LncRNA ST3Gal6-AS1/ST3Gal6 axis mediates colorectal cancer progression by regulating α-2,3 sialylation via PI3K/Akt signaling.

Sialylation is associated with cancer progression. Long noncoding RNAs (lncRNAs) have important roles in diverse diseases including cancer. The lncRNA ST3Gal6 antisense 1 (ST3Gal6-AS1) derives from the promoter region of sialyltransferase ST3Gal6. However, the mechanisms by which ST3Gal6-AS1 modulates colorectal cancer (CRC) development through sialylation remain largely unknown. Here, we found that ST3Gal6-AS1 and ST3Gal6 levels were lower in tumor tissues than adjacent normal tissues of CRC patients. The correlation between ST3Gal6-AS1 and ST3Gal6 was further validated in several types of CRC cell lines. In addition, ST3Gal6 was dysregulated and positively correlated to ST3Gal6-AS1. ST3Gal6-AS1 recruited histone methyltransferase MLL1 to the promoter region of ST3Gal6, induced H3K4me3 modification and activated ST3Gal6 transcription. Furthermore, ST3Gal6-AS1/ST3Gal6 axis mediated α-2, 3 sialylation and inhibited the activation of PI3K/Akt signaling, thereby resulting in Foxo1 nuclear translocation in CRC cells. ST3Gal6-AS1 was a target of transcription factor Foxo1 and regulated by Foxo1. ST3Gal6-AS1 also inhibited CRC cell proliferation, metastasis, and promoted cell apoptosis in vitro. Overexpression of ST3Gal6-AS1 significantly decreased the tumorigenesis, lung and liver metastasis of SW620 cells in vivo. ST3Gal6-AS1 expression was negatively correlated with tumor size, lymphatic metastasis, distant metastasis and tumor stage in CRC patients. Collectively, these data indicated that ST3Gal6-AS1, ST3Gal6, PI3K/Akt, and Foxo1 formed a positive feedback loop, which might play a key role in CRC progression.