Myeloid-derived suppressor cells in breast cancer

Converging focal radiation and immunotherapy in a preclinical model of triple negative breast cancer: contribution of VISTA blockade

Antibodies targeting the co-inhibitory receptor programmed cell death 1 (PDCD1, best known as PD-1) or its main ligand CD274 (best known as PD-L1) have shown some activity in patients with metastatic triple-negative breast cancer (TNBC), especially in a recent Phase III clinical trial combining PD-L1 blockade with taxane-based chemotherapy. Despite these encouraging findings, however, most patients with TNBC fail to derive significant benefits from PD-L1 blockade, calling for the identification of novel therapeutic approaches. Here, we used the 4T1 murine mammary cancer model of metastatic and immune-resistant TNBC to test whether focal radiation therapy (RT), a powerful inducer of immunogenic cell death, in combination with various immunotherapeutic strategies can overcome resistance to immune checkpoint blockade. Our results suggest that focal RT enhances the therapeutic effects of PD-1 blockade against primary 4T1 tumors and their metastases. Similarly, the efficacy of an antibody specific for V-set immunoregulatory receptor (VSIR, another co-inhibitory receptor best known as VISTA) was enhanced by focal RT. Administration of cyclophosphamide plus RT and dual PD-1/VISTA blockade had superior therapeutic effects, which were associated with activation of tumor-infiltrating CD8⁺ T cells and depletion of intratumoral granulocytic myeloid-derived suppressor cells (MDSCs). Overall, these results demonstrate that RT can sensitize immunorefractory tumors to VISTA or PD-1 blockade, that this effect is enhanced by the addition of cyclophosphamide and suggest that a multipronged immunotherapeutic approach may also be required to increase the incidence of durable responses in patients with TNBC.

Immune microenvironment in different molecular subtypes of ductal breast carcinoma

PURPOSE

Ductal breast carcinoma as a heterogeneous disease has different molecular subtypes associated with clinical prognosis and patients' survival. The role of immune system as a consistent part of the tumor microenvironment (TME) has been documented in progression of ductal breast carcinoma. Here, we aimed to describe the important immune cells and the immune system-associated molecules in Ductal Carcinoma In situ (DCIS) and Invasive Ductal Carcinoma (IDC) with special emphasis on their associations with different molecular subtypes and patients' prognosis.

RESULTS

The immune cells have a dual role in breast cancer (BC) microenvironment depending on the molecular subtype or tumor grade. These cells with different frequencies are present in the TME of DCIS and IDC. The presence of regulatory cells including Tregs, MDSC, Th2, Th17, M2 macrophages, HLADR^- T cells, and Tγδ cells is related to more immunosuppressive microenvironment, especially in ER^- and TN subtypes. In contrast, NK cells, CTL, Th, and Tfh cells are associated to the anti-tumor activity. These cells are higher in ER⁺ BC, although in other subtypes such as TN or HER2⁺ are associated with a favorable prognosis.

CONCLUSION

Determining the specific immune response in each subtype could be helpful in estimating the possible behavior of the tumor cells in TME. It is important to realize that different frequencies of immune cells in BC environment likely determine the patients' prognosis and their survival in each subtype. Therefore, elucidation of the distinct immune players in TME would be helpful toward developing targeted therapies in each subtype.

Differential expansion of circulating human MDSC subsets in patients with cancer, infection and inflammation

Background

Myeloid-derived suppressor cells (MDSC) are a functional myeloid cell subset that includes myeloid cells with immune suppressive properties. The presence of MDSC has been reported in the peripheral blood of patients with several malignant and non-malignant diseases. So far, direct comparison of MDSC across different diseases and Centers is hindered by technical pitfalls and a lack of standardized methodology. To overcome this issue, we formed a network through the COST Action Mye-EUNITER (www.mye-euniter.eu) with the goal to standardize and facilitate the comparative analysis of human circulating MDSC in cancer, inflammation and infection. In this manuscript, we present the results of the multicenter study Mye-EUNITER MDSC Monitoring Initiative, that involved 13 laboratories and compared circulating MDSC subsets across multiple diseases, using a common protocol for the isolation, identification and characterization of these cells.

Methods

We developed, tested, executed and optimized a standard operating procedure for the isolation and immunophenotyping of MDSC using blood from healthy donors. We applied this procedure to the blood of almost 400 patients and controls with different solid tumors and non-malignant diseases. The latter included viral infections such as HIV and hepatitis B virus, but also psoriasis and cardiovascular disorders.

Results

We observed that the frequency of MDSC in healthy donors varied substantially between centers and was influenced by technical aspects such as the anticoagulant and separation method used. Expansion of polymorphonuclear (PMN)-MDSC exceeded the expansion of monocytic MDSC (M-MDSC) in five out of six solid tumors. PMN-MDSC expansion was more pronounced in cancer compared with infection and inflammation. Programmed death-ligand 1 was primarily expressed in M-MDSC and e-MDSC and was not upregulated as a consequence of disease. LOX-1 expression was confined to PMN-MDSC.

Conclusions

This study provides improved technical protocols and workflows for the multi-center analysis of circulating human MDSC subsets. Application of these workflows revealed a predominant expansion of PMN-MDSC in solid tumors that exceeds expansion in chronic infection and inflammation.

Co-administration of sulforaphane and doxorubicin attenuates breast cancer growth by preventing the accumulation of myeloid-derived suppressor cells

Sulforaphane (SFN) is a compound derived from cruciferous plants shown to be effective in cancer prevention and suppression. Myeloid-derived suppressor cells (MDSCs) are known to inhibit anti-tumor immunity; however, whether SFN regulates the anti-tumor activity of MDSCs in breast cancer is still unknown. In the current study, we found that SFN blocked prostaglandin E2 (PGE2) synthesis in parental and doxorubicin (DOX)-resistant breast cancer 4T1 cell lines by activating NF-E2-related factor 2 (Nrf2). Nrf2-mediated reduction of PGE2 was dependent on the enhanced expression of heme oxygenase 1 (HO-1) and glutamate-cysteine ligase (GCLC), and decreased COX-2 expression in breast cancer cells. Moreover, our study further revealed that reduced PGE2 secretion from SFN-treated 4T1 cells triggered MDSCs to switch to an immunogenic phenotype, enhancing the anti-tumor activities of CD8⁺ T cells. Co-administration of SFN and DOX was more efficacious for the treatment of breast cancer in a mouse model than either agent alone, as evidenced by the significant decrease in tumor volume, MDSC expansion, and increase in cytotoxic CD8⁺ T cells. Taken together, our data indicate that SFN reverses the immunosuppressive microenvironment and is a potent adjuvant chemotherapeutic candidate in breast cancer.

Penetrable Nanoplatform for "Cold" Tumor Immune Microenvironment Reeducation

Lack of tumor-infiltration lymphocytes (TILs) and resistances by overexpressed immunosuppressive cells (principally, myeloid-derived suppressor cells (MDSCs)) in tumor milieu are two major challenges hindering the effectiveness of immunotherapy for "immune-cold" tumors. In addition, the natural physical barrier existing in solid cancer also limits deeper delivery of drugs. Here, a tumor-targeting and light-responsive-penetrable nanoplatform (Apt/PDGs^s@pMOF) is developed to elicit intratumoral infiltration of cytotoxic T cells (CTLs) and reeducate immunosuppressive microenvironment simultaneously. In particular, porphyrinic metal-organic framework (pMOF)-based photodynamic therapy (PDT) induces tumor immunogenic cell death (ICD) to promote CTLs intratumoral infiltration and hot "immune-cold" tumor. Upon being triggered by PDT, the nearly 10 nm adsorbed drug-loaded dendrimer de-shields from the nanoplatform and spreads into the deeper tumor, eliminating MDSCs and reversing immunosuppression, eventually reinforcing immune response. Meanwhile, the designed nanoplatform also has a systemic MDSC inhibition effect and moderate improvement of overall antitumor immune responses, resulting in effective suppression of distal tumors within less significant immune-related adverse effects (irAEs) induced.

