Abstract：
Immune checkpoint inhibitor therapy can provide significant clinical benefit in patients with certain cancer types including melanoma; however, objective responses are only observed for a subset of patients. Mucosal melanoma is a rare melanoma subtype associated with a poor prognosis and, compared with cutaneous melanoma, is significantly less responsive to immune checkpoint inhibitors. Spontaneous canine tumours have emerged as valuable models to inform human cancer studies. In contrast to human melanoma, most canine melanomas are mucosal-an incidence that may be leveraged to better understand the subtype in humans. However, a more comprehensive understanding of the immune landscape of the canine disease is required. Here, we quantify tumour infiltrative T and myeloid cells in canine mucosal (n = 13) and cutaneous (n = 5) melanomas using immunohistochemical analysis of CD3 and MAC387 expression, respectively. Gene expression analysis using the Canine IO NanoString panel was also performed to identify genes and pathways associated with immune cell infiltration. T and myeloid cell densities were variable with geometric means of 158.7 cells/mm2 and 166.7 cells/mm2, respectively. Elevated T cell infiltration was associated with increased expression of cytolytic genes as well as genes encoding the coinhibitory checkpoint molecules PD-1, CTLA-4, TIM-3 and TIGIT; whereas increased myeloid cell infiltration was associated with elevated expression of protumourigenic cytokines. These data provide a basic characterization of the tumour microenvironment of canine malignant melanoma and suggest that, like human melanoma, inherent variability in anti-tumour T cell responses exists and that a subset of canine melanomas may respond better to immunomodulation.
摘要：
免疫检查点抑制剂疗法可以为患有某些癌症类型（包括黑色素瘤）的患者提供显著的临床益处；然而，仅在一部分患者中观察到客观反应.粘膜黑色素瘤是一种罕见的黑色素瘤亚型，与不良预后相关，与皮肤黑色素瘤相比，对免疫检查点抑制剂的反应明显减弱。自发性犬肿瘤已成为有价值的模型，为人类癌症研究提供信息。与人类黑色素瘤相反，大多数犬黑色素瘤是粘膜的，这种发病率可能被用来更好地了解人类的亚型。然而,需要对犬病的免疫景观有更全面的了解。这里,我们使用CD3和MAC387表达的免疫组织化学分析量化犬粘膜（n=13）和皮肤（n=5）黑素瘤中的肿瘤浸润性T细胞和骨髓细胞。分别。还使用犬IONanoString面板进行基因表达分析以鉴定与免疫细胞浸润相关的基因和途径。T和骨髓细胞密度是可变的,几何平均值分别为158.7细胞/mm2和166.7细胞/mm2。升高的T细胞浸润与细胞溶解基因以及编码共抑制检查点分子PD-1、CTLA-4、TIM-3和TIGIT的基因的表达增加相关;而增加的骨髓细胞浸润与原生细胞因子的表达升高相关。这些数据提供了犬恶性黑色素瘤肿瘤微环境的基本表征，并表明，就像人类黑色素瘤一样，抗肿瘤T细胞反应存在固有的变异性，并且犬黑色素瘤的一部分可能对免疫调节反应更好。
