Metabolism and effects of 5-(beta-D-ribofuranosyl)isocytosine in P815 cells.
Metabolism and effects of 5-(beta-D-ribofuranosyl)isocytosine in P815 cells.
复制标题
P815 细胞中 5-(β-D-呋喃核糖基)异胞嘧啶的代谢和作用。
作者：
T. Chou;J. Burchenal;J. Fox;K. Watanabe;C. K. Chu;F. S. Philips
5-（β-D-呋喃核糖基）异胞嘧啶（Psil Cyd），一种C-核苷，已显示对小鼠中的P815白血病具有活性。在用[2- 14 C]psi l Cyd处理的P815细胞中，我们在核苷酸组分以及RNA和DNA中检测到放射性。标记的三磷酸核苷酸部分和RNA降解为核苷表明，存在的放射性在色谱上与psi l Cyd相同。将[2- 14 C]psi 1 Cyd掺入三磷酸核苷酸级分以及RNA和DNA的半饱和浓度分别为370、280和94微克/ml，这比氚化胞苷的半饱和浓度高100倍以上。胞苷竞争性抑制Psil Cyd的掺入。P815细胞和对1-β-D-阿拉伯呋喃糖基胞嘧啶具有抗性的P815亚系的P815细胞的核酸中的Psi 1 Cyd的磷酸化和掺入比对Psi 1 Cyd或对5-氮杂胞苷和1-β-D-阿拉伯呋喃糖基胞嘧啶两者具有抗性的P815亚系高约2- 20倍。这些数据表明，P811 Cyd的磷酸化以及可能其掺入核酸中对于P815白血病中的治疗活性是必需的。体外代谢研究还表明，psi 1 Cyd和5-氮杂胞苷是交叉抗性的，并且对psi 1 Cyd具有抗性的P815细胞对1-β-D-阿拉伯呋喃糖基胞嘧啶是间接敏感的。这些预测得到了在携带P815白血病的小鼠中进行的治疗实验的证实。
5-(beta-D-Ribofuranosyl)isocytosine (psi l Cyd), a C-nucleoside, has been shown to be active against P815 leukemia in mice. In P815 cells treated with [2-14C]psi l Cyd, we have detected radioactivity in nucleotide fractions and in RNA and DNA. Degradation to nucleosides of the labeled triphosphate nucleotide fraction and of RNA showed that the radioactivity present was chromatographically identical to psi l Cyd. Half-saturation concentrations for the incorporation of [2-14C]psi l Cyd into the triphosphate nucleotide fraction and into RNA and DNA were 370, 280, and 94 microgram/ml, respectively, which were greater than 100-fold higher than those for tritiated cytidine. The incorporation of psi l Cyd was competitively inhibited by cytidine. Phosphorylation and incorporation of psi l Cyd into nucleic acids of P815 cells and of a P815 subline resistant to 1-beta-D-arabinofuranosylcytosine are about 2- to 20-fold higher than in P815 sublines resistant to psi l Cyd or to both 5-azacytidine and 1-beta-D-arabinofuranosylcytosine. These data suggest that the phosphorylation of psi l Cyd and possibly its incorporation into nucleic acids are essential for therapeutic activity in P815 leukemias. In vitro metabolic studies also suggest that psi l Cyd and 5-azacytidine are cross-resistant and that P815 cells resistant to psi l Cyd are collaterally sensitive to 1-beta-D-arabinofuranosylcytosine. These predictions were confirmed by therapeutic experiments carried out in mice bearing P815 leukemias.