Loss of ELF5-FBXW7 stabilizes IFNGR1 to promote the growth and metastasis of triple-negative breast cancer through interferon-γ signalling

Triple-negative breast cancer (TNBC) is characterized by a high degree of immune infiltrate in the tumour microenvironment, which may influence the fate of TNBC cells. We reveal that loss of the tumour suppressive transcription factor Elf5 in TNBC cells activates intrinsic interferon-γ (IFN-γ) signalling, promoting tumour progression and metastasis. Mechanistically, we find that loss of the Elf5-regulated ubiquitin ligase FBXW7 ensures stabilization of its putative protein substrate IFN-γ receptor 1 (IFNGR1) at the protein level in TNBC. Elf5low tumours show enhanced IFN-γ signalling accompanied by an increase of immunosuppressive neutrophils within the tumour microenvironment and increased programmed death ligand 1 expression. Inactivation of either programmed death ligand 1 or IFNGR1 elicited a robust anti-tumour and/or anti-metastatic effect. A positive correlation between ELF5 and FBXW7 expression and a negative correlation between ELF5, FBXW7 and IFNGR1 expression in the tumours of patients with TNBC strongly suggest that this signalling axis could be exploited for patient stratification and immunotherapeutic treatment strategies for Elf5low patients with TNBC.

Green Tea Polyphenol EGCG Attenuates MDSCs-mediated Immunosuppression through Canonical and Non-Canonical Pathways in a 4T1 Murine Breast Cancer Model

Several studies in the past decades have reported anti-tumor activity of the bioactive compounds extracted from tea leaves, with a focus on the compound epigallocatechin-3-gallate (EGCG). However, further investigations are required to unravel the underlying mechanisms behind the anti-tumor activity of EGCG. In this study, we demonstrate that EGCG significantly inhibits the growth of 4T1 breast cancer cells in vitro and in vivo. EGCG ameliorated immunosuppression by significantly decreasing the accumulation of myeloid-derived suppressor cells (MDSCs) and increasing the proportions of CD4⁺ and CD8⁺ T cells in spleen and tumor sites in 4T1 breast tumor-bearing mice. Surprisingly, a low dose of EGCG (0.5-5 μg/mL) effectively reduced the cell viability and increased the apoptosis rate of MDSCs in vitro. EGCG down-regulated the canonical pathways in MDSCs, mainly through the Arg-1/iNOS/Nox2/NF-κB/STAT3 signaling pathway. Moreover, transcriptomic analysis suggested that EGCG also affected the non-canonical pathways in MDSCs, such as ECM-receptor interaction and focal adhesion. qRT-PCR further validated that EGCG restored nine key genes in MDSCs, including Cxcl3, Vcan, Col4a1, Col8a1, Oasl2, Mmp12, Met, Itsnl and Acot1. Our results provide new insight into the mechanism of EGCG-associated key pathways/genes in MDSCs in the murine breast tumor model.

The role of granulocyte colony‑stimulating factor in breast cancer development: A review

Granulocyte-colony-stimulating factor (G-CSF) is a member of the hematopoietic growth factor family that primarily affects the neutrophil lineage. G-CSF serves as a powerful mobilizer of peripheral blood stem cells and recombinant human G-CSF (rhG-CSF) has been used to treat granulocytopenia and neutropenia after chemotherapy for cancer patients. However, recent studies have found that G-CSF plays an important role in cancer progression. G-CSF expression is increased in different types of cancer cells, such as lung cancer, gastric cancer, colorectal cancer, invasive bladder carcinoma, glioma and breast cancer. However, it is unclear whether treatment with G-CSF has an adverse effect. The current review provides an overview of G-CSF in malignant breast cancer development and the data presented in this review are expected to provide new ideas for cancer therapy.

Conducting a Virtual Clinical Trial in HER2-Negative Breast Cancer Using a Quantitative Systems Pharmacology Model With an Epigenetic Modulator and Immune Checkpoint Inhibitors

The survival rate of patients with breast cancer has been improved by immune checkpoint blockade therapies, and the efficacy of their combinations with epigenetic modulators has shown promising results in preclinical studies. In this prospective study, we propose an ordinary differential equation (ODE)-based quantitative systems pharmacology (QSP) model to conduct an in silico virtual clinical trial and analyze potential predictive biomarkers to improve the anti-tumor response in HER2-negative breast cancer. The model is comprised of four compartments: central, peripheral, tumor, and tumor-draining lymph node, and describes immune activation, suppression, T cell trafficking, and pharmacokinetics and pharmacodynamics (PK/PD) of the therapeutic agents. We implement theoretical mechanisms of action for checkpoint inhibitors and the epigenetic modulator based on preclinical studies to investigate their effects on anti-tumor response. According to model-based simulations, we confirm the synergistic effect of the epigenetic modulator and that pre-treatment tumor mutational burden, tumor-infiltrating effector T cell (Teff) density, and Teff to regulatory T cell (Treg) ratio are significantly higher in responders, which can be potential biomarkers to be considered in clinical trials. Overall, we present a readily reproducible modular model to conduct in silico virtual clinical trials on patient cohorts of interest, which is a step toward personalized medicine in cancer immunotherapy.

Clinical relevance of systemic monocytic-MDSCs in patients with metastatic breast cancer

The overall aim of this prospective study was to delineate the role of monocytic myeloid-derived suppressor cells (Mo-MDSCs) in patients with metastatic breast cancer (MBC). MDSCs are a heterogeneous group of immunosuppressive cells often enriched in different malignancies which hold prognostic and predictive value for clinical outcomes. Here, we assessed the clinical significance of Mo-MDSCs in 54 patients with de novo or distant recurrent MBC. We show that high levels of Mo-MDSCs significantly correlated with de novo MBC (metastatic disease at initial diagnosis), estrogen receptor (ER) negativity, and liver- and bone metastasis. A trend towards an association between high levels of Mo-MDSCs and survival (P = 0.053) was also found in patients with distant recurrent ER-positive MBC. We therefore propose that an increased population of Mo-MDSCs may be related to the metastatic or immunoregulatory switch associated with transition to a more systemic disease. Our data imply that high levels of systemic Mo-MDSCs represent patients with more aggressive disease and worse outcome.

MMP9 modulates the metastatic cascade and immune landscape for breast cancer anti-metastatic therapy

Inhibition of active MMP9 early during tumorigenesis suppresses tumor cell migration, invasion, and colony formation and tilts the balance towards anti-tumor immunity by activating CD8⁺ T cells.

Metastasis, the main cause of cancer-related death, has traditionally been viewed as a late-occurring process during cancer progression. Using the MMTV-PyMT luminal B breast cancer model, we demonstrate that the lung metastatic niche is established early during tumorigenesis. We found that matrix metalloproteinase 9 (MMP9) is an important component of the metastatic niche early in tumorigenesis and promotes circulating tumor cells to colonize the lungs. Blocking active MMP9, using a monoclonal antibody specific to the active form of gelatinases, inhibited endogenous and experimental lung metastases in the MMTV-PyMT model. Mechanistically, inhibiting MMP9 attenuated migration, invasion, and colony formation and promoted CD8⁺ T cell infiltration and activation. Interestingly, primary tumor burden was unaffected, suggesting that inhibiting active MMP9 is primarily effective during the early metastatic cascade. These findings suggest that the early metastatic circuit can be disrupted by inhibiting active MMP9 and warrant further studies of MMP9-targeted anti-metastatic breast cancer therapy.

A nano-liposome formulation of the PARP inhibitor Talazoparib enhances treatment efficacy and modulates immune cell populations in mammary tumors of BRCA-deficient mice

Two recently approved PARP inhibitors provide an important new therapeutic option for patients with BRCA-mutated metastatic breast cancer. PARP inhibitors significantly prolong progression-free survival in patients, but conventional oral delivery of PARP inhibitors is hindered by limited bioavailability and off-target toxicities, thus compromising the therapeutic benefits and quality of life for patients. Here, we developed a new delivery system, in which the PARP inhibitor Talazoparib is encapsulated in the bilayer of a nano-liposome, to overcome these limitations.

Methods: Nano-Talazoparib (NanoTLZ) was characterized both in vitro and in vivo. The therapeutic efficacy and toxicity of Nano-Talazoparib (NanoTLZ) were evaluated in BRCA-deficient mice. The regulation of NanoTLZ on gene transcription and immunomodulation were further investigated in spontaneous BRCA-deficient tumors.

