Intracellular supply of dTTP is a highly regulated process and has been a key target for chemotherapeutic drug development. Thymidylate kinase (TMPK) is the key enzyme for dTTP formation in both de novo and salvage pathways. In this study, we used lentiviral-based small hairpin RNA to silence TMPK expression in p53(+/+) and p53(-/-) HCT-116 colon cancer cells. This approach was sufficient to decrease the dTTP pool gradually without affecting p53 expression and generating cytotoxicity. TMPK knockdown significantly increased doxorubicin sensitivity dramatically in p53-proficient, p53-null HCT-116, and LoVo colon cancer cells. The decrease in the dTTP pool using this approach augmented the DNA damage response and enhanced apoptotic induction after exposure to low-dose doxorubicin, leading to cell death. In contrast, silencing of thymidylate synthase which blocks the de novo pathway was incapable of sensitizing p53-null HCT-116 cells to doxorubicin-induced apoptosis because of the compensation by the salvage pathway. Our results suggest the lentiviral delivery of small hairpin RNA targeting TMPK in combination with a low dose of doxorubicin as a new approach to kill colon cancer cells regardless of p53 status.

译文

dTTP的细胞内供应是一个高度调节的过程,并且一直是化学治疗药物开发的关键目标。胸苷酸激酶 (TMPK) 是从头和挽救途径中dTTP形成的关键酶。在这项研究中,我们使用基于慢病毒的小发夹RNA来沉默结肠癌细胞中p53 (/) 和p53(-/-) HCT-116 TMPK的表达。这种方法足以逐渐减少dTTP库,而不会影响p53表达并产生细胞毒性。TMPK敲低显着提高了p53-proficient,p53-null HCT-116和LoVo结肠癌细胞中阿霉素的敏感性。使用这种方法减少的dTTP库增加了DNA损伤反应,并增强了低剂量阿霉素暴露后的凋亡诱导,导致细胞死亡。相反,由于挽救途径的补偿,阻断从头途径的胸苷酸合酶的沉默不能使p53-null HCT-116细胞对阿霉素诱导的凋亡敏感。我们的结果表明,靶向TMPK的小发夹RNA的慢病毒递送与低剂量的阿霉素相结合,是一种杀死结肠癌细胞的新方法,而与p53状态无关。

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