Minimally invasive thermal therapies have been attempted in the treatment of breast cancer, and the immune response induced by these therapies has not been fully reported. A clinical trial is performed to determine the effect of microwave ablation (MWA) in the treatment of early‐stage breast cancer. The authors perform single‐cell RNA sequencing on peripheral blood mononuclear cells (PBMCs) from six patients before and after ablation. NK and CD8⁺T cells are activated by MWA of breast cancer, with the increased inhibitory signature of CD8⁺T cells but not dysfunctional. Enhanced co‐stimulatory signature of CD4⁺ T cells is observed and increased frequency of ICOS⁺CD4⁺ T cells after MWA is confirmed by flow cytometric analysis. After ablation, T‐cell clones expand with increased T‐cell receptor diversities. Activated antigen receptor‐mediated signaling pathways are found in B cells. Enhanced interactions between B cells and CD4⁺ T cells are found, indicating that B cells are important antigen‐presenting cells that initiate CD4⁺T cells in MWA‐induced immune response. Blockade of CTLA‐4 or PD‐1 of post‐MWA PBMCs show higher T‐cell activity than that of pre‐MWA PBMCs. This study provide global characteristics of MWA‐induced systemic immune response and pave a way for the identification of potential targets to improve the immune response.

Minimally invasive therapies, such as microwave ablation (MWA), are widely used for the treatment of solid tumors. Previous studies suggest that MWA is feasible for the treatment of small breast cancer, and thermal ablation may induce adaptive antitumor immunity. However, the induced immune responses are mostly weak, and the immunomodulation effects of MWA in breast cancer are unclear. Immunostimulant OK-432 can induce tumor-specific T-cell responses and may augment the immunity induced by MWA. We treated 4T1 breast cancer bearing BALB/c mice with MWA, OK-432, MWA plus OK-432, or left without treatment. Survival time was evaluated with the Kaplan–Meyer method comparing survival curves by log-rank test. On day 25 after ablation, surviving mice received tumor rechallenge, and the rechallenged tumor volumes were calculated every 5 days. Immunohistochemistry and flow cytometry were used to evaluate the T-cell immune responses in ablated tissues and spleens. The tumor-specific immunity was assessed by enzyme-linked immunospot assays. Besides, the cytokine patterns were identified from enzyme-linked immunosorbent assay. Microwave ablation plus OK-432 resulted in longer survival than single treatment and protect most surviving mice from tumor rechallenge. Both local and systemic T-cell responses were induced by MWA and were further enhanced by subsequent administration of OK-432. Moreover, the combination of MWA and OK-432 induced stronger tumor-specific immune responses than MWA alone. In addition, OK-432 and MWA synergistically promoted the production of Th1-type but not Th2-type cytokines, and polarized T-cell responses to Th1-dominant state. The T-cell immune responses were activated by MWA in breast cancer. Furthermore, the combination of MWA and OK-432 induced Th1-type response and elicited specific antitumor immunity.

Minimally invasive thermal therapy is a successful alternative treatment to surgery in solid tumors with high complete ablation rates, however, tumor recurrence remains a concern. Central memory CD8⁺ T cells (T_CM) play important roles in protection from chronic infection and cancer. Here we find, by single-cell RNA analysis of human breast cancer samples, that although the memory phenotype of peripheral CD8⁺ T cells increases slightly after microwave ablation (MWA), the metabolism of peripheral CD8⁺ T cells remains unfavorable for memory phenotype. In mouse models, glycolysis inhibition by 2-deoxy-D-glucose (2DG) in combination with MWA results in long-term anti-tumor effect via enhancing differentiation of tumor-specific CD44^hiCD62L⁺CD8⁺ T_CM cells. Enhancement of CD8⁺ T_CM cell differentiation determined by Stat-1, is dependent on the tumor-draining lymph nodes (TDLN) but takes place in peripheral blood, with metabolic remodeling of CD8⁺ T cells lasting the entire course of the the combination therapy. Importantly, in-vitro glycolysis inhibition in peripheral CD8⁺ T cells of patients with breast or liver tumors having been treated with MWA thrice leads to their differentiation into CD8⁺ T_CM cells. Our work thus offers a potential strategy to avoid tumor recurrence following MWA therapy and lays down the proof-of-principle for future clinical trials.

Background Despite great advances in the treatment of breast cancer, innovative approaches are still needed to reduce metastasis. As a minimally invasive local therapy (not standard therapy for breast cancer), microwave ablation (MWA) has been attempted to treat breast cancer, but the local effect and immune response induced by MWA have seldom been reported. Methods The clinical study was performed to determine the complete ablation rate of MWA for early-stage breast cancer. Secondary endpoints included safety and antitumor immune response. 35 subjects from this clinical study were enrolled in the current report, and the local effect was determined by pathological examinations or follow-up. To investigate MWA-induced immune response, patients treated with surgery (n=13) were enrolled as control, and blood samples were collected before and after MWA or surgery. The immune cell populations, serum cytokines, secretory immune checkpoint molecules, and T-cell receptor sequencing were analyzed. Results Of 35 enrolled patients, 32 (91.4%) showed complete ablation. Compared with surgery, MWA induced significantly increased levels of inducible co-stimulator (ICOS)+ activated CD4+ T cells and serum interferon gamma, indicating a shift in the Th1/Th2 balance toward Th1. The activated ICOS pathway was involved in the MWA-induced adaptive immune response. T-cell receptor sequencing revealed MWA of primary tumor activated T lymphocytes expansion and recognized some cancer-specific antigens. Moreover, CD4+ effector memory T-cell response was induced by MWA, and the immune response still existed after surgical resection of the ablated tumor. Conclusions MWA may not only be a promising local therapy but also a trigger of antitumor immunity for breast cancer, opening new avenues for the treatment of breast cancer. Combinatorial strategy using additional agents which boost MWA-induced immune response could be considered as potential treatment for clinical study for early breast cancer therapy.

Our previous studies demonstrated that S100A16 promotes adipogenesis and is involved in weight gain attenuation induced by dietary calcium. Till now, the function of S100A16 in the breast cancer remains to be elucidated. In this study, we observed that S100A16 was expressed in higher levels in human breast cancer tissues compared with paired adjacent non-cancerous tissues. Further examination showed that overexpression of S100A16 in MCF-7 cells could increase cell proliferation and colony formation. One major mechanistic change was that S100A16 was able to up-regulate the transcription factors Notch1, ZEB1, and ZEB2, which had the capacities to directly repress the expression of epithelial markers E-cadherin and β-catenin but increase mesenchymal markers N-cadherin and vimentin, a characterized phenotype of epithelial-mensenchymal transition (EMT). In addition to display with morphologic change, migration and invasion were increased in S100A16 over-expressed MCF-7 cells. Importantly, knockdown of Notch1 by specific siRNA could reverse the EMT induced by S100A16 overexpression, which confirmed that Notch1 played a critical role in the process of EMT induced by S100A16. All together, our data indicated that S100A16 had a potential function to regulate some embryonic transcription factors to promote EMT in breast cancer cells which may be an important target site for the therapy of breast cancer.