Biology of plasma cell tumor development

人类浆细胞肿瘤最常见的是多发性骨髓瘤，一种无法治愈的癌症。参与这些肿瘤发展的生化病变难以表征，与这种疾病最常见的生物学相关性是白细胞介素-6的明显关键作用。 我们以前已经证明了胰岛素样生长因子受体I（IGF-IR）信号通路在小鼠浆细胞肿瘤发展中的作用。我们现在已经将这些研究扩展到人类骨髓瘤，并表征了通过该受体进行信号传导的生化元素和生物学效应。IGF-IR被发现在几乎所有的骨髓瘤细胞系中高度表达。用IGF-I刺激骨髓瘤细胞系导致两个细胞信号级联的激活。其中第一个导致有丝分裂原活化蛋白激酶的活化，随后是细胞增殖，第二个导致Akt激酶的活化，从而抑制通常诱导细胞死亡的过程。这两种途径的刺激的联合作用表明IGF-I信号传导可能在骨髓瘤细胞的存活中起重要作用。在体内测试了这种可能性，其中证明与未处理的对照相比，用IGF-I处理的SCID小鼠中的骨髓瘤系生长显著更快。与该途径的重要性相关的其他研究揭示了2/8株肿瘤抑制基因PTEN中的缺陷，该基因参与IGF信号传导的凋亡臂的调节。该基因在一个细胞系中的突变导致细胞死亡的显著抑制，并且正常PTEN基因的重新引入不仅恢复了正常功能，而且防止了体内肿瘤生长。 在试图确定病变的多发性骨髓瘤的开始或进展，我们已经开始了表达克隆研究，以确定候选基因。表达cDNA文库已从骨髓瘤细胞系构建并最初转染到NIH 3T3细胞中。转化的菌落已被分离，目前正在分析拯救的基因。这些被表征的第一个是细胞Ras基因，其在位置117处包含不常见的突变。来自这些文库的其他基因正在研究中。还将文库引入IL-6依赖性B9细胞和IL-3依赖性32D细胞中，以试图鉴定将消除对这些细胞因子的需求的表达基因。目前正在建立从早期诊断骨髓瘤患者中获得材料的方案，以构建相似的表达文库并寻找原发性疾病中的生化病变。 本项目前身为Z01 BC 05553 - 28 LG

Plasma cell tumors in humans most commonly occur as multiple myeloma, an incurable form of cancer. Biochemical lesions involved in the development of these tumors have been difficult to characterize and the most common biological association with this disease is an apparent critical role of Interleukin-6. We have previously demonstrated a role for the Insulin-like growth factor receptor I (IGF-IR) signaling pathway in murine plasma cell tumor development. We have now extended these studies to human myeloma and characterized the biochemical elements and biological effects of signaling through this receptor. IGF-IR was found to be highly expressed in virtually all myeloma lines. Stimulation of myeloma lines with IGF-I lead to activation of two cellular signaling cascades. The first of these resulted in activation of mitogen activated protein kinases followed by cellular proliferation, and the second the activation of Akt kinase leading to inhibition of processes normally inducing cell death. The combined effects of stimulation of these two pathways suggest that IGF-I signaling may play a significant role in survival of myeloma cells. This possibility was tested in vivo where it was demonstrated that myeloma lines grew significantly faster in SCID mice treated with IGF-I as compared to untreated controls. Additional studies relating to the importance of this pathway revealed defects in 2/8 lines in the tumor suppressor gene PTEN which participates in regulation of the apoptotic arm of IGF signaling. Mutation of this gene in one line lead to marked inhibition of cell death and re-introduction of a normal PTEN gene not only restored normal function, but prevented tumor growth in vivo . In an attempt to identify lesions contributing to either initiation or progression of multiple myeloma, we have initiated expression cloning studies to identify candidate genes. Expression cDNA libraries have been constructed from myeloma lines and transfected initially into NIH 3T3 cells. Transformed colonies have been isolated and rescued genes are currently being analyzed. The first of these to be characterized is a cellular Ras gene which contains an uncommon mutation at position 117. Additional genes from these libraries are under study. The libraries are also being introduced into IL-6 dependent B9 cells and IL-3 dependent 32D cells in an attempt to identify expressed genes which will abrogate the requirement for these cytokines. Protocols are currently being established to obtain materials from early diagnosis myeloma patients in order to construct similar expression libraries and search for biochemical lesions in primary disease. This project was formerly Z01 BC 05553-28 LG