Frankel Lisa B, Lykkesfeldt Anne E, Hansen Jens B, Stenvang Jan
Department of Tumor Endocrinology, Institute of Cancer Biology, Danish Cancer Society, Strandboulevarden 49, 2100 Copenhagen, Denmark.
Breast Cancer Res Treat. 2007 Aug;104(2):165-79. doi: 10.1007/s10549-006-9399-1. Epub 2006 Oct 24.
Development of resistance to antiestrogen treatment in breast cancer patients is a serious therapeutic problem. The molecular mechanisms contributing to resistance are currently unclear; however it is known that increased activation of growth signaling pathways is involved. Protein Kinase C alpha (PKCalpha) is associated with a diverse range of cancers and is previously shown to be overexpressed in three out of four antiestrogen resistant breast cancer cell lines. In this study we investigated whether PKCalpha contributes to antiestrogen resistant growth. A panel of nine resistant cell lines was investigated, all of which displayed elevated levels of PKCalpha expression relative to parental MCF-7 cells. Stable PKCalpha overexpression in MCF-7 cells significantly reduced sensitivity to the antiestrogens, tamoxifen and ICI 182,780. Two resistant cell lines were chosen for further studies: tamoxifen resistant MCF-7/TAM(R)-1 (TAM(R)-1) and ICI 182,780 resistant MCF-7/182(R)-6 (182(R)-6). Treatment with the PKCalpha inhibitor Ro-32-0432 resulted in a preferential growth inhibition of these two cell lines relative to MCF-7 cells. Moreover, transient down-regulation of PKCalpha resulted in a 30-40% growth inhibition of TAM(R)-1 and 182(R)-6, while MCF-7 remained unaffected. Stable PKCalpha knock-down in TAM(R)-1 using small hairpin RNA, resulted in a tamoxifen sensitive "MCF-7-like" growth phenotype, while the same approach in 182(R)-6 cells did not alter their sensitivity to ICI 182,780. These results demonstrate a functional contribution of PKCalpha to tamoxifen resistant growth. Furthermore, our data suggest the potential for PKCalpha as a marker for antiestrogen resistance and as a promising therapeutic target in the treatment of tamoxifen resistant breast cancer.
乳腺癌患者对抗雌激素治疗产生耐药性是一个严重的治疗难题。目前尚不清楚导致耐药性的分子机制；然而已知生长信号通路的激活增加与之相关。蛋白激酶Cα（PKCα）与多种癌症相关，先前研究表明在四分之三的抗雌激素耐药乳腺癌细胞系中其表达上调。在本研究中，我们调查了PKCα是否促成抗雌激素耐药性生长。我们研究了一组9种耐药细胞系，所有这些细胞系相对于亲本MCF - 7细胞均显示出PKCα表达水平升高。在MCF - 7细胞中稳定过表达PKCα显著降低了对抗雌激素他莫昔芬和ICI 182,780的敏感性。选择了两种耐药细胞系进行进一步研究：他莫昔芬耐药的MCF - 7/TAM(R)-1（TAM(R)-1）和ICI 182,780耐药的MCF - 7/182(R)-6（182(R)-6）。用PKCα抑制剂Ro - 32 - 0432处理导致这两种细胞系相对于MCF - 7细胞优先生长受抑制。此外，PKCα的瞬时下调导致TAM(R)-1和182(R)-6的生长抑制30 - 40%，而MCF - 7不受影响。使用小发夹RNA在TAM(R)-1中稳定敲低PKCα，导致出现对他莫昔芬敏感的“MCF - 7样”生长表型，而在182(R)-6细胞中采用相同方法并未改变它们对ICI 182,780的敏感性。这些结果证明PKCα对他莫昔芬耐药性生长具有功能性作用。此外，我们的数据表明PKCα有潜力作为抗雌激素耐药性的标志物以及作为治疗他莫昔芬耐药乳腺癌的有前景的治疗靶点。
