Hit list from the CRISPR-Cas9 screen.

Radiotherapy is a mainstay of treatment for head and neck squamous cell carcinoma (HNSCC), either definitive or adjuvant to surgery. Biological factors known to affect radiation response are hypoxia and DNA repair capacity, but several lines of evidence indicate that other genes and pathways in the tumor cells might be involved that have not been elucidated. Here, we report the results of a genome-wide CRISPR-Cas9 functional genomics screen in HNSCC cells to identify radiosensitizing genes. Remarkably, microtubule organizing genes were identified with CLASP1 as most unexpected radiosensitizing hit. Clonogenic assay confirmed the radiosensitizing effect of CLASP1 knockout. Functional analysis showed that CLASP1 knockout has major impact during S-phase, and resulted in mitotic cells with broken chromosomes and cell death. CLASP1 and possibly the microtubule machinery in broader sense seem involved in protection of HNSCC cells against radiation–induced DNA damage. This newly identified mechanism provides an outlook for novel treatment approaches in HNSCC.放射治疗是头颈部鳞状细胞癌（head and neck squamous cell carcinoma, HNSCC）的核心治疗手段，既可作为根治性治疗方案单独实施，也可作为手术术后的辅助治疗手段。已知影响肿瘤放射应答的生物学因素包括缺氧状态与DNA修复能力，但多项研究证据表明，肿瘤细胞中还存在尚未被阐明的其他基因及通路参与辐射应答调控。本研究通过在头颈鳞癌细胞中开展全基因组CRISPR-Cas9功能基因组筛选，旨在鉴定具有放射增敏效应的基因。令人意外的是，筛选结果中富集了微管组织相关基因，其中CLASP1是最出乎意料的放射增敏命中靶点。克隆形成实验验证了CLASP1敲除的放射增敏效果。功能分析显示，CLASP1敲除对细胞S期进程产生显著影响，最终导致出现染色体断裂的有丝分裂细胞并引发细胞死亡。CLASP1乃至更广泛范畴内的微管调控系统，似乎参与保护头颈鳞癌细胞免受辐射诱导的DNA损伤。这一新发现的作用机制为头颈鳞癌的新型治疗策略提供了全新的研究方向。