Zhu W Y, Jones C S, Amin S, Matsukuma K, Haque M, Vuligonda V, Chandraratna R A, De Luca L M
Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland 20892-4255, USA.
Cancer Res. 1999 Jan 1;59(1):85-90.
Treatment of estrogen receptor (ER)-positive MCF-7 human breast cancer cells with retinoic acid (RA) inhibited cell growth and increased cell adhesion to fibronectin. In contrast, ER- MDA-MB-231 cells failed to respond. Western blot analysis showed that tyrosine phosphorylation of two major bands at Mr 125,000 and Mr 68,000 was induced by RA in ER+ MCF-7 human breast carcinoma cells. However, this induction was a late phenomenon detectable at 12 and 24 h, but not within 3 h. A similar increase of tyrosine phosphorylation by RA was observed in ER+ human breast cancer cell lines T-47D and ZR-75-1, but not in the ER- cell lines MDA-MB-231, MDA-MB-453, and MDA-MB-468. Focal adhesion kinase and paxillin, which localize in focal adhesion plaques and may play important roles in the integrin signaling pathway, were identified as the major proteins showing RA-induced tyrosine phosphorylation. The retinoid X receptor-selective compound SR11237 failed to induce tyrosine phosphorylation, indicating that retinoid X receptor activation is not involved in this phenomenon. In contrast, stable overexpression of a truncated RA receptor (RAR) alpha cDNA, RARalpha403, with strong RAR dominant negative activity prevented the increase in tyrosine phosphate, suggesting that RAR signaling is involved in RA-induced tyrosine phosphorylation. Tyrosine phosphorylation was induced the most by the RAR-alpha (193836), followed by RAR-gamma (194433), but was not significantly induced by RAR-gamma (193174)-selective retinoids. This study demonstrates a coordinated albeit relatively late effect of RA on cell adhesion and tyrosine phosphorylation in ER+ human breast cancer cells and suggests RAR-alpha as the major responsible retinoid receptor.
用视黄酸（RA）处理雌激素受体（ER）阳性的MCF-7人乳腺癌细胞可抑制细胞生长，并增加细胞与纤连蛋白的黏附。相比之下，ER阴性的MDA-MB-231细胞则无此反应。蛋白质免疫印迹分析表明，在ER阳性的MCF-7人乳腺癌细胞中，RA可诱导Mr 125,000和Mr 68,000处两条主要条带的酪氨酸磷酸化。然而，这种诱导是一种晚期现象，在12小时和24小时时可检测到，但在3小时内未出现。在ER阳性的人乳腺癌细胞系T-47D和ZR-75-1中也观察到RA诱导的酪氨酸磷酸化有类似增加，但在ER阴性的细胞系MDA-MB-231、MDA-MB-453和MDA-MB-468中未观察到。黏着斑激酶和桩蛋白定位于黏着斑，可能在整合素信号通路中起重要作用，它们被确定为显示RA诱导酪氨酸磷酸化的主要蛋白质。视黄酸X受体选择性化合物SR11237未能诱导酪氨酸磷酸化，表明视黄酸X受体激活不参与此现象。相反，具有强RAR显性负活性的截短RA受体（RAR）α cDNA即RARα403的稳定过表达可阻止酪氨酸磷酸化的增加，提示RAR信号通路参与RA诱导的酪氨酸磷酸化。RAR-α（193836）诱导的酪氨酸磷酸化最为明显，其次是RAR-γ（194433），但RAR-γ（193174）选择性类视黄醇未显著诱导酪氨酸磷酸化。本研究证明了RA对ER阳性人乳腺癌细胞的细胞黏附和酪氨酸磷酸化具有协同作用，尽管这种作用相对较晚，并提示RAR-α是主要的类视黄醇受体。