Results: NanoTLZ significantly (p<0.05) prolonged the overall survival of BRCA-deficient mice compared to all of the other experimental groups, including saline control, empty nanoparticles, and free Talazoparib groups (oral and i.v.). Moreover, NanoTLZ was better tolerated than treatment with free Talazoparib, with no significant weight lost or alopecia as was observed with the free drug. After 5 doses, NanoTLZ altered the expression of over 140 genes and induced DNA damage, cell cycle arrest and inhibition of cell proliferation in the tumor. In addition, NanoTLZ favorably modulated immune cell populations in vivo and significantly (p<0.05) decreased the percentage of myeloid derived suppressor cells in both the tumor and spleen compared to control groups.

Conclusions: Our results demonstrate that delivering nanoformulated Talazoparib not only enhances treatment efficacy but also reduces off-target toxicities in BRCA-deficient mice; the same potential is predicted for patients with BRCA-deficient breast cancer.

Regulation of Immunity in Breast Cancer

Breast cancer affects millions of women worldwide, leading to many deaths and significant economic burden. Although there are numerous treatment options available, the huge potentials of immunotherapy in the management of localized and metastatic breast cancer is currently being explored. However, there are significant gaps in understanding the complex interactions between the immune system and breast cancer. The immune system can be pro-tumorigenic and anti-tumorigenic depending on the cells involved and the conditions of the tumor microenvironment. In this review, we discuss current knowledge of breast cancer, including treatment options. We also give a brief overview of the immune system and comprehensively highlight the roles of different cells of the immune system in breast tumorigenesis, including recent research discoveries. Lastly, we discuss some immunotherapeutic strategies for the management of breast cancer.

CXCL12 loaded-dermal filler captures CXCR4 expressing melanoma circulating tumor cells

Development of distant metastasis relies on interactions between cancer and stromal cells. CXCL12, also known as stromal-derived factor 1α (SDF-1α), is a major chemokine constitutively secreted in bone marrow, lymph nodes, liver and lung, playing a critical role in the migration and seeding of neoplastic cells. CXCL12 activates the CXCR4 receptor that is overexpressed in several human cancer cells. Recent evidence reveals that tumors induce pre-metastatic niches in target organ producing tumor-derived factors. Pre-metastatic niches represent a tumor growth-favoring microenvironment in absence of cancer cells. A commercially available dermal filler, hyaluronic acid (HA) -based gel, loaded with CXCL12 (CLG) reproduced a "fake" pre-metastatic niche. In vitro, B16-hCXCR4-GFP, human cxcr4 expressing murine melanoma cells efficiently migrated toward CLG. In vivo, CLGs and empty gels (EGs) were subcutaneously injected into C57BL/6 mice and 5 days later B16-hCXCR4-GFP cells were intravenously inoculated. CLGs were able to recruit a significantly higher number of B16-hCXCR4-GFP cells as compared to EGs, with reduced lung metastasis in mice carrying CLG. CLG were infiltrated by higher number of CD45-positive leukocytes, mainly neutrophils CD11b+Ly6G+ cells, myeloid CD11b+Ly6G- and macrophages F4/80. CLG recovered cells recapitulated the features of B16-hCXCR4-GFP (epithelial, melanin rich, MELAN A/ S100/ c-Kit/CXCR4 pos; α-SMA neg). Thus a HA-based dermal filler loaded with CXCL12 can attract and trap CXCR4+tumor cells. The CLG trapped cells can be recovered and biologically characterized. As a corollary, a reduction in CXCR4 dependent lung metastasis was detected.

Effects of anesthetic technique and surgery on myeloid-derived suppressor cells and prognosis in women who underwent breast cancer surgery: a prospective study

Background: Surgery and anesthesia-induced immunosuppression may play a critical role in tumor progression and metastasis. Myeloid-derived suppressor cells (MDSCs) are highly immunosuppressive myeloid cells, closely linked with tumor staging, clinical therapeutic efficacy and prognosis. This study aims to investigate the effect of anesthetic technique and surgery on the expression of MDSCs and prognosis in women who received breast cancer surgery. Methods: From March 2016 to January 2017, a total of 80 patients with breast cancer were prospectively enrolled and randomized into two anesthetic groups: sevoflurane-based anesthetic group (SEV; n=38) and propofol-based total intravenous anesthetic group (TIVA; n=42). The expression of MDSCs and prognosis between different anesthetic techniques and stresses of surgical methods were compared. The primary endpoint is the postoperative expression of MDSCs and prognosis between SEV and TIVA groups. The secondary endpoint is the VAS scores at 24 hr post-operation between SEV and TIVA groups. Results: There was no significant difference in postoperative expression of MDSCs (P=0.202) and prognosis (P=0.138) between SEV and TIVA groups. Compared to breast-conserving surgery (BCS), patients who underwent breast mastectomy had significantly fewer MDSCs (P=0.040) and lower VAS score at 24 hr post-operation (P=0.044), while no significant difference in prognosis was found (P=0.953). When MDSCs were classified as subtypes of granulocytic/polymorphonuclear (PMN)-MDSCs and monocytic (Mo)-MDSCs, it showed higher ratio of Mo-MDSCs (P=0.018) or lower ratio of (PMN)-MDSCs (P=0.022) correlates to later tumor stage. Conclusion: Sevoflurane and propofol-based anesthesia do not show significant difference in MDSCs expression and prognosis after breast cancer surgery. Compared to BCS, although mastectomy with high extent of surgical stress exhibits lower levels of MDSCs, there is no significant difference in prognosis. The ratio of MDSCs subtype correlates to tumor stage.

Frequency of Immune Cell Subtypes in Peripheral Blood Correlates With Outcome for Patients With Metastatic Breast Cancer Treated With High-Dose Chemotherapy

BACKGROUND

The frequency of circulating leukocytes has been shown to be a prognostic factor in patients being treated for different types of cancer. In breast cancer, tumor-infiltrating leukocytes may predict patient outcome, but few studies have investigated such associations for circulating leukocytes.

PATIENTS AND METHODS

Multiparametric flow cytometry was used to examine the immunophenotypes of circulating peripheral blood mononuclear cells for 88 patients with metastatic breast cancer, which was then correlated to breast cancer-specific survival. Patients had been treated either with high-dose cyclophosphamide-containing regimens (group 1, n = 51 patients) or high-dose paclitaxel-containing regimens (group 2, n = 37 patients).

RESULTS

The frequency of peripheral blood CD14⁺ monocytes indicated prognosis for patients in group 1 (but not group 2), while higher levels of CD11c⁺ dendritic cells indicated a better prognosis for patients in group 2 (but not group 1). The frequency of a number of different CD4⁺ or CD8⁺ T cell subtypes also predicted prognosis for patients in group 2. For example, patients in group 2 with a higher frequency of circulating CD4⁺ or CD8⁺ naive T cells (CD45RA⁺CD95-CD27⁺CD28⁺) showed a poorer prognosis. In contrast, T cells were not associated with prognosis for patients in group 1.

CONCLUSION

Circulating leukocytes can predict clinical outcome for patients with breast cancer. Prediction of clinical outcome in this cohort of metastatic breast cancer patients was specific to the type of chemotherapy, and this finding is likely to apply to other therapies.

Atypical Chemokine Receptor 3 (ACKR3): A Comprehensive Overview of its Expression and Potential Roles in the Immune System

Atypical chemokine receptor 3 (ACKR3), previously known as C-X-C chemokine receptor type 7 (CXCR7), has emerged as a key player in several biologic processes, particularly during development. Its CXCL11 and CXCL12 scavenging activity and atypical signaling properties, together with a new array of other nonchemokine ligands, have established ACKR3 as a main regulator of physiologic processes at steady state and during inflammation. Here, we present a comprehensive review of ACKR3 expression in mammalian tissues in search of a possible connection with the receptor function. Besides the reported roles of ACKR3 during development, we discuss the potential contribution of ACKR3 to the function of the immune system, focusing on the myeloid lineage.

