Temozolomide（TMZ）是一种用于胶质母细胞瘤（GBM）患者的标准治疗方法。然而，由于GBM细胞对化疗的耐药性机制尚不明确，TMZ的疗效中等。在这里，我们证明TMZ生成的5-氨基咪唑-4-甲酸二核苷（AICA）在GBM细胞中转化为AICA核糖基-5-磷酸（AICAR）。该转化过程由异黄嘌呤磷酸核糖转移酶1（HPRT1）催化，该酶在人类GBM中高表达。作为AMP激活蛋白激酶（AMPK）真正的激活剂，TMZ衍生的AICAR激活AMPK，磷酸化ribonucleotide reductase（RNR）的催化亚单位RRM1的T52，从而激活RNR，并增加dNTP的产生，以供应修复TMZ引起的DNA损伤所需。RRM1 T52A表达，HPRT1介导的AICAR生成的基因干扰或6-巯基嘌呤（6-MP）的给药，一种临床批准的HPRT1抑制剂，可阻断TMZ引起的AMPK激活，使脑肿瘤细胞对TMZ治疗敏感。此外，HPRT1表达水平与接受TMZ治疗的GBM患者的预后不良呈正相关。这些结果揭示了TMZ在GBM治疗中的关键双功能作用，导致化疗耐药性。我们的发现凸显了联合给药已临床批准的6-巯基嘌呤以克服TMZ的化疗耐药性并改善GBM治疗的潜力。© 2023. Springer Nature Limited.

Temozolomide (TMZ) is a standard treatment for glioblastoma (GBM) patients. However, TMZ has moderate therapeutic effects due to chemoresistance of GBM cells through less clarified mechanisms. Here, we demonstrate that TMZ-derived 5-aminoimidazole-4-carboxamide (AICA) is converted to AICA ribosyl-5-phosphate (AICAR) in GBM cells. This conversion is catalyzed by hypoxanthine phosphoribosyl transferase 1 (HPRT1), which is highly expressed in human GBMs. As the bona fide activator of AMP-activated protein kinase (AMPK), TMZ-derived AICAR activates AMPK to phosphorylate threonine 52 (T52) of RRM1, the catalytic subunit of ribonucleotide reductase (RNR), leading to RNR activation and increased production of dNTPs to fuel the repairment of TMZ-induced-DNA damage. RRM1 T52A expression, genetic interruption of HPRT1-mediated AICAR production, or administration of 6-mercaptopurine (6-MP), a clinically approved inhibitor of HPRT1, blocks TMZ-induced AMPK activation and sensitizes brain tumor cells to TMZ treatment in mice. In addition, HPRT1 expression levels are positively correlated with poor prognosis in GBM patients who received TMZ treatment. These results uncover a critical bifunctional role of TMZ in GBM treatment that leads to chemoresistance. Our findings underscore the potential of combined administration of clinically available 6-MP to overcome TMZ chemoresistance and improve GBM treatment.© 2023. Springer Nature Limited.