique provides pure populations of tumor cells, com- pared to primary cultures which contain multiple cell pop- ulations. Although many human tumor cell lines have al- ready been established, cell lines originating from epithelial tumors are still rare. To our knowledge, only four cell lines have been obtained from nonmedullary thy- roid carcinoma ($7, 9, 15), and no cell line derived from a thyroid adenoma has been reported so far. We therefore decided to conduct a study to evaluate the intrinsic radiosensitivity of four cell lines derived from human thyroid tumors. The establishment, characteriza- tion, and intrinsic radiosensitivity, at high and low dose rates, of the cell lines are presented. METHODS AND MATERIALS Tissue culture Sterile thyroid tissue was obtained at surgery. Surgical fragments were cut into small pieces and subjected to me- chanical agitation for 90 min at 37°C in a solution con- taining 0.05% trypsin and 0.029% EDTA in 0.9% NaCl. Cells were collected and washed, and 2 X lo6 cells in 7 ml of medium were seeded into 25cm2 plastic flasks for culture. Flasks were incubated at 37°C in a 5% CO2 hu- Reprintrequests to: CecileChalleton, M.D., OPRI, BP no. 35, undebted to Mrs. Ingrid Ktichenthal and Lorna Saint-Angefor 78110Le Vesinet, France. linguistic revision of the manuscript. They also thank Professor Acknowledgements-This work wassupported in part by a grant E. P. Malaisefor helpful comments. from the Fondation pour la Recherche Mtdicale. Theauthors are Acceptedfor publication5 September 1996 163