Research progress on immunotherapy in triple‑negative breast cancer (Review)

Inhibitory Impact Of Cinobufagin In Triple-Negative Breast Cancer Metastasis: Involvements Of Macrophage Reprogramming Through Upregulated MME and Inactivated FAK/STAT3 Signaling

BACKGROUND

Cinobufagin (CBG), a key bioactive component in cinobufacini, exhibits antitumor properties. This study explores CBG's impact on triple-negative breast cancer (TNBC) metastasis and elucidates the underpinning mechanism.

METHODS

Murine xenograft and orthotopic metastatic TNBC models were generated and treated with CBG. The burden of metastatic tumor in the mouse lung, the epithelial to mesenchymal transition (EMT) markers, and macrophage polarization markers within the tumors were examined. The phenotype of tumor-associated macrophages (TAMs) and mobility of TNBCs in vitro in a macrophage-TNBC cell coculture system were analyzed. Physiological targets of CBG were identified by bioinformatics analyses.

RESULTS

CBG treatment significantly alleviated lung tumor burden and EMT activity. It triggered an M2-to-M1 shift in TAMs, resulting in decreased TNBC cell migration, invasion, and EMT in vitro. CBG upregulated membrane metalloendopeptidase (MME) expression, suppressing FAK and STAT3 phosphorylation. Silencing of MME, either in mice or TAMs, counteracted CBG effects, reinstating M2 TAM predominance and enhancing TNBC cell metastasis. Cotreatment with Defactinib, a FAK antagonist, reversed M2 TAM polarization and TNBC cell metastasis. Notably, MME silencing in TNBC cells had no impact on CBG-suppressed malignant properties, indicating MME's indirect involvement in TNBC cell behavior through TAM mediation.

CONCLUSION

This study unveils CBG's ability to enhance MME expression, deactivate FAK/STAT3 signaling, and inhibit TNBC metastasis by suppressing M2-skewed macrophages.

[A recombinant adeno-associated virus expressing secretory TGF-β type Ⅱ receptor inhibits triple-negative murine breast cancer 4T1 cell proliferation and lung metastasis in mice]

OBJECTIVE

To investigate the effects of an adeno-associated virus (AAV2) vector expressing secretory transforming growth factor-β (TGF-β) type Ⅱ receptor (sTβRⅡ) extracellular domain-IgG2a Fc fusion protein (sTβRⅡ-Fc) on proliferation and migration of triple-negative murine breast cancer 4T1 cells in mice.

METHODS

The pAAV-sTβRⅡ-Fc vector expressing sTβRⅡ-Fc fusion protein constructed by molecular cloning, the capsid protein-expressing vector pAAV2 and the helper vector were co-transfected into HEK 293T cells to prepare the recombinant AAV2-sTβRⅡ virus, which was purified by density gradient centrifugation with iodixanol. Western blotting was used to examine the effects of AAV-sTβRⅡ virus on Smad2/3 phosphorylation in 4T1 cells and on expression levels of E-cadherin, vimentin and p-Smad2/3 in 4T1 cell xenografts in mice. BALB/c mice bearing subcutaneous xenografts of luciferase-expressing 4T1 cells received intravenous injections of AAV-sTβRⅡ virus, AAV-GFP virus or PBS (n=6) through the tail vein, and the proliferation and migration of 4T1 cells were analyzed with in vivo imaging. Ki67 expression in the tumor tissues and sTβRⅡ protein expressions in mouse livers were detected with immunohistochemistry and immunofluorescence staining, and tumor metastases in the vital organs were examined with HE staining.

RESULTS

The recombinant pAAV-sTβRⅡ-Fc vector successfully expressed sTβRⅡ in HEK 293T cells. Infection with AAV2-sTβRⅡ virus significantly reduced TGF-β1-induced Smad2/3 phosphorylation in 4T1 cells and effectively inhibited proliferation and lung metastasis of 4T1 xenografts in mice (P<0.05). In the tumor-bearing mice, intravenous injection of AAV-sTβRⅡ virus significantly increased E-cadherin expression, reduced vimentin and Ki67 protein expressions and Smad2/3 phosphorylation level in the tumor tissues (P<0.05 or 0.01), and induced liver-specific sTβRⅡ expression without causing body weight loss or heart, liver, spleen or kidney pathologies.

CONCLUSION

The recombinant AVV2 vector encoding sTβRⅡ extracellular domain is capable of blocking the TGF-β signaling pathway to inhibit the proliferation and lung metastasis of 4T1 cells in mice.

