Abstract:

Objective To discuss the effect of sialic acid-binding immunoglobulin-like lectin-15 （Siglec15） derived from M2 tumor-associated macrophages （M2-TAMs） on promoting the malignant biological behavior of the esophageal squamous cell carcinoma （ESCC） through bioinformatics analysis， and to validate the findings through cell experiment. Methods The Tumor Immune Estimation Resource （TIMER） online Database was used to analyze the expression differences and immune infiltration of Siglec15 in pan-cancer and adjacent normal tissues. Real-time fluorescence quantitative PCR （RT-qPCR） method was used to detect the expression levels of Siglec15 mRNA in M2-TAMs and ESCC EC109 and KYSE150 cells. Based on the non-contact co-culture of M2-TAMs and ESCC cells， the following groups were set up，such as EC109/KYSE150 group， EC109/KYSE150+si-NC group （transfected with si-NC sequence）， and EC109/KYSE150+si-Siglec15 group （transfected with si-Siglec15#1 and si-Siglec15#2 sequences）. CCK-8 method was used to detect the proliferation activities of the cells in various groups； wound healing assay was used to detect the wound healing rates of the cells in various groups； Transwell chamber assay was used to detect the numbers of migration and invasion cells in various groups； flow cytometry was used to detect the apoptotic rates of the cells in various groups. Results The bioinformatics analysis results showed that compared with adjacent normal tissue， the expression levels of Siglec15 mRNA in pan-cancer tissues such as esophageal cancer， colon cancer， and head and neck squamous cell carcinoma tissues were increased （P<0.05 or P<0.01）， and the expression level of Siglec15 mRNA in esophageal cancer tissue was significantly positively correlated with the infiltration of the macrophages （P<0.05）. Compared with the EC109 cells and KYSE150 cells， the expression level of Siglec15 mRNA in M2-TAMs was significantly increased （P<0.01）. There was no significant difference in the proliferation rate of the cells among EC109/KYSE150 group， EC109/KYSE150+si-NC group， and EC109/KYSE150+si-Siglec15 group （P>0.05）. Compared with EC109/KYSE150 group， after treated for 24 and 48 h， the wound healing rate of the cells in EC109/KYSE150+si-NC group was increased （P<0.01）， the numbers of migration and invasion cells were increased （P<0.05）， and the apoptotic rate was decreased （P<0.01）. Compared with EC109/KYSE150+si-NC group， the wound healing rates of the cells in EC109/KYSE150+si-Siglec15#1 group and EC109/KYSE150+si-Siglec15#2 group were decreased （P<0.05）， the numbers of migration and invasion cells were decreased （P<0.05）， and the apoptotic rates of the cells had no significant difference （P>0.05）. Conclusion Siglec15 derived from M2-TAMs may be a key factor in promoting the migration and invasion of the ESCC cells.

Key words: Esophageal squamous cell carcinoma, Sialic acid-binding immunoglobulin-like lectin-15, Tumor-associated macrophage, Cell migration, Cell invasion