Significance and Function of HGAL in Lymphoma

描述(申请人提供)：这个项目是基于我们的发现，人类生发中心相关淋巴瘤(HGAL)的高表达是我们克隆和鉴定的一种新基因，是弥漫性大B细胞淋巴瘤(DLBCL)和霍奇金病(HD)患者长期生存的独立预测因素。最近，我们发现HGAL介导了IL-6对生发中心(Gc)B细胞迁移的抑制作用。我们证明，IL-6诱导Lyn介导的HGAL C末端酪氨酸的磷酸化，并导致HGAL重新定位到足体结构和棘状丝状足基。我们显示了内源性HGAL和肌球蛋白II之间的相互作用，并描绘了负责这种相互作用的HGAL结构域。我们提供了HGAL磷酸化导致与肌球蛋白II相互作用增加的证据，并证明了内源性HGAL的敲除改善了IL-6对细胞迁移的抑制作用。综上所述，这些结果证实HGAL是IL-6影响淋巴细胞迁移的生理介质，并提示HGAL在GC来源的淋巴瘤中的表达可能限制肿瘤的扩散，并有利于更好的临床结果。然而，尽管在确定HGAL在细胞过程中的作用方面取得了显著进展，但HGAL介导的抑制细胞迁移以及由此导致表达HGAL的肿瘤的临床预后改善的确切机制目前尚不清楚。我们的初步数据表明，HGAL可能通过与肌球蛋白II相互作用和/或通过增加RhoA活性来影响细胞运动。然而，这些影响还需要进一步调查。在本项目中，我们将：1)确定HGAL对肌球蛋白II功能的影响；2)确定HGAL对小Rho GTP酶家族成员-RhoA蛋白及其效应物的影响；3)确定HGAL肉豆蔻酰化和棕榈酰化对其抑制细胞运动的作用；以及4)确定HGAL在转基因小鼠模型中的表达对淋巴细胞分化、成熟、运动和淋巴瘤化的影响。这些研究将扩大我们对GC淋巴细胞生物学的了解，特别强调淋巴细胞的运动和迁移。此外，这些研究将揭示潜在的新机制，调节淋巴肿瘤的扩散和进展。这些机制研究可能为新的治疗方法提供新的途径。公共卫生相关性：在诊断时预测患者结局的能力至关重要。我们之前已经克隆了一个新的基因-HGAL，它被证明是霍奇金淋巴瘤和非霍奇金淋巴瘤中一个重要的预后生物标志物。我们以前已经证明，HGAL可以抑制肿瘤的迁移和扩散。在此，我们将探讨HGAL抑制细胞迁移的分子机制。这些发现不仅将阐明肿瘤扩散的机制，而且将为新的治疗干预寻找新的潜在分子靶点。

DESCRIPTION (provided by applicant): This project is based on our findings that high expression of Human Germinal center Associated Lymphoma (HGAL) - a new gene that we cloned and characterized - is an independent predictor of prolonged survival of diffuse large B cell lymphoma (DLBCL) and Hodgkin's disease (HD) patients. Recently, we demonstrated that HGAL mediates IL-6-induced inhibition of germinal center (GC) B-cell migration. We demonstrated that IL-6 induces Lyn-mediated phosphorylation of the HGAL C-terminal tyrosine and causes HGAL relocalization to podosome-like structures and spike-like filopodia. We showed interactions between endogenous HGAL and myosin II and delineated HGAL domains responsible for the interaction. We provided evidence that HGAL phosphorylation results in increased interaction with the myosin II and demonstrated that knockdown of endogenous HGAL ameliorates the inhibitory effects of the IL-6 on cell migration. Taken together, these results identified HGAL as a physiological mediator of IL-6 effects on lymphocyte migration and suggest that HGAL expression in GC-derived lymphomas may limit tumor dissemination and predispose to better clinical outcome. However, despite the marked progress in identifying HGAL role in cellular processes, the precise mechanisms of HGAL-mediated inhibition of cell migration and consequent predisposition to better clinical outcome of tumors expressing HGAL are presently unknown. Our preliminary data demonstrates that HGAL may affect cell motility by interacting with myosin II and/or by increasing RhoA activity. However, these effects need to be further investigated. In this project we will: 1) Determine effects of HGAL on myosin II function; 2) Determine effects of HGAL on a member of the small Rho GTPase family - RhoA protein and its effectors; 3) Determine the role of HGAL myristoylation and palmytoylation on its inhibitory effects on cell motility; and 4) Determine the effects of HGAL expression in transgenic mice model on lymphocyte differentiation, maturation, motility and lymphomagenesis. These studies will expand our knowledge on biology of the GC lymphocytes, with specific emphasis on lymphocyte motility and migration. Furthermore, these studies will reveal potentially new mechanisms regulating dissemination and progression of lymphoid tumors. These mechanistic studies may provide novel approaches for new therapeutic. PUBLIC HEALTH RELEVANCE: Ability to predict patients' outcome at the time of diagnosis is of paramount significance. We have previously cloned a new gene - HGAL that was demonstrated to be an important prognostic biomarker in Hodgkin's and non-Hodgkin's lymphomas. We have shown previously that HGAL inhibit tumors migration and dissemination. Herein we will investigate molecular mechanisms of HGAL-induced inhibition of cell migration. These findings will not only elucidate the mechanisms of tumor dissemination but also will identify a new potential molecular target for novel therapeutic intervention.