ROLE OF CYSTATIN M IN BREAST TUMOR PROGRESSION

细胞-细胞相互作用的丧失、基底膜的降解和恶性上皮细胞对下层间质组织的侵袭是原发性乳腺肿瘤进展为局部和远处转移的关键事件。 越来越多的证据表明，蛋白水解酶或蛋白酶参与肿瘤进展。 近年来，几种内体/溶酶体半胱氨酸蛋白酶已被克隆，并显示在癌组织中过表达。 然而，尽管开发新疗法的巨大潜力，我们仍然对它们的蛋白水解活性的调节知之甚少。 胱抑素如胱抑素M是内体/溶酶体半胱氨酸蛋白酶的有效内源性蛋白抑制剂。胱抑素M在原发性乳腺癌中表达，但在转移性乳腺组织和许多癌细胞系中下调，因此可能代表一种新的转移抑制基因。本研究的长期目标是明确cystatin M在肿瘤生长、侵袭和转移过程中的关键控制步骤。 我们的工作假设是，半胱氨酸蛋白酶抑制剂M维持在一个休眠和非侵入性阶段的原发性乳腺肿瘤。 体内肿瘤进展本质上是复杂的。 因此，我们将开始我们的工作与建立体外模型，以确定：1。半胱氨酸蛋白酶抑制剂M是否能够抑制肿瘤细胞介导的基质降解和侵袭。 第一个具体目标将使用重组半胱氨酸蛋白酶抑制剂M以及具有改变的半胱氨酸蛋白酶抑制剂M表达的工程化人乳腺癌细胞系来解决。 这些体外研究将极大地帮助主要研究者设计和执行特定目标2的研究，该研究将分析半胱氨酸蛋白酶抑制剂M对SCID小鼠中原发性肿瘤生长、侵袭和转移的抑制功能。 该项目的整体研究所产生的新见解可能会导致设计用于治疗原发性浸润性人类乳腺癌和/或其转移的新药。

Loss of cell-cell interactions, degradation of the basement membrane and invasion of the underlying stromal tissue by malignant epithelial cells are key events in the progression of a primary breast tumor to local and distant metastases. There is increasing evidence that proteolytic enzymes, or proteases, are involved in tumor progression. In recent years several endosomal/lysosomal cysteine proteases have been cloned and shown to be overexpressed in cancer tissues. However, despite the enormous potential for development of novel therapeutics, we still understand little about the regulation of their proteolytic activity. Cystatins such as cystatin M are potent endogenous protein inhibitors of endosomal/lysosomal cysteine proteases. Cystatin M is expressed in primary human breast cancer but is downregulated in metastatic breast tissue and many cancer cell lines and could therefore represent a novel metastasis suppressor gene. The long-term objective of our studies is to define the critical steps controlled by cystatin M during tumor growth, invasion and metastasis. Our working hypothesis is that cystatin M maintains primary breast tumors in a dormant and non-invasive phase. Tumor progression in vivo is complex in nature. We will therefore begin our work with established in vitro models to determine: 1. whether cystatin M is able to inhibit tumor cell-mediated matrix degradation and invasion. The first specific aim will be addressed using recombinant cystatin M as well as engineering human breast cancer cell lines with altered expression of cystatin M. These in vitro studies should greatly help the principal investigator in designing and performing studies for specific aim 2 that will analyze the suppressing function(s) of cystatin M on primary tumor growth, invasion and metastasis in SCID mice. The new insights that should be generated by the overall research of this project may lead to the design of novel drugs for the treatment of primary invasive human breast cancers and/or their metastases.