Advances in immunotherapy delivery from implantable and injectable biomaterials

Macroscale biomaterials, such as preformed implantable scaffolds and injectable soft materials, possess powerful synergies with anti-cancer immunotherapies. Immunotherapies on their own typically have poor delivery properties, and often require repeated high-dose injections that result in serious off-tumor effects and/or limited efficacy. Rationally designed biomaterials allow for discrete localization and controlled release of immunotherapeutic agents, and have been shown in a large number of applications to improve outcomes in the treatment of cancers via immunotherapy. Among various strategies, macroscale biomaterial delivery systems can take the form of robust tablet-like scaffolds that are surgically implanted into a tumor resection site, releasing programmed immune cells or immunoregulatory agents. Alternatively they can be developed as soft gel-like materials that are injected into solid tumors or sites of resection to stimulate a potent anti-tumor immune response. Biomaterials synthesized from diverse components such as polymers and peptides can be combined with any immunotherapy in the modern toolbox, from checkpoint inhibitors and stimulatory adjuvants, to cancer antigens and adoptive T cells, resulting in unique synergies and improved therapeutic efficacy. The field is growing rapidly in size as publications continue to appear in the literature, and biomaterial-based immunotherapies are entering clinical trials and human patients. It is unarguably an exciting time for cancer immunotherapy and biomaterial researchers, and further work seeks to understand the most critical design considerations in the development of the next-generation of immunotherapeutic biomaterials. This review will discuss recent advances in the delivery of immunotherapies from localized biomaterials, focusing on macroscale implantable and injectable systems. STATEMENT OF SIGNIFICANCE: Anti-cancer immunotherapies have shown exciting clinical results in the past few decades, yet they suffer from a few distinct limitations, such as poor delivery kinetics, narrow patient response profiles, and systemic side effects. Biomaterial systems are now being developed that can overcome many of these problems, allowing for localized adjuvant delivery, focused dose concentrations, and extended therapy presentation. The field of biocompatible carrier materials is uniquely suited to be combined with immunotherapy, promising to yield significant improvements in treatment outcomes and clinical care. In this review, the first pioneering efforts and most recent advances in biomaterials for immunotherapeutic applications are explored, with a specific focus on implantable and injectable biomaterials such as porous scaffolds, cryogels, and hydrogels.

NK Cells Expressing a Chimeric Activating Receptor Eliminate MDSCs and Rescue Impaired CAR-T Cell Activity against Solid Tumors

Solid tumors are refractory to cellular immunotherapies in part because they contain suppressive immune effectors such as myeloid-derived suppressor cells (MDSCs) that inhibit cytotoxic lymphocytes. Strategies to reverse the suppressive tumor microenvironment (TME) should also attract and activate immune effectors with antitumor activity. To address this need, we developed gene-modified natural killer (NK) cells bearing a chimeric receptor in which the activating receptor NKG2D is fused to the cytotoxic ζ-chain of the T-cell receptor (NKG2D.ζ). NKG2D.ζ-NK cells target MDSCs, which overexpress NKG2D ligands within the TME. We examined the ability of NKG2D.ζ-NK cells to eliminate MDSCs in a xenograft TME model and improve the antitumor function of tumor-directed chimeric antigen receptor (CAR)-modified T cells. We show that NKG2D.ζ-NK cells are cytotoxic against MDSCs, but spare NKG2D ligand-expressing normal tissues. NKG2D.ζ-NK cells, but not unmodified NK cells, secrete proinflammatory cytokines and chemokines in response to MDSCs at the tumor site and improve infiltration and antitumor activity of subsequently infused CAR-T cells, even in tumors for which an immunosuppressive TME is an impediment to treatment. Unlike endogenous NKG2D, NKG2D.ζ is not susceptible to TME-mediated downmodulation and thus maintains its function even within suppressive microenvironments. As clinical confirmation, NKG2D.ζ-NK cells generated from patients with neuroblastoma killed autologous intratumoral MDSCs capable of suppressing CAR-T function. A combination therapy for solid tumors that includes both NKG2D.ζ-NK cells and CAR-T cells may improve responses over therapies based on CAR-T cells alone.

Tumor-derived granulocyte colony-stimulating factor diminishes efficacy of breast tumor cell vaccines

BACKGROUND

Although metastasis is ultimately responsible for about 90% of breast cancer mortality, the vast majority of breast-cancer-related deaths are due to progressive recurrences from non-metastatic disease. Current adjuvant therapies are unable to prevent progressive recurrences for a significant fraction of patients with breast cancer. Autologous tumor cell vaccines (ATCVs) are a safe and potentially useful strategy to prevent breast cancer recurrence, in a personalized and patient-specific manner, following standard-of-care tumor resection. Given the high intra-patient and inter-patient heterogeneity in breast cancer, it is important to understand which factors influence the immunogenicity of breast tumor cells in order to maximize ATCV effectiveness.

METHODS

The relative immunogenicity of two murine breast carcinomas, 4T1 and EMT6, were compared in a prophylactic vaccination-tumor challenge model. Differences in cell surface expression of antigen-presentation-related and costimulatory molecules were compared along with immunosuppressive cytokine production. CRISPR/Cas9 technology was used to modulate tumor-derived cytokine secretion. The impacts of cytokine deletion on splenomegaly, myeloid-derived suppressor cell (MDSC) accumulation and ATCV immunogenicity were assessed.

RESULTS

Mice vaccinated with an EMT6 vaccine exhibited significantly greater protective immunity than mice vaccinated with a 4T1 vaccine. Hybrid vaccination studies revealed that the 4T1 vaccination induced both local and systemic immune impairments. Although there were significant differences between EMT6 and 4T1 in the expression of costimulatory molecules, major disparities in the secretion of immunosuppressive cytokines likely accounts for differences in immunogenicity between the cell lines. Ablation of one cytokine in particular, granulocyte-colony stimulating factor (G-CSF), reversed MDSC accumulation and splenomegaly in the 4T1 model. Furthermore, G-CSF inhibition enhanced the immunogenicity of a 4T1-based vaccine to the extent that all vaccinated mice developed complete protective immunity.

CONCLUSIONS

Breast cancer cells that express high levels of G-CSF have the potential to diminish or abrogate the efficacy of breast cancer ATCVs. Fortunately, this study demonstrates that genetic ablation of immunosuppressive cytokines, such as G-CSF, can enhance the immunogenicity of breast cancer cell-based vaccines. Strategies that combine inhibition of immunosuppressive factors with immune stimulatory co-formulations already under development may help ATCVs reach their full potential.

Tumor-infiltrating lymphocytes and ductal carcinoma in situ of the breast: friends or foes?

In the past three decades, the detection rate of ductal carcinoma in situ of the breast has dramatically increased due to breast screening programs. As a consequence, about 20% of all breast cancer cases are detected in this early in situ stage. Some ductal carcinoma in situ cases will progress to invasive breast cancer, while other cases are likely to have an indolent biological behavior. The presence of tumor-infiltrating lymphocytes is seen as a promising prognostic and predictive marker in invasive breast cancer, mainly in HER2-positive and triple-negative subtypes. Here, we summarize the current understanding regarding immune infiltrates in invasive breast cancer and highlight recent observations regarding the presence and potential clinical significance of such immune infiltrates in patients with ductal carcinoma in situ. The presence of tumor-infiltrating lymphocytes, their numbers, composition, and potential relationship with genomic status will be discussed. Finally, we propose that a combination of genetic and immune markers may better stratify ductal carcinoma in situ subtypes with respect to tumor evolution.

PERK-Phosphorylated eIF2α Pathway Suppresses Tumor Metastasis Through Downregulating Expression of Programmed Death Ligand 1 and CXCL5 in Triple-Negative Breast Cancer

Endoplasmic reticulum (ER) stress has been reported to be associated with metastasis in many malignant tumors. PKR-like ER kinase-phosphorylated eukaryotic translation initiation factor 2α (PERK-p-eIF2α) pathway is one of the three main signal pathways in ER stress, however, its mechanism in regulating breast cancer (BC) relapse or metastasis was still not completely understood. Besides, drug resistance was an important factor influencing the effect of tumor treatment and whether PERK-p-eIF2α pathway was involved in the drug resistance to BC treatment also needs to be explored. The authors conducted survival analysis of ER stress-related genes in the The Cancer Genome Atlas (TCGA) database to find the candidate molecule and found that eIF2α was significantly correlated with relapse-free survival in BC patients, especially in the triple-negative BC (TNBC) patients. Furthermore, BC cell lines were used to study the downstream target of PERK-p-eIF2α. In this study, p-eIF2α could negatively regulate the expression of programmed death ligand 1 (PDL1) and C-X-C motif chemokine ligand 5 (CXCL5), which were important ligands of the immune cells such as T cells and myeloid-derived suppressor cells in the tumor microenvironment. Besides, p-eIF2α expression in highly metastatic human TNBC cells after treatment of carboplatin was significantly decreased. The data indicated the possible novel immune-related mechanism of PERK-p-eIF2α in regulating TNBC metastasis and drug resistance of carboplatin in highly metastatic TNBC.

