Research on DNA biosynthesis in human hematologic malignant cells.

本研究旨在探讨DNA重生和挽救途径在血液系统恶性细胞DNA合成中的作用，为临床合理化疗提供依据。对16种不同细胞增殖率的人血液系统恶性细胞系进行了核糖核苷酸还原酶、胸苷激酶活性和胸腺嘧啶核苷掺入率的测定。细胞增殖率与核糖核酸还原酶活性密切相关，而与胸苷激酶活性及胸腺嘧啶核苷掺入率无关。这些结果表明，在培养的人类恶性肿瘤细胞中，高增殖潜力可能主要依赖于DNA生物合成的从头开始的嘧啶途径。然后，通过检测双嘧达莫对DNA生物合成挽救途径的有效阻断剂双嘧达莫对人血液系统恶性细胞生长的影响，研究该挽救途径在血液系统恶性细胞生长中的应用范围和作用。这些数据表明，在过氧化物酶阳性的非淋巴细胞系中，脱氧核苷酸供应的挽救途径比在淋巴细胞系中更重要。挽救通路的阻滞剂，如尚未使用的潘生丁，可能在临床上有用。其次，对核糖核苷酸还原酶的组成进行了研究。核糖核苷酸还原酶由M1亚基“效应器结合亚基”和M2亚基“非铁亚基”组成。结果表明，在所有血液系统恶性细胞中，M1亚基的数量均多于M2亚基。因此，使用M2-亚基的特异性抑制剂可能会提供更多潜在的抑制细胞增殖的作用。

The role of de novo and salvage pathways for DNA biosynthesis in human hematologic malignant cells was investigated to provide further informations for appropriate chemotherapy. The activities of ribonucleotide reductase and thymidine kinase, and the thymidine incorporation rate were measured in 16 cultured human hematologic malignant cell lines with different cell proliferation rates. A close correlation was found between the cell proliferation rate and ribonucleotide reductase activity, but not thymidine kinase activity or the thymidine incorporation rate. These results indicate that in cultured human malignant cells a high potential for proliferation may depend mainly on the de novo pyrimidine pathway of DNA biosynthesis. Then, the extent of use and role of the salvage pathway of pyrimidine metabolism for DNA biosynthesis in the growth of human hematologic malignant cells were studied by examining the effect of dipyridamole, an effective blocker of this salvage pathway on their growth. The data indicate that the salvage pathway for deoxynucleotide supply is more important in peroxidase-positive non-lymphoid cell lines than in lymphoid cell lines. Blockers of salvage pathway like dipyridamole which has not been used might be useful clinically. Next, the component of ribonucleotide reductase was investigated. Ribonucleotide reductase is concisted of M1-subunit "effector binding subunit" and M2-subunit "nonhem iron subunit". It became clear that the amount of M1-subunit was more than that of M2-subunit in any hematologic malignant cells. Therefore, the use of specific inhibitor of M2-subunit might provide more potential inhibitory effect of cellular proliferation.