Herring Jason L, Sowers Mark L, Conrad James W, Hackfeld Linda C, Chang-Gu Bruce, Dilawari Rahul, Sowers Lawrence C
Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA.
MD-PhD Combined Degree Program, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555, USA.
Molecules. 2025 Aug 1;30(15):3239. doi: 10.3390/molecules30153239.
The incorporation of nucleoside analogs into DNA by polymerases, followed by their removal through base excision repair (BER), represents a promising strategy for cancer chemotherapy. In this study, we investigated the incorporation and cytotoxic effects of several nucleoside analogs-some of which are epigenetic reprogramming intermediates-in the U87 glioblastoma cell line. We found that two analogs, 5-hydroxymethyl-2'-deoxyuridine (5HmdU) and trifluorothymidine (TFT), are both cytotoxic and are efficiently incorporated into genomic DNA. In contrast, the 5-carboxy analogs-5-carboxy-2'-deoxyuridine (5CadU) and 5-carboxycytidine (5CadC)-showed no cytotoxicity and were not incorporated into DNA. Interestingly, 5-hydroxymethyl-2'-deoxycytidine (5HmdC) was cytotoxic but was not directly incorporated into DNA. Instead, it was deaminated into 5HmdU, which was then incorporated and likely responsible for the observed toxicity. 5HmdU is actively removed from DNA through the BER pathways. In contrast, TFT remains stably incorporated and is neither excised by BER nor does it hydrolyze into 5CadU-a known substrate for the DNA glycosylase SMUG1. We also found that N-benzyladenosine (BzAdo), an inhibitor of the enzyme 2'-deoxynucleoside 5'-phosphate N-hydrolase (DNPH1), enhances the cytotoxicity of 5HmdU. However, the thymidine phosphorylase inhibitor tipiracil hydrochloride (TPI) does not increase the cytotoxic effect of TFT in U87 cells. Together, these findings highlight 5HmdU and TFT as promising chemotherapeutic agents for glioblastoma, each with distinct mechanisms of action and cellular processing.
聚合酶将核苷类似物掺入DNA，随后通过碱基切除修复（BER）将其去除，这是一种很有前景的癌症化疗策略。在本研究中，我们研究了几种核苷类似物（其中一些是表观遗传重编程中间体）在U87胶质母细胞瘤细胞系中的掺入情况和细胞毒性作用。我们发现，两种类似物，5-羟甲基-2'-脱氧尿苷（5HmdU）和三氟胸苷（TFT），既有细胞毒性，又能有效地掺入基因组DNA。相比之下，5-羧基类似物——5-羧基-2'-脱氧尿苷（5CadU）和5-羧基胞苷（5CadC）——没有显示出细胞毒性，也没有掺入DNA。有趣的是，5-羟甲基-2'-脱氧胞苷（5HmdC）具有细胞毒性，但没有直接掺入DNA。相反，它被脱氨基转化为5HmdU，然后5HmdU被掺入并可能是观察到的毒性的原因。5HmdU通过BER途径从DNA中被主动去除。相比之下，TFT稳定地掺入DNA，既不被BER切除，也不会水解成5CadU（一种已知的DNA糖基化酶SMUG1的底物）。我们还发现，N-苄基腺苷（BzAdo），一种2'-脱氧核苷5'-磷酸N-水解酶（DNPH1）的抑制剂，增强了5HmdU的细胞毒性。然而，胸苷磷酸化酶抑制剂盐酸替吡嘧啶（TPI）并没有增加TFT在U87细胞中的细胞毒性作用。总之，这些发现突出了5HmdU和TFT作为胶质母细胞瘤有前景的化疗药物，它们各自具有独特的作用机制和细胞处理方式。
