An autoradiographic technique has been developed to determine the percentage of MCF-7 human breast adenocarcinoma cells in double-layer agar (DLA) culture that exhibit nuclear incorporation of 3H-thymidine (3H-TdR) after in vitro drug exposure. Depression of this percentage, termed the labeling index, correlated closely with colony count inhibition--relative to the respective control values--for cultures exposed to each of several agents including varying concentrations of 5-fluorouracil and adriamycin. If a similar autoradiographic technique can be applied to cultures from human tumor biopsy specimens, this may then lead to a clinically useful chemosensitivity assay especially applicable when DLA-cultured cell quantities are small.

中文翻译：

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确定双层琼脂培养物中MCF-7细胞化学敏感性的方法：标记指数降低和菌落计数抑制。

已经开发了一种放射自显影技术来确定双层琼脂（DLA）培养物中MCF-7人乳腺腺癌细胞的百分比，在体外药物暴露后，该细胞表现出3H-胸苷（3H-TdR）的核掺入。对于暴露于几种药物（包括不同浓度的5-氟尿嘧啶和阿霉素）的培养物，该百分比的降低（称为标记指数）与菌落计数抑制（相对于相应的对照值）密切相关。如果可以将类似的放射自显影技术应用于人类肿瘤活检标本的培养物中，那么这可能会导致临床上有用的化学敏感性测定，尤其是在DLA培养的细胞数量较少时适用。