Department of Biology, Faculty of Philosophy, Sciences and Letters at Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, São Paulo 14040‑901, Brazil.
Oncol Rep. 2020 Nov;44(5):2275-2287. doi: 10.3892/or.2020.7756. Epub 2020 Sep 7.
Information on the mechanisms that are associated with tumor resistance has the potential to provide the fundamental basis for novel therapeutic strategies. In glioblastoma (GBM), predictive biomarkers of cellular responses to temozolomide (TMZ) combined with poly‑ADP‑ribose polymerase inhibitor (PARPi) remain largely unidentified. In this context, the influence of MGMT (O6‑methylguanine DNA methyltransferase) and PTEN (phosphatase and tensin homologue deleted on chromosome ten) has been studied in addition to the occurrence of synthetic lethality involving PTEN and PARPi. The present study investigated whether PARP‑1 inhibition by NU1025 may increase the cytotoxicity of TMZ‑induced lesions in GBM cells, and whether these mechanisms can be influenced by MGMT and PTEN status. The impact of PTEN deficiency in repair pathways, and the effects of PARP‑1 inhibition and PTEN silencing, in terms of synthetic lethality, were also assessed. NU1025 combined with TMZ effectively sensitized TMZ‑resistant cells (T98G PTEN‑mutated and LN18 PTEN‑wild‑type) and TMZ‑sensitive cells (U251MG PTEN‑mutated), in contrast to NU1025 alone. However, the sensitizing effects were not observed in U87MG (PTEN‑mutated) cells, suggesting that specific genetic alterations may influence the response to drug treatment. The sensitizing effects occurred independently of MGMT activity, which was evaluated in O6‑BG‑treated cells. PTEN silencing using small interfering (si)RNA did not sensitize PTEN‑proficient cells to TMZ + NU1025, or NU1025 alone, indicating an absence of synthetic lethality. The responses to TMZ + NU1025 involved antiproliferative activity, G2/M arrest, double strand breaks and the induction of apoptosis. Following 20 days of recovery after three consecutive days of TMZ treatment, TMZ‑resistant cells were observed. However, when TMZ was combined with NU1025, the viability of T98G and LN18 cells was extremely decreased, indicating a lethal drug combination. Therefore, independently of MGMT proficiency and PTEN status, TMZ combined with PARPi may be a promising strategy that can be used to overcome TMZ acquired resistance in GBM cells.
关于与肿瘤耐药相关的机制的信息有可能为新的治疗策略提供基础。在胶质母细胞瘤（GBM）中，预测 TMZ（替莫唑胺）联合多聚 ADP 核糖聚合酶抑制剂（PARPi）的细胞反应的生物标志物在很大程度上仍未被确定。在这种情况下，除了涉及 PARPi 和 PTEN 的合成致死性之外，本研究还研究了 MGMT（O6-甲基鸟嘌呤 DNA 甲基转移酶）和 PTEN（第 10 号染色体缺失的磷酸酶和张力蛋白同源物）的影响。本研究旨在探讨 PARP-1 抑制剂 NU1025 是否可以增加 TMZ 诱导的 GBM 细胞损伤的细胞毒性，以及这些机制是否可以受到 MGMT 和 PTEN 状态的影响。还评估了 PTEN 缺陷在修复途径中的影响，以及 PARP-1 抑制和 PTEN 沉默在合成致死性方面的影响。与单独使用 NU1025 相比，NU1025 联合 TMZ 可有效增敏 TMZ 耐药细胞（T98G 中 PTEN 突变和 LN18 中 PTEN 野生型）和 TMZ 敏感细胞（U251MG 中 PTEN 突变）。然而，在 U87MG（PTEN 突变）细胞中未观察到增敏作用，表明特定的遗传改变可能影响药物治疗的反应。增敏作用独立于 MGMT 活性，在 O6-BG 处理的细胞中评估了 MGMT 活性。使用小干扰（si）RNA 沉默 PTEN 不会使 PTEN 阳性细胞对 TMZ+NU1025 敏感，也不会使 NU1025 单独敏感，表明不存在合成致死性。对 TMZ+NU1025 的反应涉及抗增殖活性、G2/M 期阻滞、双链断裂和诱导细胞凋亡。在连续 3 天 TMZ 处理后 20 天恢复期间观察到 TMZ 耐药细胞。然而，当 TMZ 与 NU1025 联合使用时，T98G 和 LN18 细胞的活力大大降低，表明这是一种致命的药物组合。因此，无论 MGMT 效率和 PTEN 状态如何，TMZ 联合 PARPi 可能是一种很有前途的策略，可以用于克服 GBM 细胞中 TMZ 获得的耐药性。
