Targeting of a Major Immune Evasion Pathway in Triple-negative Breast Cancer

靶向治疗三阴性乳腺癌的主要免疫耐药途径 摘要 检查点阻断可使一部分三阴性乳腺癌患者获得中度生存获益 癌症（TNBC），但大多数患者目前未能受益于免疫疗法。我们最近发现， 编码整合素αV和SOX 4蛋白的基因（ITGAV和SOX 4基因）使肿瘤细胞对 细胞毒性T细胞的杀伤。整合素αVβ6和SOX 4形成了一条与耐药相关的耐药途径， TNBC：整合素αVβ6通过力依赖性机制从无活性的潜伏复合物中释放TGFβ， 活性TGFβ诱导抑制T细胞介导的肿瘤免疫的SOX 4转录因子的表达。 整合素αVβ6异源二聚体在健康上皮细胞中表达水平较低，但其表达水平较低。 在许多上皮癌中高度上调，包括TNBC。TGFβ是一种重要的免疫抑制因子， 细胞因子，但由于其在不同细胞类型中的多效性生物学， 组织中这种方法为更有选择性地靶向TGFβ治疗癌症提供了机会 免疫疗法我们的初步数据表明，整合素αVβ6阻断单克隆抗体抑制SOX 4 表达并使TNBC细胞对细胞毒性T细胞敏感。这种抗体赋予一个实质性的生存效益 在对检查点阻断具有抗性的两种侵袭性TNBC小鼠模型中。在目标1中，我们将研究 整合素αVβ6 -SOX 4抗性通路作为侵袭性和高转移性肿瘤免疫治疗靶点 TNBC小鼠模型。特别是，我们将研究整合素αVβ6的抑制如何诱导大量的 CD 8 T细胞流入T细胞浸润不良的TNBC。在目标2中，我们将研究 整合素αVβ6 -SOX 4通路抑制T细胞介导的肿瘤免疫的分子机制。 初步数据表明，SOX 4转录因子抑制来自多种细胞的基因表达， 肿瘤细胞中的先天免疫途径，包括胞质dsRNA和dsDNA传感途径以及 作为1型干扰素反应途径。我们将定义SOX 4的直接转录靶点，并研究 SOX 4如何与其他转录因子合作使肿瘤细胞对T细胞介导的肿瘤产生抗性 免疫力在目的3中，我们将研究整合素αVβ6 -SOX 4通路在人TNBC中的意义。我们 假设是这种抗性途径抑制人TNBC中的T细胞浸润，因此我们将 检查人TNBC中整合素αVβ6/SOX 4表达与T细胞浸润之间的空间关系 标本高亲和力整合素αVβ6抗体和一种小分子抑制剂已经在 纤维化适应症的临床试验。因此，这里描述的研究可以为以下方面提供科学依据： 在TNBC和其他上皮来源的人类癌症中测试这种抑制剂。

Therapeutic Targeting of a Major Immune Resistance Pathway in Triple-negative Breast Cancer Abstract Checkpoint blockade results in moderate survival benefit in a subset of patients with triple-negative breast cancer (TNBC) but most patients currently fail to benefit from immunotherapy. We recently discovered that the genes encoding the integrin αV and SOX4 proteins (ITGAV and SOX4 genes) render tumor cells resistant to killing by cytotoxic T cells. Integrin αVβ6 and SOX4 form a resistance pathway that is particularly relevant to TNBC: Integrin αVβ6 releases TGFβ from an inactive latent complex by a force-dependent mechanism, and active TGFβ induces expression of the SOX4 transcription factor that inhibits T cell-mediated tumor immunity. The integrin αVβ6 heterodimer is expressed at a low level by healthy epithelial cells, but its expression is highly upregulated in many epithelial cancers, including TNBC. TGFβ is an important immunosuppressive cytokine in human tumors, but has been difficult to target due to its pleiotropic biology in different cell types and tissues. This approach provides an opportunity for more selective targeting of TGFβ for cancer immunotherapy. Our preliminary data demonstrate that an integrin αVβ6 blocking mAb inhibits SOX4 expression and sensitizes TNBC cells to cytotoxic T cells. This antibody confers a substantial survival benefit in two aggressive mouse models of TNBC that are resistant to checkpoint blockade. In Aim 1, we will study the integrin αVβ6 – SOX4 resistance pathway as an immunotherapy target in aggressive and highly metastatic mouse models of TNBC. In particular, we will examine how inhibition of integrin αVβ6 induces a substantial influx of CD8 T cells into TNBCs that are poorly infiltrated by T cells. In Aim 2, we will investigate the molecular mechanisms by which the integrin αVβ6 – SOX4 pathway inhibits T cell-mediated tumor immunity. Preliminary data demonstrate that the SOX4 transcription factor inhibits expression of genes from multiple innate immune pathways in tumor cells, including the cytosolic dsRNA and dsDNA sensing pathways as well as the type 1 interferon response pathway. We will define the direct transcriptional targets of SOX4 and study how SOX4 cooperates with other transcription factors to render tumor cells resistant to T cell-mediated tumor immunity. In Aim 3, we will study the significance of the integrin αVβ6 – SOX4 pathway in human TNBC. Our hypothesis is that this resistance pathway inhibits T cell infiltration in human TNBC, and we will therefore examine the spatial relationship between integrin αVβ6/SOX4 expression and T cell infiltration in human TNBC specimens. High-affinity integrin αVβ6 antibodies and a small molecule inhibitor are already being tested in clinical trials for fibrosis indications. The studies described here could thus provide the scientific rationale for testing of such inhibitors in TNBC and other human cancers of epithelial origin.