Role of Tcl1 and Par-4 in regulation of chronic lymphocytic leukemia

描述（由申请人提供）：慢性淋巴细胞白血病（CLL），也称为小细胞淋巴瘤，占所有非霍奇金淋巴瘤病例的近30%。这是最常见的成人白血病。尽管化疗取得了进展，但CLL患者的治疗选择有限，只有适度的疗效，特别是对于B细胞受体（BCR）、del （17p13.1）和p53突变型未突变的患者。Tcl-1是一种致癌基因，最初发现在t细胞白血病中易位，在被归类为侵袭性的CLL表型中表达水平较高。利用免疫球蛋白启动子和Eμ增强子在B细胞中表达Tcl-1癌基因，建立了CLL小鼠模型。这些小鼠在13-18个月内可再生地发展为CLL，并已被证明是人类CLL的优秀模型。par4是我们发现的一种促凋亡肿瘤抑制因子，通过Fas途径和抑制NF-κB诱导癌细胞而非正常细胞凋亡。我们做了四个新的观察。首先，b细胞受体信号通路在人CLL细胞和Eμ-Tcl-1 CLL小鼠模型中都是活跃的，这反映在Src家族蛋白酪氨酸激酶（SFK）的组成性激活上。其次，我们发现Tcl1的表达在SFK的抑制下下调，这表明BCR信号在Tcl1表达中的作用。第三，我们发现与正常小鼠相比，Par-4在Eμ-Tcl1 CLL细胞中的表达下调，而其在人CLL细胞中的表达是可变的。第四，我们发现

DESCRIPTION (provided by applicant): Chronic lymphocytic leukemia (CLL), also known as small cell lymphoma, constitutes almost 30% of all cases of non-Hodgkin's lymphoma. It is the most common adult leukemia. Despite advances in chemotherapy, treatment options for CLL patients are limited with only a modest efficacy, especially for patients with unmutated types of B cell receptors (BCR), del (17p13.1) and p53 mutations. Tcl-1, an oncogene, initially found to be translocated in T-cell leukemias, has been found to be expressed at higher levels in CLL phenotypes that are classified as aggressive. A mouse model for CLL has been generated by expressing the Tcl-1 oncogene in B cells using immunoglobulin promoter and the Eμ enhancer. These mice reproducibly develop CLL in 13-18 months and have been shown to be excellent models for human CLL. Par-4 is a pro-apoptotic tumor suppressor, discovered by us, that induces apoptosis in cancer but not normal cells using both the Fas pathway and by inhibiting NF-κB. We made four novel observations. First, the B-cell receptor signaling pathway is active both in the human CLL cells and in the Eμ-Tcl-1 mouse model of CLL as reflected by constitutive activation of Src family protein tyrosine kinases (SFK). Second, we discovered that expression of Tcl1 is down regulated upon inhibition of SFK suggesting a role for BCR signaling in Tcl1 expression. Third we found that expression of Par-4 is down-regulated in Eμ-Tcl1 CLL cells compared to normal mice, while its expression has been found to be variable in human CLL cells. Fourth we discovered that Eμ-Tcl1 cells are killed by soluble Par-4 and SAC, a specific domain of Par-4 that is cytotoxic only to tumor cells. Based on these observations we hypothesize that a balance between Tcl1 and Par-4 regulated by BCR signaling decides the fate of CLL cells between survival and death. We have three specific aims. Aim 1 will determine the importance of BCR signaling and the role of specific SFKs in the regulation of Tcl-1 and Par-4 expression using the Eμ-Tcl-1 mouse model of CLL. Aim 2 will investigate the importance of Par-4 overexpression for CLL development using a newly generated inducible Par-4 transgenic mice mouse model and the Eμ-Tcl-1 mice. Aim 2 will involve preclinical studies to test the efficacy of extracellular Par-4 and SAC to inhibit CLL growth in the Eμ-Tcl-1 mouse model. The relative importance of Tcl-1 and Par-4 will be studied in Aim 3 with primary CLL cells from patients, thus translating the basic research findings in Aims 1 and 2 to clinical samples. The collaboration between UK and OSU provides us an opportunity to integrate the basic science and pre-clinical findings from the first two Aims with studies in Aim 3 using patient derived CLL cells. The exciting aspect of these studies is the possibility that soluble Par-4 or SAC can be developed into a treatment strategy for CLL cells either in isolation or in combination with SFK inhibitors or other targets that are currently being investigated in our laboratories.