Ferroptosis induction via targeting metabolic alterations in triple-negative breast cancer

Triple-negative breast cancer (TNBC), the most aggressive form of breast cancer, presents severe threats to women's health. Therefore, it is critical to find novel treatment approaches. Ferroptosis, a newly identified form of programmed cell death, is marked by the buildup of lipid reactive oxygen species (ROS) and high iron concentrations. According to previous studies, ferroptosis sensitivity can be controlled by a number of metabolic events in cells, such as amino acid metabolism, iron metabolism, and lipid metabolism. Given that TNBC tumors are rich in iron and lipids, inducing ferroptosis in these tumors is a potential approach for TNBC treatment. Notably, the metabolic adaptability of cancer cells allows them to coordinate an attack on one or more metabolic pathways to initiate ferroptosis, offering a novel perspective to improve the high drug resistance and clinical therapy of TNBC. However, a clear picture of ferroptosis in TNBC still needs to be completely revealed. In this review, we provide an overview of recent advancements regarding the connection between ferroptosis and amino acid, iron, and lipid metabolism in TNBC. We also discuss the probable significance of ferroptosis as an innovative target for chemotherapy, radiotherapy, immunotherapy, nanotherapy and natural product therapy in TNBC, highlighting its therapeutic potential and application prospects.

Natural-Product-Derived Adjunctive Treatments to Conventional Therapy and Their Immunoregulatory Activities in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an invasive and persistent subtype of breast cancer that is likely to be resistant to conventional treatments. The rise in immunotherapy has created new modalities to treat cancer, but due to high costs and unreliable efficacy, adjunctive and complementary treatments have sparked interest in enhancing the efficacy of currently available treatments. Natural products, which are bioactive compounds derived from natural sources, have historically been used to treat or ameliorate inflammatory diseases and symptoms. As TNBC patients have shown little to no response to immunotherapy, the potential of natural products as candidates for adjuvant immunotherapy is being explored, as well as their immunomodulatory effects on cancer. Due to the complexity of TNBC and the ever-changing tumor microenvironment, there are challenges in determining the feasibility of using natural products to enhance the efficacy or counteract the toxicity of conventional treatments. In view of technological advances in molecular docking, pharmaceutical networking, and new drug delivery systems, natural products show promise as potential candidates in adjunctive therapy. In this article, we summarize the mechanisms of action of selected natural-product-based bioactive compounds and analyze their roles and applications in combination treatments and immune regulation.

Endoplasmic reticulum-targeted NIR-II phototherapy combined with inflammatory vascular suppression elicits a synergistic effect against TNBC

Recurrence and metastasis are the main reasons for failure in the treatment of triple-negative breast cancer (TNBC). Phototherapy, one of the most well-known potent cancer treatment models is highlighted by ablating primitive tumors with immunogenic cell death (ICD) and is associated with endoplasmic reticulum (ER) stress to elicit long-lasting anti-tumor immunity. However, the provoked inflammatory response after phototherapy will stimulate angiogenesis, which provides nutrition for tumor recurrence. Here, an ER-targeted nanoplatform was constructed based on hollow mesoporous Cu_2-XS (HMCu_2-XS) nanoparticles to suppress recurrence and metastasis of TNBC by combining photo-ablation and microenvironment remodeling. Profiting from the metal ion coordination and large hollow space, HMCu_2-XS can be easily modified with p-toluenesulfonamide for ER-targeting and quantitatively loaded celecoxib (CXB) as a vascular inhibitor, thus obtaining ER-HMCu_2-XS/CXB. ER-HMCu_2-XS showed great photothermal and photodynamic efficiency for ablating 4T1 tumors and inducing ICD under NIR-II laser irradiation. Compared with non-ER-targeted nanosystems, the ER-targeted nanosystem elicited stronger ICDs and recruited more immune cells. Moreover, the thermal-responsively released CXB successfully inhibited angiogenesis after photothermal therapy. The data showed that the ER-HMCu_2-XS/CXB mediated the triplicate therapeutic effect of photo-ablation, immune response activation, and vascular suppression effectively, preventing the recurrence and metastasis of TNBC. In conclusion, this work provides a synergistic strategy to enhance therapeutic outcomes in TNBC.

Efficacy and Safety of Atezolizumab Monotherapy or Combined Therapy with Chemotherapy in Patients with Metastatic Triple-negative Breast Cancer: A Systematic Review and Meta-analysis of Randomized Controlled Trials

INTRODUCTION

Several successful attempts have been recorded with PD-L1 blockade via atezolizumab monotherapy or combination therapy with chemotherapy in patients with metastatic triple-negative breast cancer (mTNBC). Due to the lack of a large-scale study, we present a meta-analysis aimed at evaluating the safety and efficacy of this promising strategy in patients with mTNBC.

