Long noncoding RNA Meg3 sponges miR-708 to inhibit intestinal tumorigenesis via SOCS3-repressed cancer stem cells growth.

BACKGROUND

Colorectal cancer (CRC) remains the most common gastrointestinal cancer and a leading cause of cancer deaths worldwide, with most showing pathologies indicating the malignant transformation of early stage intestinal stem cells. The long non-coding RNA Meg3, which functions as a tumor suppressor, has been reported to be abnormal in multiple tumorigenesis events; however, the underlying mechanism by which Meg3 contributes to the malignant proliferation of colonic stem cells remains unclear.

METHODS

We analyzed the expression levels of Meg3, miR-708, and SOCS3 in samples from Apc loss-of-function (Apc) mice and patients with CRC, particularly in colonic crypt cells. Apc mice and AMO/DSS-induced mice model (in vivo) and organoid culture system (in vitro) were used to explore the effect of the Meg3/miR-708/SOCS3 axis on tumorigenesis in the colon. In vitro, we performed RNApull-down, RNA immunoprecipitation, and luciferase reporter assays using DLD1 and RKO cell lines.

FINDINGS

The Meg3/miR-708/SOCS3 signaling axis plays a critical role in the early stage of CRC development. Our data showed Meg3 levels negatively correlate with miR-708 levels both in clinical samples and in the Apc mouse model, which indicated that Meg3 acts as a competitive endogenous RNA (ceRNA) of miR-708. Then, miR-708 served as an oncogene, inducing neoplasia in both Apc mice and cultured colonic organoids. Put together, miR-708 appears to promote malignant proliferation of colonic stem cells by targeting SOCS3/STAT3 signaling.

INTERPRETATION

These data revealed that Meg3 sponges miR-708 to inhibit CRC development via SOCS3-mediated repression of the malignant proliferation of colonic stem cells. The Meg3/miR-708/SOCS3 signaling axis provides potential targets for the diagnosis and treatment of CRC, particularly early stage CRC.