Localization and quantitation of expression of the cell motility-related protein thymosin beta15 in human breast tissue.

Thymosin beta15 is a newly discovered 5300-Da protein that binds actin monomers and inhibits actin polymerization and might thus increase cellular motility. Thymosin beta15 is upregulated at both the mRNA and protein levels in prostate cell lines in a manner directly related to their capacity to metastasize. We hypothesize that because this protein is upregulated in cells with a propensity to metastasize, it might be a useful prognostic marker in breast cancer. Because this is a newly described protein, neither the subcellular localization of thymosin beta15 or its expression in breast cancer has been examined. We describe the use of an affinity-purified polyclonal antibody to show that within breast epithelium, thymosin beta15 is localized diffusely throughout the cytoplasm and that thymosin beta15 is upregulated in malignant (compared with benign) breast tissue. In contrast to the prostate model, thymosin beta15 is upregulated in nonmetastatic breast cancer and even ductal carcinoma in situ (compared with benign breast tissue), and, consequently, it might represent a potential early marker for breast malignancy. Additional studies are needed to evaluate the precise role and prognostic value of thymosin beta15 in breast cancer.

细胞运动相关蛋白胸腺素β15在人乳腺组织中表达的定位和定量。

胸腺素β15是一种新发现的5300-Da蛋白，它结合肌动蛋白单体并抑制肌动蛋白聚合，因此可能增加细胞运动性。胸腺素β15在前列腺细胞系的mRNA和蛋白水平上以与其转移能力直接相关的方式被上调。我们假设，因为这种蛋白在有转移倾向的细胞中上调，它可能是乳腺癌的一个有用的预后标志。因为这是一种新描述的蛋白质，胸腺素β15的亚细胞定位或其在乳腺癌中的表达都没有被检测。我们描述了使用亲和纯化的多克隆抗体来显示在乳腺上皮细胞中，胸腺素β15广泛分布于整个细胞质中，并且胸腺素β15在恶性乳腺组织(与良性相比)中上调。与前列腺模型相反，胸腺素β15在非转移乳腺癌甚至导管原位癌中上调(与良性乳腺组织相比)，因此，它可能代表乳腺恶性肿瘤的潜在早期标志物。需要额外的研究来评估胸腺素β15在乳腺癌中的确切作用和预后价值。