Khalkhali-Ellis Zhila, Christian Abby L, Kirschmann Dawn A, Edwards Elijah M, Rezaie-Thompson Maryam, Vasef Mohammad A, Gruman Lynn M, Seftor Richard E B, Norwood Laura E, Hendrix Mary J C
Department of Anatomy and Cell Biology and the Holden Comprehensive Cancer Center at The University of Iowa, Iowa City, Iowa 52242-1109, USA.
Clin Cancer Res. 2004 Jan 15;10(2):449-54. doi: 10.1158/1078-0432.ccr-1002-03.
Mammary epithelial cells and the majority of breast cancer tumors require estrogen for continued growth. Antiestrogen therapy alone, or in combination with other drugs, has long been a common procedure for breast cancer treatment and prophylaxis. Thus, there is a critical need to elucidate the mechanism(s) of action of antiestrogen treatment, especially for patients who are at risk of breast cancer development or who are currently receiving hormone therapy. In this study, we examined the ability of hormones to regulate the expression of a tumor suppressor gene, maspin, which is a serine protease inhibitor (serpin) that plays an important role in mammary gland development and is silenced during breast cancer progression. Specifically, our hypothesis tested the clinical efficacy of tamoxifen to regulate maspin expression.
We used maspin promoter luciferase reporter plasmids that were transfected into normal human mammary epithelial (HMEC1331) and MCF-7 breast cancer cells, followed by determination of the effect of hormones and their antagonists on maspin promoter activity. At the protein level, cytosolic fractions from both cell types before and after hormone treatment were subjected to Western blot analysis to determine maspin level.
Our studies revealed that the antiestrogen tamoxifen induces maspin promoter activity. Interestingly, antiandrogen flutamide could also induce maspin in both cell lines tested. These observations were further confirmed in patient tissues. These novel findings provide a new mechanism of action for tamoxifen under normal and pathological conditions. More significantly, these findings could have a potential impact on future therapeutic intervention strategies for breast cancer.
乳腺上皮细胞和大多数乳腺癌肿瘤需要雌激素来持续生长。单独使用抗雌激素疗法或与其他药物联合使用，长期以来一直是乳腺癌治疗和预防的常见方法。因此，迫切需要阐明抗雌激素治疗的作用机制，特别是对于有乳腺癌发生风险或正在接受激素治疗的患者。在本研究中，我们研究了激素调节肿瘤抑制基因maspin表达的能力，maspin是一种丝氨酸蛋白酶抑制剂（serpin），在乳腺发育中起重要作用，在乳腺癌进展过程中沉默。具体而言，我们的假设测试了他莫昔芬调节maspin表达的临床疗效。
我们使用maspin启动子荧光素酶报告质粒转染正常人乳腺上皮（HMEC1331）和MCF-7乳腺癌细胞，然后测定激素及其拮抗剂对maspin启动子活性的影响。在蛋白质水平上，对激素处理前后两种细胞类型的胞质组分进行蛋白质印迹分析以确定maspin水平。
我们的研究表明，抗雌激素他莫昔芬可诱导maspin启动子活性。有趣的是，抗雄激素氟他胺也可在两种测试细胞系中诱导maspin。这些观察结果在患者组织中得到进一步证实。这些新发现为他莫昔芬在正常和病理条件下提供了一种新的作用机制。更重要的是，这些发现可能对未来乳腺癌的治疗干预策略产生潜在影响。
