MECHANISMS OF ABERRANT IG EXPRESSION IN CHRONIC LEUKEMIA

慢性淋巴细胞白血病（CLL）是最常见的形式 白血病在西方国家，其特点是 主要成熟的CD 5 +B淋巴细胞的单克隆增殖。 表面免疫球蛋白（IG）表达，通常减少 在CLL中，通常需要B29基因的蛋白产物， B细胞抗原受体复合物（BCR）易位至 细胞表面和信号转导。 因为B29是必不可少的 用于B细胞抗原的细胞内组装和转运 受体复合物的细胞表面，我们假设， 干扰B29基因可能导致表达减少 以及白血病C11细胞表面IG的功能。 我们的研究 现在发现B29基因的表达异常， CLL。 对18例慢性淋巴细胞白血病的临床分析表明， 超过80%的患者B29表达较低或缺失， 直接影响其表面IG表达水平。 其中一半 表面B29低/-病例没有或几乎检测不到 通过RNA酶保护测定的B29 mRNA。 到目前为止，所有的CLL 具有正常B29 mRNA水平的样本具有点突变， 或通过RT-PCR和测序鉴定的截短， 显著影响B29蛋白的结构和/或功能。 本研究提案的主要目标是确定 CLL中B29基因的特异性畸变谱， 确定其后果，然后最终将这些 疾病发病机制的异常。 PCR/SSCP分析 来自更多CLL病例的基因组DNA预计将 确定B29突变，将通过直接 测序 RNA酶保护试验和RT-PCR将用于 鉴定可变剪接和其他B29 mRNA变体。 突变B29构建体与其他rBCR的共转染 组分表达载体应该复制在 CLL。 原代CLL细胞维持在表达CD 40 L的载体上。 蛋鸡将被正常的B29牛痘病毒感染 表达载体并测定BCR表面表达。 BCR 信号转导、细胞周期进程和对 还将测定“校正的”CLL细胞的凋亡。 从 研究提出，它将清楚地表明，突变 针对这些B29突变的治疗， 在CLL中诱导IG表面表达增加， CLL对细胞毒化疗的敏感性。

Chronic Lymphocytic leukemia (CLL) is the most prevalent form of leukemia in Western countries, and is characterized by a monoclonal proliferation of primarily mature CD5+B lymphocytes. Surface immuno-globulin (Ig) expression, which is often decreased in CLL, normally requires the protein product of the B29 gene for translocation of the B cell antigen receptor complex (BCR) to the cell surface and for signal transduction. Because B29 is essential for intracellular assembly and transport of the B cell antigen receptor complex to the cell surface, we postulate that a perturbationin the B29 gene could result in diminished expression and function of surface ig in leukemic Cll cells. Our studies have now revealed aberrations in the expression of the B29 gene in CLL. Analysis of 18 unselected cases of CLL demonstrate that over 80% had low to absent B29 expression which correlated directly to their level of surface ig expression. Half of these surface B29low/-cases had either no or barely detectable levels of B29 mRNA by RNAse protection assay. To date, all of the CLL samples with normal B29 mRNA levels have had point mutations or truncations identified by RT-PCR and sequencing which would significantly effect the structure and/or function of B29 protein. The primary objectives of this research proposal ae to define the spectrum of specific aberrations of the B29 gene in CLL, to determine their consequences and then finally to relate these abnormalities to disease pathogenesis. PCR/SSCP analysis of genomic DNA from a larger panel of CLL cases is expected to identify B29 mutations which will be confirmed by direct sequencing. RNAse protection assays and RT-PCR will be used to identify alternative spliced and other B29 mRNA variants. Cotransfection of mutant B29 constructs with othe rBCR component expression vectors should reproduce the defects seen in CLL. Primary CLL cells maintained on a CD40L expressing geeder layer will be infected with a normal B29 vaccinia viral expression vector and assayed for BCR surface expression. BCR signal transduction, cell cycle progression and sensitivity to apoptosis of "corrected" CLL cells will also be determined. From the studies proposed, it will be clearly demonstrated that mutations of directed at correctign these B29 mutations are expected to induce increased ig surface expression in CLL and may improve the sensitivity of CLL to cytotoxic chemotherapy.