鉴于局部晚期直肠癌（LARC）新辅助化学放疗（nCRT）的效果难以预测，本研究旨在表征能够促进病理完全缓解（pCR）的有效生物标志物。我们利用压力循环技术（PCT）辅助脉冲数据独立采集（PulseDIA）质谱技术，在两家医院中的58名LARC患者的nCRT前切片中，量化了6483个高置信度蛋白质丰度。与非pCR患者相比，pCR患者在nCRT前具有更高的长期无病生存率（DFS）和更高的肿瘤免疫浸润，尤其是CD8 + T细胞浸润。 FOSL2被选为预测pCR的候选生物标志物，在pCR患者中明显上调，并在另外54例LARC患者的nCRT前切片中通过免疫组织化学验证。 FOSL2表达能够通过多反应监测（MRM）高效预测pCR（AUC =0.939，特异度=1.000，敏感度=0.850），高FOSL2表达与长期DFS（p=0.044）相关。当用模拟nCRT进行处理时，FOSL2足够性导致更明显的细胞增殖抑制，更明显的细胞周期阻滞和细胞凋亡的促进。此外，FOSL2-WT肿瘤细胞经过nCRT后，发现CXCL10分泌和异常的胞质dsDNA积累，这可能提高CD8 + T细胞浸润和CD8 + T细胞介导的细胞毒作用，促进nCRT诱导的抗肿瘤免疫力。本研究揭示了LARC患者nCRT前的蛋白质组学，突出显示了实现pCR患者肿瘤中的免疫激活。我们确定了FOSL2作为预测pCR的有前途的生物标志物，并通过促进CD8 + T细胞浸润，推动长期DFS。版权所有©2023 Elsevier B.V.发布。

The outcome of neoadjuvant chemoradiotherapy (nCRT) remains highly unpredictable for individuals with locally advanced rectal cancer (LARC). We set out to characterize effective biomarkers that promote a pathological complete response (pCR). We quantified the abundances of 6483 high-confidence proteins in pre-nCRT biopsies of 58 LARC patients from two hospitals with pressure cycling technology (PCT)-assisted pulse data-independent acquisition (PulseDIA) mass spectrometry. Compared with non-pCR patients, pCR patients achieved long-term disease-free survival (DFS) and had higher tumor immune infiltration, especially CD8+ T cell infiltration, before nCRT. FOSL2 was selected as the candidate biomarker for predicting pCR and was found to be significantly upregulated in pCR patients, which was verified in another 54 pre-nCRT biopsies of LARC patients by immunohistochemistry. FOSL2 expression was able to predict pCR by multiple reaction monitoring (MRM) with high efficiency (Area under curve (AUC) = 0.939, specificity = 1.000, sensitivity = 0.850), and high FOSL2 expression was associated with long-term DFS (p = 0.044). When treated with simulated nCRT, FOSL2 sufficiency resulted in more significant inhibition of cell proliferation, and more significant promotion of cell cycle arrest and cell apoptosis. Moreover, CXCL10 secretion with abnormal cytosolic dsDNA accumulation was found in FOSL2-WT tumor cells over nCRT, which might elevate CD8+ T-cell infiltration and CD8+ T-cell-mediated cytotoxicity to promote nCRT-induced antitumor immunity. Our study revealed proteomic profiles in LARC patients before nCRT and highlighted immune activation in the tumors of patients who achieved pCR. We identified FOSL2 as a promising biomarker to predict pCR and promote long-term DFS by contributing to CD8+ T-cell infiltration.Copyright © 2023. Published by Elsevier B.V.