Abstract: Objective To investigate the effects of Leucine⁃rich repeats containing G protein⁃coupled receptor 4 (LGR4) on the proliferation, apoptosis, invasion, migration and epithelial mesenchymal transition (EMT) of nasopharyngeal carcinoma (NPC) cell lines C666⁃1. Methods The differential genes were obtained by intersection of GEO database sequencing data GSE89804, GSE15903 and GSE103611 using Venn diagram. The expression of LGR4 in NPC tissues, corresponding normal tissues，NPC tumor tissues with and without distant metastasis were analyzed by the bioinformatic analysis. The expression levels of LGR4 in NPC cell lines C666⁃1 and normal nasopharyngeal cell lines NP69 were detected by RT⁃qPCR and Western blot. NPC cell lines C666⁃1 were divided into the NC group ( negative control lentivirus), the KD1 group and the KD2 group (Knock Down). The expression of LGR4 and epithelial marker E⁃cadherin were detected by Western blot. Cell proliferation, apoptosis, invasion and migration were detected by CCK⁃8, clone formation assays, flow cytometry, scratch assay and Transwell assay. Results Venn diagram showed that the differential gene of GSE89804, GSE15903 and GSE103611 data sets was LGR4. The results of GSE12452 dataset showed that the LGR4 was up⁃regulated in NPC tissues by constrast with corresponding normal tissues (P<0.05). The results of GSE103611 dataset showed that the LGR4 was up⁃regulated in NPC tumor tissues with distant metastasis by contrast with NPC tumor tissues without distant metastasis (P<0.05). Compared with the mRNA and protein expression levels of NP69 cell lines, those of LGR4 were significantly up⁃regulated in NPC cell lines C666⁃1 (all P<0.001). Compared with the NC group, the knockdown of LGR4 inhibited the proliferation (all P<0.05), invasion and migration (all P<0.001), and promoted the apoptosis and protein expression of E⁃cadherin in C666⁃1 cell lines (all P<0.001). Conclusions  The expression of LGR4 is up⁃regulated in NPC cell lines C666⁃1. The knockdown of LGR4 could inhibit the proliferation, invasion, migration and promote apoptosis and EMT of NPC cell lines C666⁃1.

Key words: Nasopharyngeal carcinoma, Leucine-rich repeats containing G protein-coupledreceptor4(LGR4), Proliferation, Apoptosis, Invasion, Migration, Epithelial mesenchymal transition