Simboli-Campbell M, Narvaez C J, van Weelden K, Tenniswood M, Welsh J
Department of Biochemistry, University of Ottawa, Canada.
Breast Cancer Res Treat. 1997 Jan;42(1):31-41. doi: 10.1023/a:1005772432465.
1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the active metabolite of vitamin D2 inhibits breast cancer cell growth both in vivo and in vitro. In addition to its anti-proliferative effects, 1,25(OH)2D3 induces morphological and biochemical markers of apoptosis in MCF-7 cells. In the studies reported here, we compared the effects of 1,25(OH)2D3 and EB1089, a low calcemic vitamin D analog, on cell cycle kinetics and apoptosis in MCF-7 cells. Both vitamin D compounds reduced viable MCF-7 cell number in a time and dose dependent manner, with EB1089 approximately 50 fold more potent than 1,25(OH)2D3. Flow cytometric analysis indicated that both agents induced cell cycle arrest in G, G1 which was associated with accumulation of the hypophosphorylated form of the retinoblastoma (Rb) protein. MCF-7 cells treated with either 1,25(OH)2D3 or EB1089 for 48 h exhibited characteristics of apoptosis, including cytoplasmic condensation, pyknotic nuclei, condensed chromatin and DNA fragmentation. Cells treated with either agent exhibited up regulation of proteins associated with mammary gland regression (clusterin and cathepsin B) and down regulation of the anti-apoptotic protein bcl-2. These studies demonstrate that, despite its lower calcemic activity in vivo, the vitamin D analog EB1089 induces effects that are indistinguishable from those of 1,25(OH)2D3 on cell number, cell cycle and indices of apoptosis in MCF-7 cells in vitro. In addition, since both agents rapidly down regulate estrogen receptor, disruption of estrogen dependent signalling may play a role in the induction of apoptosis by vitamin D compounds in MCF-7 cells.
1,25 - 二羟维生素D3 [1,25(OH)2D3]是维生素D的活性代谢产物，它在体内和体外均能抑制乳腺癌细胞的生长。除了具有抗增殖作用外，1,25(OH)2D3还能诱导MCF - 7细胞凋亡的形态学和生化标志物。在本文报道的研究中，我们比较了1,25(OH)2D3和低钙血症维生素D类似物EB1089对MCF - 7细胞周期动力学和凋亡的影响。两种维生素D化合物均以时间和剂量依赖性方式降低了MCF - 7活细胞数量，其中EB1089的效力比1,25(OH)2D3强约50倍。流式细胞术分析表明，两种药物均诱导细胞周期停滞于G0/G1期，这与视网膜母细胞瘤（Rb）蛋白的低磷酸化形式的积累有关。用1,25(OH)2D3或EB1089处理48小时的MCF - 7细胞表现出凋亡特征，包括细胞质浓缩、核固缩、染色质浓缩和DNA片段化。用任何一种药物处理的细胞均表现出与乳腺退化相关的蛋白质（簇集蛋白和组织蛋白酶B）上调以及抗凋亡蛋白bcl - 2下调。这些研究表明，尽管维生素D类似物EB1089在体内的降钙活性较低，但它在体外对MCF - 7细胞的细胞数量、细胞周期和凋亡指标所诱导的作用与1,25(OH)2D3无法区分。此外，由于两种药物均能迅速下调雌激素受体，雌激素依赖性信号通路的破坏可能在维生素D化合物诱导MCF - 7细胞凋亡中起作用。
