The tumor microenvironment is composed of tumor cells, fibroblasts, endothelial cells and infiltrating immune cells, which may inhibit or promote tumor growth and progression. The objectives of this retrospective study were to characterize the density of tumor-associated macrophages (TAMs) in breast cancer, and to correlate the density of TAMs with clinicopathological parameters. Paraffin-embedded specimens and clinicopathological data, including up to 5 years follow-up information, were obtained from 172 breast cancer patients. Immunohistochemical staining for CD68 (marker for macrophages) was performed and evaluated in a blinded fashion. We found that TAMs were significantly frequent in high histopathological grade breast cancer patients. Breast cancer patients with a high density of TAMs had significantly lower rates of disease-free survival and 5-year overall survival than patients with low density of TAMs. Furthermore, high-infiltration of TAMs indicated worse survival rate for patients with node-negative breast cancer. In conclusion, the number of TAMs in the tumor stroma is an independent predictor of survival time for breast cancer patients. High-infiltration of TAMs is a significant unfavorable prognostic factor for patients with invasive breast cancer and, as such, is a potentially useful prognostic marker for breast cancer.

Objectives: Long non‐coding RNAs (lncRNAs) have been demonstrated as crucial regulators in cancer, but whether they are involved in the immune response of cancer cells remains largely undiscovered. GATA3‐AS1 is a novel lncRNA that was upregulated in breast cancer (BC) according to online databases. However, its role in triple‐negative breast cancer (TNBC) was elusive.Methods: GATA3‐AS1 expression in BC tissues and adjacent normal tissues was obtained from online databases. Loss‐of‐function assays were designed and conducted to verify the functional role of GATA3‐AS1 in TNBC cells. Bioinformatic analysis and mechanism experiments were applied to explore the downstream molecular mechanism of GATA3‐AS1. Similarly, the upstream mechanism which led to the upregulation of GATA3‐AS1 in TNBC cells was also investigated.Results: GATA3‐AS1 was markedly overexpressed in TNBC tissues and cells. Knockdown of GATA3‐AS1 suppressed TNBC cell growth and enhanced the resistance of TNBC cells to immune response. GATA3‐AS1 induced the deubiquitination of PD‐L1 through miR‐676‐3p/COPS5 axis. GATA3‐AS1 destabilized GATA3 protein by promoting GATA3 ubiquitination.Conclusion: GATA3‐AS1 contributed to TNBC progression and immune evasion through stabilizing PD‐L1 protein and degrading GATA3 protein, offering a new target for the treatment of TNBC.

The microenvironment of lymph node metastasized tumors (LNMT) determines tumor progression and response to therapy, but a systematic study of LNMT is lacking. Here, we generate single-cell maps of primary tumors (PTs) and paired LNMTs in 8 breast cancer patients. We demonstrate that the activation, cytotoxicity, and proliferation of T cells are suppressed in LNMT compared with PT.CD4⁺CXCL13⁺T cells in LNMT are more likely to differentiate into an exhausted state. Interestingly,LAMP3⁺dendritic cells in LNMT display lower T cell priming and activating ability than in PT. Additionally, we identify a subtype ofPLA2G2A⁺cancer-associated fibroblasts enriched in HER2⁺breast cancer patients that promotes immune infiltration. We also show that the antigen-presentation pathway is downregulated in malignant cells of the metastatic lymph node. Altogether, we characterize the microenvironment of LNMT and PT, which may shed light on the individualized therapeutic strategies for breast cancer patients with lymph node metastasis.

Current therapies for HER2-positive breast cancer have limited efficacy in patients with triple-positive breast cancer (TPBC). We conduct a multi-center single-arm phase 2 trial to test the efficacy and safety of an oral neoadjuvant therapy with pyrotinib, letrozole and dalpiciclib (a CDK4/6 inhibitor) in patients with treatment-naïve, stage II–III TPBC with a Karnofsky score of ≥70 (NCT04486911). The primary endpoint is the proportion of patients with pathological complete response (pCR) in the breast and axilla. The secondary endpoints include residual cancer burden (RCB)−0 or RCB-I, objective response rate (ORR), breast pCR (bpCR), safety and changes in molecular targets (Ki67) from baseline to surgery. Following 5 cycles of 4-week treatment, the results meet the primary endpoint with a pCR rate of 30.4% (24 of 79; 95% confidence interval (CI), 21.3–41.3). RCB-0/I is 55.7% (95% CI, 44.7–66.1). ORR is 87.4%, (95% CI, 78.1–93.2) and bpCR is 35.4% (95% CI, 25.8–46.5). The mean Ki67 expression reduces from 40.4% at baseline to 17.9% (P < 0.001) at time of surgery. The most frequent grade 3 or 4 adverse events are neutropenia, leukopenia, and diarrhoea. There is no serious adverse event- or treatment-related death. This fully oral, chemotherapy-free, triplet combined therapy has the potential to be an alternative neoadjuvant regimen for patients with TPBC.