Long noncoding RNA SGO1-AS1 inactivates TGFβ signaling by facilitating TGFB1/2 mRNA decay and inhibits gastric carcinoma metastasis.

BACKGROUND: Although thousands of long noncoding RNAs (lncRNAs) have been annotated, only a few lncRNAs have been characterized functionally. In this study, we aimed to identify novel lncRNAs involved in the progression of gastric carcinoma (GC) and explore their regulatory mechanisms and clinical significance in GC.

METHODS: A lncRNA expression microarray was used to identify differential lncRNA expression profiles between paired GCs and adjacent normal mucosal tissues. Using the above method, the lncRNA SGO1-AS1 was selected for further study. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and in situ hybridization (ISH) were performed to detect SGO1-AS1 expression in GC tissues. Gain-of-function and loss-of-function analyses were performed to investigate the functions of SGO1-AS1 and its upstream and downstream regulatory mechanisms in vitro and in vivo.

RESULTS: SGO1-AS1 was downregulated in gastric carcinoma tissues compared to adjacent normal tissues, and its downregulation was positively correlated with advanced clinical stage, metastasis status and poor patient prognosis. The functional experiments revealed that SGO1-AS1 inhibited GC cell invasion and metastasis in vitro and in vivo. Mechanistically, SGO1-AS1 facilitated TGFB1/2 mRNA decay by competitively binding the PTBP1 protein, resulting in reduced TGFβ production and, thus, preventing the epithelial-to-mesenchymal transition (EMT) and metastasis. In addition, in turn, TGFβ inhibited SGO1-AS1 transcription by inducing ZEB1. Thus, SGO1-AS1 and TGFβ form a double-negative feedback loop via ZEB1 to regulate the EMT and metastasis.

CONCLUSIONS: SGO1-AS1 functions as an endogenous inhibitor of the TGFβ pathway and suppresses gastric carcinoma metastasis, indicating a novel potential target for GC treatment.