Slapak C A, Kharbanda S, Saleem A, Kufe D W
Laboratory of Clinical Pharmacology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
J Biol Chem. 1993 Jun 15;268(17):12267-73.
Previous studies have demonstrated that human HL-60 myeloid leukemia cells differentiate in response to phorbol esters. This event is associated with induction of the c-jun early response gene and appearance of a monocytic phenotype. The present studies have examined the effects of vincristine-selected, multidrug resistance on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced HL-60 cell differentiation. The results demonstrate that multidrug-resistant HL-60 cells, designated HL-60/vinc, fail to respond to TPA with an increase in c-jun transcripts or other phenotypic characteristics of monocytic differentiation. By contrast, treatment of HL-60/vinc cells with okadaic acid, an inhibitor of serine/threonine protein phosphatases, induces c-jun transcription, growth arrest, and expression of the c-fms gene. Studies were also performed with an HL-60/vinc revertant (HL-60/vinc/R) line that has regained partial sensitivity to vincristine. The finding that HL-60/vinc/R cells respond to TPA with induction of a monocytic phenotype, but not c-jun expression, suggests that c-jun induction is not obligatory for monocytic differentiation. Other studies further demonstrate that the jun-B and fra-1 genes are induced by TPA in both HL-60/vinc and HL-60/vinc/R cells, whereas c-fos expression is attenuated in the HL-60/vinc line. Since TPA activates protein kinase C (PKC), we examined translocation of PKC from the cytosol to the membrane fraction. Although HL-60 and HL-60/vinc/R cells demonstrated translocation of PKC activity, this subcellular redistribution was undetectable in HL-60/vinc cells. Activity of the mitogen-activated protein kinase family with associated phosphorylation of c-Jun Y-peptide was markedly diminished in TPA-treated HL-60/vinc cells, but not in response to okadaic acid. Taken together, these findings suggest that vincristine resistance confers insensitivity to TPA-induced differentiation and can include defects in PKC-mediated signaling events and induction of jun/fos early response gene expression.
先前的研究表明，人类HL-60髓系白血病细胞会对佛波酯产生分化反应。这一事件与c-jun早期反应基因的诱导及单核细胞表型的出现有关。目前的研究检测了长春新碱筛选出的多药耐药性对12-O-十四烷酰佛波醇-13-乙酸酯（TPA）诱导的HL-60细胞分化的影响。结果表明，多药耐药的HL-60细胞，即HL-60/长春新碱细胞，对TPA无反应，c-jun转录本或单核细胞分化的其他表型特征均未增加。相比之下，用丝氨酸/苏氨酸蛋白磷酸酶抑制剂冈田酸处理HL-60/长春新碱细胞，可诱导c-jun转录、生长停滞及c-fms基因的表达。还对一种已恢复对长春新碱部分敏感性的HL-60/长春新碱回复株（HL-60/长春新碱/R）进行了研究。HL-60/长春新碱/R细胞对TPA有反应并诱导出单核细胞表型，但不诱导c-jun表达，这一发现表明c-jun的诱导并非单核细胞分化所必需。其他研究进一步证明，TPA在HL-60/长春新碱细胞和HL-60/长春新碱/R细胞中均能诱导jun-B和fra-1基因，而HL-60/长春新碱细胞系中c-fos的表达减弱。由于TPA激活蛋白激酶C（PKC），我们检测了PKC从胞质溶胶向膜部分的转位。虽然HL-60和HL-60/长春新碱/R细胞显示出PKC活性的转位，但在HL-60/长春新碱细胞中未检测到这种亚细胞再分布。在TPA处理的HL-60/长春新碱细胞中，丝裂原活化蛋白激酶家族的活性及相关的c-Jun Y肽磷酸化明显降低，但对冈田酸无反应。综上所述，这些发现表明长春新碱耐药性导致对TPA诱导的分化不敏感，可能包括PKC介导的信号转导事件缺陷以及jun/fos早期反应基因表达的诱导缺陷。
