Comparison of in vitro drug sensitivity by inhibition of tritium release from [5-3H]-2'-deoxyuridine and a clonogenic assay.
In a search for a rapid and simple method to determine drug-induced cell lethality, the inhibition of tritium release from [5-3H]-2'-deoxyuridine (ITR) was compared with a standard clonogenic assay. Seven drugs were studied. After a 4 hr incubation period, [5-3H]-2'-deoxyuridine was added to cultures of human colon carcinoma cells (HCT-8) in vitro and four dose-response curves were generated for each drug by sampling the culture medium for tritiated H2O formation 4, 24, 48 and 72 hr later. These curves were compared to those obtained by a standard clonogenic assay. The ED50 values for 5 of the 7 drugs tested, methotrexate, 5-fluorouracil, doxorubicin, vincristine and cisplatin, as measured by inhibition of HCT-8 colony growth, were within 3 times the values observed with the metabolic assay. The ITR highly overestimated the cytotoxicity of 5-fluoro-2'-deoxyuridine: the irreversible inhibition of thymidylate synthase by this nucleoside resulted in an ED50 value 100-fold lower than that observed with the clonogenic assay. Opposite results were obtained with 5-fluorouridine. These data indicate that the ITR can be used to determine drug sensitivity of these cells to a host of compounds although it cannot be used indiscriminately for every antineoplastic agent as a cytotoxicity assay.
Aschele
C
C
Department of Medical Oncology, Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy.
Romanini
A
A
Nicolin
A
A
Rosso
R
R
Sobrero
A
A
D000230:Adenocarcinoma; D000970:Antineoplastic Agents / Q000494:pharmacology*; D003110:Colonic Neoplasms; D003114:Colony-Forming Units Assay / Q000379:methods*; D003857:Deoxyuridine / Q000378:metabolism*; D006801:Humans; D011865:Radioisotope Dilution Technique; D014316:Tritium; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D014410:Tumor Stem Cell Assay / Q000379:methods*
D000970:Antineoplastic Agents; D014316:Tritium; D003857:Deoxyuridine