Immune checkpoint inhibitors for triple-negative breast cancer: From immunological mechanisms to clinical evidence

Honokiol in the treatment of triple-negative breast cancer: a network pharmacology approach and experimental validation

Triple-negative breast cancer (TNBC) is a rare and highly metastatic form of cancer. Honokiol (HNK), a biphenolic compound, has been utilized in TNBC treatment, though its specific targets remain unclear. This study aimed to elucidate the effects of HNK on TNBC by combining network pharmacology predictions and experimental validation to uncover its mechanisms. MDA-MB 231 and MDA-MB 468 cells were pre-treated with varying doses of HNK for 24 h. Cell viability, proliferation, and apoptosis were assessed using CCK8 and FACS assays, whereas a wound healing assay was used to evaluate cell migration. A tubule formation assay was used to assess blood vessel formation in HUVECs. Additionally, in vivo activity was confirmed using a zebrafish xenograft model. Network pharmacology and molecular docking predicted active ingredients, key targets, and potential mechanisms of HNK against TNBC. Results indicated that HNK induces apoptosis in MDA-MB 231 and MDA-MB 468 cells and inhibits their migration and proliferation. Furthermore, HNK suppressed blood vessel formation. Zebrafish xenograft experiments validated HNK's inhibitory effect on TNBC cells in vivo. Network pharmacology identified 36 potential HNK targets against TNBC, including HSP90AA1, AKT1, EGFR, ERBB2, HSP90AB1, PGR, MDM2, HDAC1, NR3C1, and MAPK14. Key signaling pathways such as PI3K-Akt, MAPK, Rap1, Ras, and FoxO were implicated in HNK's anti-TNBC mechanism. Molecular docking demonstrated spontaneous interactions between HNK and the targeted proteins. In conclusion, HNK may reduce angiogenesis by blocking the EGFR and HSP90AB1 pathways thereby decreasing proliferation and increasing apoptosis in TNBC cells.

RBM15 Drives Breast Cancer Cell Progression and Immune Escape via m6A-Dependent Stabilization of KPNA2 mRNA

BACKGROUND

Breast cancer is the most frequently diagnosed cancer among women worldwide with high morbidity and mortality. Previous studies have indicated that RNA-binding motif protein-15 (RBM15), an N6-methyladenosine (m6A) writer, is implicated in the growth of breast cancer cells. Herein, we aimed to explore the function and detailed mechanism of RBM15 in breast cancer.

METHODS

In this research, UALCAN databases were applied to analyze the expression of RBM15 or Karyopherin-2 alpha (KPNA2) in BRCA. RBM15 and KPNA2 mRNA levels were determined using real-time quantitative polymerase chain reaction (RT-qPCR) assay. RBM15, KPNA2, and Programmed cell death ligand 1 (PD-L1) protein levels were measured using western blot. Cell proliferation, migration, and invasion were assessed using 5-ethynyl-2'-deoxyuridine (EdU) and Transwell assays. The biological role of RBM15 on breast cancer tumor growth was verified using the xenograft tumor model in vivo. Effects of breast cancer cells on the proliferation and apoptosis of CD8+ T cells were analyzed using flow cytometry. Interaction between RBM15 and KPNA2 was validated using methylated RNA immunoprecipitation (MeRIP) and dual-luciferase reporter assays.

RESULTS

RBM15 and KPNA2 were highly expressed in breast cancer tissues and cell lines. Furthermore, RBM15 silencing might suppress breast cancer cell proliferation, migration, invasion, and lymphocyte immunity in vitro, as well as block tumor growth in vivo. At the molecular level, RBM15 might improve the stability and expression of KPNA2 mRNA via m6A methylation.

CONCLUSION

RBM15 might contribute to the malignant progression and immune escape of breast cancer cells partly by modulating the stability of KPNA2 mRNA, providing a promising therapeutic target for breast cancer.

Low expression of TOX predicts poor prognosis of patients with breast cancer in the real world: A retrospective study

Background

TOX is a transcription factor that is implicated in the regulation of T cell exhaustion in tumors. TOX has been proven to have prognostic value in some malignant tumors. We aim to analyze the expression of TOX in breast cancer patients, and the association between TOX and prognostic significance in patients with breast cancer.

