Campbell M J, Gombart A F, Kwok S H, Park S, Koeffler H P
Department of Medicine, Division of Medical Sciences, University of Birmingham, Clinical Research Institute, Queen Elizabeth Hospital, Edgbaston, Birmingham, B15 2TH, UK.
Oncogene. 2000 Oct 19;19(44):5091-7. doi: 10.1038/sj.onc.1203888.
The anti-proliferative action of the seco-steroid hormone 1alpha, 25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] extends to some, but not all breast and prostate cancer cell lines. By elucidating the molecular mechanisms mediating the sensitivity of these cells, we can identify critical target genes regulated directly or indirectly by 1alpha,25(OH)2D3 and pathways potentially disrupted during transformation. In this study, we demonstrated the induction of expression of BRCA1 mRNA and protein as well as transcriptional activation from the BRCA1-promoter by 1alpha,25(OH)2D3 in the sensitive breast cancer cell line MCF-7. This was not observed in the 1alpha,25(OH)2D3-resistant breast cancer cell line MDA-MB-436. The induction of BRCA1 mRNA was blocked by cyclohexamide. This indicated that transcriptional activation was mediated indirectly by the vitamin D receptor (VDR). Inhibition of VDR protein levels by stable transformation of the anti-sense VDR in MCF-7 reduced the sensitivity of MCF-7 to 1alpha,25(OH)2D3 by 50-fold. In addition, the induction of BRCA1 protein and transcriptional activation of a BRCA1 promoter-luciferase reporter construct was abrogated in the stable transformant with the greatest reduction of VDR levels. Examination of other breast and prostate cancer cell lines revealed that sensitivity to the anti-proliferative effects of 1alpha, 25(OH)2D3 was strongly associated with an ability to modulate BRCA1 protein. Furthermore, the expression of the estrogen receptor in these cell lines strongly correlated with their sensitivity to 1alpha,25(OH)2D3 and their ability to modulate BRCA1 expression. Taken together, our data support a model whereby the anti-proliferative effects of 1alpha,25(OH)2D3 are mediated, in part, by the induction of BRCA1 gene expression via transcriptional activation by factors induced by the VDR and that this pathway is disrupted during the development of prostate and breast cancers.
甾体激素1α,25 - 二羟基维生素D3[1α,25(OH)2D3]的抗增殖作用适用于部分而非全部乳腺癌和前列腺癌细胞系。通过阐明介导这些细胞敏感性的分子机制，我们能够识别由1α,25(OH)2D3直接或间接调控的关键靶基因，以及在转化过程中可能被破坏的信号通路。在本研究中，我们证明了在敏感的乳腺癌细胞系MCF - 7中，1α,25(OH)2D3可诱导BRCA1 mRNA和蛋白的表达以及BRCA1启动子的转录激活。在对1α,25(OH)2D3耐药的乳腺癌细胞系MDA - MB - 436中未观察到这种现象。BRCA1 mRNA的诱导被环己酰亚胺阻断。这表明转录激活是由维生素D受体(VDR)间接介导的。通过在MCF - 7中稳定转染反义VDR抑制VDR蛋白水平，使MCF - 7对1α,25(OH)2D3的敏感性降低了50倍。此外，在VDR水平降低最显著的稳定转染细胞中，BRCA1蛋白的诱导和BRCA1启动子 - 荧光素酶报告基因构建体的转录激活被消除。对其他乳腺癌和前列腺癌细胞系的检测表明，对1α,25(OH)2D3抗增殖作用的敏感性与调节BRCA1蛋白的能力密切相关。此外，这些细胞系中雌激素受体的表达与其对1α,25(OH)2D3的敏感性以及调节BRCA1表达的能力密切相关。综上所述，我们的数据支持这样一种模型，即1α,25(OH)2D3的抗增殖作用部分是通过VDR诱导的因子转录激活BRCA1基因表达来介导的，并且该信号通路在前列腺癌和乳腺癌的发生发展过程中被破坏。
