Hyaluronan Receptors in Prostate Cancer Progression

描述（由申请人提供）：透明质酸（HA）是一种高分子量阴离子多糖，在原发性前列腺肿瘤中升高。转移性前列腺癌细胞将透明质酸合成并组装成细胞周围基质，这对于体外非锚定肿瘤生长和体内肿瘤生长/血管生成至关重要。与对照组相比，表达高透明质酸合酶的前列腺肿瘤细胞在体外也更容易粘附在微血管（如骨髓）内皮细胞上，这暗示细胞周透明质酸参与了转移性前列腺肿瘤细胞在体内向骨和其他器官的归巢。事实上，我们已经提出，在转移性前列腺肿瘤细胞调整和定植不同组织（如骨）时，通过为其提供一个粘附的、富含生长因子的保护性微环境，组装富含ha的细胞外基质的能力可能为转移性前列腺肿瘤细胞提供一种选择性优势。转移性、不依赖雄激素的人前列腺癌细胞系表达高水平的两种HA受体：CD44和细胞表面RHAMM（基因名称为HMMR，也称为CD168），我们已经证明它们相互关联，并在功能上协同促进运动和侵袭，特别是通过ras转化途径。通过RNA干扰任一受体抑制CD44和/或Rhamm的内源性表达，可显著降低体外锚定非依赖性生长，而添加外源性HA可逆转这一现象。总的来说，这些和其他研究使我们提出，前列腺癌的进展是透明质酸驱动的。初步数据显示，RHAMM、HA和透明质酸酶1 （HYal1）在人前列腺癌中升高，特别是随着Gleason评分的增加，RHAMM蛋白表达增加。相反，与正常或良性增生组织相比，CD44蛋白在前列腺癌中的表达显著降低。除了在增殖和迁移/侵袭中发挥作用外，CD44还是一种内吞受体，它内化和靶向HA进行溶酶体破坏。因此，在前列腺癌中观察到的HA增加至少部分是由于CD44蛋白表达减少。CD44水平的降低和HYal 1水平的升高都有望促进HA/HA片段的积累，从而产生支持肿瘤的微环境。相反，由于在低CD44的环境中存在大量的RHAMM和HA/HA片段，化学计量有利于RHAMM-HA-CD44相互作用。数据表明，细胞表面RHAMM维持CD44在细胞表面，否定其内吞功能并促进其信号功能，“超激活”剩余的CD44，从而增加肿瘤的侵袭性。本研究的工作模型是，前列腺肿瘤扩张过程中，HA基质被合成、组装并破碎，通过与肿瘤细胞表面的RHAMM/HA/CD44复合物相互作用，形成有利于肿瘤细胞存活、生长和侵袭的微环境。我们建议选择性干扰HA/肿瘤细胞相互作用是一种可行的新辅助治疗方法，以提高当前治疗的有效性。公共卫生相关性：前列腺癌是美国男性癌症死亡的第二大原因。提出的项目将研究与恶性进展相关的前列腺肿瘤微环境分子组成的肿瘤相关变化。本提案的重点是确定这些变化促进进展的机制，并使用化合物（特定的合成肽）破坏这些机制来抑制肿瘤的生长、侵袭和转移。

DESCRIPTION (provided by applicant): Hyaluronan (HA) is a high molecular weight anionic polysaccharide that is elevated in primary prostate tumors. Metastatic prostate cancer cells synthesize and assemble HA into a pericellular matrix that is important for anchorage-independent tumor growth in vitro and tumor growth/angiogenesis in vivo. Prostate tumor cells that express elevated hyaluronan synthases also adhere more readily to microvessel (e.g. bone marrow) endothelial cells in vitro than controls implicating pericellular hyaluronan in the homing of metastatic prostate tumor cells to bone and other organs in vivo. Indeed, we have proposed that an ability to assemble an HA-rich pericellular matrix may offer metastasizing prostate tumor cells a selective advantage by providing them with an adhesive, growth factor-rich protective microenvironment as they adjust and colonize distinct tissues such as bone. Metastatic, androgen independent human prostate carcinoma cell lines express high levels of two HA receptors: CD44 and cell surface RHAMM (gene name is HMMR, also designated CD168), which we have shown to co-associate and which functionally collaborate to promote motility and invasion, particularly through Ras-transformation pathways. Inhibiting endogenous expression of CD44 and/or Rhamm with RNA interference of either receptor significantly reduces anchorage-independent growth in vitro, which is reversed by the addition of exogenous HA. Collectively, these and other studies have led us to propose that prostate cancer progression is hyaluronan-driven. Preliminary data show that RHAMM, HA and Hyaluronidase 1 (HYal1) are elevated in human prostate cancer and in particular RHAMM protein expression increases with increasing Gleason scores. In contrast, CD44 protein expression is significantly decreased in prostate cancer compared to normal or benign hyperplastic tissue. In addition to its role in proliferation and migration/invasion, CD44 is an endocytic receptor that internalizes and targets HA for lysosomal destruction. Therefore the increased HA observed in prostate cancer is at least partly due to decreased CD44 protein expression. Both the decreased CD44 levels and elevated HYal 1 are expected to promote HA/HA fragment accumulation producing a tumor-supporting microenvironment. Conversely, because abundant RHAMM and HA/HA fragments are present in an environment of low CD44, the stoichiometry favors RHAMM-HA-CD44 interactions. Data indicate that cell surface RHAMM maintains CD44 on the cell surface, negating its endocytic function and promoting its signaling function, "hyper-activating" the remaining CD44 resulting in increased aggressiveness of the tumor. The working model for this proposal is that as an HA matrix is synthesized, assembled and then fragmented by the expanding prostate tumor, it creates a microenvironment which facilitates tumor cell survival, growth and invasion by interacting with RHAMM/HA/CD44 complexes on the surface of tumor cells. We propose that selective interference with the HA/tumor cell interaction is a viable neoadjuvant therapeutic approach in patients to enhance the effectiveness of current therapies. PUBLIC HEALTH RELEVANCE: Prostate cancer is the second leading cause of cancer deaths in men in the United States. The projects proposed will study tumor associated changes in the molecular composition of prostate tumor microenvironments which are linked to malignant progression. The focus of this proposal is to determine the mechanisms by which these changes contribute to progression and to use compounds (specific synthetic peptides) that disrupt these mechanisms to inhibit tumor growth, invasion and metastasis.