Department of Pathology, Kazan State Medical University, 420012 Kazan, Russia.
Central Research Laboratory, Kazan State Medical University, 420012 Kazan, Russia.
Int J Mol Sci. 2020 Nov 22;21(22):8842. doi: 10.3390/ijms21228842.
Activation of the phosphoinositide 3-kinase (PI3K)/Akt/mTOR pathway is well documented for a broad spectrum of human malignancies supporting their growth and progression. Accumulating evidence has also implicated AKT as a potent modulator of anti-cancer therapies via regulation of DNA damage response and repair (DDR) induced by certain chemotherapeutic agents and ionizing radiation (IR). In the present study, we examined the role of AKT signaling in regulating of Rad51 turnover and cytotoxic effects of topoisomerase II inhibitor, doxorubicin (Dox) in soft tissue sarcomas (STS) and gastrointestinal stromal tumors (GIST) in vitro. Blocking of AKT signaling (MK-2206) enhanced cytotoxic and pro-apoptotic effects of Dox in vast majority of STS and GIST cell lines. The phosphorylated form of Akt co-immunoprecipitates with Rad51 after Dox-induced DNA damage, whereas Akt inhibition interrupts this interaction and decreases Rad51 protein level by enhancing protein instability via proteasome-dependent degradation. Inhibition of Akt signaling in Dox-treated cells was associated with the increased number of γ-H2AX-positive cells, decrease of Rad51 foci formation and its colocalization with γ-H2AX foci, thereby revealing unsuccessful DDR events. This was also in consistency with an increase of tail moment (TM) and olive tail moment (OTM) in Dox-treated GIST and STS cells cultured in presence of Akt inhibitor after Dox washout. Altogether, our data illustrates that inhibition of AKT signaling is STS and GIST might potentiate the cytotoxic effect of topoisomerase II inhibitors via attenuating the homology-mediated DNA repair.
磷酸肌醇 3-激酶（PI3K）/Akt/mTOR 途径的激活在广泛的人类恶性肿瘤中得到了充分的证实，支持它们的生长和进展。越来越多的证据也表明，AKT 通过调节某些化疗药物和电离辐射（IR）诱导的 DNA 损伤反应和修复（DDR），成为抗癌治疗的有效调节剂。在本研究中，我们研究了 AKT 信号在调节拓扑异构酶 II 抑制剂阿霉素（Dox）在软组织肉瘤（STS）和胃肠道间质瘤（GIST）中的 Rad51 周转率和细胞毒性作用中的作用。阻断 AKT 信号（MK-2206）增强了绝大多数 STS 和 GIST 细胞系中 Dox 的细胞毒性和促凋亡作用。Dox 诱导 DNA 损伤后，磷酸化形式的 Akt 与 Rad51 共免疫沉淀，而 Akt 抑制通过增强蛋白酶体依赖性降解来中断这种相互作用并降低 Rad51 蛋白水平。在 Dox 处理的细胞中抑制 Akt 信号与 γ-H2AX 阳性细胞数量增加、Rad51 焦点形成减少及其与 γ-H2AX 焦点的共定位有关，从而揭示了不成功的 DDR 事件。这也与在用 Akt 抑制剂处理的 GIST 和 STS 细胞中，在用 Dox 洗脱后，在 Akt 抑制剂存在下培养时，Dox 处理的 GIST 和 STS 细胞的尾部矩（TM）和橄榄尾部矩（OTM）增加一致。总之，我们的数据表明，抑制 AKT 信号可能通过减弱同源介导的 DNA 修复来增强拓扑异构酶 II 抑制剂对 STS 和 GIST 的细胞毒性作用。
