Immunotherapy for Metastatic Triple Negative Breast Cancer: Current Paradigm and Future Approaches

Immunohistochemical Detection of Indoleamine 2,3-Dioxygenase in Spontaneous Mammary Carcinomas of 96 Pet Rabbits

For mammary carcinomas in pet rabbits, prognostic biomarkers are poorly defined, and treatment is limited to surgical excision. Additional treatment options are needed for rabbit patients for which surgery is not a suitable option. In human breast cancer, the immunosuppressive enzyme indoleamine 2,3-dioxygenase 1 (IDO1) represents a prognostic biomarker and possible therapeutic target. This retrospective immunohistochemical study examined IDO1 in 96 pet rabbit mammary carcinomas with known mitotic count, hormone receptor status, and percentage of stromal tumor infiltrating lymphocytes (TILs). Tumors were obtained from 96 pet rabbits with an average of 5.5 years. All rabbits with reported sex (n = 88) were female or female-spayed. Of the carcinomas, 94% expressed IDO1, and 86% had sparse TILs consistent with cold tumors. Statistically significant correlations existed between a higher percentage of IDO1-positive tumor cells, lower mitotic counts, and increased estrogen receptor expression. The threshold for significance was IDO1 staining in >10% of tumor cells. These results lead to the assumption that IDO1 expression contributes to tumorigenesis and may represent a prognostic biomarker and possible therapeutic target also in pet rabbit mammary carcinomas. They also support the value of rabbits for breast cancer research.

Immunotherapeutic Strategies Targeting Breast Cancer Stem Cells

Breast cancer is the most commonly diagnosed cancer in women and is a leading cause of cancer death in women worldwide. Despite the implementation of multiple treatment options, including immunotherapy, breast cancer treatment remains a challenge. In this review, we aim to summarize present challenges in breast cancer immunotherapy and recent advancements in overcoming treatment resistance. We elaborate on the inhibition of signaling cascades, such as the Notch, Hedgehog, Hippo, and WNT signaling pathways, which regulate the self-renewal and differentiation of breast cancer stem cells and, consequently, disease progression and survival. Cancer stem cells represent a rare population of cancer cells, likely originating from non-malignant stem or progenitor cells, with the ability to evade immune surveillance and develop resistance to immunotherapeutic treatments. We also discuss the interactions between breast cancer stem cells and the immune system, including potential agents targeting breast cancer stem cell-associated signaling pathways, and provide an overview of the emerging approaches to breast cancer stem cell-targeted immunotherapy. Finally, we consider the development of breast cancer vaccines and adoptive cellular therapies, which train the immune system to recognize tumor-associated antigens, for eliciting T cell-mediated responses to target breast cancer stem cells.

Current usage of pembrolizumab in triple negative breast cancer (TNBC)

INTRODUCTION

The use of immune checkpoint inhibitors (ICI) targeting the PD-1/PD-L1 pathway has changed the landscape in the treatment of triple negative breast cancer (TNBC). The ICI pembrolizumab in combination with chemotherapy now forms a standard of care for the treatment of advanced PD-L1 positive TNBC and as part of neoadjuvant therapy for high-risk early-stage disease. Evidence in this space is rapidly advancing.

AREAS COVERED

This review aims to highlight the evolving role of immunotherapy in TNBC management and to discuss current challenges. The studies in this review were searched from PubMed and ClinicalTrials.gov.

EXPERT OPINION

The KEYNOTE-522 trial demonstrated that the addition of peri-operative pembrolizumab to neoadjuvant chemotherapy improves patient outcomes in early-stage TNBC. However, critical questions remain including how to select which patients truly gain benefit from the addition of pembrolizumab; the optimal duration of therapy, and the optimal adjuvant therapy depending on pathologic response.

Pharmacological Mechanism of Mume Fructus in the Treatment of Triple-Negative Breast Cancer Based on Network Pharmacology

