Hintelmann Katharina, Berenz Thomas, Kriegs Malte, Christiansen Sabrina, Gatzemeier Fruzsina, Struve Nina, Petersen Cordula, Betz Christian, Rothkamm Kai, Oetting Agnes, Rieckmann Thorsten
Department of Otorhinolaryngology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Department of Radiotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Front Oncol. 2021 Jul 20;11:683688. doi: 10.3389/fonc.2021.683688. eCollection 2021.
In head and neck squamous cell carcinoma (HNSCC), tumors positive for human papillomavirus (HPV) represent a distinct biological entity with favorable prognosis. An enhanced radiation sensitivity of these tumors is evident in the clinic and on the cellular level when comparing HPV-positive and HPV-negative HNSCC cell lines. We could show that the underlying mechanism is a defect in DNA double-strand break repair associated with a profound and sustained G2 arrest. This defect can be exploited by molecular targeting approaches additionally compromising the DNA damage response to further enhance their radiation sensitivity, which may offer new opportunities in the setting of future de-intensified regimes. Against this background, we tested combined targeting of PARP and the DNA damage-induced intra-S/G2 cell cycle checkpoints to achieve effective radiosensitization. Enhancing CDK1/2 activity through the Wee1 inhibitor adavosertib or a combination of Wee1 and Chk1 inhibition resulted in an abrogation of the radiation-induced G2 cell cycle arrest and induction of replication stress as assessed by H2AX and chromatin-bound RPA levels in S phase cells. Addition of the PARP inhibitor olaparib had little influence on these endpoints, irrespective of checkpoint inhibition. Combined PARP/Wee1 targeting did not result in an enhancement in the absolute number of residual, radiation induced 53BP1 foci as markers of DNA double-strand breaks but it induced a shift in foci numbers from S/G2 to G1 phase cells. Most importantly, while sole checkpoint or PARP inhibition induced moderate radiosensitization, their combination was clearly more effective, while exerting little effect in p53/G1 arrest proficient normal human fibroblasts, thus indicating tumor specificity. We conclude that the combined inhibition of PARP and the intra-S/G2 checkpoint is a highly effective approach for the radiosensitization of HPV-positive HNSCC cells and may represent a viable alternative for the current standard of concomitant cisplatin-based chemotherapy. studies to further evaluate the translational potential are highly warranted.
在头颈部鳞状细胞癌（HNSCC）中，人乳头瘤病毒（HPV）呈阳性的肿瘤代表着一种具有良好预后的独特生物学实体。当比较HPV阳性和HPV阴性的HNSCC细胞系时，这些肿瘤在临床和细胞水平上均表现出增强的放射敏感性。我们能够证明其潜在机制是与深刻且持续的G2期停滞相关的DNA双链断裂修复缺陷。这种缺陷可通过分子靶向方法加以利用，这些方法会进一步损害DNA损伤反应，从而进一步增强其放射敏感性，这可能为未来的减强度治疗方案带来新机遇。在此背景下，我们测试了联合靶向聚（ADP - 核糖）聚合酶（PARP）和DNA损伤诱导的S期/G2期细胞周期检查点，以实现有效的放射增敏作用。通过Wee1抑制剂阿瓦斯丁或联合抑制Wee1和Chk1来增强细胞周期蛋白依赖性激酶1/2（CDK1/2）的活性，导致放射诱导的G2期细胞周期停滞被消除，并诱导了复制应激，这通过S期细胞中的H2AX和染色质结合的复制蛋白A（RPA）水平得以评估。无论检查点抑制情况如何，添加PARP抑制剂奥拉帕尼对这些终点指标影响甚微。联合靶向PARP/Wee1并未导致作为DNA双链断裂标志物的残留放射诱导的53BP1病灶绝对数量增加，但它诱导了病灶数量从S/G2期细胞向G1期细胞的转移。最重要的是，虽然单独的检查点抑制或PARP抑制可诱导中度放射增敏作用，但它们的联合显然更有效，同时对p53/G1期停滞功能正常的人成纤维细胞影响很小，从而表明具有肿瘤特异性。我们得出结论，联合抑制PARP和S期/G2期检查点是使HPV阳性HNSCC细胞放射增敏的一种高效方法，并且可能代表了当前基于顺铂同步化疗标准的一种可行替代方案。非常有必要开展进一步评估其转化潜力的研究。
