Tamoxifen Inhibits TRPV6 Activity via Estrogen Receptor-Independent Pathways in TRPV6-Expressing MCF-7 Breast Cancer Cells
Tamoxifen Inhibits TRPV6 Activity via Estrogen Receptor-Independent Pathways in TRPV6-Expressing MCF-7 Breast Cancer Cells
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DOI：
10.1158/1541-7786.mcr-09-0188
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发表时间：
2009-12-01
影响因子：
5.2
通讯作者：
Hediger, Matthias A.
中科院分区：
文献类型：
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作者：
Bolanz, Katrin A.;Kovacs, Gergely Gy.;Hediger, Matthias A.
与正常乳腺组织相比，上皮钙通道TRPV 6在乳腺癌中上调。选择性雌激素受体调节剂他莫昔芬广泛用于乳腺癌治疗。以前，我们表明，他莫昔芬抑制TRPV 6转染非洲爪蟾卵母细胞的钙摄取。在这项研究中，我们研究了三苯氧胺对瞬时转染EYFP-C1-TRPV 6的MCF-7乳腺癌细胞中TRPV 6功能和细胞内钙稳态的影响。使用Fura-2用荧光显微镜测量TRPV 6活性。转染细胞的基础钙水平高于未转染细胞在含钙溶液中，但不是在名义上无钙缓冲液。钙和钡的基础流入也增加。在转染细胞中，10 μ mol/L他莫昔芬降低基础细胞内钙浓度的基础钙水平的非转染细胞。三苯氧胺使转染细胞中钙和钡的转运率降低50%。雌激素受体拮抗剂ICI 182，720不能阻断这种抑制作用。类似地，在MDA-MB-231雌激素受体阴性细胞中也观察到他莫昔汀诱导的抑制作用。三苯氧胺的作用被蛋白激酶C的激活完全阻断。用钙磷蛋白C抑制蛋白激酶C可降低TRPV 6活性，但不改变他莫昔芬的作用。这些发现说明了他莫昔芬如何在雌激素受体阴性乳腺癌中有效，并表明他莫昔芬和蛋白激酶C抑制剂用于乳腺癌治疗的治疗效果可能涉及TRPV 6介导的钙离子进入。这项研究强调了TRPV 6作为乳腺癌治疗靶点的可能作用。(Mol Cancer Res 2009;7（12）：2000-10）
The epithelial calcium channel TRPV6 is upregulated in breast carcinoma compared with normal mammary gland tissue. The selective estrogen receptor modulator tamoxifen is widely used in breast cancer therapy. Previously, we showed that tamoxifen inhibits calcium uptake in TRPV6-transfected Xenopus oocytes. In this study, we examined the effect of tamoxifen on TRPV6 function and intracellular calcium homeostasis in MCF-7 breast cancer cells transiently transfected with EYFP-C1-TRPV6. TRPV6 activity was measured with fluorescence microscopy using Fura-2. The basal calcium level was higher in transfected cells compared with nontransfected cells in calcium-containing solution but not in nominally calcium-free buffer. Basal influxes of calcium and barium were also increased. In transfected cells, 10 mu mol/L tamoxifen reduced the basal intracellular calcium concentration to the basal calcium level of nontransfected cells. Tamoxifen decreased the transport rates of calcium and barium in transfected cells by 50%. This inhibitory effect was not blocked by the estrogen receptor antagonist, ICI 182,720. Similarly, a tamoxiten-induced inhibitory effect was also observed in MDA-MB-231 estrogen receptor-negative cells. The effect of tamoxifen was completely blocked by activation of protein kinase C. Inhibiting protein kinase C with calphostin C decreased TRPV6 activity but did not alter the effect of tamoxifen. These findings illustrate how tamoxifen might be effective in estrogen receptor-negative breast carcinomas and suggest that the therapeutic effect of tamoxifen and protein kinase C inhibitors used in breast cancer therapy might involve TRPV6-mediated calcium entry. This study highlights a possible role of TRPV6 as therapeutic target in breast cancer therapy. (Mol Cancer Res 2009;7(12):2000-10)