Caltagirone S, Ranelletti F O, Rinelli A, Maggiano N, Colasante A, Musiani P, Aiello F B, Piantelli M
Department of Pathology, Gabriele D'Annunzio University, Chieti, Italy.
Am J Respir Cell Mol Biol. 1997 Jul;17(1):51-9. doi: 10.1165/ajrcmb.17.1.2728.
The antiestrogen tamoxifen is thought to antagonize the effects of estrogens by competing with them for estrogen receptor (ER) binding. However, tarnoxifen can also reverse multidrug resistance, synergize with cisplatin cytotoxicity, and inhibit growth in ER-negative lung cancer cells. In addition to ERs, rat and human target tissues contain a second binding macromolecule termed the type II estrogen binding site (type II EBS). It has been shown that tamoxifen and flavonoids, a widely distributed class of natural substances with a variety of biologic actions, bind to type II EBS and inhibit the growth of several tumor cell types. At present, conflicting data about ERs and an absence of data about type II EBSs exist for lung tumors. We have tested non-small-cell lung carcinoma cell lines and primary tumor cells for the presence of ERs and type II EBSs and have evaluated the effects of tamoxifen and quercetin (pentahydroxyflavone) on the growth of these cells. Using a whole-cell assay and nuclear and cytosolic radiobinding experiments with [3H]estradiol as tracer, we have found that SK-LU1, SW900, ChaGo-K-1, H441, H661, and A549 cells, as well as primary tumors, bind estrogen specifically. This binding results mainly from the presence of a large number of type II EBSs, whereas ERs are absent or present at low concentrations. Type II EBSs bound tamoxifen and quercetin with similar affinity. Cell counts and a thymidine incorporation assay showed that both compounds inhibit cell growth in a concentration-dependent manner at concentrations ranging from 10 nM to 1 microM. Neither ipriflavone, an isoflavone, nor rutin, the 3-rhamnosylglucoside of quercetin, bound type II EBSs or inhibited cell growth. These findings suggest that tamoxifen and quercetin could regulate lung cancer cell growth through a binding interaction with type II EBSs. This mechanism could also be active in vivo, in that we have observed that nuclear and cytosolic type II EBSs were present in all primary lung cancers tested (n = 12), and that tamoxifen and quercetin were effective in inhibiting in vitro bromodeoxyuridine (BrdU) incorporation and proliferation-cell nuclear antigen expression by neoplastic cells in these cancers.
抗雌激素药物他莫昔芬被认为是通过与雌激素竞争雌激素受体（ER）结合来拮抗雌激素的作用。然而，他莫昔芬还能逆转多药耐药性，增强顺铂的细胞毒性，并抑制雌激素受体阴性肺癌细胞的生长。除了雌激素受体外，大鼠和人类的靶组织中还含有另一种被称为II型雌激素结合位点（II型EBS）的结合大分子。研究表明，他莫昔芬和黄酮类化合物（一类广泛分布且具有多种生物学作用的天然物质）能与II型EBS结合，并抑制多种肿瘤细胞类型的生长。目前，关于肺癌中雌激素受体存在相互矛盾的数据，且关于II型EBS的数据缺失。我们检测了非小细胞肺癌细胞系和原发性肿瘤细胞中雌激素受体和II型EBS的存在情况，并评估了他莫昔芬和槲皮素（五羟基黄酮）对这些细胞生长的影响。使用全细胞分析以及以[3H]雌二醇为示踪剂的细胞核和细胞质放射性结合实验，我们发现SK-LU1、SW900、ChaGo-K-1、H441、H661和A549细胞以及原发性肿瘤都能特异性结合雌激素。这种结合主要是由于大量II型EBS的存在，而雌激素受体不存在或浓度很低。II型EBS以相似的亲和力结合他莫昔芬和槲皮素。细胞计数和胸腺嘧啶核苷掺入实验表明，这两种化合物在10 nM至1 microM的浓度范围内均以浓度依赖性方式抑制细胞生长。异黄酮类药物依普黄酮和槲皮素的3-鼠李糖基葡萄糖苷芦丁既不与II型EBS结合，也不抑制细胞生长。这些发现表明，他莫昔芬和槲皮素可能通过与II型EBS的结合相互作用来调节肺癌细胞的生长。这种机制在体内也可能是活跃的，因为我们观察到在所有检测的原发性肺癌（n = 12）中都存在细胞核和细胞质II型EBS，并且他莫昔芬和槲皮素能有效抑制这些癌症中肿瘤细胞的体外溴脱氧尿苷（BrdU）掺入和增殖细胞核抗原表达。
