Immune checkpoints: A therapeutic target in triple negative breast cancer

Type I Interferon Activates PD-1 Expression through Activation of the STAT1-IRF2 Pathway in Myeloid Cells

PD-1 (Programmed cell death protein 1) regulates the metabolic reprogramming of myeloid-derived suppressor cells and myeloid cell differentiation, as well as the type I interferon (IFN-I) signaling pathway in myeloid cells in the tumor microenvironment. PD-1, therefore, is a key inhibitory receptor in myeloid cells. However, the regulation of PD-1 expression in myeloid cells is unknown. We report that the expression level of PDCD1, the gene that encodes the PD-1 protein, is positively correlated with the levels of IFNB1 and IFNAR1 in myeloid cells in human colorectal cancer. Treatment of mouse myeloid cell lines with recombinant IFNβ protein elevated PD-1 expression in myeloid cells in vitro. Knocking out IFNAR1, the gene that encodes the IFN-I-specific receptor, diminished the inductive effect of IFNβ on PD-1 expression in myeloid cells in vitro. Treatment of tumor-bearing mice with a lipid nanoparticle-encapsulated IFNβ-encoding plasmid (IFNBCOL01) increased IFNβ expression, resulting in elevated PD-1 expression in tumor-infiltrating myeloid cells. At the molecular level, we determined that IFNβ activates STAT1 (signal transducer and activator of transcription 1) and IRFs (interferon regulatory factors) in myeloid cells. Analysis of the cd279 promoter identified IRF2-binding consensus sequence elements. ChIP (chromatin immunoprecipitation) analysis determined that the pSTAT1 directly binds to the irf2 promoter and that IRF2 directly binds to the cd279 promoter in myeloid cells in vitro and in vivo. In colon cancer patients, the expression levels of STAT1, IRF2 and PDCD1 are positively correlated in tumor-infiltrating myeloid cells. Our findings determine that IFNβ activates PD-1 expression at least in part by an autocrine mechanism via the stimulation of the pSTAT1-IRF2 axis in myeloid cells.

Prognostic significance of programmed death-1 and programmed death ligand-1 proteins in breast cancer

In numerous studies related to tumor prognosis, programmed death-ligand 1 (PD-L1) has been identified as a biomarker. This work aimed to determine the prognostic importance of PD-L1 in breast cancer. We searched electronic databases such as PubMed, Google scholar, home pages of publishing groups, medical, clinical, and pharmaceutical sciences journals, as well as other relevant sources to discover the importance of PD-1 and PD-L1 expression in breast cancer therapies and also recurrence. The keywords used in this search were autoimmunity, programmed cell death, PD-L1 or PD-1, and breast cancer. Our inclusion criteria included studies showing the synergy between the expression of PD-L1 and PD-1 in primary breast cancers as prognostic markers and this research was limited to humans only. We included review articles, original research, letters to the editor, case reports, and short communications in our study, published in English. We focused our work on PD-L1 mRNA expression in breast cancer cell lines. PD-L1 expression has been decisively demonstrated to be a high-risk factor for breast cancer with a bad prognosis.

The Immune Checkpoint Inhibitor LAG-3 and Its Ligand GAL-3 in Vulvar Squamous Neoplasia