Methods

313 breast cancer patients were enrolled into this study. The expression of TOX was determined by immunohistochemistry assay. Survival curves were performed by Kaplan-Meier and log-rank test. The potential independent factors were assessed by Cox regression analyses. Nomogram models, calibration curve, decision curve analyses were applied to analyze the clinical utility of predictive models.

Results

According to semi-quantitative scoring, 129 patients were classified into low group, and 184 patients were classified into high group. Patients with high expression of TOX had a longer survival than those with low expression of TOX (DFS: 71.70 vs. 64.05 months, χ2 = 11.6300, P = 0.00065; OS: 81.03 vs. 73.72 months, χ2 = 11.4200, P = 0.00073). Based on Cox regression analyses, multivariate analysis indicated that TOX was the potential prognostic factor for both DFS (HR: 0.412, 95 % CI: 0.248-0.684, P = 0.001) and OS (HR: 0.395, 95 % CI: 0.237-0.660, P < 0.0001). Calibration curve analysis showed that the predicted line was well-matched with baseline regarding postoperative 1-, 3-, and 5-year survival rate.

Conclusions

The expression of TOX is a potential prognostic factor, and can be a promising biomarker for predicting survival in breast cancer patients.

Immunoglobulin-binding protein and Toll-like receptors in immune landscape of breast cancer

Breast cancer (BC) is a complex disease exhibiting significant heterogeneity and encompassing various molecular subtypes. Among these, triple-negative breast cancer (TNBC) stands out as one of the most challenging types, characterized by its aggressive nature and poor prognosis. This review embarks on a comprehensive exploration of the immune landscape of BC, with a primary focus on the functional and structural characterization of immunoglobulin-binding protein (BiP) and its pivotal role in regulating the unfolded response (UPR) pathway of proteins. Moreover, we unravel the multifaceted functions of BiP in BC, with a special emphasis on the involvement of cell surface BiP in TNBC metastasis, drug resistance, and its contribution to the formation of the tumor microenvironment (TME). We also provide mechanistic insights into how ER-resident BiP mediates the sensitization of drug-resistant BC to different treatment strategies, thereby offering promising avenues for therapeutic intervention. We also delve into the role of Toll-like receptors (TLRs), shedding light on their diverse expression patterns across BC and their influence on modulating the tumor immune response. Understanding the interplay between BiP, TLRs, and the immune response, especially in TNBC, opens avenues for novel immunotherapies. Future research should focus on developing targeted therapies that activate ER-resident BiP or inhibit cell surface BiP, and modulate TLR signaling. Moreover, exploring BiP as a biomarker for TNBC diagnosis, prognosis, and treatment response will be crucial for personalized medicine.

Inflammation-Triggering Engineered Macrophages (MacTriggers) Enhance Reactivity of Immune Checkpoint Inhibitor Only in Tumor Tissues

Background: We have previously reported engineered macrophages (MacTriggers) that can accelerate the release of tumor necrosis factor-α in response to M2 polarization. MacTriggers are characterized by two original characteristics of macrophages: (1) migration to tumors; and (2) polarization to the M2 phenotype in tumors. Intravenously administered MacTriggers efficiently accumulated in the tumors and induced tumor-specific inflammation. This study reports a novel methodology for enhancing the anti-tumor effects of immune checkpoint inhibitors (ICIs). Results: In this study, we newly found that the intravenously administered MacTriggers in BALB/c mouse models upregulated the expression levels of immune checkpoint proteins, such as programmed cell death (PD)-1 in CD8+ T cells and PD-ligand 1 (PD-L1) in cancer cells and macrophages. Consequently, in two ICI-resistant tumor-inoculated mouse models, the combined administration of MacTrigger and anti-PD-1 antibody (aPD-1) synergistically inhibited tumor growth, whereas monotherapy with aPD-1 did not exhibit anti-tumor effects. This synergistic effect was mainly from aPD-1 enhancing the tumor-attacking ability of CD8+ T cells, which could infiltrate into the tumors following MacTrigger treatment. Importantly, no side effects were observed in normal tissues, particularly in the liver and spleen, indicating that the MacTriggers did not enhance the aPD-1 reactivity in normal tissues. This specificity was from the MacTriggers not polarizing to the M2 phenotype in normal tissues, thereby avoiding inflammation and increased PD-1/PD-L1 expression. MacTriggers could enhance aPD-1 reactivity only in tumors following tumor-specific inflammation induction. Conclusions: Our findings suggest that the MacTrigger and aPD-1 combination therapy is a novel approach for potentially overcoming the current low ICI response rates while avoiding side effects.

