Novel Association Of DJ-1 With HER3 Potentiates HER3 Activation And Signaling In Breast Cancer

[Objectives]HER3 has emerged as a new therapeutic target for cancer.Currently,more than a dozen anti-HER3 antibodies are in clinical trials for treatment of various cancers.However,limited understanding of the complex HER3 signaling in cancer and lack of established biomarkers have made it challenging to stratify cancer patients who can benefit from HER3 targeted therapies.The binding of ligands such as NRG-1 to HER3 induces heterodimerization of HER3 with other HER family receptors,particularly HER2,resulting in HER3 phosphorylation and signaling.DJ-1 is a highly conserved protein and has been implicated in Parkinsons’s disease.Overexpression of DJ-1 has been reported in many cancer types including breast cancer and various previous studies implicated DJ-1 as an oncogene.Despite strong experimental evidence,the molecular mechanisms of DJ-1 in cancer remain obscure.In recent years,the role of radiotherapy in breast cancer treatment plays an important role,but some patients’ prognosis is not ideal.Based on the above reasons,this experiment is designed to explore whether there is a certain relationship between DJ-1 and HER3,its effect on breast cancer cells,and validate its radiosensitivity mechanism from the cellular level in order to provide a better certain theoretical basis for HER3.targeted therapy.[Materials and methods]By immunoprecipitation,immunofluorescence and proximity ligation assay(PLA),we demonstrated the role of relationship between DJ-1 and HER3 in breast cancer.Then from the celluer level,we verified NRG-1 could influence the role of relationship between DJ-1 and HER3 in breast cancer cells.NRG-1 promotes the exocrine effect of DJ-1 in MCF-7 cells,HER3 knockdown inhibited the NRG-1-induced DJ-1 exocrine HER3 overexpression and increased the NRG-1-induced DJ-1 exocrine.Based on the breast cancer cell lines with DJ-1 knockdown or DJ-1 overexpression,by the means of WB and PCR technology we analysed the mRNA and protein level of HER3;meanwhile,we explored the variation of HER3 signaling pathways,cell proliferation,cell migration assays and 3D cell cultures.Then,we also validated DJ-1 knockdown and overexpression effected on tumor growth and sensitivity of tumors to anti-HER3 antibody treatment in vivo,respectively.Besides,breast cancer cells were available to radiotherapy in order to observe the expression changes of HER3 protein and mRNA.[Results]DJ-1 association with HER3 protects HER3 from ubiquitination and degradation through the proteasomal pathway in breast cancer cells.However,neuregulin 1(NRG-1)mediated HER3 activation results in a reduced association of DJ-1 with HER3.DJ-1 shRNA knockdown in cancer cells resulted in decreased levels of HER3 and its downstream signaling through the PI3K/AKT and ERK pathways.DJ-1 shRNA knockdown cancer cells significantly reduced cell proliferation and migration in vitro and tumor growth in vivo.Conversely,overexpression of DJ-1 increased HER3 levels and promoted cancer cell proliferation in vitro and tumor growth in vivo.Notably,cancer cells with high DJ-1 expression showed more sensitivity than DJ-1 knockdown cells to anti-HER3 antibody inhibition.Besides,from the cellular cells by the means of PCR and WB,we verified that the HER3 protein and mRNA reduced along with the increase of irradiation dose.[Conclusion]In this study,we identified DJ-1/PARK7(Parkinson Protein 7)as a novel interaction partner of HER3 and demonstrated the potential of DJ-1 as a biomarker for anti-HER3 cancer therapy.