Nuclear Aurora kinase A triggers programmed death-ligand 1-mediated immune suppression by activating MYC transcription in triple-negative breast cancer

Background:Increasing studies have reported that oncogenes regulate components of the immune system,suggesting that this is a mechanism for tumorigenesis.Aurora kinase A(AURKA),a serine/threonine kinase,is involved in cell mitosis and is essential for tumor cell proliferation,metastasis,and drug resistance.However,the mechanism by which AURKA is involved in immune response regulation is unclear.Therefore,this study aimed to investigate the role of AURKA in immune regulation in triple-negative breast cancer(TNBC).Methods:Peripheral blood mononuclear cells(PBMCs)were co-cultured with TNBC cells.The xCELLigence Real-Time Cell Analyzer-MP system was used to detect the killing efficiency of immune cells on TNBC cells.The expression of immune effector molecules was tested by quantitative real-time polymerase chain reaction(qRT-PCR)to evaluate immune function.Furthermore,to validate AURKA-regulated immune response in vivo,4T1 murine breast cancer cell line with AURKA overexpression or downregulation was engrafted into BALB/c mice.The distribution and proportion of immune cells in tumors were further evaluated by immunohistochemistry and flow cytometry.Results:Downregulation of AURKA in TNBC cells increased immune response by activating CD8^(+)T cell proliferation and activity.Nuclear rather than cytoplasmic AURKA-derived programmed death-ligand 1(PD-L1)expression was independent of its kinase activity.Mechanistic investigations showed that nuclear AURKA increased PD-L1 expression via an MYC-dependent pathway.PD-L1 overexpression mostly reversed AURKA silencing-induced expression of immune effector molecules,including interleukin-(IL-2),interferon-γ(IFN-γ),and perforin.Moreover,AURKA expression was negatively correlated with the enrichment and activity of tumor-infiltrating CD8^(+)T cells in 4T1 engrafted BALB/c mouse model.Conclusions:Nuclear AURKA elevated PD-L1 expression via an MYCdependent pathway and contributed to immune evasion in TNBC.Therapies targeting nuclear AURKA may restore immune responses against tumors.

Single-cell atlas reveals a distinct immune profile fostered by T cell-B cell crosstalk in triple negative breast cancer

Background:Characterizing the unique immune microenvironment of each tumor is of great importance for better predicting prognosis and guiding cancer immunotherapy.However,the unique features of the immune microenvironment of triple negative breast cancer(TNBC)compared with other subtypes of breast cancer remain elusive.Therefore,we aimed to depict and compare the immune landscape among TNBC,human epidermal growth factor receptor 2-positive(HER2^(+))breast cancer,and luminal-like breast cancer.Methods:Single-cell RNA sequencing(scRNA-seq)was performed on CD45^(+)immune cells isolated from human normal breast tissues and primary breast tumors of various subtypes.By analyzing the scRNA-seq data,immune cell clusters were identified and their proportions as well as transcriptome features were compared among TNBC,human HER2^(+)breast cancer,and luminal-like breast cancer.Pseudotime and cell-cell communication analyses were also conducted to characterize the immune microenvironment.Results:ScRNA-seq data of 117,958 immune cells were obtained and 31 immune clusters were identified.A unique immunosuppressive microenvironment in TNBC was decoded as compared to that in HER2^(+)or luminal-like breast cancer,which was characterized by higher proportions of regulatory T cells(Tregs)and exhausted CD8+T cells and accompanied by more abundant plasma cells.Tregs and exhausted CD8+T cells in TNBC exhibited increased immunosuppression signature and dysfunctional scores.Pseudotime analyses showed that B cells tended to differentiate to plasma cells in TNBC.Cell-cell communication analyses indicated that these unique features are fostered by the diversified T cell-B cell crosstalk in TNBC.Based on the T cell-B cell crosstalk,a prognostic signaturewas established that could effectively predict the prognosis status for patients with TNBC.Additionally,it was found that TNBC had a higher proportion of cytotoxic natural killer(NK)cells,whereas HER2^(+)or luminal-like breast cancer lost this feature,suggesting thatHER2^(+)or luminal-like breast cancer,but not TNBC,may benefit from NK-based immunotherapy.Conclusions:This study identified a distinct immune feature fostered by T cell-B cell crosstalk in TNBC,which provides better prognostic information and effective therapeutic targets for breast cancer.