Neuro-Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA.
Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA.
Neuro Oncol. 2024 Jun 3;26(6):1083-1096. doi: 10.1093/neuonc/noad252.
The cell cycle is tightly regulated by checkpoints, which play a vital role in controlling its progression and timing. Cancer cells exploit the G2/M checkpoint, which serves as a resistance mechanism against genotoxic anticancer treatments, allowing for DNA repair prior to cell division. Manipulating cell cycle timing has emerged as a potential strategy to augment the effectiveness of DNA damage-based therapies.
In this study, we conducted a forward genome-wide CRISPR/Cas9 screening with repeated exposure to the alkylating agent temozolomide (TMZ) to investigate the mechanisms underlying tumor cell survival under genotoxic stress.
Our findings revealed that canonical DNA repair pathways, including the Ataxia-telangiectasia mutated (ATM)/Fanconi and mismatch repair, determine cell fate under genotoxic stress. Notably, we identified the critical role of PKMYT1, in ensuring cell survival. Depletion of PKMYT1 led to overwhelming TMZ-induced cytotoxicity in cancer cells. Isobologram analysis demonstrated potent drug synergy between alkylating agents and a Myt1 kinase inhibitor, RP-6306. Mechanistically, inhibiting Myt1 forced G2/M-arrested cells into an unscheduled transition to the mitotic phase without complete resolution of DNA damage. This forced entry into mitosis, along with persistent DNA damage, resulted in severe mitotic abnormalities. Ultimately, these aberrations led to mitotic exit with substantial apoptosis. Preclinical animal studies demonstrated that the combination regimen involving TMZ and RP-6306 prolonged the overall survival of glioma-bearing mice.
Collectively, our findings highlight the potential of targeting cell cycle timing through Myt1 inhibition as an effective strategy to enhance the efficacy of current standard cancer therapies, potentially leading to improved disease outcomes.
细胞周期受到检查点的严格调控，这些检查点在控制细胞周期的进程和时间方面起着至关重要的作用。癌细胞利用 G2/M 检查点作为对细胞毒性抗癌治疗的抵抗机制，允许在细胞分裂前进行 DNA 修复。操纵细胞周期时间已成为增强基于 DNA 损伤的治疗效果的潜在策略。
在这项研究中，我们进行了正向全基因组 CRISPR/Cas9 筛选，对烷基化剂替莫唑胺（TMZ）进行重复暴露，以研究在遗传毒性应激下肿瘤细胞存活的机制。
我们的研究结果表明，包括共济失调毛细血管扩张突变（ATM）/范可尼和错配修复在内的经典 DNA 修复途径决定了遗传毒性应激下的细胞命运。值得注意的是，我们确定了 PKMYT1 在确保细胞存活方面的关键作用。PKMYT1 的耗竭导致癌症细胞在 TMZ 诱导的细胞毒性作用下不堪重负。等剂量图分析表明，烷化剂和 Myt1 激酶抑制剂 RP-6306 之间存在强大的药物协同作用。在机制上，抑制 Myt1 迫使 G2/M 期阻滞的细胞在不完全解决 DNA 损伤的情况下进入无计划的有丝分裂阶段。这种强制性进入有丝分裂，加上持续的 DNA 损伤，导致严重的有丝分裂异常。最终，这些异常导致有丝分裂退出并伴有大量细胞凋亡。临床前动物研究表明，TMZ 和 RP-6306 的联合方案延长了荷瘤小鼠的总生存期。
总之，我们的研究结果强调了通过抑制 Myt1 来靶向细胞周期时间的潜力，作为增强当前标准癌症治疗效果的有效策略，可能会改善疾病结果。
