Kim Mi Kyoung, Park Gwang Hun, Eo Hyun Ji, Song Hun Min, Lee Jin Wook, Kwon Min Ji, Koo Jin Suk, Jeong Jin Boo
Department of Bioresource Sciences, Andong National University, Andong 760749, Republic of Korea.
Department of Medicinal Plant Resources, Andong National University, Andong 760749, Republic of Korea.
Fitoterapia. 2015 Mar;101:162-8. doi: 10.1016/j.fitote.2015.01.010. Epub 2015 Jan 20.
Tanshinone I (TAN I) as one of the naturally occurring diterpenes from Salvia miltiorrhizae Bunge (Danshen) has been reported to exhibit an anti-cancer activity. However, the underlying mechanisms are still poorly understood. Thus, we performed in vitro study to elucidate the biological mechanism by which TAN I may induce the inhibition of cell growth in human colorectal cancer cells. The treatment of TAN I suppressed the cell proliferation in HCT116 and SW480 cells and decreased the level of cyclin D1 protein. However, the mRNA level of cyclin D1 did not changed by TAN I treatment. Inhibition of proteasomal degradation by MG132 blocked TAN I-mediated cyclin D1 downregulation and the half-life of cyclin D1 was decreased in the cells treated with TAN I. In addition, phosphorylation of cyclin D1 at threonine-286 was increased by TAN I and a point mutation of threonine-286 to alanine attenuated TAN I-mediated cyclin D1 downregulation. Inhibition of ERK1/2 suppressed cyclin D1 phosphorylation and subsequent downregulation by TAN I. From these results, we suggest that TAN I-mediated cyclin D1 downregulation may result from proteasomal degradation through its ERK1/2-mediated phosphorylation of threonine-286. In conclusion, the current study provides new mechanistic link between TAN I, cyclin D1 downregulation and cell growth in human colorectal cancer cells.
丹参酮I（TAN I）作为丹参中天然存在的二萜类化合物之一，已被报道具有抗癌活性。然而，其潜在机制仍知之甚少。因此，我们进行了体外研究，以阐明TAN I抑制人结肠癌细胞生长的生物学机制。TAN I处理可抑制HCT116和SW480细胞的增殖，并降低细胞周期蛋白D1蛋白水平。然而，TAN I处理并未改变细胞周期蛋白D1的mRNA水平。MG132抑制蛋白酶体降解可阻断TAN I介导的细胞周期蛋白D1下调，且在TAN I处理的细胞中细胞周期蛋白D1的半衰期缩短。此外，TAN I可增加细胞周期蛋白D1苏氨酸-286位点的磷酸化，将苏氨酸-286突变为丙氨酸可减弱TAN I介导的细胞周期蛋白D1下调。抑制ERK1/2可抑制细胞周期蛋白D1的磷酸化以及随后TAN I介导的下调。从这些结果来看，我们认为TAN I介导的细胞周期蛋白D1下调可能是由于其通过ERK1/2介导的苏氨酸-286磷酸化导致蛋白酶体降解所致。总之，本研究揭示了TAN I、细胞周期蛋白D1下调与人类结肠癌细胞生长之间新的机制联系。