Efficacy and safety of first-line treatment for metastatic triple-negative breast cancer: A network meta-analysis

Background

Metastatic triple-negative breast cancer (mTNBC) is an aggressive histological subtype with poor prognosis. Several first-line treatments are currently available for mTNBC. This study conducted a network meta-analysis to compare these first-line regimens and to determine the regimen with the best efficacy.

Methods

A systematic search of PubMed, EMBASE, the Cochrane Central Register of Controlled Bases, and minutes of major conferences was performed. Progression-free survival (PFS), overall survival (OS), and objective response rate (ORR) were analyzed via network meta-analysis using the R software (R Core Team, Vienna, Austria). The efficacy of the treatment regimens was compared using hazard ratios and 95% confidence intervals.

Results

A total of 29 randomized controlled trials involving 4607 patients were analyzed. The ranking was based on the surface under the cumulative ranking curve. Network meta-analysis results showed that cisplatin combined with nab-paclitaxel or paclitaxel was superior to docetaxel plus capecitabine in terms of PFS and ORR. For programmed death-ligand 1 (PD-L1) and breast cancer susceptibility gene (BRCA) mutation-positive tumors, atezolizumab/pembrolizumab combined with nab-paclitaxel and talazoparib was superior to docetaxel plus capecitabine. No significant difference was observed among the treatments in OS. Neutropenia, diarrhea, and fatigue were common serious adverse events.

Conclusion

Cisplatin combined with nab-paclitaxel or paclitaxel is the preferred first-line treatment for mTNBC. For PD-L1 and BRCA mutation-positive tumors, atezolizumab/pembrolizumab combined with nab-paclitaxel and talazoparib is an effective treatment option. Neutropenia, diarrhea, and fatigue are frequently occurring serious adverse events.

Early-stage triple negative breast cancer: the therapeutic role of immunotherapy and the prognostic value of pathological complete response

Triple negative breast cancer (TNBC) represents an aggressive disease associated with a high risk of recurrence after curative treatment and a poor prognosis in the metastatic setting. Chemotherapy was for years the only treatment available in the early and metastatic setting, due to the lack of actionable targets. Clinical practice has changed following the results obtained with the addition of immunotherapy to standard chemotherapy, the development of novel drugs [i.e. antibody-drug conjugates (ADCs)], and the use of targeted treatments for patients carrying germline pathogenic breast cancer susceptibility genes (BRCA) 1 or BRCA 2 variants. The treatment of early-stage disease has had a shift in clinical practice since July 2021, after the Food and Drug Administration (FDA) approval of pembrolizumab in association with chemotherapy as neoadjuvant treatment for TNBC and as a single agent in the subsequent adjuvant setting. This intensive treatment based on the combination of a poly-chemotherapy and an immune checkpoint inhibitor (ICI) led to the improvement of short- and long-term outcomes, but it has highlighted some new unmet clinical needs in the treatment of early-stage TNBC: the selection of the most effective adjuvant therapy and the integration of pembrolizumab with other therapeutic strategies [capecitabine, poly(ADP-ribose) polymerase (PARP) inhibitors] based on the achievement of pathologic complete response (pCR); the identification of predictive biomarkers to select patients who could most benefit from the addition of ICI, to minimize toxicities and to maximize outcomes; the possibility of de-escalating chemotherapy in favor of immune-combo or novel agents, such as ADCs; the role of immunotherapy in estrogen receptor (ER)-low patients. The advent of immunotherapy not only addresses current challenges in TNBC treatment but also holds the promise of a radical transformation in its therapeutic paradigm, enhancing significantly clinical outcomes and offering new perspectives for patients grappling with this aggressive form of breast cancer.

Addition of immune checkpoint inhibitors to chemotherapy versus chemotherapy alone in patients with triple-negative breast cancer: A systematic review and meta-analysis

BACKGROUND

Triple-negative breast cancer (TNBC) is a relatively common malignant tumor with high mortality rates. There are limited treatment options and current therapy regimens often fall short of providing positive outcomes. The development of immune checkpoint inhibitors (ICIs) have provided a vital treatment option although efficacy has varied. Here, we review patient response to current TNBC treatment with and without the addition of ICIs.