Modeling combination therapy for breast cancer with BET and immune checkpoint inhibitors

CTLA-4 is an immune checkpoint expressed on active anticancer T cells. When it combines with its ligand B7 on dendritic cells, it inhibits the activity of the T cells. The Bromo- and Extra-Terminal (BET) protein family includes proteins that regulate the expression of key oncogenes and antiapoptotic proteins. BET inhibitor (BETi) has been shown to reduce the expression of MYC by suppressing its transcription factors and to down-regulate the hypoxic transcriptome response to VEGF-A. This paper develops a mathematical model of the treatment of cancer by combination therapy of BETi and CTLA-4 inhibitor. The model shows that the two drugs are positively correlated in the sense that the tumor volume decreases as the dose of each of the drugs is increased. The model also considers the effect of the combined therapy on levels of myeloid-derived suppressor cells (MDSCs) and the overexpression of TNF-α, which may predict gastrointestinal side effects of the combination.

CAR T cell therapy for breast cancer: harnessing the tumor milieu to drive T cell activation

BACKGROUND

The adoptive transfer of T cells redirected to tumor via chimeric antigen receptors (CARs) has produced clinical benefits for the treatment of hematologic diseases. To extend this approach to breast cancer, we generated CAR T cells directed against mucin1 (MUC1), an aberrantly glycosylated neoantigen that is overexpressed by malignant cells and whose expression has been correlated with poor prognosis. Furthermore, to protect our tumor-targeted cells from the elevated levels of immune-inhibitory cytokines present in the tumor milieu, we co-expressed an inverted cytokine receptor linking the IL4 receptor exodomain with the IL7 receptor endodomain (4/7ICR) in order to transform the suppressive IL4 signal into one that would enhance the anti-tumor effects of our CAR T cells at the tumor site.

METHODS

First (1G - CD3ζ) and second generation (2G - 41BB.CD3ζ) MUC1-specific CARs were constructed using the HMFG2 scFv. Following retroviral transduction transgenic expression of the CAR±ICR was assessed by flow cytometry. In vitro CAR/ICR T cell function was measured by assessing cell proliferation and short- and long-term cytotoxic activity using MUC1+ MDA MB 468 cells as targets. In vivo anti-tumor activity was assessed using IL4-producing MDA MB 468 tumor-bearing mice using calipers to assess tumor volume and bioluminescence imaging to track T cells.

RESULTS

In the IL4-rich tumor milieu, 1G CAR.MUC1 T cells failed to expand or kill MUC1+ tumors and while co-expression of the 4/7ICR promoted T cell expansion, in the absence of co-stimulatory signals the outgrowing cells exhibited an exhausted phenotype characterized by PD-1 and TIM3 upregulation and failed to control tumor growth. However, by co-expressing 2G CAR.MUC1 (signal 1 - activation + signal 2 - co-stimulation) and 4/7ICR (signal 3 - cytokine), transgenic T cells selectively expanded at the tumor site and produced potent and durable tumor control in vitro and in vivo.

CONCLUSIONS

Our findings demonstrate the feasibility of targeting breast cancer using transgenic T cells equipped to thrive in the suppressive tumor milieu and highlight the importance of providing transgenic T cells with signals that recapitulate physiologic TCR signaling - [activation (signal 1), co-stimulation (signal 2) and cytokine support (signal 3)] - to promote in vivo persistence and memory formation.

Implantable Synthetic Immune Niche for Spatiotemporal Modulation of Tumor-Derived Immunosuppression and Systemic Antitumor Immunity: Postoperative Immunotherapy

The development of biomaterial-based immune niches that can modulate immunosuppressive factors in tumor microenvironment (TME) will be a key technology for improving current cancer immunotherapy. Here, implantable, engineered 3D porous scaffolds are designed to generate synergistic action between myeloid-derived suppressor cell (MDSC)-depleting agents, which can accommodate the establishment of a permissive immunogenic microenvironment to counteract tumor-induced immunosuppression, and cancer vaccines consisting of whole tumor lysates and nanogel-based adjuvants, which can generate tumor antigen-specific T cell responses. The local peritumoral implantation of the synthetic immune niche (termed immuneCare-DISC, iCD) as a postsurgical treatment in an advanced-stage primary 4T1 breast tumor model generates systemic antitumor immunity and prevents tumor recurrence at the surgical site as well as the migration of residual tumor cells into the lungs, resulting in 100% survival. These therapeutic outcomes are achieved through the inhibition of immunosuppressive MDSCs in tumors and spleens by releasing gemcitabine and recruitment/activation of dendritic cells, enhanced population of CD4⁺ and CD8⁺ T cells, and increased IFN-γ production by cancer vaccines from the iCD. This combined spatiotemporal modulation of tumor-derived immunosuppression and vaccine-induced immune stimulation through the iCD is expected to provide an immune niche for prevention of postoperative tumor recurrence and metastasis.

Harnessing the immune system in the battle against breast cancer

Breast cancer is the most prevalent malignancy in women and the second most common cause of cancer-related death worldwide. Despite major innovations in early detection and advanced therapeutics, up to 30% of women with node-negative breast cancer and 70% of women with node-positive breast cancer will develop recurrence. The recognition that breast tumors are infiltrated by a complex array of immune cells that influence their development, progression, and metastasis, as well as their responsiveness to systemic therapies has sparked major interest in the development of immunotherapies. In fact, not only the native host immune system can be altered to promote potent antitumor response, but also its components can be manipulated to generate effective therapeutic strategies. We present here a review of the major approaches to immunotherapy in breast cancers, both successes and failures, as well as new therapies on the horizon.

Towards predictive biomarkers for immunotherapy response in breast cancer patients

Immunotherapy using anti-PD(L)1 has revolutionized treatment for various tumor types. Early data have shown durable responses in a small subgroup of breast cancer patients. So far, the response rates appear higher for breast tumors that are triple negative, PDL1-positive and/or harbor high levels of immune cells. Both comprehensive analyses of the breast tumor microenvironment and exploiting research on biomarkers in other cancer types, such as melanoma and lung cancer, may contribute to the discovery of accurate biomarkers to select breast cancer patients for immunotherapy. Here we summarize key features of the breast tumor microenvironment as well as putative predictive biomarkers established in other tumor types. Insights from both fields can guide future studies to enable personalized breast cancer immunotherapy.

Monitoring the responsiveness of T and antigen presenting cell compartments in breast cancer patients is useful to predict clinical tumor response to neoadjuvant chemotherapy

Background

Vaccination of mice with tumors treated with Doxorubicin promotes a T cell immunity that relies on dendritic cell (DC) activation and is responsible for tumor control in vaccinated animals. Despite Doxorubicin in combination with Cyclophosphamide (A/C) is widely used to treat breast cancer patients, the stimulating effect of A/C on T and APC compartments and its correlation with patient’s clinical response remains to be proved.

Methods

In this prospective study, we designed an in vitro system to monitor various immunological readouts in PBMCs obtained from a total of 17 breast cancer patients before, and after neoadjuvant anti-tumor therapy with A/C.

Results

The results show that before treatment, T cells and DCs, exhibit a marked unresponsiveness to in vitro stimulus: whereas T cells exhibit poor TCR internalization and limited expression of CD154 in response to anti-CD3/CD28/CD2 stimulation, DCs secrete low levels of IL-12p70 and limited CD83 expression in response to pro-inflammatory cytokines. Notably, after treatment the responsiveness of T and APC compartments was recovered, and furthermore, this recovery correlated with patients’ residual cancer burden stage.

Conclusions

Our results let us to argue that the model used here to monitor the T and APC compartments is suitable to survey the recovery of immune surveillance and to predict tumor response during A/C chemotherapy.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3982-1) contains supplementary material, which is available to authorized users.