Vulvar squamous cell carcinoma (vSCC), although rare, carries significant morbidity and a high rate of recurrence. Treatment options beyond surgical excision remain limited. Lymphocyte activation gene-3 (LAG-3) and its binding partner galectin-3 (GAL-3) are an immuno-inhibitory checkpoint pair that represent potential immunotherapy targets for the treatment of vSCC. This study examined the expression of LAG-3 and GAL-3 alongside programmed cell death ligand-1 expression in invasive SCC and vulvar intraepithelial neoplasia (VIN) by immunohistochemical analysis of formalin-fixed paraffin-embedded tissue. A total of 35 cases were selected for evaluation: 13 VIN3 [human papillomavirus (HPV)-associated VIN/usual-type VIN], 2 differentiated VIN (dVIN), 16 HPV-associated vSCC, and 4 dVIN-associated vSCC. LAG-3+ tumor-infiltrating lymphocytes were identified in 91% (32/35) of cases of vulvar squamous neoplasia. Tumor cells were positive for GAL-3 in 71% of the vulvar neoplasia cases. HPV-associated vSCC was more likely to demonstrate GAL-3 tumoral positivity when compared with dVIN-associated vSCC (24/29 vs. 1/6, P=0.004). We observed co-expression of all 3 immunomarkers in 40% (14/35) of cases evaluated. In light of these findings, use of immunomodulatory drugs that target the LAG-3/GAL-3 pathway may be potentially beneficial in vSCC and efficacy may be increased when combined with anti-programmed cell death ligand-1 therapy.

Crosstalk between non-coding RNAs expression profile, drug resistance and immune response in breast cancer

Drug resistance is one of the most critical challenges facing researchers in treating breast cancer. Despite numerous treatments for breast cancer, including conventional chemical drugs, monoclonal antibodies, and immunotherapeutic drugs known as immune checkpoint inhibitors (ICI), many patients resist various approaches. In recent years, the relationship between gene expression profiles and drug resistance phenotypes has attracted much attention. Non-coding RNAs (ncRNAs) are regulatory molecules that have been shown to regulate gene expression and cell transcriptome. Two categories, microRNAs and long non-coding RNAs have been more considered and studied among these ncRNAs. Studying the role of different ncRNAs in chemical drug resistance and ICI resistance together can be beneficial in selecting more effective treatments for breast cancer. Changing the expression and action mechanism of these regulatory molecules on drug resistance phenotypes is the main topic of this review article.

Expression of the Immune Checkpoints LAG-3 and PD-L1 in High-grade Serous Ovarian Carcinoma: Relationship to Tumor-associated Lymphocytes and Germline BRCA Status

Ovarian high-grade serous carcinomas (HGSC) have shown lackluster responses to immunotherapies targeting the PD-1/PD-L1 axis, perhaps due to the coexistence of other mechanisms of immune evasion in this tumor type. Lymphocyte activation gene-3 (LAG-3) is another inhibitory immune checkpoint often expressed on tumor-associated lymphocytes which is targeted by drugs currently in clinical trials. Forty-eight HGSC with known germline BRCA mutation status were immunohistochemically stained for LAG-3, CD8, and FOXP3. Positive tumor-associated lymphocytes were enumerated and averaged over 10 high-power fields (HPF). PD-L1 immunostaining was also preformed and expression was evaluated on tumor cells and using the combined positive score (CPS). The average number of LAG-3-positve tumor-associated lymphocytes was 6/HPF (range: 0-25.6). Cytotoxic (CD8) T cells averaged 30/HPF (range: 0-168.9), and regulatory (FOXP3) cells averaged 6.6/HPF (range: 0-76.3). Tumoral PD-L1 expression of ≥1% was observed in 27% (13/48) of cases, with only 8% (4/48) showing >5% staining; 81% (39/48) cases had a CPS ≥1. LAG-3-positive lymphocytes and PD-L1 expression were positively correlated, even after controlling for the overall level of CD8 and FOX3P lymphocyte infiltration. Germline BRCA status was not significantly associated with LAG-3, CD8, FOXP3, or PD-L1 expression. These findings indicate that immunotherapies targeting LAG-3 may benefit some ovarian HGSC patients, particularly when used in conjunction with anti-PD-1/PD-L1 approaches. The typically limited expression of LAG-3 and PD-L1 suggests that immunotherapeutic response may be muted in most HGSC even with a combination approach.

The expression of programmed death-ligand 1 in patients with invasive breast cancer

Background

The purpose of this study is to investigate the association between protein expression of programmed death-ligand 1 (PD-L1) and the clinicopathological features of patients with invasive breast cancer.

