Background: Breast cancer is the most frequent cancer in women. Green tea has been studied for breast cancer chemopreventive and possibly chemotherapeutic effects due to its high content in polyphenolic compounds, including epigallocatechin-3-gallate (EGCG).

Method: This review is based on literature research that included papers registered on the Medline® database. The research was conducted through PubMed, applying the following query: “EGCG”AND "breast cancer”. The result was a total of 88 articles in which this review stands on.

Results: In vitro, EGCG shows antioxidant or pro-oxidant properties, depending on the concentration and exposure time. EGCG blocks cell cycle progression and modulates signaling pathways that affect cell proliferation and differentiation. EGCG also induces apoptosis, negatively modulates different steps involved in metastasis, and targets angiogenesis by inhibiting VEGF transcription. In vivo investigations have shown that oral administration of EGCG results in the reduction of tumor growth and in antimetastatic and antiangiogenic effects in animal xenograft and allograft models.

Discussion: Much remains unknown about the molecular mechanisms involved in the protective effects of EGCG on mammary carcinogenesis. In addition, more studies in vivo are necessary to determine the potential toxicity of EGCG at higher doses and to elucidate its interactions with other drugs.

Conclusion: A protective effect of EGCG has been shown in different experimental models and under different experimental conditions, suggesting clinical implications of EGCG for breast cancer prevention and therapy. The data presented in this review support the importance of further investigations.

背景：乳腺癌是女性最常见的癌症。由于绿茶中含有高含量的多酚化合物，包括表没食子儿茶素 3-没食子酸酯 (EGCG)，绿茶已被研究用于乳腺癌的化学预防和可能的化学治疗作用。

方法：本综述基于文献研究，包括在 Medline® 数据库中注册的论文。该研究是通过 PubMed 进行的，应用以下查询：“EGCG”AND“breast cancer”。结果共有 88 篇文章，该评论在其中。

结果：在体外，EGCG 显示出抗氧化或促氧化特性，具体取决于浓度和暴露时间。EGCG 阻断细胞周期进程并调节影响细胞增殖和分化的信号通路。EGCG 还诱导细胞凋亡，负向调节参与转移的不同步骤，并通过抑制 VEGF 转录来靶向血管生成。体内研究表明，在动物异种移植物和同种异体移植物模型中，口服 EGCG 可减少肿瘤生长，并具有抗转移和抗血管生成作用。

讨论：关于 EGCG 对乳腺癌发生保护作用的分子机制仍有很多未知。此外，还需要更多的体内研究来确定较高剂量 EGCG 的潜在毒性并阐明其与其他药物的相互作用。

结论：EGCG 的保护作用已在不同的实验模型和不同的实验条件下显示出来，表明 EGCG 对乳腺癌预防和治疗的临床意义。本综述中提供的数据支持进一步调查的重要性。