Our study aims to find the relevant mechanism of Mume Fructus in the treatment of triple-negative breast cancer (TNBC) by network pharmacology analysis and experimental validation. The effective compounds of Mume Fructus and TNBC-related target genes were imported into Cytoscape to construct a Mume Fructus-effective compounds-disease target network. The common targets of Mume Fructus and TNBC were determined by drawing Venn diagrams. Then, the intersection targets were transferred to the STRING database to construct a protein-protein interaction (PPI) network. To investigate the mechanism of Mume Fructus in treatment of TNBC, breast cancer cell (MDA-MB-231) was treated with Mume Fructus and/or transfected with small interference RNA-PKM2(siPKM2). CCK-8 assay, cell clonal formation assay, transwell, flow cytometry, qRT-PCR, and western blotting were performed. Eight effective compounds and 145 target genes were obtained, and the Mume Fructus- effective compounds-disease target network was constructed. Then through the analysis of the PPI network, we obtained 10 hub genes including JUN, MAPK1, RELA, AKT1, FOS, ESR1, IL6, MAPK8, RXRA, and MYC. KEGG enrichment analysis showed that JUN, MAPK1, RELA, FOS, ESR1, IL6, MAPK8, and RXRA were enriched in the Th17 cell differentiation signaling pathway. Loss of PKM2 and Mume Fructus both inhibited the malignant phenotype of MDA-MB-231 cells. And siPKM2 further aggravated the Mume Fructus inhibition of malignancy of breast cancer cells. Network pharmacology analysis suggests that Mume Fructus has multiple therapeutic targets for TNBC and may play a therapeutic role by modulating the immune microenvironment of breast cancer.

The safety and efficacy of systemic delivery of a new liver-de-targeted TGFβ signaling inhibiting adenovirus in an immunocompetent triple negative mouse mammary tumor model

Aberrant TGFβ signaling is linked to metastasis and tumor immune escape of many cancers including metastatic triple negative breast cancer (mTNBC). Previously, we have found that oncolytic adenoviruses expressing a TGFβ signaling inhibitory protein (sTGFβRIIFc) induced immune activation in a mouse TNBC (4T1) immunocompetent subcutaneous model with intratumoral injection. Systemic administration of adenoviruses can be a superior route to treat mTNBC but faces the challenges of increased toxicity and viral clearance. Thus, we created a liver-de-targeted sTGFβRIIFc- and LyP-1 peptide-expressing adenovirus (mHAdLyp.sT) with enhanced breast cancer cell tropism. Its safety and immune response features were profiled in the 4T1 model. Our data showed that the systemic administration of mHAdLyp.sT resulted in reduced hepatic and systemic toxicity. mHAdLyp.sT was also effective in increasing Th1 cytokines and anti-tumor cell populations by cytokine analysis, spleen/tumor qRT-PCR, and flow cytometry. We further tested the therapeutic effects of mHAdLyp.sT alone and in combination with immune checkpoint inhibitors (ICIs). mHAdLyp.sT alone and with all ICI combinations elicited significant inhibition of lung metastasis by histological analysis. When mHAdLyp.sT was combined with both anti-PD-1 and anti-CTLA-4 antibodies, primary 4T1 tumor growth was also significantly inhibited. We are confident in advancing this new treatment option for mTNBC.

New hopes for the breast cancer treatment: perspectives on the oncolytic virus therapy

Oncolytic virus (OV) therapy has emerged as a promising frontier in cancer treatment, especially for solid tumours. While immunotherapies like immune checkpoint inhibitors and CAR-T cells have demonstrated impressive results, their limitations in inducing complete tumour regression have spurred researchers to explore new approaches targeting tumours resistant to current immunotherapies. OVs, both natural and genetically engineered, selectively replicate within cancer cells, inducing their lysis while sparing normal tissues. Recent advancements in clinical research and genetic engineering have enabled the development of targeted viruses that modify the tumour microenvironment, triggering anti-tumour immune responses and exhibiting synergistic effects with other cancer therapies. Several OVs have been studied for breast cancer treatment, including adenovirus, protoparvovirus, vaccinia virus, reovirus, and herpes simplex virus type I (HSV-1). These viruses have been modified or engineered to enhance their tumour-selective replication, reduce toxicity, and improve oncolytic properties.Newer generations of OVs, such as Oncoviron and Delta-24-RGD adenovirus, exhibit heightened replication selectivity and enhanced anticancer effects, particularly in breast cancer models. Clinical trials have explored the efficacy and safety of various OVs in treating different cancers, including melanoma, nasopharyngeal carcinoma, head and neck cancer, and gynecologic malignancies. Notably, Talimogene laherparepvec (T-VEC) and Oncorine have. been approved for advanced melanoma and nasopharyngeal carcinoma, respectively. However, adverse effects have been reported in some cases, including flu-like symptoms and rare instances of severe complications such as fistula formation. Although no OV has been approved specifically for breast cancer treatment, ongoing preclinical clinical trials focus on four groups of viruses. While mild adverse effects like low-grade fever and nausea have been observed, the effectiveness of OV monotherapy in breast cancer remains insufficient. Combination strategies integrating OVs with chemotherapy, radiotherapy, or immunotherapy, show promise in improving therapeutic outcomes. Oncolytic virus therapy holds substantial potential in breast cancer treatment, demonstrating safety in trials. Multi-approach strategies combining OVs with conventional therapies exhibit more promising therapeutic effects than monotherapy, signalling a hopeful future for OV-based breast cancer treatments.