Triple negative breast cancer - prognostic role of immune-related factors: a systematic review

PURPOSE

Treatment of breast cancer has been increasingly successful in recent years with the advent of HER2-receptor targeted treatment and endocrine treatment. However, the triple negative subgroup of breast cancer (TNBC) (estrogen-, progesterone- and HER2-receptor negative) still lacks targeted treatment options. TNBC is a type of breast cancer that often affects younger women, and generally has a worse prognosis than other types of breast cancer. Recently, the complex role of the immune system in cancer growth, elimination and metastasis has been the object of increased attention. There is hope that a more detailed understanding of the intricate roles of the constituents of the immune system, will hold potential both as prognostic or predictive markers of cancer progression, but also as treatment targets for a wide range of tumors, including TNBC. The aim of this review is to provide an overview of the cellular immune microenvironment in TNBC, and to highlight areas in which TNBC may differ from other types of breast cancer.

MATERIAL AND METHODS

A search of PubMed was made using the terms 'triple negative breast cancer' and 'tumor infiltrating lymphocytes', 'CD8', 'CD4', 'B cells', 'natural killer cells', 'macrophages', myeloid derived suppressor cells', 'dendritic cells', 'immune check point inhibitor', 'CTLA-4' and 'PD-L1'.

RESULTS

We find that whilst factors such as TILs and certain subgroups of TILs (e.g., CD8 + and regulator T-cells) have been extensively researched, none of these markers are currently applicable to routine clinical practice. Also, TNBC differs from other types of breast cancer with regards to cellular composition of the immune infiltrate and PD-L1 expression, and the prognostic significance of these.

CONCLUSIONS

Immune-related factors have the potential as both prognostic and predictive biomarkers for new treatments targeting the immune system in breast cancer. However, multivariate analyses, taking other well-known factors into account, are required to determine the true value of these biomarkers. Also, differences between TNBC and other types of breast cancer may have implications for treatment and use of immune-related factors as biomarkers.

CXCR2+ MDSCs promote breast cancer progression by inducing EMT and activated T cell exhaustion

Although myeloid-derived suppressor cells (MDSCs) have been demonstrated to contribute to tumor initiation, progression and metastasis, however, which MDSC subsets are preferentially expanded and activated, and what's the key molecular mechanism responsible for specific MDSC subsets in promoting tumor progression need to be fully addressed. Here we identify that Ly6GmiLy6CloCD11b+CXCR2+ subpopulation (named CXCR2+ MDSCs) are predominately expanded and recruited in systemic and local tumor microenvironment during breast cancer progression and metastasis. The proportion of CXCR2+ MDSCs is inversely correlated with the infiltration of CD4+ or CD8+ T cells. Besides, CXCR2+ MDSCs promote breast cancer growth and metastasis to lung and/or lymph node in vivo. Furthermore, CXCR2+ MDSCs induce epithelial mesenchymal transition (EMT) of breast cancer cells via IL-6. Moreover, CXCR2+ MDSCs upregulate the expression of immunosuppressive molecules programmed cell death protein 1(PD1), PD1 ligand 1 (PDL1), lymphocyte activation gene 3 protein (LAG3), cytotoxic T lymphocyte antigen 4 (CTLA4), and T cell immunoglobulin domain and mucin domain protein 3 (TIM3) on CD4+ or CD8+ T cells, and induce exhaustion of the activated T cells partially via IFN-γ. These results demonstrate that CXCR2+ MDSCs accelerate breast cancer progression via directly inducing cancer cell EMT and indirectly promoting T cell exhaustion, suggesting that CXCR2+ MDSCs may be a potential therapeutic target of breast cancer.

Immunotherapy for breast cancer: past, present, and future

Immunotherapy has shown promise in many solid tumors including melanoma and non-small cell lung cancer with an evolving role in breast cancer. Immunotherapy encompasses a wide range of therapies including immune checkpoint inhibition, monoclonal antibodies, bispecific antibodies, vaccinations, antibody-drug conjugates, and identifying other emerging interventions targeting the tumor microenvironment. Increasing efficacy of these treatments in breast cancer patients requires identification of better biomarkers to guide patient selection; recognizing when to initiate these therapies in multi-modality treatment plans; establishing novel assays to monitor immune-mediated responses; and creating combined systemic therapy options incorporating conventional treatments such as chemotherapy and endocrine therapy. This review will focus on the current role and future directions of many of these immunotherapies in breast cancer, as well as highlighting clinical trials that are investigating several of these active issues.

One microenvironment does not fit all: heterogeneity beyond cancer cells

Human cancers exhibit formidable molecular heterogeneity, to a large extent accounting for the incomplete and transitory efficacy of current anti-cancer therapies. However, neoplastic cells alone do not manifest the disease, but conscript a battery of non-tumor cells to enable and sustain hallmark capabilities of cancer. Escaping immunosurveillance is one of such capabilities. Tumors evolve immunosuppressive microenvironment to subvert anti-tumor immunity. In this review, we will focus on tumor-associated myeloid cells, which constitute an essential part of the immune microenvironment and reciprocally interact with cancer cells to establish malignancy toward metastasis. The diversity and plasticity of these cells constitute another layer of heterogeneity, beyond the heterogeneity of cancer cells themselves. We envision that immune microenvironment co-evolves with the genetic heterogeneity of tumor. Addressing the question of how genetically distinct tumors shape and are shaped by unique immune microenvironment will provide an attractive rationale to develop novel immunotherapeutic modalities. Here, we discuss the complex nature of tumor microenvironment, with an emphasis on the cellular and functional heterogeneity among tumor-associated myeloid cells as well as immune environment heterogeneity in the context of a full spectrum of human breast cancers.

Impact of the Tumor Microenvironment on Tumor-Infiltrating Lymphocytes: Focus on Breast Cancer

Immunotherapy is revolutionizing cancer care across disciplines. The original success of immune checkpoint blockade in melanoma has already been translated to Food and Drug Administration-approved therapies in a number of other cancers, and a large number of clinical trials are underway in many other disease types, including breast cancer. Here, we review the basic requirements for a successful antitumor immune response, with a focus on the metabolic and physical barriers encountered by lymphocytes entering breast tumors. We also review recent clinical trials of immunotherapy in breast cancer and provide a number of interesting questions that will need to be answered for successful breast cancer immunotherapy.

How many diseases is triple negative breast cancer: the protagonism of the immune microenvironment

Triple negative breast cancer (TNBC) is a type of breast cancer (BC) that does not express the oestrogen and the progesterone receptors and the human epidermal growth factor receptor type 2 (HER2). Since there are no positive markers to reliably classify TNBC, these tumours are not yet treated with targeted therapies. Perhaps for this reason they are the most aggressive form of breast carcinomas. However, the clinical observation that these patients do not carry a uniformly dismal prognosis, coupled with data coming from pathology and epidemiology, suggests that this negative definition is not capturing a single clinical entity, but several. We critically evaluate this evidence in this paper, reviewing clinical and epidemiological data and new studies that aim to subclassify TNBC. Moreover, evidence on the role of tumour infiltrating lymphocytes (TILs) on TNBC progression, response to chemotherapy and patient outcome have been published. The heterogeneity, observed even at TILs level, highlights the idea that TNBC is much more than a single disease with a unique treatment. The exploration of the immune environment present at the tumour site could indeed help in answering the question 'How many diseases is TNBC' and will help to define prognosis and eventually develop new therapies, by stimulating the immune effector cells or by inhibiting immunological repressor molecules. In this review, we focus on the prospect of the patient's diverse immune signatures within the tumour as potential biomarkers and how they could be modulated to fight the disease.

Granulocytic myeloid-derived suppressor cells suppress virus-specific CD8+ T cell responses during acute Friend retrovirus infection

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) can suppress T cell responses in several different diseases. Previously these suppressive cells were observed to expand in HIV patients and in a mouse retrovirus model, yet their suppressive effect on virus-specific CD8+ T cells in vitro and in vivo has not been characterized thus far.

RESULTS

We used the Friend retrovirus (FV) model to demonstrate that MDSCs expand and become activated during the late phase of acute FV infection. Only the subpopulation of granulocytic MDSCs (gMDSCs) but not monocytic MDSC suppressed virus-specific CD8+ T cell proliferation and function in vitro. gMDSCs expressed arginase 1, high levels of the inhibitory ligand PD-L1 and the ATP dephosphorylating enzyme CD39 on the cell surface upon infection. All three molecules were involved in the suppressive effect of the gMDSCs in vitro. MDSC depletion experiments in FV-infected mice revealed that they restrict virus-specific CD8+ T cell responses and thus affect the immune control of chronic retroviruses in vivo.

