Aberrant expression of immune check point molecules, programmed death ligand (PD-L1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) has been reported in many human cancers with increased protein and gene expression correlated with an aggressive behaviour in some neoplasms. Additionally, PD-L1 blockade has been shown to be an effective therapy for some human cancers. Canine mammary gland tumours have previously been shown to produce PD-L1 protein, but there are no previous studies investigating CTLA-4 in these common canine neoplasms. The present study investigated protein and gene expression of PD-L1 and CTLA-4 using immunohistochemistry and RT-PCR in 41 histologically-malignant, outcome-known CMGTs. The PD-L1 and CTLA-4 immunostaining scores of the mammary gland tumours that subsequently metastasised were significantly higher than those of tumours which did not metastasise (PD-L1: p = 0.005, CTLA-4: p = 0.003). Gene expression of PD-L1 and CTLA-4 was also significantly higher in tumours which subsequently metastasised (PD-L1: p = 0.023, CTLA-4: p = 0.022). Further, higher PD-L1 or CTLA-4 immunostaining scores correlated with shorter survival times of dogs (PD-L1: r_s = - 0.42, p = 0.008, CTLA-4: r_s = - 0.4, p = 0.01) while PD-L1 immunostaining was independently prognostic of survival time (Δ F = 4.9, p = 0.035). These findings suggest that higher protein and gene expression of PD-L1 and CTLA-4 by tumour cells increases the chances of metastasis and measuring these proteins may predict likely neoplasm behaviour. Additionally, if increased expression of these proteins promotes metastasis, blocking PD-L1 or CTLA-4 may be beneficial to treat canine mammary gland tumours.

在许多人类癌症中，已经报道了免疫检查点分子，程序性死亡配体（PD-L1）和细胞毒性T淋巴细胞抗原-4（CTLA-4）的异常表达，这些蛋白质和基因的表达与某些肿瘤的侵袭行为有关。此外，PD-L1阻断剂已被证明是对某些人类癌症的有效疗法。先前已证明犬乳腺肿瘤可产生PD-L1蛋白，但以前没有研究在这些常见犬肿瘤中研究CTLA-4。本研究使用免疫组织化学和RT-PCR技术在41个组织学恶性，结局已知的CMGT中研究了PD-L1和CTLA-4的蛋白质和基因表达。p  = 0.005，CTLA-4：p  = 0.003）。在随后转移的肿瘤中，PD-L1和CTLA-4的基因表达也明显更高（PD-L1：p  = 0.023，CTLA-4：p  = 0.022）。此外，更高的PD-L1或CTLA-4免疫染色评分与狗的较短的存活时间相关（：PD-L1 ř_小号- 0.42，= p  = 0.008，CTLA-4：[R_小号= - 0.4，p  = 0.01），而PD -L1免疫染色可独立预测生存时间（ΔF = 4.9，p = 0.035）。这些发现表明，肿瘤细胞中PD-L1和CTLA-4的更高的蛋白质和基因表达增加了转移的机会，并且测量这些蛋白质可能预示可能的肿瘤行为。另外，如果这些蛋白的表达增加促进转移，则阻断PD-L1或CTLA-4可能对治疗犬乳腺肿瘤有益。