Optimized Design of Hyaluronic Acid-Lipid Conjugate Biomaterial for Augmenting CD44 Recognition of Surface-Engineered NK Cells

Triple-negative breast cancer (TNBC) presents treatment challenges due to a lack of detectable surface receptors. Natural killer (NK) cell-based adaptive immunotherapy is a promising treatment because of the characteristic anticancer effects of killing malignant cells directly by secreting cytokines and lytic granules. To maximize the cancer recognition ability of NK cells, biomaterial-mediated ex vivo cell surface engineering has been developed for sufficient cell membrane immobilization of tumor-targeting ligands via hydrophobic anchoring. In this study, we optimized amphiphilic balances of NK cell coating materials composed of CD44-targeting hyaluronic acid (HA)-poly(ethylene glycol) (PEG)-lipid to improve TNBC recognition and the anticancer effect. Changes in the modular design of our material by differentiating hydrophilic PEG length and incorporating lipid amount into HA backbones precisely regulated the amphiphilic nature of HA-PEG-lipid conjugates. The optimized biomaterial demonstrated improved anchoring into NK cell membranes and facilitating the surface presentation level of HA onto NK cell surfaces. This led to enhanced cancer targeting via increasing the formation of immune synapse, thereby augmenting the anticancer capability of NK cells specifically toward CD44-positive TNBC cells. Our approach addresses targeting ability of NK cell to solid tumors with a deficiency of surface tumor-specific antigens while offering a valuable material design strategy using amphiphilic balance in immune cell surface engineering techniques.

Current and future trends in neoadjuvant immunotherapy for the treatment of triple-negative breast cancer

Triple-negative breast cancer (TNBC) comprises 15-20% of all breast cancers (BC). Lacking targeted therapy options, TNBC becomes the focal point of clinical investigations aiming not only to identify drugs with enhanced response potential but also to uncover new immunological and/or metabolic pathways conducive to more effective treatments. Currently, neoadjuvant treatment for TNBC relies on standard chemotherapy in conjunction with immunotherapy, given the improved response observed with this drug combination. This review delves into the latest therapeutic updates in TNBC treatment and explores potential advancements shaping the future landscape of this disease in the neoadjuvant setting.

Cancer cell-derived exosomal miR-20a-5p inhibits CD8+ T-cell function and confers anti-programmed cell death 1 therapy resistance in triple-negative breast cancer

Circulating miRNAs (cirmiRNAs) can be packaged into the exosomes, participating in intercellular communication, which affects the malignant progression and therapy resistance of triple-negative breast cancer (TNBC). Currently, immune checkpoint inhibitors that regulate T-cell function, especially antibodies against programmed cell death 1 (PD-1) or its ligand PD-L1, are emerging as new promising therapy for TNBC patients. However, only very limited patients showed complete or partial response to anti-PD-1 treatment. Dysfunction of CD8+ T cells is one of the key reasons for the immune escape of TNBC. The regulation of exosome-derived cirmiRNAs on CD8+ T cells in TNBC deserves more investigation. Here, the cirmiR-20a-5p level was significantly upregulated in the plasma of TNBC patients and culture supernatant of TNBC cells. High abundance of cirmiR-20a-5p was correlated with a worse prognosis of TNBC. cirmiR-20a-5p was secreted in the form of exosomes by TNBC cells. Exosomal cirmiR-20a-5p was internalized into CD8+ T cells and resulted into the dysfunction of CD8+ T. A mechanism study uncovered that cirmiR-20a-5p targeted the nuclear protein ataxia-telangiectasia (NPAT) and decreased NPAT expression in CD8+ T cells. An in vivo xenograft mouse model showed that cirmiR-20a-5p conferred TNBC to anti-PD-1 treatment resistance. Collectively, these findings indicated that cirmiR-20a-5p released by TNBC cells via exosome promotes cancer cell growth and leads to the immunosuppression by inducing CD8+ T cell dysfunction. This study suggests that targeting cirmiR-20a-5p might be a novel strategy for overcoming the resistance of TNBC to anti-PD-1 immunotherapy.

Third-line Treatment for Metastatic Triple-negative Breast Cancer: A Systematic Review and Network Meta-analysis

OBJECTIVE

Metastatic triple-negative breast cancer (mTNBC) is an invasive histologic subtype with a poor prognosis and rapid progression. Currently, there is no standard therapy for the third-line treatment of mTNBC. In this study, we conducted a network meta-analysis to compare regimens and determine treatment outcomes.

