Division of Biotechnology Review and Research 1, Office of Biotechnology Products, Office of Pharmaceutical Quality, Center for Drug Evaluation and Research, U.S. Food and Drug Administration (FDA), Silver Spring, MD 20993, USA.
Int J Mol Sci. 2023 Jul 20;24(14):11694. doi: 10.3390/ijms241411694.
Atezolizumab is an immune checkpoint inhibitor (ICI) targeting PD-L1 for treatment of solid malignancies. Immune checkpoints control the immune tolerance, and the adverse events such as hepatotoxicity induced by ICIs are often considered as an immune-related adverse event (irAE). However, PD-L1 is also highly expressed in normal tissues, e.g., hepatocytes. It is still not clear whether, targeting PD-L1 on hepatocytes, the atezolizumab may cause damage to liver cells contributing to hepatotoxicity. Here, we reveal a novel mechanism by which the atezolizumab induces hepatotoxicity in human hepatocytes. We find that the atezolizumab treatment increases a release of LDH in the cell culture medium of human hepatocytes (human primary hepatocytes and THLE-2 cells), decreases cell viability, and inhibits the THLE-2 and THLE-3 cell growth. We demonstrate that both the atezolizumab and the conditioned medium (T-CM) derived from activated T cells can induce necroptosis of the THLE-2 cells, which is underscored by the fact that the atezolizumab and T-CM enhance the phosphorylation of RIP3 and MLKL proteins. Furthermore, we also show that necrostatin-1, a necrosome inhibitor, decreases the amount of phosphorylated RIP3 induced by the atezolizumab, resulting in a reduced LDH release in the culture media of the THLE-2 cells. This finding is further supported by the data that GSK872 (a RIP3 inhibitor) significantly reduced the atezolizumab-induced LDH release. Taken together, our data indicate that the atezolizumab induces PD-L1-mediated necrosome formation, contributing to hepatotoxicity in PD-L1-human hepatocytes. This study provides the molecular basis of the atezolizumab-induced hepatotoxicity and opens a new avenue for developing a novel therapeutic approach to reducing hepatotoxicity induced by ICIs.
阿替利珠单抗是一种针对 PD-L1 的免疫检查点抑制剂（ICI），用于治疗实体恶性肿瘤。免疫检查点控制免疫耐受，ICI 引起的肝毒性等不良反应通常被认为是免疫相关不良反应（irAE）。然而，PD-L1 在正常组织中也高度表达，例如肝细胞。目前尚不清楚阿替利珠单抗是否通过靶向肝细胞上的 PD-L1 导致肝细胞损伤，从而导致肝毒性。在这里，我们揭示了阿替利珠单抗在人肝细胞中引起肝毒性的一种新机制。我们发现，阿替利珠单抗治疗增加了人肝细胞（人原代肝细胞和 THLE-2 细胞）培养上清液中 LDH 的释放，降低了细胞活力，并抑制了 THLE-2 和 THLE-3 细胞的生长。我们证明，阿替利珠单抗和激活的 T 细胞来源的条件培养基（T-CM）均可诱导 THLE-2 细胞发生坏死性凋亡，这一点得到了以下事实的支持：阿替利珠单抗和 T-CM 增强了 RIP3 和 MLKL 蛋白的磷酸化。此外，我们还表明，坏死体抑制剂 necrostatin-1 可降低阿替利珠单抗诱导的磷酸化 RIP3 的量，从而减少 THLE-2 细胞培养上清液中 LDH 的释放。这一发现得到了以下数据的进一步支持：RIP3 抑制剂 GSK872 显著降低了阿替利珠单抗诱导的 LDH 释放。综上所述，我们的数据表明，阿替利珠单抗诱导 PD-L1 介导的坏死体形成，导致 PD-L1-人肝细胞的肝毒性。这项研究为阿替利珠单抗诱导的肝毒性提供了分子基础，并为开发降低 ICI 诱导的肝毒性的新治疗方法开辟了新途径。
