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

作者：Liu, Yi; Li, Zhongjun; Zhang, Maolei; Zhou, Huangkai; Wu, Xujia; Zhong, Jian; Xiao, Feizhe; Huang, Nunu; Yang, Xuesong; Zeng, Rong; Yang, Lixuan; Xia, Zhibo; Zhang, Nu^*

来源：NEURO-ONCOLOGY, 2021, 23(5): 743-756.

DOI：10.1093/neuonc/noaa279

• CircRNA
• EGFR
• glioblastoma
• iORF
• rolling translation

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 (circEGFR) 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. Deprivation of rtEGFR in brain tumor-initiating cells (BTICs) attenuated tumorigenicity and enhanced the anti-GBM effect. @@@ Conclusion. Our findings identified the endogenous rolling-translated protein and provided strong clinical evidence that targeting rtEGFR could improve the efficiency of EGFR-targeting therapies in GBM.

• 单位
  1; 南方医科大学; 中山大学