The Effect of Deazaadenosines on the X-Ray Response of Human Tumor Cell Spheroid

研究了腺苷二氮杂衍生物对x射线致潜在致死损伤（PLDR）修复的影响。1-和7-去氮杂腺苷（C^1-和C^7-Ado）辐照后可有效抑制高原期HeLa RC-355细胞的PLDR，而3-去氮杂腺苷（C^3-Ado）对修复无影响。C^1-Ado对x射线照射的人骨肉瘤细胞多细胞球体的PLDR也有抑制作用。由于已知C^7-Ado在哺乳动物细胞中被磷酸化，而C^3-Ado不被磷酸化，因此我们研究了该途径对PLDR抑制的意义。检测C^1-Ado对RC-355细胞腺苷激酶缺陷型x射线PLDR的影响。药物对变异细胞没有任何作用。结果表明，腺苷激酶的活性对药物的修复抑制作用至关重要。在C^1-和C^7-Ado处理的RC-355细胞中，通过HPLC分析核苷酸进一步研究了去氮腺苷的细胞代谢。分析表明，这些药物被代谢成三磷酸盐。随着药物剂量的增加，三磷酸地氮腺苷的相对比例增加。另一方面，正常ATP的含量降低，使deaza-ATP和ATP的总量保持不变。GTP和UTP的池大小在10 ~ 50 mM的浓度范围内基本保持不变。这些结果表明，去氮核苷和去氮核苷被腺苷代谢酶识别为正常底物。然而，已经证明C^1-Ado不被细胞腺苷脱氨酶代谢。由于C^1-Ado酶负责多种腺苷类似物的细胞内失活，因此预计C^1-Ado在组织中相对稳定。此外，该药物还具有高水溶性和低细胞毒性等特性，具有临床应用的可行性。结果表明，C^1-Ado有望成为提高恶性肿瘤放射治疗效率的临床药物原型。少

The effects of deaza-derivatives of adenosine on the repair of the X-ray-induced potentially lethal damage (PLDR) were studied. Post-irradiation treatment with 1- and 7-deazaadenosines (C^1- and C^7-Ado) effectively suppressed PLDR in plateau-phase HeLa RC-355 cells, while 3-deazaadenosine (C^3-Ado) had no effect on the repair. C^1-Ado also inhibited PLDR of the X-irradiated multicellular spheroid of human osteosarcoma cells. Since it has been known that C^7-Ado is phosphorylated in mammalian cells while C^3-Ado is not, the significance of the pathway for the PLDR inhibition was studied. The effect of C^1-Ado on X-ray PLDR of the adenosine kinase-deficient variant of RC-355 cells was tested. The drug did not exert any effect on the variant cells. The result indicated that the activity of adenosine kinase is essential for the repair inhibitory effect of the drug. Further cellular metabolism of the deazaadenosines was investigated by HPLC analysis of the nucleotides in log- and plateau-p … More hase RC-355 cells treated with C^1- and C^7-Ado.Analysis showed that these drugs were metabolized into tri-phosphates. Increases in the relative ratios of deazaadenosine triphosphates were observed with increased doses of the drugs. On the other hand, the content of normal ATP was decreased, so that the total amount of deaza-ATP and ATP was constant. The pool size of GTP and UTP remained almost constant within the concentration range tested (10-50 mM). These results suggest that the deazanucleosides and deazanucleotides are recognized as normal substrates by the adenosine-metabolizing enzymes. However, it has been shown that C^1-Ado is not metabolized by cellular adenosine deaminase. Since the enzyme is responsible for the intracellular inactivation of a variety of adenosine analogs, C^1-Ado is expected to be relatively stable in the tissue. In addition, the drug also has properties, such as its high water solubility and the low cytotoxicity, which make it feasible for clinical use. It is concluded that C^1-Ado is a promising candidate for a prototype of a clinical drug which would improve the efficiency of radiation treatment of malignant tumors. Less