Programmed cell-death ligand 1 (PD-L1) has been shown to induce potent T-cell mediated anti-tumoral immunity. The significance of PD-L1 expression in the prognosis of breast cancer (BC) remains controversial and its prevalence and prognostic value in breast cancer from Middle Eastern ethnicity is lacking. A total of 1003 unselected Middle Eastern breast cancers were analyzed for PD-L1 expression using immunohistochemistry. PD-L1 expression, seen in 32.8% (329/1003) of cases, was significantly associated with poor prognostic indicators such as younger patients, high-grade tumors, estrogen-receptor (ER)-negative, progesterone-receptor (PR)-negative, and triple-negative breast cancers (TNBC) as well as high Ki-67 index. We also found a significant association between PD-L1 expression and deficient mismatch repair protein expression. No association was found between PD-L1 expression and clinical outcome. However, on further subgroup analysis, PD-L1 expression was found to be an independent marker for favorable overall survival and recurrence-free survival in TNBC. In conclusion, we demonstrated strong association between PD-L1 and mismatch repair deficiency in Middle Eastern BC patients and that PD-L1 overexpression in tumor cells was an independent prognostic marker in TNBCs from Middle Eastern ethnicity. Overall, these findings might help in the development of more appropriate treatment strategies for BC in Middle Eastern population.

中文翻译：

---

中东乳腺癌中的 PD-L1 蛋白表达预测三阴性乳腺癌的良好结果

程序性细胞死亡配体 1 (PD-L1) 已被证明可诱导有效的 T 细胞介导的抗肿瘤免疫。PD-L1 表达在乳腺癌 (BC) 预后中的意义仍然存在争议，并且缺乏其在中东种族乳腺癌中的患病率和预后价值。使用免疫组织化学分析了总共 1003 例未选择的中东乳腺癌的 PD-L1 表达。在 32.8% (329/1003) 的病例中观察到 PD-L1 表达与不良预后指标显着相关，例如年轻患者、高级别肿瘤、雌激素受体 (ER) 阴性、孕激素受体 (PR)-阴性和三阴性乳腺癌 (TNBC) 以及高 Ki-67 指数。我们还发现 PD-L1 表达与错配修复蛋白表达缺陷之间存在显着关联。未发现 PD-L1 表达与临床结果之间存在关联。然而，在进一步的亚组分析中，发现 PD-L1 表达是 TNBC 良好总体生存率和无复发生存率的独立标志物。总之，我们证明了中东 BC 患者 PD-L1 与错配修复缺陷之间的强关联，并且肿瘤细胞中的 PD-L1 过表达是中东种族 TNBC 的独立预后标志物。总体而言，这些发现可能有助于为中东人群的 BC 制定更合适的治疗策略。我们证明了中东 BC 患者的 PD-L1 与错配修复缺陷之间的强关联，并且肿瘤细胞中的 PD-L1 过表达是中东种族 TNBC 的独立预后标志物。总体而言，这些发现可能有助于为中东人群的 BC 制定更合适的治疗策略。我们证明了中东 BC 患者的 PD-L1 与错配修复缺陷之间的强关联，并且肿瘤细胞中的 PD-L1 过表达是中东种族 TNBC 的独立预后标志物。总体而言，这些发现可能有助于为中东人群的 BC 制定更合适的治疗策略。