We investigated the novel molecular mechanisms of the antitumor effect of berberine. In this study, two different human cell lines (breast cancer MCF7 cells and non-tumorigenic epithelial MCF12A cells) were treated with various concentrations of berberine. Treatment with 1 and 10 μM berberine inhibited proliferation with G₀/G₁ cell cycle arrest in both cell lines, and treatment with 100 μM berberine triggered a marked level of cell death in MCF7 cells but not in MCF12A cells. Berberine increased the level of p53 protein and of its target p21 both time- and dose-dependently in MCF7 cells. At any concentration of berberine, immediate uptake (within 15 min) followed by predominantly mitochondrial accumulation were observed by confocal microscopy in both cell lines. At high concentrations (10 or 100 μM), accumulation in the nucleolus became prominent after the transition to the nucleoplasm, especially remarkable in MCF7 cells. Therefore, we evaluated the possibility of berberine-induced nucleolar stress and observed the disappearance of ribosomal protein (RP)L5 from the nucleolus and accumulation of p53 protein in the nucleus after treatment with 10 or 100 μM berberine in MCF7 cells. We also detected the accumulation of RPL5 and RPL11 in the nucleoplasm fraction where they bind to Mdm2. Moreover, downregulation of RPL5 inhibited berberine-driven induction of p53 and p21 and cell death in MCF7 cells. Whereas, in MCF12A cells, down-regulation of RPL5 had little effect on the growth inhibitory effect of high concentration of berberine. These results indicated that cell growth inhibition and cell death induced by higher doses (>10 μM) of berberine in MCF7 cells were due to the upregulation of p53 under the nucleolar stress response caused by a significant accumulation of berberine in the nucleoli.

我们研究了小ber碱抗肿瘤作用的新型分子机制。在这项研究中，两种不同的人类细胞系（乳腺癌MCF7细胞和非致瘤性上皮MCF12A细胞）用不同浓度的小ber碱处理。用1和10μM小ber碱处理可抑制G ₀ / G ₁增殖两个细胞系中的细胞周期停滞，并用100μM小ber碱处理触发了MCF7细胞中明显的细胞死亡水平，但未触发MCF12A细胞中。小ber碱在时间和剂量上均增加了MCF7细胞中p53蛋白及其靶标p21的水平。在任何浓度的小ber碱中，通过共聚焦显微镜在两个细胞系中均观察到立即摄取（15分钟内），然后主要是线粒体积累。在高浓度（10或100μM）下，向核质过渡后，核仁中的积累变得尤为明显，在MCF7细胞中尤为明显。因此，我们评估了黄连素诱导的核仁应激的可能性，并观察了MCF7细胞中用10或100μM的小ber碱处理后核仁中核糖体蛋白（RP）L5的消失以及p53蛋白在核中的积累。我们还检测到RPL5和RPL11在与Mdm2结合的核质部分中的积累。此外，RPL5的下调抑制了黄连素驱动的p53和p21诱导以及MCF7细胞的细胞死亡。而在MCF12A细胞中，RPL5的下调对高浓度小ber碱的生长抑制作用影响很小。这些结果表明，高剂量诱导细胞生长抑制和细胞死亡（>