CONCLUSIONS

Our study demonstrates that MDSCs become activated and expand during the acute phase of retrovirus infection. Their suppressive activity on virus-specific CD8+ T cells may contribute to T cell dysfunction and the development of chronic infection.

Myeloid-derived suppressor cell and macrophage exert distinct angiogenic and immunosuppressive effects in breast cancer

The immunosuppressive tumor microenvironment is a key obstacle to hinder a cancer immunotherapy. Myeloid-derived suppressor cells (MDSCs) have been considered as a major player in immunosuppression. In this study, we find that tumor-infiltrating MDSCs (tiMDSCs) are less immunosuppressive than tumor-associated macrophages (TAMs) in multiple murine orthotopic breast tumor models. Compared to TAMs, tiMDSCs produce higher levels of pro-inflammatory factors and lower levels of anti-inflammatory factors. Furthermore, tiMDSCs are preferentially located in hypoxic areas and are more pro-angiogenic than TAMs. Consistent with these functional disparities, a shift from tiMDSCs to TAMs is observed during the progression of breast cancer. Moreover, infiltration of tiMDSCs is also noted in distal colonization of breast cancer cells in the lung. Taken together, our findings indicate that tiMDSCs are more pro-angiogenic and promote tumor initiation, while TAMs are more immunosuppressive and facilitate tumor immune evasion. This study suggests that selectively targeting on TAMs could alleviate the immunosuppressive tumor microenvironment and potentiate cancer immunotherapy.

Tumor infiltrating leukocyte density is independent of tumor grade and molecular subtype in aggressive breast cancer of Western Kenya

Background

Tumors commonly are infiltrated by leukocytes, or tumor infiltrating leukocytes (TILs). It remains unclear, however, if the density and type of individual TILs has a direct or simply correlative role in promoting poor prognosis in breast cancer patients. Breast cancer in Kenyan women is aggressive with presentation at a young age, with advanced grade (grade III), large tumor size (>2.0 cm), and poor prognosis. We previously observed that the tumors were predominantly estrogen receptor positive (ER+) but also included both a high percentage of triple negative tumors and also increased immune cell infiltration within the tumors. We used breast tumor tissues from each patient to make tissue microarrays that were then stained for leukocyte and myeloid markers including CD4, CD8, CD20, CD25, CD68, and CD163 using immunohistochemical techniques. The immune cell infiltration into the cancer tissue included increased numbers of macrophages (CD68+), helper T cells (CD4+), and CD25+ lymphocytes compared to benign tissue.

Results

This study characterized the grade, molecular subtypes, and proliferation index of these tumors and determined if TIL density was enriched across any of these factors. We analyzed 49 malignant patient tissue samples for this study. The patient population had a mean age of 51.9 years. The tumors analyzed were heterogeneous by grade: grade I (6%), grade II (47%), and grade III (39%). Most patients presented with large tumors (>2.0 cm) (69%). We classified the tumors into molecular subtypes based on clinical marker expression. Based on this analysis, the molecular subtype distribution was heterogeneous with luminal B (41%), basal/triple negative (TN) (37%), luminal A (14%) and HER2 (8%) breast cancer subtypes. While the basal/TN subtype had a much higher proliferative index (Ki-67+) than did the other molecular subtypes, we did not see a significant correlation between TIL density and either subtype or tumor grade. Therefore, TIL density is independent of molecular subtype and grade.

Conclusion

This study identified a Kenyan patient cohort that develops large, high-grade tumors primarily of the luminal B and basal molecular subtypes. After analyzing the TILs within these tumors, we found that immune cell infiltration of these tumors correlated with increased proliferation but not grade or molecular subtype. Future research is required to determine if the aberrant recruitment of TILs to tumors contributes to cancer progression and response to cancer treatments.

Enhanced Survival with Implantable Scaffolds That Capture Metastatic Breast Cancer Cells In Vivo

The onset of distant organ metastasis from primary breast cancer marks the transition to a stage IV diagnosis. Standard imaging modalities often detect distant metastasis when the burden of disease is high, underscoring the need for improved methods of detection to allow for interventions that would impede disease progression. Here, microporous poly(ε-caprolactone) scaffolds were developed that capture early metastatic cells and thus serve as a sentinel for early detection. These scaffolds were used to characterize the dynamic immune response to the implant spanning the acute and chronic foreign body response. The immune cell composition had stabilized at the scaffold after approximately 1 month and changed dramatically within days to weeks after tumor inoculation, with CD11b(+)Gr1(hi)Ly6C(-) cells having the greatest increase in abundance. Implanted scaffolds recruited metastatic cancer cells that were inoculated into the mammary fat pad in vivo, which also significantly reduced tumor burden in the liver and brain. Additionally, cancer cells could be detected using a label-free imaging modality termed inverse spectroscopic optical coherence tomography, and we tested the hypothesis that subsequent removal of the primary tumor after early detection would enhance survival. Surgical removal of the primary tumor following cancer cell detection in the scaffold significantly improved disease-specific survival. The enhanced disease-specific survival was associated with a systemic reduction in the CD11b(+)Gr1(hi)Ly6C(-) cells as a consequence of the implant, which was further supported by Gr-1 depletion studies. Implementation of the scaffold may provide diagnostic and therapeutic options for cancer patients in both the high-risk and adjuvant treatment settings. Cancer Res; 76(18); 5209-18. ©2016 AACR.

Complement C3-dependent uptake of targeted liposomes into human macrophages, B cells, dendritic cells, neutrophils, and MDSCs

Antitumor immunity in cancer patients is heavily modulated by cells of the innate immune system. Antigen-presenting cells, including dendritic cells, macrophages, and B cells, initiate immune recognition of tumor antigen by displaying antigen to effector cells. Countering this immune stimulation are immunosuppressive cells which include M2 macrophages, N2 neutrophils, and myeloid-derived suppressor cells (MDSCs). To create effective cancer immunotherapies, it is critical that we can target these important cell types of the immune system with immunostimulatory compounds. A commonality of these cell types is the complement receptor, which recognizes pathogens that are bound to activated complement C3 in human blood. To target the complement receptor, we have created a liposome that has a small molecule, orthopyridyl disulfide (OPSS), conjugated to its surface. OPSS forms a disulfide bond with activated complement C3, which then targets liposomes for uptake by dendritic cells, macrophages, B cells, MDSCs, and neutrophils in human blood. Internalization is efficient and specific to cells that display the complement receptor. Liposomes are a versatile drug delivery device. Possible applications for this system include delivery of toll-receptor agonists or tumor antigen to antigen-presenting cells and delivery of immunostimulatory drugs to M2, N2, and MDSC immunosuppressive cells.

ZEB1-regulated inflammatory phenotype in breast cancer cells

Zinc finger E‐box binding protein 1 (ZEB1) and ZEB2 induce epithelial‐mesenchymal transition (EMT) and enhance cancer progression. However, the global view of transcriptional regulation by ZEB1 and ZEB2 is yet to be elucidated. Here, we identified a ZEB1‐regulated inflammatory phenotype in breast cancer cells using chromatin immunoprecipitation sequencing and RNA sequencing, followed by gene set enrichment analysis (GSEA) of ZEB1‐bound genes. Knockdown of ZEB1 and/or ZEB2 resulted in the downregulation of genes encoding inflammatory cytokines related to poor prognosis in patients with cancer, including IL6 and IL8, therefore suggesting that ZEB1 and ZEB2 have similar functions in terms of the regulation of production of inflammatory cytokines. Antibody array and ELISA experiments confirmed that ZEB1 controlled the production of the IL‐6 and IL‐8 proteins. The secretory proteins regulated by ZEB1 enhanced breast cancer cell proliferation and tumor growth. ZEB1 expression in breast cancer cells also affected the growth of fibroblasts in cell culture, and the accumulation of myeloid‐derived suppressor cells in tumors in vivo. These findings provide insight into the role of ZEB1 in the progression of cancer, mediated by inflammatory cytokines, along with the initiation of EMT.

