本工作重点利用乳腺癌标本和细胞研究程序性死亡配体2（PD-L2）在乳腺癌进展中的作用。乳腺癌患者和健康人血清中可溶性PD-L2（sPD-L2）水平通过酶联免疫吸附测定对个体进行分析，并通过免疫组织化学评估 416 例切除的乳腺癌标本中的 PD-L2 水平。同时进行体外细胞实验和体内动物实验，分析PD-L2与乳腺癌侵袭、迁移的关系。乳腺癌患者体内sPD-L2浓度较对照组显着升高。此外，sPD-L2浓度高的乳腺癌患者具有较高的Ki67值（≥30%）和肿瘤分级。 PD-L2在79.09%的癌症样本中表达，与孕激素受体（PR）和人表皮生长因子受体2（HER2）呈正相关。此外，我们发现敲低 PD-L2 抑制了 MCF-7 和 MDA-MB231 细胞的迁移和侵袭能力。我们的研究结果表明，敲低 PD-L2 抑制了肿瘤生长，为重要的生物学功能提供了新的见解。版权所有 © 2024 孙玉玲等人。

This work focused on investigating the role of programmed death ligand 2 (PD-L2) in the progression of breast cancer by utilizing breast cancer specimens and cells.The serum levels of soluble PD-L2 (sPD-L2) in breast cancer patients and healthy individuals were analyzed by means of the enzyme-linked immunosorbent assay, and the PD-L2 levels within 416 resected breast cancer specimens were assessed through immunohistochemistry. Concurrently, in vitro cell experiments and in vivo animal experiments were carried out to analyze the relationship between PD-L2 and the invasion and migration of breast cancer.The concentration of sPD-L2 in breast cancer patients significantly increased compared to that in the control groups. Additionally, breast cancer patients with high concentrations of sPD-L2 had higher Ki67 values (≥30%) and tumor grades. PD-L2 was expressed in 79.09% of the cancer samples, which exhibited a positive correlation with the progesterone receptor (PR) and the human epidermal growth factor receptor 2 (HER2). Furthermore, we discovered that knockdown of PD-L2 inhibited the migratory and invasive abilities of both MCF-7 and MDA-MB231 cells.Our findings demonstrated that knockdown of PD-L2 suppressed tumor growth, providing novel insights into important biological functions.Copyright © 2024 Yuling Sun et al.