Rolling-translated EGFR variants sustain EGFR signaling and promote glioblastoma tumorigenicity

作者：Yi Liu, Zhongjun Li, Maolei Zhang, Huangkai Zhou, Xujia Wu, Jian Zhong, Feizhe Xiao, Nunu Huang, Xuesong Yang, Rong Zeng, Lixuan Yang, Zhibo Xia, Nu Zhang · 发表于：Neuro-Oncology · 年份：2020 · DOI：10.1093/neuonc/noaa279 · 被引用次数：131 · 研究领域：Circular RNAs in diseases、Glioma Diagnosis and Treatment、Cancer-related molecular mechanisms research

BACKGROUND: Aberrant epidermal growth factor receptor (EGFR) activation is observed in over 50% of cases of adult glioblastoma (GBM). Nevertheless, EGFR antibodies are ineffective in clinical GBM treatment, suggesting the existence of redundant EGFR activation mechanisms. Whether circular RNA (circRNA) encodes a protein involved in EGFR-driven GBM remains unclear. We reported an unexpected mechanism in which circular EGFR RNA (circ-EGFR) encodes a novel EGFR variant to sustained EGFR activation. METHOD: We used RNA-seq, Northern blot, and Sanger sequencing to confirm the existence of circ-EGFR. Antibodies and a liquid chromatograph tandem mass spectrometer were used to identify circ-EGFR protein products. Lentivirus-transfected stable cell lines were used to assess the biological functions of the novel protein in vitro and in vivo. Clinical implications of circ-EGFR were assessed using 97 pathologically diagnosed GBM patient samples. RESULTS: The infinite open reading frame (iORF) in circ-EGFR translated repeating amino acid sequences via rolling translation and programmed -1 ribosomal frameshifting (-1PRF) induced out-of-frame stop codon (OSC), forming a polymetric novel protein-complex, which we termed rolling-translated EGFR (rtEGFR). rtEGFR directly interacted with EGFR, maintained EGFR membrane localization and attenuated EGFR endocytosis and degradation. Importantly, circ-EGFR levels correlated with the EGFR signature and predicted the poor prognosis of GBM patients. De...