Yen A, Forbes M E
Department of Pathology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853.
Cancer Res. 1990 Mar 1;50(5):1411-20.
HL-60 human nonlymphocytic leukemia cells undergo terminal differentiation along either the myeloid or monocytic pathway in a process previously shown to involve two sequential steps, early events leading to a precommitment state and late events leading to onset of terminal differentiation. The present report shows that bromodeoxyuridine induces the early events leading to precommitment. In this course bromodeoxyuridine causes the rapid down regulation of the c-myc protooncogene. The course is similar to other common inducers of HL-60 differentiation including retinoic acid, dimethyl sulfoxide, 1,25-dihydroxyvitamin D3, and sodium butyrate. HL-60 cells which were initially exponentially proliferating were exposed to 10 microM bromodeoxyuridine for 24 h, a period corresponding to one division cycle in these cells. When the cells were subsequently exposed to either retinoic acid or 1,25-dihydroxyvitamin D3, onset of G1/0 specific growth arrest and display of the differentiated phenotype occurred within 24 h. This is in contrast to the 48-h exposure needed for onset of terminal differentiation if either inducer is used singly during continuous exposure, as has been reported previously. Thus bromodeoxyuridine consummated the early events, including the rapid down regulation of c-myc message levels, which occur during the first division cycle of the induced cellular metabolic cascade leading to onset of terminal differentiation. The ability of bromodeoxyuridine to drive events in the metabolic cascade leading to onset of terminal differentiation was specific for early events, inasmuch as it was relatively ineffective at driving late events. Down regulation of c-myc was not in itself sufficient to result in subsequent terminal differentiation, since pulse exposure to bromodeoxyuridine followed by culture in inducer free medium resulted in little G1/0 specific growth arrest or phenotypic differentiation. Continuous exposure to bromodeoxyuridine, in contrast, resulted in significant G1/0 specific growth arrest but little phenotypic differentiation, indicating that the regulation of cell cycle transit and differentiation are separable.
HL-60人非淋巴细胞白血病细胞沿髓系或单核细胞途径进行终末分化，此前已证明该过程涉及两个连续步骤，早期事件导致预决定状态，晚期事件导致终末分化的开始。本报告表明，溴脱氧尿苷诱导导致预决定的早期事件。在此过程中，溴脱氧尿苷导致c-myc原癌基因迅速下调。该过程与HL-60分化的其他常见诱导剂相似，包括视黄酸、二甲基亚砜、1,25-二羟基维生素D3和丁酸钠。最初呈指数增殖的HL-60细胞暴露于10微摩尔溴脱氧尿苷24小时，这一时期相当于这些细胞的一个分裂周期。随后当细胞暴露于视黄酸或1,25-二羟基维生素D3时，在24小时内出现G1/0特异性生长停滞并表现出分化表型。这与之前报道的如果在连续暴露期间单独使用任何一种诱导剂，终末分化开始需要48小时的暴露形成对比。因此，溴脱氧尿苷完成了早期事件，包括在诱导细胞代谢级联反应的第一个分裂周期中发生的c-myc信使水平的迅速下调，该级联反应导致终末分化的开始。溴脱氧尿苷驱动导致终末分化开始的代谢级联反应中的事件的能力对早期事件具有特异性，因为它在驱动晚期事件方面相对无效。c-myc的下调本身不足以导致随后的终末分化，因为脉冲暴露于溴脱氧尿苷后在无诱导剂培养基中培养几乎没有导致G1/0特异性生长停滞或表型分化。相比之下，持续暴露于溴脱氧尿苷导致显著的G1/0特异性生长停滞，但几乎没有表型分化，表明细胞周期进程和分化的调节是可分离的。