METHODS

A systematic search of PubMed, Cochrane, and EMBASE library databases was done to search eligible studies published from their inception through April 3, 2022. The primary outcome indicators used were progression-free survival (PFS), overall survival (OS), pathological complete response rate (pCR) and objective remission rate (ORR), while adverse events (AEs) were also analyzed. Publication bias and sensitivity analyses and were performed to evaluate the quality of assessment.

RESULTS

Overall, the meta-analysis looked at seven randomized controlled trials (RCTs) that included 4631 patients with TNBC. Results showed an improvement in PFS for patients receiving ICI in addition to chemotherapy (CT) in both the intent-to-treat (ITT) population and PD-L1 positive patients. Increased pCR rates were observed in all patients irrespective of PD-L1 status as well as increased ORR in the ITT which was more notable in PD-L1 positive subjects. While significant improvement in OS was observed only in PD-L1 positive individuals, the use of ICIs plus CT resulted in severe adverse reactions, specifically immune-related.

CONCLUSIONS

This study supports the increased efficacy of ICIs in combination with CT compared to CT alone in patients with TNBC, with the most notable benefit observed in PD-L1 positive patients. However, combination therapy increases the risk of adverse reactions which warrants further investigation.

Oncoinformatic screening of the gene clusters involved in the HER2-positive breast cancer formation along with the in silico pharmacodynamic profiling of selective long-chain omega-3 fatty acids as the metastatic antagonists

The HER2-positive patients occupy ~ 30% of the total breast cancer patients globally where no prevalent drugs are available to mitigate the frequent metastasis clinically except lapatinib and neratinib. This scarcity reinforced researchers' quest for new medications where natural substances are significantly considered. Valuing the aforementioned issues, this research aimed to study the ERBB2-mediated string networks that work behind the HER2-positive breast cancer formation regarding co-expression, gene regulation, GAMA-receptor-signaling pathway, cellular polarization, and signal inhibition. Following the overexpression, promotor methylation, and survivability profiles of ERBB2, the super docking position of HER2 was identified using the quantum tunneling algorithm. Supramolecular docking was conducted to study the target specificity of EPA and DHA fatty acids followed by a comprehensive molecular dynamic simulation (100 ns) to reveal the RMSD, RMSF, Rg, SASA, H-bonds, and MM/GBSA values. Finally, potential drug targets for EPA and DHA in breast cancer were constructed to determine the drug-protein interactions (DPI) at metabolic stages. Considering the values resulting from the combinational models of the oncoinformatic, pharmacodynamic, and metabolic parameters, long-chain omega-3 fatty acids like EPA and DHA can be considered as potential-targeted therapeutics for HER2-positive breast cancer treatment.

The entanglement of extracellular matrix molecules and immune checkpoint inhibitors in cancer: a systematic review of the literature

Introduction

Immune-checkpoint inhibitors (ICIs) have emerged as a core pillar of cancer therapy as single agents or in combination regimens both in adults and children. Unfortunately, ICIs provide a long-lasting therapeutic effect in only one third of the patients. Thus, the search for predictive biomarkers of responsiveness to ICIs remains an urgent clinical need. The efficacy of ICIs treatments is strongly affected not only by the specific characteristics of cancer cells and the levels of immune checkpoint ligands, but also by other components of the tumor microenvironment, among which the extracellular matrix (ECM) is emerging as key player. With the aim to comprehensively describe the relation between ECM and ICIs' efficacy in cancer patients, the present review systematically evaluated the current literature regarding ECM remodeling in association with immunotherapeutic approaches.

Methods

This review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines and was registered at the International Prospective Register of Systematic Reviews (PROSPERO, CRD42022351180). PubMed, Web of Science, and Scopus databases were comprehensively searched from inception to January 2023. Titles, abstracts and full text screening was performed to exclude non eligible articles. The risk of bias was assessed using the QUADAS-2 tool.

