B-CELL PROGENITORS AND BONE MARROW MICROENVIRONMENT

B系急性淋巴细胞白血病（ALL）是最常见的形式， 儿童白血病 白血病细胞表达形态、表型和 与B淋巴细胞相同的基因型特征 正常骨髓（BM）中的祖细胞。 正常未成熟B细胞和 来自大多数B系ALL病例的细胞在体外迅速死亡，除非它们 由BM衍生的基质饲养层支持。 长期 本研究的目的是确定相似性和差异性 正常B细胞祖细胞的生长需求与其 肿瘤对应物。 这一目标将通过三个 相互关联的具体目标：1）定义基质细胞类型， 正常和白血病人未成熟B细胞; 2）鉴定生长 影响这些细胞存活、增殖和分化的因素 基质饲养层上的细胞; 3）确定细胞和分子 对于未成熟B细胞粘附到BM基质层是必需的。 这项研究的假设是白血病B细胞 前体可以在不足以维持其 正常的同行。 在目标1中，BM基质制备物的能力 在不同培养条件下生长的BM源性基质细胞 将评估支持正常和白血病母细胞的细胞系。 在目标2中，要解决的第一个问题是， 骨髓基质层的作用是通过可溶性的、膜结合的 或基质结合生长因子。 关键的识别 白血病细胞和正常B细胞的生长因子 成熟阶段将尝试通过测试的影响， 向培养物中加入细胞因子或用 特异性抗体 目标3旨在确定粘附分子， 在允许正常和白血病B- BM基质层上的细胞前体，并定义 在不同成熟阶段的正常B细胞与不同的 骨髓基质细胞成分。 支持正常和白血病的微环境的定义 B细胞祖细胞应该增加对B细胞个体发育的理解， 白血病发生 也有可能是新的临床相关的 将根据其体外试验结果确定患者亚组。 增长要求。 本项目中建立的技术应 适用于检测抗白血病药物的体外模型。

B-lineage acute lymphoblastic leukemia (ALL) is the commonest form of leukemia in children. Leukemic cells express morphologic, phenotypic and genotypic features which appear identical to those of B lymphocyte progenitors in normal bone marrow (BM). Normal immature B cells and cells from most cases of B-lineage ALL rapidly die in vitro unless they are supported by BM-derived stromal feeder layers. the long-term objective of this research is to define the similarities and differences between the growth requirements of normal B cell progenitors and their neoplastic counterparts. This goal will be attempted through three interrelated specific aims: 1) define the stromal cell types supporting normal and leukemic human immature B cells; 2) identify the growth factors that affect survival, proliferation and differentiation of these cells on stromal feeder layers; 3) determine the cells and molecules essential for adhesion of immature B cells to BM stromal layers. The hypothesis underlying this research is that leukemic B-cell precursors can expand in microenvironments inadequate to sustain their normal counterparts. In Aim 1, the ability of BM stromal preparations grown under different culture conditions and of BM-derived stromal cell lines to support both normal and leukemic blast cells will be evaluated. In Aim 2, the first question to be addressed is whether the beneficial effects of BM stromal layers are mediated through soluble, membrane-bound or matrix-bound growth factors. The identification of the essential growth factors for leukemic cells and for normal B cells at various maturative stages will be attempted by testing the effects of either adding cytokines to the cultures or neutralizing their activity with specific antibodies. Aim 3 seeks to identify the adhesion molecules that play a central role in permitting the growth of normal and leukemic B- cell precursors on BM stromal layers, and to define the pattern of adhesion of normal B cells at various stages of maturation to different BM stromal cell components. The definition of the microenvironments that support normal and leukemic B-cell progenitors should increase understanding of B-cell ontogeny and leukemogenesis. It is also possible that new clinically relevant subgroups of patients will be identified on the basis of their in vitro growth requirements. The techniques established in this project should be applicable to in vitro models for testing of antileukemic agents.