Department of Biomedicine and Prevention, University of Rome Tor Vergata, Hospital Foundation Policlinico Tor Vergata, Rome, Italy.
Department of Biomedicine and Prevention, University of Rome Tor Vergata, Hospital Foundation Policlinico Tor Vergata, Rome, Italy.
Int J Radiat Oncol Biol Phys. 2017 Feb 1;97(2):381-388. doi: 10.1016/j.ijrobp.2016.10.018. Epub 2016 Oct 19.
The identification of predictive biomarkers for neoadjuvant chemoradiation therapy (CRT) is a current clinical need. The heterodimer Ku70/80 plays a critical role in DNA repair and cell death induction after damage. The aberrant expression and localization of these proteins fail to control DNA repair and apoptosis. sClusterin is the Ku70 partner that sterically inhibits Bax-dependent cell death after damage in some pathologic conditions. This study sought to evaluate the molecular relevance of Ku70-Ku80-Clu as a molecular cluster predicting the response to neoadjuvant CRT in patients with locally advanced rectal cancer (LARC).
Patients enrolled in this study underwent preoperative CRT followed by surgical excision. A retrospective study based on individual response, evaluated by computed tomography and diffusion-weighted magnetic resonance imaging, identified responder (56%) and no-responder patients (44%). Ku70/80 and Clu expression were observed in biopsy specimens obtained before and after treatment with neoadjuvant CRT from the same LARC patients. In vitro studies before and after irradiation were also performed on radioresistant (SW480) and radiosensitive (SW620) colorectal cancer cell lines, mimicking sensitive or resistant tumor behavior.
We found a conventional nuclear localization of Ku70/80 in pretherapeutic tumor biopsies of responder patients, in agreement with their role in DNA repair and regulating apoptosis. By contrast, in the no-responder population we observed an unconventional overexpression of Ku70 in the cytoplasm (P<.001). In this context we also overexpression of sClu in the cytoplasm, which accorded with its role in stabilizing of Bax-Ku70 complex, inhibiting Bax-dependent apoptosis. Strikingly, Ku80 in these tumor tissues was lost (P<.005). In vitro testing of colon cancer cells finally confirmed the results observed in tumor biopsy specimens, proving that Ku70/80-Clu deregulation is extensively involved in the resistance mechanism.
These results strongly suggest a potential role of these proteins as a new prognostic tool to predict the response to chemoradiation in LARC.
鉴定新辅助放化疗（CRT）的预测生物标志物是当前的临床需求。异二聚体 Ku70/80 在损伤后 DNA 修复和细胞死亡诱导中起关键作用。这些蛋白的异常表达和定位不能控制 DNA 修复和细胞凋亡。sClusterin 是 Ku70 的伴侣，在某些病理条件下，它在损伤后通过阻止 Bax 依赖性细胞死亡来发挥作用。本研究旨在评估 Ku70-Ku80-Clu 作为分子簇的分子相关性，以预测局部晚期直肠癌（LARC）患者对新辅助 CRT 的反应。
本研究纳入的患者接受术前 CRT 后行手术切除。一项基于个体反应的回顾性研究（通过计算机断层扫描和扩散加权磁共振成像评估），确定了应答者（56%）和无应答者（44%）。在来自同一 LARC 患者的新辅助 CRT 前后的活检标本中观察到 Ku70/80 和 Clu 表达。还对模拟敏感或耐药肿瘤行为的耐辐射（SW480）和放射敏感（SW620）结肠癌细胞系进行了放射前后的体外研究。
我们发现应答者患者的治疗前肿瘤活检中 Ku70/80 具有常规核定位，这与其在 DNA 修复和调节细胞凋亡中的作用一致。相比之下，在无应答者人群中，我们观察到 Ku70 异常表达在细胞质中（P<.001）。在这种情况下，我们还观察到细胞质中 sClu 的过度表达，这与其在稳定 Bax-Ku70 复合物、抑制 Bax 依赖性细胞凋亡中的作用一致。引人注目的是，这些肿瘤组织中 Ku80 丢失（P<.005）。对结肠癌细胞的体外测试最终证实了肿瘤活检标本中观察到的结果，证明 Ku70/80-Clu 失调广泛参与耐药机制。
这些结果强烈表明这些蛋白作为预测 LARC 对放化疗反应的新预后工具具有潜在作用。