Results

After employing relevant MeSH and key terms, we identified a total of 5070 studies. Among them, 2540 duplicates, 1521 reviews or commentaries were found and excluded. Following title and abstract screening, the full text was analyzed, and 47 studies meeting the eligibility criteria were retained. The studies included in this systematic review comprehensively recapitulate the latest observations associating changes of the ECM composition following remodeling with the traits of the tumor immune cell infiltration. The present study provides for the first time a broad view of the tight association between ECM molecules and ICIs efficacy in different tumor types, highlighting the importance of ECM-derived proteolytic products as promising liquid biopsy-based biomarkers to predict the efficacy of ICIs.

Conclusion

ECM remodeling has an important impact on the immune traits of different tumor types. Increasing evidence pinpoint at ECM-derived molecules as putative biomarkers to identify the patients that would most likely benefit from ICIs treatments.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022351180, identifier CRD42022351180.

Current therapeutic approaches and promising perspectives of using bioengineered peptides in fighting chemoresistance in triple-negative breast cancer

Breast cancer is a collation of malignancies that manifest in the mammary glands at the early stages. Among breast cancer subtypes, triple-negative breast cancer (TNBC) shows the most aggressive behavior, with apparent stemness features. Owing to the lack of response to hormone therapy and specific targeted therapies, chemotherapy remains the first line of the TNBC treatment. However, the acquisition of resistance to chemotherapeutic agents increase therapy failure, and promotes cancer recurrence and distant metastasis. Invasive primary tumors are the birthplace of cancer burden, though metastasis is a key attribute of TNBC-associated morbidity and mortality. Targeting the chemoresistant metastases-initiating cells via specific therapeutic agents with affinity to the upregulated molecular targets is a promising step in the TNBC clinical management. Exploring the capacity of peptides as biocompatible entities with the specificity of action, low immunogenicity, and robust efficacy provides a principle for designing peptide-based drugs capable of increasing the efficacy of current chemotherapy agents for selective targeting of the drug-tolerant TNBC cells. Here, we first focus on the resistance mechanisms that TNBC cells acquire to evade the effect of chemotherapeutic agents. Next, the novel therapeutic approaches employing tumor-targeting peptides to exploit the mechanisms of drug resistance in chemorefractory TNBC are described.

Immune-Checkpoint Inhibitors: A New Line of Attack in Triple-Negative Breast Cancer

Poor prognosis is a distinctive feature of triple-negative breast cancer (TNBC). Chemotherapy has long represented the main and unique treatment for patients with TNBC. Recently, immune checkpoint inhibitors (ICIs) were investigated in several clinical trials and were approved for clinical use in TNBC patients that express programmed cell death protein-1 (PD-1) in combination with chemotherapy in the first-line setting. ICIs are also being investigated in the neoadjuvant and adjuvant settings for TNBC. This chapter aims to discuss different ICIs used to treat all TNBC stages to date.

PDLIM2 is highly expressed in Breast Cancer tumour-associated macrophages and is required for M2 macrophage polarization

The PDZ-LIM domain-containing protein 2 (PDLIM2) regulates cell polarity and the protein stability of key transcription factors in epithelial and hemopoietic cells. We previously reported that PDLIM2 is more highly expressed in Triple Negative Breast Cancer (TNBC) than in other breast cancer types or normal breast tissue. In the course of the TNBC study, it was noted that PDLIM2 was highly expressed in the stroma of PDLIM2-expressing tumours. Here, we investigated the phenotype of these stromal cells and whether any infiltrating immune population was linked to PDLIM2 expression. We found that high PDLIM2 expression in breast tumours was associated with higher levels of infiltrating M2 macrophages, but was not associated with infiltrating T cell sub-populations. We then tested whether PDLIM2 contributes to macrophage differentiation or function by using cultures of bone marrow-derived macrophages from wildtype and Pdlim2 knockout mice. This demonstrated that PDLIM2 is required for naïve macrophage migration and for the full adoption of IL-4-induced M2 polarization, including expression of M2 phenotypic markers, cell adhesion and cell migration. TLR4-, TLR3- or IFNγ-induced M1 macrophage activity was less dependent on PDLIM2. Finally, analysis of publicly available breast cancer datasets showed that high PDLIM2 expression is associated with increased M2 macrophage infiltration. We conclude that PDLIM2 expression influences the tumour associated stroma and, in particular, M2 macrophage infiltration that may contribute to the progression of TNBC or other subsets of breast cancer.

