The role of nuclear PD-L1 in breast tumor cell division, progression and therapy response

三阴性乳腺癌[雌激素受体(ER)、孕激素受体(PR)和人类 表皮生长因子受体2(HER2)阴性乳腺癌是乳腺癌的一种侵袭性亚型 目前还没有批准的靶向治疗方法。虽然标准化疗降低了 疾病事件，新辅助化疗后残留TNBC的患者局部区域风险较高 尽管手术切除和积极的术后放射治疗，肿瘤复发。因此，更好地 了解TNBC进展的机制并寻找新的治疗方法 在标准治疗方面取得进展的患者是非常需要的。PD-L1在 TNBC，相对于正常乳腺组织和其他乳腺癌亚型。PD-L1的异常表达 肿瘤是逃避宿主免疫系统清除的重要手段。程序化的约束 死亡配体1(PD-L1)与其受体结合，程序性细胞死亡蛋白1(PD-1)传递抑制T细胞死亡的信号。 细胞激活。因此，消除PD-1/PD-L1与治疗性抗体的相互作用已被探索 作为增强抗肿瘤免疫力的一种手段。尽管PD-L1在T细胞调节中的细胞外作用 已经对PD-L1的反应进行了很好的研究，PD-L1在癌症中的潜在细胞内功能在很大程度上仍然存在 未知。令人惊讶的是，我们发现TNBC的增殖需要PD-L1和PD-L1的子集定位 在细胞核中，并与粘附素相互作用，粘附素是一种对适当的染色体至关重要的蛋白质复合体 细胞周期中的排列和分离。我们的初步数据表明PD-L1直接调节 在TNBC中的衔接作用。戏剧性地击倒PD-L1导致染色体不完全分离 抑制TNBC细胞增殖，而对正常细胞无影响。正在检验的中心假说 在这项建议中，PD-L1调节三重阴性乳腺的细胞周期和染色体稳定性 肿瘤(TNBC)，靶向PD-L1的细胞内/核功能或通路(有丝分裂和 由PD-L1调节的粘附素)具有治疗作用。我们建议对这一中心假设进行检验 目的1，确定PD-L1在调节细胞周期、基因组稳定性和 通过研究核PD-L1可能调节凝聚力的确切机制来促进肿瘤细胞的增殖。 目的研究PD-L1在细胞周期和有丝分裂中的调控作用。目的3、评价PD-L1的抑制作用 核在染色体分离、肿瘤生长和放化疗反应中的作用 在动物模型中。这项工作的圆满完成带来的总体影响将更加完整 了解PD-L1在肿瘤发病机制中的作用。此外，我们的工作将导致更多的设计 通过定义新的策略为TNBC患者提供合理和有效的联合治疗，不仅 通过抑制有丝分裂来加强癌症治疗，但也释放了患者免疫的抗肿瘤活性 系统。

Triple negative breast cancer (TNBC) [estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) negative breast cancer is an aggressive subtype of breast cancer for which there are no approved targeted therapies. While standard chemotherapy reduces the risk of a disease event, patients with residual TNBC after neoadjuvant chemotherapy have a high risk of locoregional recurrence despite surgical resection and aggressive postoperative radiotherapy. Therefore, better understanding mechanisms of TNBC progression and identifying novel treatment approaches for patients who have progressed on standard treatment are of great needs. PD-L1 is overexpressed in TNBC, relative to normal breast tissue and other breast cancer subtypes. Aberrant PD-L1 expression on tumors is an important means of evading elimination by its host immune system. The binding of programmed death ligand 1 (PD-L1) to its receptor, programmed cell death protein 1 (PD-1) transmits signals that inhibit T- cell activation. Therefore, abrogating the PD-1/PD-L1 interaction with therapeutic antibodies has been explored as a means to enhance antitumor immunity. Although the extracellular role of PD-L1 in the regulation of T-cell responses has been well studied, potential intracellular functions of PD-L1 in cancer remain largely unknown. Surprisingly, we have found that TNBC proliferation requires PD-L1 and a subset of PD-L1 localizes in the nucleus and interacts with cohesin, a protein complex that is important for appropriate chromosome alignment and segregation during the cell cycle. Our Preliminary Data suggest that PD-L1 directly regulates cohesion function in TNBC. Knocking down PD-L1 dramatically causes incomplete chromosome segregation and inhibits TNBC cell proliferation, while has no effect on normal cells. The central hypothesis being tested in this proposal is that PD-L1 regulates cell cycle and chromosomal stability in triple negative breast cancer (TNBC), and targeting the intracellular/nuclear function of PD-L1 or pathways (mitosis and cohesin) regulated by PD-L1 is of therapeutic use. We propose to test this central hypothesis in the following Specific Aims: Aim 1, Determine the role of PD-L1 in regulation of cell cycle, genomic stability, and tumor cell proliferation by studying the exact mechanisms by which nuclear PD-L1 might regulate cohesion. Aim 2, Study the regulation of PD-L1 during cell cycle and mitosis. Aim 3, Evaluate the inhibition of PD-L1 nuclear function on chromosome segregation, tumor growth and response to radiochemotherapy both in vitro and in animal models. The overall impact from the successful completion of this work will be a more complete understanding of the role of PD-L1 in cancer pathogenesis. In addition, our work will lead to the design of more rational and effective combination therapies for TNBC patients by defining novel strategies that not only enhance cancer therapy by inhibiting mitosis but also unleash the antitumor activity of the patient’s immune system.