To explore the function and mechanism of long non-coding RNA MIR503HG in esophageal squamous cell carcinoma (ESCC).

The MIR503HG expression data in 60, 119 and 23 cases of ESCC and their paired adjacent tissues were chosen from three ESCC datasets GSE53622, GSE53624 and GSE130078, respectively. The expression data of MIR503HG in 81 ESCC tissues and 271 unpaired normal esophageal tissues were screened from the combined dataset of Cancer Genome Atlas and Genotype-Tissue Expression Database (TCGA+ GTEx). The MIR503HG knockdown plasmid was constructed, packaged into lentivirus. The lentivirus was used to infect with esophageal squamous cell carcinoma cell lines KYSE30 and KYSE510 to screen out the stable MIR503HG knockdown cell lines. ESCC cell line KYSE30 was transiently transfected with miRNA mimics to overexpress hsa-miR-503-3p and hsa-miR-503-5p.The expression levels of MIR503HG, hsa-miR-503-3p and hsa-miR-503-5p were detected by quantitative real-time polymerase chain reaction. The proliferation ability of the cells was detected by cell counting kit 8 and clone formation assay. The invasion and migration ability of the cells were detected by Transwell assay. Cell cycle was detected by flow cytometry. The effect of MIR503HG on the proliferation of ESCC was detected by xenograft experiment in BALB/c-nu/nu mice.

Both GEO and TCGA+ GTEx databases showed that the expression of MIR503HG in ESCC tissues was higher than that in adjacent tissues and normal esophageal tissues (P<0.01). Compared with shNC group, the proliferation rates of KYSE30 and KYSE510 cells after knockdown of MIR503HGwere significantly inhibited (P<0.001). The colony formation numbers of KYSE30 cells in shMIR503HG1 group and shMIR503HG2 group were (2.00±1.41) and (1.33±0.47), respectively, significantly lower than that of the shNC group (P=0.002). The clone formation numbers of KYSE510 cells in shMIR503HG1 group and shMIR503HG2 group were (174.67±15.97) and (80.33±6.34), respectively, significantly lower than that of the shNC group (P<0.001). The invasive numbers of KYSE30 cells in shMIR503HG1 group and shMIR503HG2 group were 75.33±6.02 and 45.67±7.59, significantly lower than that of the shNC group(P<0.001). The migrating number of KYSE30 cells in shMIR503HG1 group and shMIR503HG2 group were 244.00±10.23 and 210.67±13.52, significantly lower than that of the shNC group(P<0.001), and the cell cycle was arrested in G₀/G₁ phase. The xenograft experiment showed that the subcutaneous tumor in shMIR503HG group was significantly smaller than that in shNC group, and the tumor weight in shMIR503HG group was (0.097±0.026) g, which was lower than (0.166±0.021) g in shNC group (P<0.001). After knockdown of MIR503HG, the relative expression levels of hsa-miR-503-3p in KYSE30 cells of shMIR503HG1 group and shMIR503HG2 group were 0.66±0.02 and 0.58±0.00, respectively, the relative expression levels of hsa-miR-503-5p were 0.64±0.00 and 0.68±0.03, respectively, which were all lower than those in shNC group (P<0.01). After knockdown of MIR503HG, overexpression of hsa-miR-503-3p and hsa-miR-503-5p attenuated the inhibitory effects of knockdown of MIR503HG on proliferation (P<0.001), invasion (P<0.01) and migration (P<0.001) of KYSE30 cells.

MIR503HG promotes the proliferation, invasion and migration of ESCC cells by regulating hsa-miR-503 pathway and can be used as a new potential target for targeted therapy of ESCC.

Esophageal squamous cell carcinoma; MIR503HG; Hsa-miR-503; Cell proliferation; Invasion; Migration