The TGF-Beta/MUC4 Signaling Axis in Circulating Tumor Cells of Metastatic Breast Cancer

项目摘要 转移是大多数乳腺癌死亡的原因，标准治疗未能 有效地靶向转移细胞。血液中的循环肿瘤细胞（CTC）依赖于身体 保护和化学信号的血小板生存和种子转移病灶。一种这样的化学信号是 转化生长因子β（TGF-β），其在由血小板分泌后，已显示调节CTC 基因表达和行为。TGF-β还显示上调细胞表面的表达， 糖蛋白粘蛋白-4（MUC 4）在各种细胞环境中的作用。MUC 4与肿瘤发展有关， 维持，最近观察到有助于血小板-CTC相互作用。这就提出了一个问题， 血小板分泌的TGF-β是否可以上调CTC-MUC 4，增强血小板-CTC相互作用， 产生正反馈回路。推动这项研究的假设是，血小板-TGF-β 上调CTC-MUC 4，增强CTC-血小板结合并增强转移性细胞存活。具体目标1 将使用细胞，分子， 和生物化学技术，并在体外评估MUC 4依赖性细胞侵袭性。具体目标2将 使用体外结合测定表征MUC 4在血小板-肿瘤细胞相互作用中的作用。第3章将 使用尾静脉和原位异种移植评估体内血小板-TGF-β和CTC-MUC 4串扰的作用 转移的肿瘤小鼠模型。这项研究的成功完成将揭示一种新型的血小板- CTC串扰，暴露了转移细胞存活的重要手段，并阐明了一种潜在的 乳腺癌转移预防的新治疗靶点。

PROJECT SUMMARY Metastasis is responsible for the majority of breast cancer deaths, and standard-of-care treatments fail to effectively target metastasizing cells. Circulating tumor cells (CTCs) in the bloodstream rely on the physical protection and chemical signals of platelets to survive and seed metastatic lesions. One such chemical signal is transforming growth factor beta (TGF-β), which, after secretion by platelets, has been shown to modulate CTC gene expression and behavior. TGF-β has also been shown to upregulate expression of the cell-surface glycoprotein Mucin-4 (MUC4) in various cellular contexts. MUC4 has been implicated in tumor development and maintenance and was recently observed to contribute to platelet-CTC interactions. This raises the question of whether platelet-secreted TGF-β may be upregulating CTC-MUC4, enhancing platelet-CTC interaction and generating a positive feedback loop. The hypothesis driving the proposed studies is that platelet-TGF-β upregulates CTC-MUC4, reinforcing CTC-platelet binding and enhancing metastatic cell survival. Specific Aim 1 will determine the effects of platelet-derived TGF-β on tumor cell MUC4 expression using cellular, molecular, and biochemical techniques, and assess MUC4-dependent cellular aggressiveness in vitro. Specific Aim 2 will characterize the role of MUC4 in platelet-tumor cell interactions using in vitro binding assays. Specific Aim 3 will assess the effects of platelet-TGF-β and CTC-MUC4 crosstalk in vivo using tail vein and orthotopic xenograft tumor mouse models of metastasis. Successful completion of this research will reveal a novel form of platelet- CTC crosstalk, exposing an important means by which metastasizing cells survive and illuminating a potential new therapeutic target for breast cancer metastatic prevention.