Methods

Clinicopathological data of 651 patients with invasive breast carcinoma were collected over a 1-year period. Patients whose breast tissue samples did not express genes for the estrogen receptor (ER), progesterone receptor (PR), or human epidermal growth factor receptor-2 (HER2) were classified as triple-negative breast cancer (TNBC). The correlations of PD-L1 expression with clinicopathological features and overall survival were determined using Pearson's correlation coefficient and logistic binary regression analysis, respectively.

Results

Positive expression of PD-L1 was detected in 47% of patients with invasive breast carcinoma, compared with 69.3% of TNBC patients (P<0.05). Furthermore, expression of PD-L1 in patients with invasive breast carcinoma was significantly correlated with WHO grade, tumor size, vascular invasion, pathological stage, and the expression of ER, PR, nuclear associated antigen Ki67 (Ki67), p53 gene, cytokeratin 5/6 (CK5/6), and epidermal growth factor receptor (EGFR) (P<0.05). Logistic binary regression analysis showed that WHO grade, Ki67, p53, and EGFR were independent risk factors for the expression of PD-L1 in patients with invasive breast cancer. Moreover, PD-L1 expression in TNBC patients was significantly correlated with WHO grade, neuro-invasion, Ki67, CK5/6, and EGFR (P<0.05), but it was not correlated with age, tumor size, vascular invasion, number of lymph nodes, pathological stage, or the expression of ER, PR, p53, androgen receptor (AR), or vascular endothelial growth factor receptor (VEGFR) (P>0.05).

Conclusions

The high expression rate of PD-L1 in invasive breast cancer is closely related to some clinicopathological features. Thus, immunotherapy with PD-L1 inhibitors could be a potential treatment strategy for patients with invasive breast cancer.

CAR T-cell therapy for triple-negative breast cancer: Where we are

Triple-negative breast cancer (TNBC) is the most complex and challenging breast cancer subtype to treat, and chemotherapy remains the standard of care. Clinically, TNBC has a relatively high rate of recurrence and poor prognosis, which leads to a significant effort to discover novel strategies to treat patients with these tumors. Currently, chimeric antigen receptor (CAR) T cell-based immunotherapy redirects the patient's immune system directly to recognize and eradicate tumor-associated antigens (TAAs) expressing tumor cells being explored as a treatment for TNBC. A steadily increasing research in CAR T-cell therapy targeting different TAAs in TNBC has reported. In this review, we introduce the CAR technology and summarize the potential TAAs, available CARs, the antitumor activity, and the related toxicity of CARs currently under investigation for TNBC. We also highlight the potential strategies to prevent/reduce potential "on target, off tumor" toxicity induced by CAR T-cell therapy. This review will help to explore proper targets to expand further the CAR T-cell therapy for TNBCs in the clinic.

Interferon Signaling Is Diminished with Age and Is Associated with Immune Checkpoint Blockade Efficacy in Triple-Negative Breast Cancer

Immune checkpoint blockade (ICB) therapy, which targets T cell-inhibitory receptors, has revolutionized cancer treatment. Among the breast cancer subtypes, evaluation of ICB has been of greatest interest in triple-negative breast cancer (TNBC) due to its immunogenicity, as evidenced by the presence of tumor-infiltrating lymphocytes and elevated PD-L1 expression relative to other subtypes. TNBC incidence is equally distributed across the age spectrum, affecting 10% to 15% of women in all age groups. Here we report that increased immune dysfunction with age limits ICB efficacy in aged TNBC-bearing mice. The tumor microenvironment in both aged mice and patients with TNBC shows decreased IFN signaling and antigen presentation, suggesting failed innate immune activation with age. Triggering innate immune priming with a STING agonist restored response to ICB in aged mice. Our data implicate age-related immune dysfunction as a mechanism of ICB resistance in mice and suggest potential prognostic utility of assessing IFN-related genes in patients with TNBC receiving ICB therapy. SIGNIFICANCE: These data demonstrate for the first time that age determines the T cell-inflamed phenotype in TNBC and affects response to ICB in mice. Evaluating IFN-related genes from tumor genomic data may aid identification of patients for whom combination therapy including an IFN pathway activator with ICB may be required.This article is highlighted in the In This Issue feature, p. 1143.

