[Study on the effect and mechanisms of SIGLEC-15 on laryngeal squamous cell carcinoma]

Objective: To investigate the effect of sialic acid combined with immunoglobulin-like lectin 15 (SIGLEC-15) on laryngeal squamous cell carcinoma (LSCC) and underlying mechanisms. Methods: The Cancer Genome Atlas (TCGA), Cancer Cell Line Encyclopedia (CCLE) and Gene Expression Profiling Interactive Analysis (GEPIA2) databases were used for bioinformatics analysis. Cell Counting Kit-8 (CCK8), flow cytometry, and Transwell method were used respectively to detect proliferation, apoptosis, cell cycle, metastasis and invasion behaviors of the cells. Gene chip method was used for detecting up-regulated and down-regulated genes and performing enrichment analysis of differential genes. Western Blotting (WB) and Quantitative Real-time PCR (qPCR) were used to detect the expressions of proteins. Tumor formation experiments in nude mice were used to detect the effect of SIGLEC-15 on the growth of transplanted tumors. Wilcoxon rank sum test, t-test and Log-rank test were used for statistical analysis. Results: SIGLEC-15 was highly expressed in laryngeal squamous cell carcinoma and closely related to life in being. TU686^SIGLEC-15-with low expression of SIGLEC-15 was constructed. Compared to TU686^SIGLEC-15+, TU686^SIGLEC-15-showed significantly reduced activities of proliferation (48 h: 1.32±0.23 vs. 2.56±0.37, t=6.59, P<0.05), migration (1 036.52±51.22 vs. 1 819.62±180.24, t=7.22, P<0.05) and invasion (469.21±112.25 vs. 961.45±102.03, t=7.85, P<0.05); early increased apoptosis ((23.27±1.12)% vs. (5.64±1.61)%, t=11.32, P<0.05); blocked cell cycle at G0/G1 ((59.32±3.65)% vs. (35.46±3.57)%, t=9.85, P<0.05); the knockdown of SIGLEC-15 resulted in up-regulation of 864 genes, down-regulation of 357 genes, with significant changes in molecules of cell cycle, apoptosis and JAK/STAT signal pathways, and the expressions of p-JAK2, p-STAT3, Caspase-3, Bad, Bcl-2, and Cyclin d1 proteins. Tumor formation experiments in nude mice showed that at 8 weeks after the tumors were implanted, the growth transplanted tumors of TU686 SIGLEC-15-cell group was slower than that of TU686 SIGLEC-15+cell group, with significant difference in the mean tumor weights between two groups ((0.382±0.054) g vs. (1.277±0.126) g, t=8.44, P<0.05), while the expression of SIGLEC-15 was lower in the transplanted tumors of SIGLEC-15 knockdown group compared to control group, with significant difference(11.29±2.17 vs. 36.25±7.56, t=9.28, P<0.05). Conclusion: SIGLEC-15 is highly expressed in LSCC and can promote the progression of LSCC through the JAK2-STAT3 pathway.