CircRNA <i>CDR1as</i>: a novel diagnostic and prognostic biomarker for gastric cancer

Circular RNA (circRNA) <i>CDR1as</i> is emerging as a vital tumour regulator. This study aimed to investigate its diagnostic and prognostic value and molecular mechanisms for gastric cancer (GC). <i>CDR1as</i> expression in GC and adjacent normal tissues (n = 82), paired plasma (n = 65) and plasma exosome samples (n = 68) from GC patients and healthy controls were determined by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Correlations between <i>CDR1as</i> level and clinicopathological factors of GC patients were analysed. Its diagnostic and prognostic value was evaluated by receiver operating characteristic (ROC) curves and Cox regression analysis combined with Kaplan-Meier plots. <i>CDR1as-</i>regulated proteins and signalling pathways were identified by quantitative proteomics and bioinformatic analysis. <i>CDR1as</i> was downregulated in GC tissues and associated with tumour size and neural invasion. Plasma- and exosome-derived <i>CDR1as</i> was upregulated in GC patients while plasma-derived <i>CDR1as</i> level was related to lymphatic metastasis. Area under ROC curve (AUC) of tissue-, plasma- and exosome-derived <i>CDR1as</i> was 0.782, 0.641, 0.536 while combination of plasma <i>CDR1as</i>, serum CEA and CA19-9 increased AUC to 0.786. Distal metastasis, TNM stage and tissue-derived <i>CDR1as</i> level were independent predictors for overall survival (OS) of patients. MiRNA signalling networks and glycine, serine and threonine metabolism were regulated by CDR1as and HSPE1 might be a key protein. <i>CDR1as</i> is a crucial regulator and promising biomarker for GC diagnosis and prognosis. <i>CDR1as</i> level in tumour tissues and plasma of GC patients was associated with tumour progression. The findings indicate that <i>CDR1as</i> is involved in GC progression and is a potential diagnostic and prognostic biomarker.