PD-1 and PD-L1 Expression in Male Breast Cancer in Comparison with Female Breast Cancer

BACKGROUND

Male breast cancer is rare, as it represents less than 1% of all breast cancer cases. In addition, male breast cancer appears to have a different biology than female breast cancer. Programmed death-1 (PD-1) and its ligand, programmed death-ligand 1 (PD-L1), seem to have prognostic and predictive values in a variety of cancers, including female breast cancer. However, the role of PD-1 and PD-L1 expression in male breast cancer has not yet been studied.

OBJECTIVES

To compare PD-1 and PD-L1 expression in male breast cancer to female breast cancer and to evaluate prognostic values in both groups.

PATIENTS AND METHODS

Tissue microarrays from formalin-fixed paraffin-embedded resection material of 247 female and 164 male breast cancer patients were stained for PD-1 and PD-L1 by immunohistochemistry.

RESULTS

PD-1 expression on tumor-infiltrating lymphocytes was significantly less frequent in male than in female cancers (48.9 vs. 65.3%, p = 0.002). In contrast, PD-L1 expression on tumor and immune cells did not differ between the two groups. In male breast cancer, PD-1 and tumor PD-L1 were associated with grade 3 tumors. In female breast cancer, PD-1 and PD-L1 were associated with comparably worse clinicopathological variables. In a survival analysis, no prognostic value was observed for PD-1 and PD-L1 in either male and female breast cancer. In a subgroup analysis, female patients with grade 3/tumor PD-L1-negative or ER-negative/immune PD-L1-negative tumors had worse overall survival.

CONCLUSIONS

PD-1 seems to be less often expressed in male breast cancer compared to female breast cancer. Although PD-1 and PD-L1 are not definite indicators for good or bad responses, male breast cancer patients may therefore respond differently to checkpoint immunotherapy with PD-1 inhibitors than female patients.

Reduced Breast Tumor Growth after Immunization with a Tumor-Restricted MUC1 Glycopeptide Conjugated to Tetanus Toxoid

Preventive vaccination against tumor-associated endogenous antigens is considered to be an attractive strategy for the induction of a curative immune response concomitant with a long-lasting immunologic memory. The mucin MUC1 is a promising tumor antigen, as its tumor-associated form differs from the glycoprotein form expressed on healthy cells. Due to aberrant glycosylation in tumor cells, the specific peptide epitopes in its backbone are accessible and can be bound by antibodies induced by vaccination. Breast cancer patients develop per se only low levels of T cells and antibodies recognizing tumor-associated MUC1, and clinical trials with tumor-associated MUC1 yielded unsatisfactory therapeutic effects, indicating an urgent need to improve humoral immunity against this tumor entity. Herein, we demonstrate that preventive vaccination against tumor-associated human MUC1 results in a specific humoral immune response, a slowdown of tumor progression and an increase in survival of breast tumor-bearing mice. For preventive vaccination, we used a synthetic vaccine containing a tumor-associated glycopeptide structure of human MUC1 coupled to Tetanus Toxoid. The glycopeptide consists of a 22mer huMUC1 peptide with two immune dominant regions (PDTR and GSTA), glycosylated with the sialylated carbohydrate ST_N on serine-17. PyMT (polyomavirus middle T-antigen) and human MUC1 double-transgenic mice expressing human tumor-associated MUC1 on breast tumor tissue served as a preclinical breast cancer model.

PD-L1 and IDO expression in cervical and vulvar invasive and intraepithelial squamous neoplasias: implications for combination immunotherapy

AIMS

The immunoregulatory enzyme indoleamine dioxygenase 2,3 (IDO) has been implicated in cervical and vulvar squamous carcinomas (SCC) and may represent a mechanism of resistance to anti-PD-1/anti-PD-L1 therapy. However, the relationship between IDO and PD-L1 has not been well-investigated.

