Abstract：
A hypoxic environment occurs predominantly in tumors. During the growth phase of a tumor, it grows until it exceeds its blood supply, leaving regions of the tumor in which the oxygen pressure is dramatically low. They are virtually absent in normal tissues, thus creating perfect conditions for selective bioreductive therapy of tumors. To this aim, a novel series of cytotoxic radiosensitizer agents were synthesized by linking the nitroimidazole scaffold with oxadiazole or triazole rings. The majority of the compounds exhibited moderate to excellent antiproliferative activities toward HCT116 cell line under normoxic and hypoxic conditions. The structure-activity relationship study revealed that compounds containing the free thiol group either in the oxadiazoles 11a,b or the triazoles 21a,b-23a,b demonstrated the strongest antiproliferative activity, which proves that the free thiol group plays a crucial role in the antiproliferative activity of our compounds under both normoxic (half-maximal inhibitory concentration [IC50 ] = 12.50-24.39 µM) and hypoxic conditions (IC50 = 4.69-11.56 µM). Radiosensitizing assay of the four most active cytotoxic compounds 11b and 21-23b assured the capability of the compounds to enhance the sensitivity of the tumor cells to the DNA damaging activity of γ-radiation (IC50 = 2.23-5.18 µM). To further investigate if the cytotoxicity of our most active compounds was due to a specific signaling pathway, the online software SwissTargetPrediction was exploited and a molecular docking study was done that proposed cyclin-dependent kinase 2 (CDK2) enzyme to be the most promising target. The CDK2 inhibitory assay assured this assumption as five out of six compounds demonstrated a comparable inhibitory activity with roscovitine, among which compound 21b showed threefold more potent inhibitory activity in comparison with the reference compound. A further biological evaluation proved compound 21b to have an apoptotic activity and cell cycle arrest activity at the G1 and S phases. During the AutoQSAR analysis, the model demonstrated excellent regression between the predicted and experimental activity with r2 = 0.86. Subsequently, we used the model to predict the activity of the test set compounds that came with r2 = 0.95.
摘要：
缺氧环境主要发生在肿瘤中。在肿瘤的生长期，它生长直到超过它的血液供应，留下的肿瘤区域的氧分压非常低。它们在正常组织中几乎不存在，从而为肿瘤的选择性生物还原治疗创造了完美的条件。为了这个目标,通过将硝基咪唑支架与恶二唑或三唑环连接，合成了一系列新型的细胞毒性放射增敏剂。大多数化合物在常氧和低氧条件下对HCT116细胞系表现出中等至优异的抗增殖活性。构效关系研究表明，在恶二唑11a中含有游离巯基的化合物，b或三唑21a，b-23a,B表现出最强的抗增殖活性，这证明了游离巯基在常氧（半最大抑制浓度[IC50]=12.50-24.39µM）和低氧条件（IC50=4.69-11.56µM）下在我们化合物的抗增殖活性中起着至关重要的作用。四种最具活性的细胞毒性化合物11b和21-23b的放射增敏试验确保了化合物增强肿瘤细胞对γ-辐射的DNA损伤活性的敏感性的能力(IC50=2.23-5.18µM)。为了进一步研究我们最活跃的化合物的细胞毒性是否归因于特定的信号通路，利用在线软件SwissTargetPrediction,并进行了分子对接研究,提出细胞周期蛋白依赖性激酶2(CDK2)酶是最有希望的靶标.CDK2抑制测定确保了这一假设，因为六种化合物中有五种表现出与roscovitine相当的抑制活性，其中化合物21b与参比化合物相比显示出三倍更有效的抑制活性。进一步的生物学评价证明化合物21b在G1和S期具有凋亡活性和细胞周期停滞活性。在AutoQSAR分析期间，该模型显示了预测活性和实验活性之间的良好回归，r2=0.86。随后，我们使用该模型来预测r2=0.95的测试集化合物的活性。
