Chu Sau-Tung, Huang Chorng-Chih, Huang Chun-Jen, Cheng Jin-Shiung, Chai Kuo-Liang, Cheng He-Hsiung, Fang Yi-Chien, Chi Chao-Chuan, Su Hsing-Hao, Chou Chiang-Ting, Jan Chung-Ren
Department of Otolaryngology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan.
J Recept Signal Transduct Res. 2007;27(5-6):353-67. doi: 10.1080/10799890701699660.
The purpose of this study was to explore the effect of tamoxifen on cytosolic free Ca(2+) concentrations (Ca(2+)) and cell viability in OC2 human oral cancer cells. Ca(2+) and cell viability were measured by using the fluorescent dyes fura-2 and WST-1, respectively. Tamoxifen at concentrations above 2 microM increased Ca(2+) in a concentration-dependent manner. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+). The tamoxifen-induced Ca(2+) influx was sensitive to blockade of L-type Ca(2+) channel blockers but insensitive to the estrogen receptor antagonist ICI 182,780 and protein kinase C modulators. In Ca(2+)-free medium, after pretreatment with 1 muM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor), tamoxifen-induced Ca(2+) rises were substantially inhibited; and conversely, tamoxifen pretreatment inhibited a part of thapsigargin-induced Ca(2+) rises. Inhibition of phospholipase C with 2 microM U73122 did not change tamoxifen-induced Ca(2+) rises. At concentrations between 10 and 50 microM tamoxifen killed cells in a concentration-dependent manner. The cytotoxic effect of 23 microM tamoxifen was not reversed by prechelating cytosolic Ca(2+) with BAPTA. Collectively, in OC2 cells, tamoxifen induced Ca(2+) rises, in a nongenomic manner, by causing Ca(2+) release from the endoplasmic reticulum, and Ca(2+) influx from L-type Ca(2+) channels. Furthermore, tamoxifen-caused cytotoxicity was not via a preceding Ca(2+) rise.
本研究的目的是探讨他莫昔芬对OC2人口腔癌细胞胞质游离钙离子浓度（[Ca(2+)]i）及细胞活力的影响。分别使用荧光染料fura-2和WST-1测定[Ca(2+)]i和细胞活力。浓度高于2 microM的他莫昔芬以浓度依赖的方式增加[Ca(2+)]i。去除细胞外Ca(2+)可部分降低Ca(2+)信号。他莫昔芬诱导的Ca(2+)内流对L型Ca(2+)通道阻滞剂的阻断敏感，但对雌激素受体拮抗剂ICI 182,780和蛋白激酶C调节剂不敏感。在无Ca(2+)培养基中，用1 microM毒胡萝卜素（一种内质网Ca(2+)泵抑制剂）预处理后，他莫昔芬诱导的[Ca(2+)]i升高被显著抑制；相反，他莫昔芬预处理可抑制部分毒胡萝卜素诱导的[Ca(2+)]i升高。用2 microM U73122抑制磷脂酶C不会改变他莫昔芬诱导的[Ca(2+)]i升高。在10至50 microM浓度范围内，他莫昔芬以浓度依赖的方式杀死细胞。用BAPTA预螯合胞质Ca(2+)不能逆转23 microM他莫昔芬的细胞毒性作用。总体而言，在OC2细胞中，他莫昔芬通过引起内质网Ca(2+)释放和L型Ca(2+)通道Ca(2+)内流，以非基因组方式诱导[Ca(2+)]i升高。此外，他莫昔芬引起的细胞毒性并非通过先前的[Ca(2+)]i升高介导。
