Objective To investigate the expression of immunoglobulin γ-1 heavy chain constant region(IGHG1)in acute myeloid leukemia(AML)THP-1 cells and its influence on cell proliferation,apoptosis,and invasion via its regulation of the transforming growth factor β(TGF-β)/Smad pathway.Methods Bone marrow specimens from nine children with AML and eight children with fractures,human bone marrow stromal HS-5 cells,and human AML THP-1 and HL60 cells were used in the research.Western blot was used to detect IGHG1 protein expression.THP-1 cells were divided into a blank group(without any treatment),si-NC group,si-IGHG1-1 group,si-IGHG1-2 group,si-IGHG1-3 group,TGF-β group,si-IGHG1-1+TGF-β group,and si-IGHG1-1+TGF-β +LY364947 group.Cell proliferation was measured by CCK-8 method.Flow cytometry and Transwell experiment were performed to measure apoptosis and invasion.Western blot was used to detect the protein expression of IGHG1,TGF-β,p-Smad2 and p-Smad3 in each group of cells.Results Compared with the bone marrow of children with fractures,the bone marrow of children with AML(P<0.05)had significantly higher expression levels of IGHG1((0.24±0.03)vs(0.87±0.12)).Compared with HS-5 cells,human AML THP-1 and HL60 cells had significantly increased expression levels of IGHG1((0.89±0.14)(0.75±0.08)vs(0.21±0.02))(P<0.05).Compared with the blank group,the si-IGHG1-1 group of THP-1 cells showed significantly reduced OD450 values(24 h,48 h,72 h),invading cell numbers and protein expression of TGF-β,p-Smad2,p-Smad3 and their apoptosis rate was increased(P<0.05),while the corresponding indexes showed the opposite trend in the TGF-β group(P<0.05).TGF-β reversed the effects of silencing IGHG1 on the proliferation,apoptosis and invasion of THP-1 cells.Compared with the si-IGHG1-1+TGF-β group,the si-IGHG1-1+TGF-β+LY364947 group had significantly decreased TGF-β,p-Smad2,p-Smad3 and protein levels,OD450 values and cell invasion numbers and the apoptosis rate was increased(P<0.05).Conclusions IGHG1 is highly expressed in AML cells.Silencing the IGHG1 gene can inhibit the proliferation and invasion of AML cells and promote the apoptosis of AML cells.This mechanism may be related to the inhibition of the TGF-β/Smad pathway.