METHODS AND RESULTS

Sixty-five cases of cervical and vulvar intraepithelial neoplasia and SCC were assessed for IDO and PD-L1 expression. Overall, tumoral PD-L1 expression was seen in 72% of SCC, while 50% expressed IDO; co-expression was seen in 42%. Using the combined positive score (CPS) threshold of 1 to account for both tumoral and immune staining, 83% of SCC expressed PD-L1, 61% expressed IDO and 53% showed co-expression. Cervical SCCs were significantly more likely than human papillomavirus (HPV)-related vulvar SCCs to express tumoral IDO (75% versus 13%, P < 0.001) and demonstrate an IDO CPS ≥ 1 (88% versus 25%, P < 0.001); no significant differences were seen for PD-L1. Additionally, there were no significant differences in IDO and PD-L1 expression in dVIN-associated versus HPV-associated vulvar SCC. In contrast to SCC, the majority of intraepithelial lesions were entirely negative for tumoral PD-L1 and IDO and had a CPS score of <1.

CONCLUSIONS

In summary, IDO and PD-L1 co-expression is common in cervical SCCs and, to a lesser extent, vulvar SCCs. These data suggest a role for combination immunotherapy in a subset of cervical SCCs as well as select vulvar SCCs. Expression for both markers is less common in intraepithelial lesions, providing no strong support for this form of immunotherapy in the absence of invasion.

IDO expression in breast cancer: an assessment of 281 primary and metastatic cases with comparison to PD-L1

The immune inhibitory enzyme indoleamine 2,3-dioxygenase (IDO) has been associated with immune evasion in numerous malignancies and may mark these cancers as susceptible to anti-IDO therapies. We herein address IDO expression in breast cancers, examine the relationship between IDO and PD-L1, and investigate IDO fidelity across breast cancer primaries and metastases. IDO and PD-L1 expression was assessed in tissue microarrays containing 242 invasive primary breast cancers, 20 nodal metastases, and 19 distant metastases. IDO and PD-L1 were scored by extent in the tumor cells and immune infiltrate. Tumor IDO staining was seen in 14% of primaries including 38% of triple-negative cancers. IDO immune cell staining was seen in 14% of primaries and 29% of triple-negative cancers. Tumoral IDO and PD-L1 co-expression was seen in 8% of primaries, including 70% of tumoral PD-L1-positive cases. Immune IDO and PD-L1 co-expression was identified in 14% of primaries, including 48% of immune PD-L1-positive cases. Tumoral and immune cell IDO was conserved in 94% of matched primary/metastasis. In summary, IDO expression is common among high-grade, triple-negative breast cancers and is frequently associated with PD-L1 co-expression, suggesting that IDO might be a mechanism of anti-PD-1/PD-L1 immunotherapy resistance and that dual therapy may be of utility. Tumoral and immune cell IDO expression shows fidelity between primary and metastatic sites in treatment-naïve cancers, arguing against IDO as an independent driver for metastatic spread. Clinical trials are needed to assess the efficacy of IDO inhibition relative to IDO expression, as well as its possible role in combination with anti-PD-1/PD-L1 immunotherapy.

High mammographic density in women is associated with protumor inflammation

Background

Epidemiological studies have consistently shown that increased mammographic density (MD) is a strong risk factor for breast cancer. We previously observed an elevated number of vimentin⁺/CD45⁺ leukocytes in high MD (HMD) epithelium. In the present study, we aimed to investigate the subtypes of immune cell infiltrates in HMD and low MD (LMD) breast tissue.

Methods

Fifty-four women undergoing prophylactic mastectomy at Peter MacCallum Cancer Centre or St. Vincent’s Hospital were enrolled. Upon completion of mastectomy, HMD and LMD areas were resected under radiological guidance in collaboration with BreastScreen Victoria and were subsequently fixed, processed, and sectioned. Fifteen paired HMD and LMD specimens were further selected according to their fibroglandular characteristics (reasonable amount [> 20%] of tissue per block on H&E stains) for subsequent IHC analysis of immune cell infiltration.

