A Comprehensive Immunologic Portrait of Triple-Negative Breast Cancer

Background Triple-negative breast cancer (TNBC) is a high-risk malignancy due to its high capacity for invasion and lack of targeted therapy. Immunotherapy continues to demonstrate efficacy in a variety of cancers, and thus may be a promising strategy for TNBC given the limited therapeutic options currently available for TNBC. In this study, we performed a comprehensive portrait of immunologic landscape of TNBC based on 2 large-scale breast cancer genomic data. Methods We compared expression levels of immune-related genes and gene-sets among TNBC, non-TNBC, and normal tissue, and within TNBCs of different genotypic or phenotypic features. Moreover, we explored the association of immune-related genes or gene-sets expression and survival prognosis in TNBC patients. Results We found that almost all analyzed immune-related gene-sets had significantly higher expression levels in TNBC than non-TNBC. These highly expressed gene-sets in TNBC included 15 immune cell type and function, human leukocyte antigen (HLA), cancer testis (CT), tumor-infiltrating lymphocytes (TILs), immune cell infiltrate, regulatory T (Treg) cells, immune checkpoint, cytokine and cytokine receptor, metastasis-promoting, pro-inflammatory and parainflammation (PI) gene-sets. Moreover, TP53-mutated, TNBC had significantly higher expression levels of the immune checkpoint, Treg, PI, and CT gene-sets, and lower expression levels of the immune cell infiltrate gene-set than TP53-wildtype TNBC. Furthermore, we found that elevated expression of most of the immune-related genes in TNBC was associated with the ER-status, while some were associated with both ER-and HER2-status. Elevated expression of the immune-related genes in TNBC was also associated with the high tumor mutation burden (TMB) in TNBC. Finally, elevated expression of the immune-related gene-sets was likely to be associated with better survival prognosis in TNBC. Conclusions Our findings suggest that TNBC is a breast cancer subtype with particularly strong immunogenicity, and therefore could be propitious to immunotherapeutic options.