Long noncoding RNA CASC2 suppresses esophageal squamous cell carcinoma progression by increasing SOCS1 expression

Esophageal squamous cell carcinoma (ESCC) is one of the leading causes of cancer-related deaths worldwide. Emerging evidence suggests the involvement of long noncoding RNAs (lncRNAs) in tumorigenesis. LncRNA Cancer Susceptibility Candidate 2 (CASC2) has been demonstrated to act as a tumor suppressor contributing to the development and progression of several cancers. However, the functional significance and underlying mechanism of CASC2 in ESCC progression has not been well elucidated.

The expression levels of CASC2 in ESCC tissues were detected by qRT-PCR. CASC2 overexpression and knockdown models were established and used to investigate the functional role of CASC2 in ESCC cells. RIP, RNA pull-down and dual-luciferase assay was used to detect the association between CASC2 and miR-155. The interaction between CASC2 and Suppressor Of Cytokine Signaling 1 (SOCS1) was assessed by RIP and RNA pull-down assays.

In the present study, we found that CASC2 was significantly downregulated in ESCC tissues and positively correlated with overall survival time of patients with ESCC. Functional assays demonstrated that CASC2 suppressed proliferation, migration and invasion, as well as enhanced drug sensitivity in ESCC cells. Mechanistically, CASC2 inhibited ESCC progression by upregulating the expression of SOCS1 via two different ways. CASC2 acted as competing endogenous RNA (ceRNA) for miR-155 to post-transcriptionally increase SOCS1 expression. On the other hand, CASC2 was capable of interacting with SOCS1 protein and suppressing its degradation.

Conclusively, these results demonstrated that CASC2 could exert as a tumor suppressive lncRNA in ESCC progression via regulating SOCS1.