METHODS

A comprehensive literature search was conducted using electronic databases to identify eligible RCTs. Twelve studies, including 2479 mTBNC patients treated with atezolizumab monotherapy or in combination with chemotherapy, were included up to January 2022. The PRISMA checklist protocol and the I2 statistic were applied for quality assessment and heterogeneity tests of the selected trials, respectively. Fixed and random-effects models were estimated based on the heterogeneity tests, and statistical analysis was performed using CMA.

RESULTS

Our pooled findings demonstrated that the median overall survival (OS) and progression-free survival (PFS) were 16.526 and 5.814 months in mTNBC patients, respectively. Furthermore, when comparing efficacy indicators between PD-L1-positive and PD-L1-negative groups, mTNBC patients with PD-L1 had better OS, PFS, and ORR than PD-L1-negative patients. Also, the immune-related adverse event incident for alopecia was higher (51.9%) than other complications across atezolizumab therapy.

CONCLUSION

Moreover, the pooled analysis indicated that the overall rate of lung metastasis following atezolizumab therapy was 42.8%, which was higher than the rates of metastasis in bone (26.9%), brain (5.4%), and lymph node (6.5%). Atezolizumab showed a manageable safety profile and had promising and durable anti-tumor efficacy in TMBC patients. Higher PD-L1 expression may be closely correlated with better clinical efficacy.

Effect of N6-methyladenosine (m6A) regulator-related immunogenes on the prognosis and immune microenvironment of breast cancer

Background

Breast cancer is one of the most common malignant tumor and the prognosis remains unsatisfying. Various studies demonstrate that m6A modulators are new predictors of prognosis in immune microenvironment. We aimed to identify several m6A regulator-related immunogenes and explore the relationship between m6A regulator-related immunogenes and breast cancer prognosis as well as the tumor immune microenvironment (TIME).

Methods

RNA sequencing data and clinical information on 21 m6A regulators in 1,047 breast cancer samples were downloaded from The Cancer Genome Atlas (TCGA), and immune gene data were downloaded from InnateDB. Kaplan-Meier survival analysis was conducted with log-rank test using the survival package. An m6A-related immunogene-prognostic signature was then constructed, followed by immune infiltration and checkpoint analyses.

Results

A risk prognostic signature of m6A regulator-related immunogenes, including TOX, PSME2, MCTS1, NFKBIE, SH3BP4, RSPH1, JAK1, MLLT4, and PTGES3, was constructed. Furthermore, univariate and multivariate Cox regression analyses suggested that the tumor stage and risk score could be independent prognostic factors for patients with breast cancer. Immune infiltration analysis showed that the infiltration levels of T cells, memory B cells, activated NK cells, and macrophages between the high- and low-risk groups were significantly different. In addition, checkpoint analyses demonstrated that the levels of immune checkpoint genes, such as those of LAG3, PDCD1, CTLA4, and HAVCR2, were downregulated in the high-risk group compared to those in the low-risk group.

Conclusions

Our findings suggest that the m6A regulator-related risk prognostic signature can predict the prognosis of breast cancer and that it is related to the immune microenvironment.

PD-L1-Positive High-Grade Triple-Negative Breast Cancer Patients Respond Better to Standard Neoadjuvant Treatment-A Retrospective Study of PD-L1 Expression in Relation to Different Clinicopathological Parameters

Triple negative breast cancer (TNBC) is typically a high-grade breast cancer with poorest clinical outcome despite available treatment modalities with chemo-, immuno- and radiotherapy. The status of tumor-infiltrating lymphocytes (TILs) is a prognostic factor closely related to programmed death ligand 1 (PD-L1) expressed on T lymphocytes modulating antitumor immunity. Immune-checkpoint inhibitors (ICI) are showing promising results in a subset of breast cancer patients in both neo- and adjuvant settings. Pathologic complete response (pCR) after neoadjuvant treatment was found to be associated with better prognosis. We analyzed the prognostic and predictive significance of PD-L1 (SP142 assay) immunohistochemical expression on TNBC patients' samples as illustrated by pCR with regard to its relation to treatment regimen, stage, BRCA mutational status and outcome. Furthermore, we analyzed a few other clinicopathological parameters such as age, TILs and proliferation index. The study highlighted a positive role of PD-L1 evaluation for personalized pCR probability assessment. Although considerable research was made on comparison of PD-L1 level in TNBC with different patient parameters, to our best knowledge, the relation of PD-L1 status to pCR while taking treatment regimen and stage into consideration was so far not investigated.