ADAMTS9 Is A Functional Tumor Suppressor Through Suppressing EGFR And TGF?1/T?R(?/?)in Human Breast Cancer

Objective: Chromosome region 3p12-14 is an important tumor suppressor gene(TSG)locus for multiple cancers.ADAMTS9,a member of the metalloprotease large family,has been identified as a 3p14.2 TSG inactivated in several carcinomas,but little known about its abnormality and functions in breast cancer(BrCa)pathogenesis.Methods: The expression level of ADAMTS9 was examined by quantitative reverse transcription polymerase chain reaction(qRT-PCR).The effects of its tumor-suppressive functions were elucidated by cell proliferation assay,colony formation assay,flow cytometric analysis,trans-well assay,wound healing assay and tube formation assay in ADAMTS9-transfected and vector-transfected BrCa cell lines.Furthermore,the effects of ADAMTS9 on AKT pathway were determined by Western blot assay.Results: ADAMTS9 was significantly downregulated in breast primary tumors compared with paired surgical margin tissues.Ectopic expression of ADAMTS9 in BrCa cell lines induced significant growth suppression,cell cycle arrest in G0–G1 phase,enhanced apoptosis,and reduced cell migration and invasion.Conditioned culture medium from ADAMTS9-transfected BT549 cells markedly disrupted human umbilical vein endothelial cell(HUVEC)tube formation ability on Matrigel.Furthermore,ADAMTS9 inhibited BrCa progression via inhibiting AKT signaling and regulating its downstream targets(MDM2,p53,p21,p27,E-cadherin,VIM,SNAIL,VEGFA,NF?B-p65 and MMP2).Moreover,ADAMTS9 reduced phosphorylation levels of EGFR and AKT after treatment with EGF,suppressed the activation of AKT after treatment with TGF?1,and enhanced the negative effect of LY2109761(selective TGF-? receptor type I/II dual inhibitor)on phosphorylation of AKT.Conclusions: Our results indicate that ADAMTS9 is inactivated in BrCa,and acts as an efficient TSG for BrCa by blocking AKT activities through suppressing its upstream activators EGFR and TGF?1/T?R(I/II).