Downregulation of integrin subunit alpha 7 expression sustains anoikis resistance in osteosarcoma
Objective To investigate the expression of integrin subunit alpha 7(ITGA7)in osteo-sarcoma and its role and mechanism in pulmonary metastasis of osteosarcoma.Methods The mRNA and protein expression levels of ITGA7 in osteosarcoma were determined using the gene expression omnibus(GEO)database(52 cases of osteosarcoma tissues and 12 controls)and cell lines(HOS cells and hFOB 1.19 cells).Lentiviral transduction was employed to knock down and overexpress ITGA7 in HOS cells.We compared the growth of HOS cell spheres in 6 independent samples under conditions of floating culture.RNA-seq technology was employed to assess downstream gene changes in HOS cells overexpressing ITGA7 across 3 independent samples.The comparison of continuous variables between two groups was conducted using an unpaired t-test,while the comparison among three groups was performed using one-way ANOVA.Results Results from the GEO database showed a significant decrease in ITGA7 mRNA levels in osteosar-coma tissues compared to control tissues(7.45±0.10 vs.7.61±0.04,t=9.64,P＜0.01),and both mRNA(0.59±0.16 vs.1.02±0.25,t=3.59,P＜0.01)and protein levels(1.32±0.28 vs.2.34± 0.40,t=5.03,P＜0.01)of ITGA7 were downregulated in osteosarcoma cell lines.Following ITGA7 knockdown,the diameter of osteosarcoma cell spheres was significantly larger than the control group[(310.21±32.62)μm vs.(230.84±21.66)μm,t=4.96,P＜0.01],while overexpression of ITGA7 resulted in significantly smaller cell sphere diameters than the control group[(116.03±12.91)μm vs.(230.84±21.66)μm,t=11.12,P＜0.01].RNA-seq results revealed significant upregulation of 391 genes and downregulation of 293 genes in the ITGA7 overexpression group,among which 37 anoikis-related genes were upregulated,and 12 anoikis-related genes were downregulated.Furthermore,quantita-tive polymerase chain reaction(qPCR)confirmed a significant upregulation of B cell lymphoma/leukemia-2 associated X protein(bax)(1.74±0.30 vs.0.92±0.15,t=5.98,P＜0.01)and Bak 1(3.52±0.57 vs.1.06±0.21,t=9.82,P＜0.01)expression levels and a significant downregulation of B cell lympho-ma/leukemia-2(bcl-2)(0.43±0.22 vs.1.09±0.24,t=4.85,P＜0.01)in the ITGA7 overexpression group.Conclusion ITGA7 is downregulated in osteosarcoma,and its overexpression promotes anoikis in osteosarcoma.Low levels of ITGA7 in osteosarcoma play a crucial role in maintaining its resistance to anoikis and may have a significant impact on pulmonary metastasis of osteosarcoma.
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