Comparative Oncology Laboratory, Schools of Medicine and Veterinary Medicine, University of California, Davis, CA 95616.
Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390.
Proc Natl Acad Sci U S A. 2022 May 31;119(22):e2123202119. doi: 10.1073/pnas.2123202119. Epub 2022 May 26.
p73, a p53 family member, undergoes alternative splicing at the 3′ end to produce multiple isoforms, but their expression and activity are largely unknown. Thus, CRISPR was used to knock out exon 12 (E12) in human cancer cell lines and mice, leading to isoform switch from p73α to isoform p73α1. We found that p73α1 is naturally expressed and induced by DNA damage. We also found that knockout of E12 suppresses cell growth and migration in H1299 and MIA PaCa-2 cells and promotes cellular senescence in mouse embryonic fibroblasts. Similarly, ectopic expression of p73α1 suppresses cell proliferation, whereas knockdown of p73α1 restores the cell proliferative and migratory capacities of E12 cells. Consistently, we found that E12 mice are not prone to spontaneous tumors. Instead, E12 mice are prone to systemic inflammation and exhibit elevated TNFα expression in inflamed tissues. Moreover, we found that Notch1, a master regulator of the inflammatory response, is regulated by p73α1 and highly expressed in E12 cells and inflamed E12 mouse tissues. Furthermore, through knockdown of p73α1 and/or Notch1 in E12 cells, we found that Notch1 is necessary for p73α1-mediated growth suppression. Together, these data suggest that p73α1 plays a critical role in tumor suppression and the inflammatory response via Notch1.
p73 是 p53 家族的一员，在 3'端通过选择性剪接产生多种异构体，但它们的表达和活性在很大程度上是未知的。因此，我们使用 CRISPR 敲除人癌细胞系和小鼠中的外显子 12（E12），导致 p73α 向异构体 p73α1 的异构体转换。我们发现 p73α1 是自然表达的，并可被 DNA 损伤诱导。我们还发现敲除 E12 可抑制 H1299 和 MIA PaCa-2 细胞的生长和迁移，并促进小鼠胚胎成纤维细胞的细胞衰老。同样，异位表达 p73α1 可抑制细胞增殖，而敲低 p73α1 可恢复 E12 细胞的增殖和迁移能力。一致地，我们发现 E12 小鼠不易发生自发性肿瘤。相反，E12 小鼠易发生全身炎症，并在炎症组织中表现出 TNFα 表达升高。此外，我们发现 Notch1 是炎症反应的主要调节因子，受 p73α1 调节，在 E12 细胞和炎症 E12 小鼠组织中高表达。此外，通过在 E12 细胞中敲低 p73α1 和/或 Notch1，我们发现 Notch1 是 p73α1 介导的生长抑制所必需的。总之，这些数据表明 p73α1 通过 Notch1 在肿瘤抑制和炎症反应中发挥关键作用。
