STEM CELL AGE AND X-RAY CHEMOTHERAPY LEUKEMOGENESIS

X射线/烷化剂诱导白血病的机制尚不清楚。 小鼠长期骨髓培养物或克隆 白细胞介素-3（IL-3）依赖的多能造血祖细胞 1000万分之一到十万分之一摩尔 L-苯丙氨酸芥（L-PAM）在体外24个月诱导变异 具有包括稳定标记染色体的异常的细胞系， IL-3的生长需求降低了一万倍， 向红细胞/嗜碱性粒细胞/中性粒细胞谱系的分化能力，但 没有可检测的体内致白血病性。 相比之下， 至十万分之一的L-PAM暴露或50-500戈伊X-照射， 纯化的骨髓基质培养物或克隆基质细胞系诱导 相同的IL-3依赖系在琼脂覆盖物中的集落形成， 在系统中没有可检测的IL-3的情况下， 的 300个这样的单独去除和传代培养的集落，25个是IL-3 25例中有3例在体外产生白血病。 连续 需要将覆盖的造血靶细胞暴露14-21天 通过这种致白血病基质因子诱导可检测的转化 （LSF）。 我们现在建议阐明基质细胞表型参与 体液间接转化造血干细胞的机制 细胞通过L-PAM处理或X-照射的骨髓基质细胞。 方法将 包括蛋白质生物化学;长期骨髓培养;纯化 基质和造血干细胞培养物;对照，先前 照射或烷化剂处理的小鼠;测定 粒细胞-巨噬细胞祖细胞（GM-CFUc），多能性 造血干细胞重建试验、脾集落试验 （CFU），以及体内克隆细胞系的白血病发生性的测定。 这些 研究应有助于阐明辐照和烷基化的机理 在联合化疗存活的患者中诱导白血病， 放射治疗恶性肿瘤。

The mechanism of x-ray/alkylating agent induced leukemia is unknown. Chronic exposure of murine long-term bone marrow cultures or clonal Interleukin-3 (IL-3) dependent multipotential hematopoietic progenitor cell lines to one-ten-millionth to one one-hundred thousandth molar L-Phenylalanine Mustard (L-PAM) over 24 months in vitro induces variant cell lines with abnormalities including stable marker chromosomes, ten-thousandfold decreased IL-3 growth requirement, and altered differentiation capacity to erythroid/basophil/neutrophil lineages, but with no detectable in vivo leukemogenicity. In contrast, one-ten-millionth to one one-hundred thousandth L-PAM exposure or 50-500 Gy x-irradiation of purified marrow stromal cultures or a clonal stromal cell line induces colony formation by the same IL-3 dependent lines in agar overlay at one-hundred thousand in the absence of detectable IL-3 in the system. Of 300 such individually removed and subcultured colonies, 25 were IL-3 independent and 3 of the 25 produced leukemia in vitro. Continuous exposure of overlaid hematopoietic target cells for 14-21 days was required to induce detectable transformation by this leukemogenic stromal factor (LSF). We now propose to elucidate the stromal cell phenotype(s) involved and the mechanism of humoral indirect transformation of hematopoietic stem cells by L-PAM treated or x-irradiated marrow stromal cells. Methods will include protein biochemistry; long-term bone marrow cultures; purified stromal and hematopoietic stem cell cultures from; control, previously irradiated or alkylating agent treated mice; assays for granulocyte-macrophage progenitor cells (GM-CFUc), pluripotential hematopoietic stem cells by reconstitution assay, spleen colony assay (CFUs), and assays for leukemogenecity of clonal cell lines in vivo. These studies should help elucidate the mechanism of irradiation and alkylating induced leukemia in patients surviving combination chemotherapy and irradiation therapy for malignancy.