METHODS

We performed a systematic search of PubMed, EMBASE, the Cochrane Central Register of Controlled Bases, and the minutes of major conferences. Progression-free survival, overall survival, and objective response rate were analyzed through network meta-analysis using the R software (R Core Team). The efficacy of the treatment regimens was compared using hazard ratios, odds ratios, and 95% CIs.

RESULTS

We evaluated 15 randomized controlled trials involving 6,010 patients. Compared with the physician's choice treatment, sacituzumab govitecan showed significant advantages in progression-free survival and overall survival, with hazard ratio values of 0.41 (95% CI: 0.32-0.52) and 0.48 (95% CI, 0.39-0.60). In terms of objective response rate, sacituzumab govitecan is the best-performing therapy (odds ratio: 10.82; 95% CI: 5.58-20.97). Adverse events among grades 3 to 5 adverse reactions, the incidence of neutropenia and leukopenia in each regimen was higher, whereas the incidence of fever, headache, hypertension, and rash was lower.

CONCLUSION

Compared with the treatment of the physician's choice, sacituzumab govitecan appears more efficacious and is the preferred third-line treatment for mTNBC.

Enhancing Cancer Chemo-Immunotherapy: Innovative Approaches for Overcoming Immunosuppression by Functional Nanomaterials

Chemotherapy is a critical modality in cancer therapy to combat malignant cell proliferation by directly attacking cancer cells and inducing immunogenic cell death, serving as a vital component of multi-modal treatment strategies for enhanced therapeutic outcomes. However, chemotherapy may inadvertently contribute to the immunosuppression of the tumor microenvironment (TME), inducing the suppression of antitumor immune responses, which can ultimately affect therapeutic efficacy. Chemo-immunotherapy, combining chemotherapy and immunotherapy in cancer treatment, has emerged as a ground-breaking approach to target and eliminate malignant tumors and revolutionize the treatment landscape, offering promising, durable responses for various malignancies. Notably, functional nanomaterials have substantially contributed to chemo-immunotherapy by co-delivering chemo-immunotherapeutic agents and modulating TME. In this review, recent advancements in chemo-immunotherapy are thus summarized to enhance treatment effectiveness, achieved by reversing the immunosuppressive TME (ITME) through the exploitation of immunotherapeutic drugs, or immunoregulatory nanomaterials. The effects of two-way immunomodulation and the causes of immunoaugmentation and suppression during chemotherapy are illustrated. The current strategies of chemo-immunotherapy to surmount the ITME and the functional materials to target and regulate the ITME are discussed and compared. The perspective on tumor immunosuppression reversal strategy is finally proposed.

The Cell-Autonomous Pro-Metastatic Activities of PD-L1 in Breast Cancer Are Regulated by N-Linked Glycosylation-Dependent Activation of STAT3 and STAT1

PD-L1 has been characterized as an inhibitory immune checkpoint, leading to the suppression of potential anti-tumor immune activities in many cancer types. In view of the relatively limited efficacy of immune checkpoint blockades against PD-L1 in breast cancer, our recent study addressed the possibility that in addition to its immune-inhibitory functions, PD-L1 promotes the pro-metastatic potential of the cancer cells themselves. Indeed, our published findings demonstrated that PD-L1 promoted pro-metastatic functions of breast cancer cells in a cell-autonomous manner, both in vitro and in vivo. These functions fully depended on the integrity of the S283 intracellular residue of PD-L1. Here, using siRNAs and the S283A-PD-L1 variant, we demonstrate that the cell-autonomous pro-metastatic functions of PD-L1-tumor cell proliferation and invasion, and release of the pro-metastatic chemokine CXCL8-required the activation of STAT3 and STAT1 in luminal A and triple-negative breast cancer cells. The cell-autonomous pro-metastatic functions of PD-L1 were potently impaired upon inhibition of N-linked glycosylation (kifunensine). Site-specific mutants at each of the N-linked glycosylation sites of PD-L1 (N35, N192, N200, and N219) revealed that they were all required for PD-L1-induced pro-metastatic functions to occur; the N219 site was the main regulator of STAT3 and STAT1 activation, with accompanying roles for N192 and N200 (depending on the cell type). Using a T cell-independent mouse system, we found that cells expressing N35A-PD-L1 and N219A-PD-L1 had a significantly lower tumorigenic and metastatic potential than cells expressing WT-PD-L1. TCGA analyses revealed significant associations between reduced survival and high levels of α-mannosidase II (inferring on N-linked glycosylation) in breast cancer patients. These findings suggest that N-linked glycosylation of PD-L1 may be used to screen for patients who are at greater risk of disease progression, and that modalities targeting N-linked glycosylated PD-L1 may lead to the inhibition of its cell-autonomous pro-metastatic functions and to lower tumor progression in breast cancer.

