In triple-negative breast cancer (TNBC), the benefit of combining chemotherapy with checkpoint inhibitors is still not very clear. We utilize single-cell RNA- and ATAC-sequencing to examine the immune cell dynamics in 22 patients with advanced TNBC treated with paclitaxel or its combination with the anti-PD-L1 atezolizumab. We demonstrate that high levels of baseline CXCL13⁺ T cells are linked to the proinflammatory features of macrophages and can predict effective responses to the combination therapy. In responsive patients, lymphoid tissue inducer (LTi) cells, follicular B (Bfoc) cells, CXCL13⁺ T cells, and conventional type 1 dendritic cells (cDC1) concertedly increase following the combination therapy, but instead decrease after paclitaxel monotherapy. Our data highlight the importance of CXCL13⁺ T cells in effective responses to anti-PD-L1 therapies and suggest that their reduction by paclitaxel regimen may compromise the clinical outcomes of accompanying atezolizumab for TNBC treatment.

Breast cancer is the most common cancer worldwide. The occurrence of breast cancer is associated with many risk factors, including genetic and hereditary predisposition. Breast cancers are highly heterogeneous. Treatment strategies for breast cancer vary by molecular features, including activation of human epidermal growth factor receptor 2 (HER2), hormonal receptors (estrogen receptor [ER] and progesterone receptor [PR]), gene mutations (e.g., mutations of breast cancer 1/2 [ BRCA1/2 ] and phosphatidylinositol‐4,5‐bisphosphate 3‐kinase catalytic subunit alpha [ PIK3CA ]) and markers of the immune microenvironment (e.g., tumor‐infiltrating lymphocyte [TIL] and programmed death‐ligand 1 [PD‐L1]). Early‐stage breast cancer is considered curable, for which local‐regional therapies (surgery and radiotherapy) are the cornerstone, with systemic therapy given before or after surgery when necessary. Preoperative or neoadjuvant therapy, including targeted drugs or immune checkpoint inhibitors, has become the standard of care for most early‐stage HER2‐positive and triple‐negative breast cancer, followed by risk‐adapted post‐surgical strategies. For ER‐positive early breast cancer, endocrine therapy for 5‐10 years is essential. Advanced breast cancer with distant metastases is currently considered incurable. Systemic therapies in this setting include endocrine therapy with targeted agents, such as CDK4/6 inhibitors and phosphoinositide 3‐kinase (PI3K) inhibitors for hormone receptor‐positive disease, anti‐HER2 targeted therapy for HER2‐positive disease, poly(ADP‐ribose) polymerase inhibitors for BRCA1/2 mutation carriers and immunotherapy currently for part of triple‐negative disease. Innovation technologies of precision medicine may guide individualized treatment escalation or de‐escalation in the future. In this review, we summarized the latest scientific information and discussed the future perspectives on breast cancer.

Over the past 2 decades, there has been an extraordinary progress in the regimens developed for the treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer. Trastuzumab, pertuzumab, lapatinib, and ado-trastuzumab emtansine (T-DM1) are commonly recommended anti-HER2 target agents by the U.S. Food and Drug Administration. This review summarizes the most significant and updated research on clinical scenarios related to HER2-positive breast cancer management in order to revise the guidelines of everyday clinical practices. In this article, we present the data on anti-HER2 clinical research of neoadjuvant, adjuvant, and metastatic studies from the past 2 decades. We also highlight some of the promising strategies that should be critically considered. Lastly, this review lists some of the ongoing clinical trials, findings of which may soon be available.

Combining immune checkpoint blockade (ICB) with chemotherapy shows promise for treating triple-negative breast cancer (TNBC), though the mechanisms remain incompletely understood. Here, we integrate published and new single-cell RNA sequencing (scRNA-seq) data to investigate the tumor immune microenvironment (TIME) in TNBC patients treated with paclitaxel (PTX), nab-paclitaxel (Nab-PTX), and their combinations with the anti-PD-L1 antibody atezolizumab (ATZ). Compared to ATZ plus PTX, ATZ plus Nab-PTX rewires TCF7⁺ stem-like effector memory CD8⁺ T cells (Tsem) and CD4⁺ T follicular helper (Tfh) cells. Nab-paclitaxel, unlike PTX, also reshapes the myeloid compartment, expanding mast cells and pro-inflammatory macrophages. Our analyses in human TNBC and murine models underscore the crucial role of mast cells in orchestrating anti-tumor immune responses, likely by promoting the recruitment and activation of T and B cells. In vivo experiments demonstrate that activating mast cells alongside PD-L1 blockade attenuates TNBC progression, suggesting mast cells as a promising adjunct for enhancing ICB therapy efficacy.