Analysis of the mechanism of chemical carcinogenesis and short-term screening of tumor-promoters using clonogenic a ssay

在N-丁基-N-(4-羟基丁基)亚硝胺(BBN)治疗大鼠乳头状瘤前，观察到软琼脂中的集落形成，集落形成的数量与BBN的用量有关。结果表明，糖精钠和几种氨基酸作为大鼠膀胱癌促进剂，经亚致癌剂量的BBN处理后，均能诱导大鼠膀胱细胞集落形成，提示BBN的促癌活性与集落诱导活性之间可能存在相关性。用维甲酸处理小鼠皮肤，可抑制7，12-二甲基苯并[a]菲(DMBA)对12-0-十四酰佛波醇-13-乙酸酯(TPA)诱导的小鼠表皮细胞软琼脂集落形成。日粮中添加维生素A醋酸酯的效果。还观察了去甲二氢愈创木酸(NDGA)和盐酸奎尼卡林对大鼠膀胱细胞软琼脂集落形成的影响。亚致癌剂量的BBN对糖精钠诱导的膀胱细胞软琼脂集落形成有抑制作用。因此，将克隆形成实验应用于致癌实验可能有助于分析致癌的早期事件，并为寻找新的促癌因子和抗促癌因子提供一种短期筛选方法。

Colony formation in soft agar was observed with bladder cells prior to papilloma development in rats treated with N- Butyl-N-(4-hydroxybutyl)nitrosamine(BBN), and the number of colonies formed was dependent on the quantity of BBN consumed. It was then demonstrated that sodium saccharin and several amino acids, which are known to act as rat bladder cancer promoters, induce colony formation of rat bladder cells after treatment with subcarcinogenic dose of BBN, suggesting that there may be a correlation between tumor-promoting activity and colony inducing activity.Effect of anti-tumor-promoter on colony formation was then assessed in two-stage mouse skin carcinogenesis experiment. Soft agar colony formation of mouse epidermal cells induced by 12-0- tetradecanoylphorbol-13-acetate(TPA) after single application of 7,12-dimethylbenz[a]anthracene(DMBA) was inhibited by treatment of skin with retinoic acid. Effect of dietary retinyl acetate. nordihydroguaiaretic acid(NDGA) and quinacrine hydrochloride on soft agar colony formation of rat bladder cells was also eaaluated. Soft agar colony formation of bladder cells induced by sodium saccharin after treatment with subcarcinogenic dose of BBN was inhibited by the administration of retinyl acetate or NDGA. suggesting the possible anti-tumor-promoting activity of the two agents.Thus, an application of clonogenic assay to carcinogenesis experiment could be useful to analyse early events in carcinogenesis and provide a short-term screening method for detecting new tumor-promoters and anti-tumor-promoters.