Objective:To investigate the effect of ligand of numb-protein X1(LNX1)on the proliferation,invasion and migration of renal clear cell carcinoma cells and its underlying molecular mechanism. Methods:Gene Expression Profiling Interactive Analysis(GEPIA)database was used to analyze the mRNA expression level of LNX1 in renal clear cell carcinoma tissues and its relationship with the prognosis of patients with renal clear cell carcinoma.LNX1 gene specific shRNA(shLNX1)was delivered into renal clear cell carcinoma cell lines 786-O and ACHN by lentiviral infection,and flag-LNX1 plasmid was delivered into 786-O and ACHN cells by transient transfection.CCK-8 assay and colony formation assay were used to assess the effects of LNX1 silencing or overexpression on the proliferation of 786-O and ACHN cells.Transwell assay was used to evaluate the effects of LNX1 silencing or overexpression on the invasion and migration of 786-O and ACHN cells.Bioinformatics analysis was used to screen the downstream target genes of LNX1.Western blotting was used to examine the effects of LNX1 silencing or overexpression on the expression level of T-lymphoma invasion and metastasis-inducing protein 1(TIAM1)as well as the expression levels of total and phosphorylated ERK(phospho-ERK,p-ERK)in the ERK signaling pathway downstream of TIAM1 in 786-O and ACHN cells.786-O and ACHN cells overexpressing LNX1 were treated with proteasome inhibitor MG132,and the protein expression level of TIAM1 was analyzed by Western blotting.Finally,myc-TIAM1 recombinant plasmid was transfected into LNX1-overexpressing cells.Then,the expression levels of proteins in the ERK signaling pathway and the abilities of proliferation,invasion and migration of 786-O and ACHN cells were examined by Western blotting,colony formation assay and Transwell assay,respectively. Results:The mRNA expression level of LNX1 in renal clear cell carcinoma tissue was decreased(P＜0.05)and was positively correlated with the survival time of patients with renal clear cell carcinoma(P＜0.001).LNX1-silencing 786-O and ACHN cells and LNX1-overexpressing 786-O and ACHN cells were constructed successfully.After LNX1 silencing,the proliferation,invasion and migration of 786-O and ACHN cells were significantly enhanced(all P＜0.05).After LNX1 overexpression,the abilities of proliferation,invasion and migration of 786-O and ACHN cells were significantly decreased(all P＜0.05).Bioinformatics analysis identified TIAM1 as a potential target of LNX1.After silencing LNX1,the protein expression levels of TIAM1 and p-ERK were significantly increased(all P＜0.05),while the expression level of ERK remained unchanged.After LNX1 overexpression,the protein expression levels of TIAM1 and p-ERKwere significantly decreased(all P＜0.01),while the expression level of ERK was unchanged.Treatment with proteasome inhibitor MG132 increased the protein expression level of TIAM1 in LNX1-overexpressing 786-O and ACHN cells(P＜0.01 and P＜0.001).After LNX1-overexpressing cells were transfected with myc-TIAM1 plasmid,the protein expression level of p-ERK was increased,the abilities of cell proliferation,invasion and migration were enhanced(all P＜0.05),and the expression level of ERK protein remained unchanged. Conclusion:LNX1 inhibits the proliferation,invasion and migration of renal clear cell carcinoma cells by degrading TIAM1 which further regulates the phosphorylation of ERK.