Hyaluronan Receptors in Prostate Cancer Progression

描述(申请人提供)：透明质酸(HA)是一种高相对分子质量的阴离子多糖，在原发性前列腺癌中升高。转移性前列腺癌细胞合成和组装透明质酸形成细胞外基质，对肿瘤的体外生长和体内血管生成具有重要作用。在体外，表达升高的透明质酸合成酶的前列腺肿瘤细胞也比对照组更容易与微血管(如骨髓)内皮细胞黏附，这意味着细胞周围的透明质酸在体内转移到骨和其他器官的前列腺癌细胞的归巢中。事实上，我们已经提出，组装富含HA的细胞周围基质的能力可能会为转移的前列腺癌细胞提供选择性优势，因为当它们调整和定植不同的组织(如骨)时，可以为它们提供一个粘连的、富含生长因子的保护性微环境。转移性、雄激素非依赖性的人前列腺癌细胞株高水平表达两种HA受体：CD44和细胞表面RHAMM(基因名称为HMMR，也被命名为CD168)，我们已经证明这两种受体相互关联，并在功能上协同促进运动和侵袭，特别是通过RAS转化途径。用任一受体的RNA干扰抑制CD44和/或RHAMM的内源性表达显著降低体外锚定非依赖性生长，外源HA可逆转这一作用。总而言之，这些和其他研究使我们提出前列腺癌的进展是由透明质酸驱动的。初步数据显示，RHAMM、HA和透明质酸酶1(HYAL1)在前列腺癌中升高，尤其是RHAMM蛋白的表达随着Gleason评分的增加而增加。相反，与正常或良性增生组织相比，前列腺癌组织中CD44蛋白的表达显著降低。除了在增殖和迁移/侵袭中的作用外，CD44还是一种内源性受体，内化并靶向HA以破坏溶酶体。因此，在前列腺癌中观察到的HA的增加至少部分是由于CD44蛋白表达的减少。CD44水平的降低和HYal 1的升高都有望促进HA/HA片段的积聚，产生支持肿瘤的微环境。相反，由于在低CD44的环境中存在丰富的RHAMM和HA/HA片段，因此化学计量比有利于RHAMM-HA-CD44的相互作用。数据表明，细胞表面RHAMM维持细胞表面的CD44，否定其内吞功能，促进其信号功能，过度激活剩余的CD44，从而增加肿瘤的侵袭性。这一方案的工作模式是，当HA基质被不断扩大的前列腺癌合成、组装和裂解时，它通过与肿瘤细胞表面的rhamm/HA/CD44复合体相互作用，创造一个促进肿瘤细胞生存、生长和侵袭的微环境。我们认为，对HA/肿瘤细胞相互作用的选择性干扰是一种可行的新辅助治疗方法，可以提高现有治疗的有效性。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肿瘤相关的前列腺癌微环境分子组成的变化，这些微环境与恶性进展有关。这项建议的重点是确定这些变化促进进展的机制，并使用破坏这些机制的化合物(特定的合成肽)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.