B7-H4 (VTCN1) is a member of the CD28/B7 family of immune co-inhibitory molecules. The relationship of tumor and stromal B7-H4 protein expression with PD-L1, tumor infiltrating lymphocytes (TILs) and its association with clinico-pathological variables are not well defined. Herein, we explore the expression level of B7-H4 protein in breast cancer and evaluate its association with TILs, levels of PD-L1 expression, and clinico-pathological characteristics in two independent populations. In this study, we used multiplexed automated quantitative immunofluorescence (QIF) to measure the levels of B7-H4 and PD-L1 protein and determined TILs through pathologist assessment of H&E-stained preparations in over a thousand breast cancer cases from two institutions represented in tissue microarray format. Associations between the marker levels, major clinico-pathological variables, and survival were analyzed. We detected B7-H4 protein was highly expressed in both breast cancer and stromal cells. Its expression was independent of breast cancer intrinsic subtypes. PD-L1 expression was higher in triple negative breast cancers. Neither B7-H4 nor PD-L1 were associated with survival in breast cancer. Our study shows there is a mutually exclusive pattern of B7-H4 with both tumor PD-L1 expression and TILs in all breast cancers, independent of breast cancer intrinsic subtype. This exclusive pattern suggests that some breast tumors may preferentially use one B7-related immune evasion mechanism/pathway. This could explain the clinical benefit that is seen only in a fraction of patients with immune checkpoint inhibitors directed exclusively towards PD-L1 in breast cancer.

B7-H4 (VTCN1) 是免疫共抑制分子 CD28/B7 家族的成员。肿瘤和基质 B7-H4 蛋白表达与 PD-L1、肿瘤浸润淋巴细胞 (TIL) 的关系及其与临床病理变量的关联尚未明确。在此，我们探讨了乳腺癌中 B7-H4 蛋白的表达水平，并评估了其与两个独立人群中 TIL、PD-L1 表达水平和临床病理特征的相关性。在这项研究中，我们使用多重自动定量免疫荧光 (QIF) 来测量 B7-H4 和 PD-L1 蛋白的水平，并通过病理学家对来自组织中代表的两个机构的 1000 多个乳腺癌病例中的 H&E 染色制剂进行评估来确定 TIL。微阵列格式。分析了标志物水平、主要临床病理变量和生存率之间的关联。我们检测到 B7-H4 蛋白在乳腺癌和基质细胞中高表达。其表达与乳腺癌内在亚型无关。PD-L1 在三阴性乳腺癌中表达较高。B7-H4 和 PD-L1 均与乳腺癌的生存无关。我们的研究表明，在所有乳腺癌中，B7-H4 与肿瘤 PD-L1 表达和 TIL 都存在相互排斥的模式，与乳腺癌固有亚型无关。这种独特的模式表明，一些乳腺肿瘤可能会优先使用一种 B7 相关的免疫逃避机制/途径。这可以解释仅在一小部分使用专门针对 PD-L1 的免疫检查点抑制剂治疗乳腺癌的患者中看到的临床益处。