Garcia Patrick L, Miller Aubrey L, Zeng Ling, van Waardenburg Robert C A M, Yang Eddy S, Yoon Karina J
Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL, United States.
Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, AL, United States.
Front Oncol. 2022 Jun 20;12:925718. doi: 10.3389/fonc.2022.925718. eCollection 2022.
We reported previously that the BET inhibitor (BETi) JQ1 decreases levels of the DNA repair protein RAD51 and that this decrease is concomitant with increased levels of DNA damage. Based on these findings, we hypothesized that a BETi would augment DNA damage produced by radiation and function as a radiosensitizer. We used clonogenic assays to evaluate the effect of JQ1 ± ionizing radiation (IR) on three pancreatic cancer cell lines . We performed immunofluorescence assays to assess the impact of JQ1 ± IR on DNA damage as reflected by levels of the DNA damage marker γH2AX, and immunoblots to assess levels of the DNA repair protein RAD51. We also compared the effect of these agents on the clonogenic potential of transfectants that expressed contrasting levels of the principle molecular targets of JQ1 (BRD2, BRD4) to determine whether levels of these BET proteins affected sensitivity to JQ1 ± IR. The data show that JQ1 + IR decreased the clonogenic potential of pancreatic cancer cells more than either modality alone. This anticlonogenic effect was associated with increased DNA damage and decreased levels of RAD51. Further, lower levels of BRD2 or BRD4 increased sensitivity to JQ1 and JQ1 + IR, suggesting that pre-treatment levels of BRD2 or BRD4 may predict sensitivity to a BETi or to a BETi + IR. We suggest that a BETi + IR merits evaluation as therapy prior to surgery for pancreatic cancer patients with borderline resectable disease.
我们之前报道过，BET抑制剂（BETi）JQ1可降低DNA修复蛋白RAD51的水平，且这种降低与DNA损伤水平的增加同时出现。基于这些发现，我们推测BETi会增强辐射产生的DNA损伤，并起到放射增敏剂的作用。我们使用克隆形成试验来评估JQ1 ± 电离辐射（IR）对三种胰腺癌细胞系的影响。我们进行免疫荧光试验，以评估JQ1 ± IR对DNA损伤的影响，这可通过DNA损伤标志物γH2AX的水平反映出来；并进行免疫印迹试验，以评估DNA修复蛋白RAD51的水平。我们还比较了这些药物对表达不同水平JQ1主要分子靶点（BRD2、BRD4）的转染子克隆形成潜力的影响，以确定这些BET蛋白的水平是否会影响对JQ1 ± IR的敏感性。数据显示，JQ1 + IR比单独使用任何一种方式都更能降低胰腺癌细胞的克隆形成潜力。这种抗克隆形成作用与DNA损伤增加和RAD51水平降低有关。此外，较低水平的BRD2或BRD4会增加对JQ1和JQ1 + IR的敏感性，这表明BRD2或BRD4的预处理水平可能预测对BETi或BETi + IR的敏感性。我们建议，对于患有边缘可切除疾病的胰腺癌患者，在手术前应评估BETi + IR作为治疗方法的效果。