Results

Overall, immune cell infiltrates were predominantly present in breast ducts and lobules rather than in the stroma, with CD68⁺ macrophages and CD20⁺ B lymphocytes also surrounding the vasculature. Macrophages, dendritic cells (DCs), B lymphocytes, and programmed cell death protein 1 (PD-1) expression were significantly increased in HMD epithelium compared with LMD. Moreover, significantly higher levels of DCs, CD4⁺ T cells, and PD-1 were also observed in HMD stroma than in LMD stroma. The increased expression of interleukin (IL)-6 and IL-4, with unaltered interferon-γ, indicate a proinflammatory microenvironment.

Conclusions

Our work indicates that the immune system may be activated very early in breast cancer development and may in part underpin the breast cancer risk associated with HMD.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-1010-2) contains supplementary material, which is available to authorized users.

Hypothesis: can the abscopal effect explain the impact of adjuvant radiotherapy on breast cancer mortality?

Radiotherapy is an integral component of loco-regional therapy for breast cancer. Randomized controlled trials indicate that increasing the extent of extirpative surgery primarily reduces the risk of local recurrences, while the addition of radiotherapy to surgery can also reduce the risk of distant recurrences, thereby lowering breast cancer-specific mortality. This may suggest an “abscopal” effect beyond the immediate zone of loco-regional irradiation that favorably perturbs the natural history of distant micrometastases. Immunological phenomena such as “immunogenic cell death” provide a plausible mechanistic link between the local and systemic effects of radiation. Radiotherapy treatment can stimulate both pro-immunogenic and immunosuppressive pathways with a potential net beneficial effect on anti-tumor immune activity. Upregulation of programmed cell death ligand (PD-L1) by radiotherapy is an immunosuppressive pathway that could be approached with anti-PD-L1 therapy with potential further improvement in survival. The world overview of randomized trials indicates that the breast cancer mortality reduction from adjuvant radiotherapy is delayed relative to that of adjuvant systemic treatments, and similar delays in the separation of survival curves are evident in the majority of randomized immunotherapy trials demonstrating treatment efficacy. In this article, we hypothesize that an abscopal effect may explain the benefit of radiotherapy in reducing breast cancer mortality, and that It might be possible to harness and augment this effect with systemic agents to reduce the risk of late recurrences.

Carbohydrate-based vaccines for oncotherapy

Cancer is still one of the most serious threats to human worldwide. Aberrant patterns of glycosylation on the surface of cancer cells, which are correlated with various cancer development stages, can differentiate the abnormal tissues from the healthy ones. Therefore, tumor-associated carbohydrate antigens (TACAs) represent the desired targets for cancer immunotherapy. However, these carbohydrate antigens may not able to evoke powerful immune response to combat with cancer for their poor immunogenicity and immunotolerance. Different approaches have been developed to address these problems. In this review, we want to summarize the latest advances in TACAs based anticancer vaccines.

Improved resection and prolonged overall survival with PD-1-IRDye800CW fluorescence probe-guided surgery and PD-1 adjuvant immunotherapy in 4T1 mouse model

An intraoperative technique to accurately identify microscopic tumor residuals could decrease the risk of positive surgical margins. Several lines of evidence support the expression and immunotherapeutic effect of PD-1 in breast cancer. Here, we sought to develop a fluorescence-labeled PD-1 probe for in vivo breast tumor imaging and image-guided surgery. The efficacy of PD-1 monoclonal antibody (PD-1 mAb) as adjuvant immunotherapy after surgery was also assessed. PD-1-IRDye800CW was developed and examined for its application in tumor imaging and image-guided tumor resection in an immunocompetent 4T1 mouse tumor model. Fluorescence molecular imaging was performed to monitor probe biodistribution and intraoperative imaging. Bioluminescence imaging was performed to monitor tumor growth and evaluate postsurgical tumor residuals, recurrences, and metastases. The PD-1-IRDye800CW exhibited a specific signal at the tumor region compared with the IgG control. Furthermore, PD-1-IRDye800CW-guided surgery combined with PD-1 adjuvant immunotherapy inhibited tumor regrowth and microtumor metastases and thus improved survival rate. Our study demonstrates the feasibility of using PD-1-IRDye800CW for breast tumor imaging and image-guided tumor resection. Moreover, PD-1 mAb adjuvant immunotherapy reduces cancer recurrences and metastases emanating from tumor residuals.