Development of a Mobile-Based Self-care Application for Patients with Breast Cancer-Related Lymphedema in Iran

BACKGROUND

Due to the chronic, progressive, and debilitating nature of breast cancer-related lymphedema (BCRL), it is necessary to observe and maintain self-care management accordingly. This study was conducted to develop a mobile application based on the Android operating system for self-care management of Iranian patients with BCRL.

METHODS

An applied developmental study was conducted in 2020. The users' information needs assessment as well as design, development, implementation, and evaluation of the mobile app for self-care management of patients with BCRL was done by searching the literature, reviewing the existing mobile applications, and surveying the users' needs. The mobile app was designed using the Android Studio environment and Java programming language in the Android operating system. The usability of the app was evaluated by 30 patients with BCRL using the questionnaire for user interface satisfaction-seventh version (QUIS 7).

RESULTS

The mobile app for BCRL included demographic information, clinical information, lifestyle and system functions (drug use, nutrition, exercise, smoking cessation, communication, and test time reminder). User usability evaluation of the app content and functions confirmed that it was appropriate and satisfactory for the self-management of women with BCRL.

CONCLUSION

The mobile app was appropriate in terms of the content, function, and quality for improving the patients' lifestyle and education and self-management of BCRL symptoms according to its usability evaluation from the end-users' (patients) perspective. It is suggested that studies should be performed to confirm the effectiveness and identify the clinical significance of the app.

KEYNOTE-522, IMpassion031 and GeparNUEVO: changing the paradigm of neoadjuvant immune checkpoint inhibitors in early triple-negative breast cancer

Stage I-III triple-negative breast cancer accounts for approximately 15-20% of new diagnoses of early breast cancer. Novel systemic treatment options have recently been assessed as part of the neoadjuvant approach, such as the addition of immune checkpoint inhibitors to cytotoxic chemotherapy. However, several questions remain unanswered, including the identification of predictors of response to immunotherapy in this setting, and further efforts aimed at identifying reliable predictors and clarifying the effective role of PD-L1 status, tumor mutational burden, tumor-infiltrating lymphocytes and other biomarkers are warranted. Herein we will provide an overview of recent clinical studies of neoadjuvant immune checkpoint inhibitors in patients with triple-negative breast cancer, especially focusing on the recently presented and published KEYNOTE-522, IMpassion031 and GeparNUEVO trials.

Tumor Cell-Autonomous Pro-Metastatic Activities of PD-L1 in Human Breast Cancer Are Mediated by PD-L1-S283 and Chemokine Axes

Simple Summary

Triple-negative breast cancer (TNBC) is an aggressive disease that responds in a limited manner to immune checkpoint blockades targeting the PD-L1/PD-1 axis, suggesting that PD-L1 potentiates TNBC progression via pathways not related to immune suppression. We demonstrated that, in human breast cancer cells, PD-L1 expression increased in a cell-autonomous manner tumor cell growth, invasion and release of pro-metastatic factors; these activities were elevated by exposure to PD-1 and were markedly impaired in S283-mutated PD-L1-expressing cells. Invasion of WT-PD-L1-expressing TNBC cells depended on autocrine chemokine circuits, involving CXCR1/2, CCR2, CCR5 and their ligands. In T cell-deficient mice, WT-PD-L1 exhibited increased tumor growth and metastasis by TNBC cells, whereas S283A-PD-L1-expressing cells showed a very poor tumorigenic and metastatic profile. These findings on cell-autonomous and PD-1-induced pro-metastatic activities of PD-L1 in cancer cells suggest that treatments targeting PD-L1 could improve the efficacy of immune-targeting checkpoint inhibitors, e.g., anti-PD-1 or anti-CTLA-4 in TNBC.

