Biology of plasma cell tumor development

人类浆细胞瘤最常见的形式是多发性骨髓瘤，这是一种无法治愈的癌症。参与这些肿瘤发展的生化病变一直难以表征，与这种疾病最常见的生物学关联是白细胞介素-6的明显关键作用。我们之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信号传导的生化要素和生物学效应。发现IGF-IR在几乎所有骨髓瘤系中都高度表达。用igf - 1刺激骨髓瘤细胞系可激活两个细胞信号级联反应。前者导致有丝分裂原激活蛋白激酶的激活，随后导致细胞增殖，后者导致Akt激酶的激活，从而抑制通常诱导细胞死亡的过程。刺激这两种通路的综合作用表明，igf - 1信号可能在骨髓瘤细胞的存活中发挥重要作用。这种可能性在体内进行了测试，结果表明，与未治疗的对照组相比，接受igf - 1治疗的SCID小鼠的骨髓瘤细胞系生长明显更快。关于这一途径重要性的其他研究发现，2/8的细胞系中肿瘤抑制基因PTEN存在缺陷，PTEN参与IGF信号通路凋亡分支的调节。该基因在一个细胞系中的突变导致细胞死亡的明显抑制，重新引入正常的PTEN基因不仅恢复了正常功能，而且在体内阻止了肿瘤的生长。在试图确定病变有助于启动或进展多发性骨髓瘤，我们已经启动了表达克隆研究，以确定候选基因。从骨髓瘤细胞系中构建了表达cDNA文库，并初步转染到NIH 3T3细胞中。转化的菌落已经被分离出来，拯救的基因目前正在被分析。首先要描述的是细胞Ras基因，它在位置117处包含一个不常见的突变。这些文库中的其他基因正在研究中。这些文库也被引入到依赖IL-6的B9细胞和依赖IL-3的32D细胞中，试图识别表达的基因，这些基因将消除对这些细胞因子的需求。目前正在制定方案，从早期诊断的骨髓瘤患者中获取材料，以构建相似的表达文库并搜索原发疾病中的生化病变。这个项目的前身是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