The expression profiles and regulation of PD-L1 in tumor-induced myeloid-derived suppressor cells

Programmed death-ligand 1 (PD-L1) is an inhibitory ligand that binds to PD-1 to suppress T cell activation. PD-L1 is constitutively expressed and inducible in tumor cells, but the expression profiles and regulatory mechanism of PD-L1 in myeloid-derived suppressor cells (MDSCs) are largely unknown. We report that PD-L1 is abundantly expressed in tumor-infiltrating leukocytes in human patients with both microsatellite instable and microsatellite stable colon cancer. About 60% CD11b⁺CD33⁺HLA-DR^- MDSCs from peripheral blood of human colon cancer patients are PD-L1⁺. PD-L1⁺ MDSCs are also significantly higher in tumor-bearing mice than in tumor-free mice. Interestingly, the highest PD-L1⁺ MDSCs were observed in the tumor microenvironment in which 56-71% tumor-infiltrating MDSCs are PD-L1⁺in vivo. In contrast, PD-L1⁺ MDSCs are significantly less in secondary lymphoid organs and peripheral blood as compared to the tumor tissues, whereas bone marrow MDSCs are essentially PD-L1^- in tumor-bearing mice. IFNγ is highly expressed in cells of the tumor tissues and IFNγ neutralization significantly decreased PD-L1⁺ MDSCs in the tumor microenvironment in vivo. However, IFNγ-activated pSTAT1 does not bind to the cd274 promoter in MDSCs. Instead, pSTAT1 activates expression of IRF1, IRF5, IRF7 and IRF8 in MDSCs, and only pSTAT1-activated IRF1 binds to a unique IRF-binding sequence element in vitro and chromatin in vivo in the cd274 promoter to activate PD-L1 transcription. Our data determine that PD-L1 is highly expressed in tumor-infiltrating MDSCs and in a lesser degree in lymphoid organs, and the pSTAT1-IRF1 axis regulates PD-L1 expression in MDSCs.

High PD-L1 expression was associated with poor prognosis in 870 Chinese patients with breast cancer

Background

To investigate the role of PD-L1 expression in tumor recurrence and metastasis in Chinese patients with breast cancer.

Methods

Suitable tissue samples were available from 870 patients with breast cancer. Paraffin-embedded tumor sections were stained with PD-L1 antibody. The correlations between PD-L1 expression and clinical characteristics, ER/PR/HER2 status and survival parameters were analyzed. Kaplan-Meier and univariate Cox proportional hazards model analyses were used to compare the survival of patients with high PD-L1 expression and patients with no PD-L1 expression.

Results

The median follow-up time was 98 months(range, 17–265 months). The positive rate of PD-L1 expression in breast cancer was 21.7% (189/870). PD-L1 high expression was inversely associated with larger tumor size, higher tumor grade, more positive lymph node number, as well as negative ER and PR status. PD-L1 expression was particularly higher in TNBC compared with non-TNBC, although no statistical significance was observed. Nomogram logistic regression results based on clinical and pathological features showed that the following factors were more likely associated with high PD-L1 expression: patient age younger than 35 years, larger tumor size, lymphovascular invasion and advanced stage. Our data indicated that patients with high PD-L1 expression had poor DFS, DMFS and overall survival compared with those with no PD-L1 expression. Univariate Cox proportional hazards model analysis showed that PD-L1 was an independent prognostic factor for tumor prognosis.