Myeloid-derived suppressor cells are increased and correlated with type 2 immune responses, malnutrition, inflammation, and poor prognosis in patients with breast cancer

Myeloid-derived suppressor cells (MDSCs) have been identified in the majority of patients and experimental mice with tumors by their suppression of T cell activation. MDSCs have also been reported to be associated with chronic inflammation. In advanced cancer, the T helper (Th) cell balance tends to shift from Th1 to Th2 predominance, and immune function, including cell-mediated immunity, is impaired by cytokines produced by Th2 cells. The present study examined the correlations between MDSC levels and inflammation, immune suppression, malnutrition, and poor prognosis in 155 patients with breast cancer. The levels of MDSCs in preoperative patients and in patients with recurrent breast cancer were significantly higher compared with postoperative patients, patients with recurrent breast cancer who received chemotherapy and healthy volunteers. The MDSC levels of preoperative patients were significantly positively correlated with interleukin (IL)-6 production by peripheral blood mononuclear cells (PBMCs), the neutrophil/lymphocyte ratio and C-reactive protein, and were negatively correlated with the production of interferon-γ and IL-12, serum concentration of rapid turnover protein, and the stimulation index. These patients were divided into two groups based on the levels of MDSCs. In preoperative patients with MDSC levels >1.0% of total PBMCs, the overall survival of patients with stage IV disease was significantly shorter compared with other disease stages, and was also significantly shorter compared with patients with MDSC levels <1.0% of total PBMCs. Thus, the MDSC levels of preoperative patients may function as a good prognostic indicator, particularly in patients with advanced breast cancer.

Glycolysis regulates the expansion of myeloid-derived suppressor cells in tumor-bearing hosts through prevention of ROS-mediated apoptosis

Immunotherapy aiming to rescue or boost antitumor immunity is an emerging strategy for treatment of cancers. The efficacy of immunotherapy is strongly controlled by the immunological milieu of cancer patients. Myeloid-derived suppressor cells (MDSCs) are heterogeneous immature myeloid cell populations with immunosuppressive functions accumulating in individuals during tumor progression. The signaling mechanisms of MDSC activation have been well studied. However, there is little known about the metabolic status of MDSCs and the physiological role of their metabolic reprogramming. In this study, we discovered that myeloid cells upregulated their glycolytic genes when encountered with tumor-derived factors. MDSCs exhibited higher glycolytic rate than their normal cell compartment did, which contributed to the accumulation of the MDSCs in tumor-bearing hosts. Upregulation of glycolysis prevented excess reactive oxygen species (ROS) production by MDSCs, which protected MDSCs from apoptosis. Most importantly, we identified the glycolytic metabolite, phosphoenolpyruvate (PEP), as a vital antioxidant agent able to prevent excess ROS production and therefore contributed to the survival of MDSCs. These findings suggest that glycolytic metabolites have important roles in the modulation of fitness of MDSCs and could be potential targets for anti-MDSC strategy. Targeting MDSCs with analogs of specific glycolytic metabolites, for example, 2-phosphoglycerate or PEP may diminish the accumulation of MDSCs and reverse the immunosuppressive milieu in tumor-bearing individuals.

MicroRNA-20b promotes the accumulation of CD11b+Ly6G+Ly6Clow myeloid-derived suppressor cells in asthmatic mice

miR-20b is a member of the miR-106a-363 gene cluster, which has been shown to play an important role in a variety of diseases, including cancer, inflammation, and autoimmune diseases. Our previous study indicated that miR-20b has an inhibitory effect on airway inflammation in asthmatic mice, but the exact mechanism is unclear. In this study, we report that the ratio of CD11b+Ly6G+Ly6Clow cells, but not the amount of CD11b+Ly6C+Ly6G– cells, was increased in the lung tissue of asthmatic mice after intranasal instillation with miR-20b mimics, while Th2-type cytokines (interleukin (IL)-4 and IL-13) were significantly decreased in the bronchoalveolar lavage fluid. In addition, the transcription factor CREB regulated the expression of miR-20b. Our findings suggest that miR-20b can induce the accumulation of myeloid-derived suppressor cells in the lungs of asthmatic mice, which may be a mechanism by which miR-20b inhibits airway inflammation in asthmatic mice. Thus, miR-20b may be used as a target for the effective treatment of asthma in the future.

Systematic Pan-Cancer Analysis Reveals Immune Cell Interactions in the Tumor Microenvironment

With the recent advent of immunotherapy, there is a critical need to understand immune cell interactions in the tumor microenvironment in both pan-cancer and tissue-specific contexts. Multidimensional datasets have enabled systematic approaches to dissect these interactions in large numbers of patients, furthering our understanding of the patient immune response to solid tumors. Using an integrated approach, we inferred the infiltration levels of distinct immune cell subsets in 23 tumor types from The Cancer Genome Atlas. From these quantities, we constructed a coinfiltration network, revealing interactions between cytolytic cells and myeloid cells in the tumor microenvironment. By integrating patient mutation data, we found that while mutation burden was associated with immune infiltration differences between distinct tumor types, additional factors likely explained differences between tumors originating from the same tissue. We concluded this analysis by examining the prognostic value of individual immune cell subsets as well as how coinfiltration of functionally discordant cell types associated with patient survival. In multiple tumor types, we found that the protective effect of CD8+ T cell infiltration was heavily modulated by coinfiltration of macrophages and other myeloid cell types, suggesting the involvement of myeloid-derived suppressor cells in tumor development. Our findings illustrate complex interactions between different immune cell types in the tumor microenvironment and indicate these interactions play meaningful roles in patient survival. These results demonstrate the importance of personalized immune response profiles when studying the factors underlying tumor immunogenicity and immunotherapy response. Cancer Res; 77(6); 1271-82. ©2017 AACR.

Myeloid cells in circulation and tumor microenvironment of breast cancer patients

Pathological conditions including cancers lead to accumulation of a morphological mixture of highly immunosuppressive cells termed as myeloid-derived suppressor cells (MDSC). The lack of conclusive markers to identify human MDSC, due to their heterogeneous nature and close phenotypical and functional proximity with other cell subsets, made it challenging to identify these cells. Nevertheless, expansion of MDSC has been reported in periphery and tumor microenvironment of various cancers. The majority of studies on breast cancers were performed on murine models and hence limited literature is available on the relation of MDSC accumulation with clinical settings in breast cancer patients. The aim of this study was to investigate levels and phenotypes of myeloid cells in peripheral blood (n = 23) and tumor microenvironment of primary breast cancer patients (n = 7), compared with blood from healthy donors (n = 21) and paired non-tumor normal breast tissues from the same patients (n = 7). Using multicolor flow cytometric assays, we found that breast cancer patients had significantly higher levels of tumor-infiltrating myeloid cells, which comprised of granulocytes (P = 0.022) and immature cells that lack the expression of markers for fully differentiated monocytes or granulocytes (P = 0.016). Importantly, this expansion was not reflected in the peripheral blood. The immunosuppressive potential of these cells was confirmed by expression of Arginase 1 (ARG1), which is pivotal for T-cell suppression. These findings are important for developing therapeutic modalities to target mechanisms employed by immunosuppressive cells that generate an immune-permissive environment for the progression of cancer.

Glucocorticoid receptor expression on circulating leukocytes differs between healthy male and female adults

Introduction

The glucocorticoid receptor (GR) is a key receptor involved in inflammatory responses and is influenced by sex steroids. This study measured GR expression on circulating leukocyte subtypes in males and females.

Methods

A total of 23 healthy adults (12 female) participated in this study. GR expression was measured in leukocyte subtypes using flow cytometry. Peripheral blood mononuclear cell (PBMC) gene expression of GR (NR3C1), GR β, TGF-β1 and 2, and glucocorticoid-induced leucine zipper (GILZ) were determined by real-time polymerase chain reaction.

Results

Leukocyte GR was lower in females, particularly in granulocytes, natural killer cells, and peripheral blood mononuclear cells (p≤0.01). GR protein expression was different across leukocyte subtypes, with higher expression in eosinophils compared with granulocytes, T lymphocytes, and natural killer cells (p<0.05). There was higher gene expression of GR β in males (p=0.03).

Conclusions

This is the first study to identify sexual dimorphism in GR expression in healthy adults using flow cytometry. These results may begin to explain the sexual dimorphism seen in many diseases and sex differences in glucocorticoid responsiveness.