Objective:To explore the effects of deleted in lung and esophageal cancer 1 (DLEC1) on osteosarcoma cells and the underlying mechanism.Methods:Immunohistochemical staining for DLEC1 was scored in sixteen paired osteosarcoma tissues and adjacent normal tissues obtained. The present study was conducted on human osteosarcoma 143B cells which were randomly divided into two groups, pDC316-DLEC1 transfection group and pDC316-Null transfection group. Differences in the proportion of EdU-positive cells, cell cycle distribution, proportion of apoptosis cells, number of migrating and invasive cells, expression of epithelial-mesenchymal transformation (EMT) markers (E-cadherin and vimentin), relative protein expression levels of NF-κB, AKT and ERK signaling pathways were assessed between the pDC316-DLEC1 and pDC316-Null transfection groups in in vitro study. The subcutaneous inoculation model and tail vein injection model were developed to evaluate the differences in subcutaneous tumor volume, subcutaneous tumor weight and pulmonary tumor nodules between the above two groups in in vivo study.Results:The DLEC1 immunostaining scores for osteosarcoma tissues and adjacent normal tissues were 2.88±1.15 and 4.25±1.06, respectively. The proportions of EdU-positive cells (36.47%±1.90% vs 51.47%±2.89%) and S phase cells (33.31%±0.61 vs 43.77%±1.47%) were decreased, while G0/G1 phase cells (46.87%±0.73% vs 35.47%±1.14%) and apoptotic cells (13.83%±1.01% vs 3.30%±0.26%) were increased in the pDC316-DLEC1 transfection group compared to those in the pDC316-Null transfection group. Decreased number of migrating cells (199.00±12.53 vs 369.67±10.02) and invasive cells (104.67±9.07 vs 299.67±12.06) and relative expression of vimentin mRNA (0.59±0.02 vs 1.00±0.02) and protein (0.54±0.08 vs 1.00±0.00) were observed in the pDC316-DLEC1 transfection group, while relative expression of E-cadherin mRNA (2.40±0.05 vs 1.00±0.02) and protein(1.98±0.10 vs 1.00±0.00) in the pDC316-DLEC1 transfection group were higher than those in the pDC316-Null transfection group. The relative protein expression of NF-κB (p65), p-AKT (Ser473) and p-ERK (Thr202/Tyr204) in the pDC316-DLEC1 transfection group were decreased by 51.67%±4.04%, 64.67%±5.51% and 48.67%±4.73% compared to those in the pDC316-Null transfection group. In in vivo study, 143B cells in the pDC316-DLEC1 transfection group formed smaller (320.00±145.22 mm 3vs 798.00±221.94 mm 3) and lighter (0.49±0.17 g vs 0.88±0.14 g) subcutaneous tumors and less metastatic lung nodules (7.71±1.80 vs 20.86±3.53) compared with those in the pDC316-Null transfection group. Conclusion:Overexpression of DLEC1 could suppress the NF-κB/AKT/ERK signaling pathways in 143B cells, which further induces G0/G1 arrest and apoptosis that ultimately inhibits cell proliferation and reduces the metastatic potential through reversing EMT.