Abstract

Therapies targeting the PD-L1/PD-1 axis have recently been introduced to triple-negative breast cancer (TNBC) with limited efficacy, suggesting that this axis promotes tumor progression through mechanisms other than immune suppression. Here, we over-expressed WT-PD-L1 in human TNBC cells (express endogenous PD-L1) and in luminal-A breast cancer cells (no endogenous PD-L1 expression) and demonstrated that cell-autonomous PD-L1 activities lead to increased tumor cell growth, invasion and release of pro-metastatic factors (CXCL8, sICAM-1, GM-CSF). These activities were promoted by PD-1 and were inhibited by mutating S283 in PD-L1. Invasion of WT-PD-L1-cells required signaling by chemokine receptors CXCR1/2, CCR2 and CCR5 through autocrine circuits involving CXCL8, CCL2 and CCL5. Studies with T cell-deficient mice demonstrated that cell-autonomous WT-PD-L1 activities in TNBC cells increased tumor growth and metastasis compared to knock-out (KO)-PD-L1-cells, whereas S283A-PD-L1-expressing cells had minimal ability to form tumors and did not metastasize. Overall, our findings reveal autonomous and PD-1-induced tumor-promoting activities of PD-L1 that depend on S283 and on chemokine circuits. These results suggest that TNBC patients whose tumors express PD-L1 could benefit from therapies that prevent immune suppression by targeting PD-1/CTLA-4, alongside with antibodies to PD-L1, which would allow maximal impact by mainly targeting the cancer cells.

Roles of HLA-G/KIR2DL4 in Breast Cancer Immune Microenvironment

Human leukocyte antigen (HLA)-G is a nonclassical MHC Class I molecule, which was initially reported as a mediator of immune tolerance when expressed in extravillous trophoblast cells at the maternal-fetal interface. HLA-G is the only known ligand of killer cell immunoglobulin-like receptor 2DL4 (KIR2DL4), an atypical family molecule that is widely expressed on the surface of NK cells. Unlike other KIR receptors, KIR2DL4 contains both an arginine-tyrosine activation motif in its transmembrane region and an immunoreceptor tyrosine-based inhibitory motif (ITIM) in its cytoplasmic tail, suggesting that KIR2DL4 may function as an activating or inhibitory receptor. The immunosuppressive microenvironment exemplified by a rewired cytokine network and upregulated immune checkpoint proteins is a hallmark of advanced and therapy-refractory tumors. Accumulating evidence has shown that HLA-G is an immune checkpoint molecule with specific relevance in cancer immune escape, although the role of HLA-G/KIR2DL4 in antitumor immunity is still uncharacterized. Our previous study had shown that HLA-G was a pivotal mediator of breast cancer resistance to trastuzumab, and blockade of the HLA-G/KIR2DL4 interaction can resensitize breast cancer to trastuzumab treatment. In this review, we aim to summarize and discuss the role of HLA-G/KIR2DL4 in the immune microenvironment of breast cancer. A better understanding of HLA-G is beneficial to identifying novel biomarker(s) for breast cancer, which is important for precision diagnosis and prognostic assessment. In addition, it is also necessary to unravel the mechanisms underlying HLA-G/KIR2DL4 regulation of the immune microenvironment in breast cancer, hopefully providing a rationale for combined HLA-G and immune checkpoints targeting for the effective treatment of breast cancer.

Black Phosphorus, an Emerging Versatile Nanoplatform for Cancer Immunotherapy

Black phosphorus (BP) is one of the emerging versatile nanomaterials with outstanding biocompatibility and biodegradability, exhibiting great potential as a promising inorganic nanomaterial in the biomedical field. BP nanomaterials possess excellent ability for valid bio-conjugation and molecular loading in anticancer therapy. Generally, BP nanomaterials can be classified into BP nanosheets (BPNSs) and BP quantum dots (BPQDs), both of which can be synthesized through various preparation routes. In addition, BP nanomaterials can be applied as photothermal agents (PTA) for the photothermal therapy (PTT) due to their high photothermal conversion efficiency and larger extinction coefficients. The generated local hyperpyrexia leads to thermal elimination of tumor. Besides, BP nanomaterials are capable of producing singlet oxygen, which enable its application as a photosensitizer for photodynamic therapy (PDT). Moreover, BP nanomaterials can be oxidized and degraded to nontoxic phosphonates and phosphate under physiological conditions, improving their safety as a nano drug carrier in cancer therapy. Recently, it has been reported that BP-based PTT is capable of activating immune responses and alleviating the immunosuppressive tumor microenvironment by detection of T lymphocytes and various immunocytokines, indicating that BP-based nanocomposites not only serve as effective PTAs to ablate large solid tumors but also function as an immunomodulation agent to eliminate discrete tumorlets. Therefore, BP-mediated immunotherapy would provide more possibilities for synergistic cancer treatment.