The Safety and Efficacy of Systemic Delivery of a New Liver-de-targeted TGFβ Signaling Inhibiting Adenovirus in an Immunocompetent Triple Negative Mouse Mammary Tumor Model

Aberrant TGFβ signaling is linked to metastasis and tumor immune escape of many cancers including metastatic triple negative breast cancer (mTNBC). Previously, we have found that oncolytic adenoviruses expressing a TGFβ signaling inhibitory protein (sTGFβRIIFc) induced immune activation in a mouse TNBC (4T1) immunocompetent subcutaneous model with intratumoral injection. Systemic administration of adenoviruses can be a superior route to treat mTNBC but faces the challenges of increased toxicity and viral clearance. Thus, we created a liver-de-targeted sTGFβRIIFc- and LyP-1 peptide-expressing adenovirus (mHAdLyp.sT) with enhanced breast cancer cell tropism. Its safety and immune response features were profiled in the 4T1 model. Our data showed that the systemic administration of mHAdLyp.sT resulted in reduced hepatic and systemic toxicity. mHAdLyp.sT was also effective in increasing Th1 cytokines and anti-tumor cell populations by cytokine analysis, spleen/tumor qRT-PCR, and flow cytometry. We further tested the therapeutic effects of mHAdLyp.sT alone and in combination with immune checkpoint inhibitors (ICIs). mHAdLyp.sT alone and with all ICI combinations elicited significant inhibition of lung metastasis by histological analysis. When mHAdLyp.sT was combined with both anti-PD-1 and anti-CTLA-4 antibodies, primary 4T1 tumor growth was also significantly inhibited. We are confident in advancing this new treatment option for mTNBC.

The immunogram of inflammatory breast cancer

Inflammatory breast cancer (IBC) is the most aggressive and fatal clinical presentation of breast cancer. Despite the term "inflammatory", based on the clinical presentation, IBC is biologically driven by an immunosuppressive tumor microenvironment (TME). Whether IBC can be switched into an immune-inflamed TME by immune-checkpoint inhibitors (ICIs) is a matter of debate. Presently, measurable biomarkers of IBC-TME have never been synthetized into a comprehensive portray of the immune-milieu (i.e., an immunogram), describing the immune-vulnerability of IBC and potentially predicting the response to ICIs. We propose an immunogram for IBC, based on preclinical and clinical studies, including six parameters: the presence of immune-effector cells, of immune-suppressive cells and of immune checkpoints, the general immune status, the activation of immune-suppressive pathways, the tumor foreignness. The IBC immunogram suggests the existence of a preexisting immune TME that is suppressed by mechanisms of immune-escape but might be restored by ICIs. The combination of chemotherapy and ICIs in patients with IBC is based on a strong biological rationale. However, the design and the development of clinical trials assessing the incorporation of ICIs raise many methodological and practical issues. In parallel with the further comprehension of IBC biology, the prospective validation and integration of biomarkers predictive of response to ICIs are warranted.

Immune Biomarkers in Triple-Negative Breast Cancer: Improving the Predictivity of Current Testing Methods

Triple-negative breast cancer (TNBC) poses a significant challenge in terms of prognosis and disease recurrence. The limited treatment options and the development of resistance to chemotherapy make it particularly difficult to manage these patients. However, recent research has been shifting its focus towards biomarker-based approaches for TNBC, with a particular emphasis on the tumor immune landscape. Immune biomarkers in TNBC are now a subject of great interest due to the presence of tumor-infiltrating lymphocytes (TILs) in these tumors. This characteristic often coincides with the presence of PD-L1 expression on both neoplastic cells and immune cells within the tumor microenvironment. Furthermore, a subset of TNBC harbor mismatch repair deficient (dMMR) TNBC, which is frequently accompanied by microsatellite instability (MSI). All of these immune biomarkers hold actionable potential for guiding patient selection in immunotherapy. To fully capitalize on these opportunities, the identification of additional or complementary biomarkers and the implementation of highly customized testing strategies are of paramount importance in TNBC. In this regard, this article aims to provide an overview of the current state of the art in immune-related biomarkers for TNBC. Specifically, it focuses on the various testing methodologies available and sheds light on the immediate future perspectives for patient selection. By delving into the advancements made in understanding the immune landscape of TNBC, this study aims to contribute to the growing body of knowledge in the field. The ultimate goal is to pave the way for the development of more personalized testing strategies, ultimately improving outcomes for TNBC patients.