Conclusions

PD-L1 expression is an important indicator of unfavorable prognosis in breast cancer patients.

Trial Watch: Immunotherapy plus radiation therapy for oncological indications

Malignant cells succumbing to some forms of radiation therapy are particularly immunogenic and hence can initiate a therapeutically relevant adaptive immune response. This reflects the intrinsic antigenicity of malignant cells (which often synthesize a high number of potentially reactive neo-antigens) coupled with the ability of radiation therapy to boost the adjuvanticity of cell death as it stimulates the release of endogenous adjuvants from dying cells. Thus, radiation therapy has been intensively investigated for its capacity to improve the therapeutic profile of several anticancer immunotherapies, including (but not limited to) checkpoint blockers, anticancer vaccines, oncolytic viruses, Toll-like receptor (TLR) agonists, cytokines, and several small molecules with immunostimulatory effects. Here, we summarize recent preclinical and clinical advances in this field of investigation.

Trial Watch-Small molecules targeting the immunological tumor microenvironment for cancer therapy

Progressing malignancies establish robust immunosuppressive networks that operate both systemically and locally. In particular, as tumors escape immunosurveillance, they recruit increasing amounts of myeloid and lymphoid cells that exert pronounced immunosuppressive effects. These cells not only prevent the natural recognition of growing neoplasms by the immune system, but also inhibit anticancer immune responses elicited by chemo-, radio- and immuno therapeutic interventions. Throughout the past decade, multiple strategies have been devised to counteract the accumulation or activation of tumor-infiltrating immunosuppressive cells for therapeutic purposes. Here, we review recent preclinical and clinical advances on the use of small molecules that target the immunological tumor microenvironment for cancer therapy. These agents include inhibitors of indoleamine 2,3-dioxigenase 1 (IDO1), prostaglandin E2, and specific cytokine receptors, as well as modulators of intratumoral purinergic signaling and arginine metabolism.

Immune response in breast cancer brain metastases and their microenvironment: the role of the PD-1/PD-L axis

BACKGROUND

A better understanding of immune response in breast cancer brain metastases (BCBM) may prompt new preventive and therapeutic strategies.

METHODS

Immunohistochemical expression of stromal tumor-infiltrating lymphocytes (TILs: CD4, CD8, CTLA4), macrophage/microglial cells (CD68), programmed cell death protein 1 receptor (PD-1), programmed cell death protein 1 receptor ligand (PD-L)1, PD-L2 and glial fibrillary acid protein was assessed in 84 BCBM and their microenvironment.

RESULTS

Median survival after BCBM excision was 18.3 months (range 0-99). Median number of CD4+, CD8+ TILs and CD68+ was 49, 69 and 76 per 1 mm(2), respectively. PD-L1 and PD-L2 expression in BCBM was present in 53 % and 36 % of cases, and was not related to BCBM phenotype. PD-1 expression on TILs correlated positively with CD4+ and CD8+ TILs (r = 0.26 and 0.33), and so did CD68+ (r = 0.23 and 0.27, respectively). In the multivariate analysis, survival after BCBM excision positively correlated with PD-1 expression on TILs (hazard ratio (HR) = 0.3, P = 0.003), CD68+ infiltration (HR = 0.2, P < 0.001), brain radiotherapy (HR = 0.1, P < 0.001), endocrine therapy (HR = 0.1, P < 0.001), and negatively with hormone-receptor-negative/human epidermal growth factor receptor 2 (HER2)-positive phenotype of primary tumor (HR = 2.6, P = 0.01), HER2 expression in BCBM (HR = 4.9, P = 0.01).

CONCLUSIONS

PD-L1 and PD-L2 expression is a common occurrence in BCBM, irrespective of primary tumor and BCBM phenotype. Favorable prognostic impact of PD-1 expression on TILs suggests a beneficial effect of preexisting immunity and implies a potential therapeutic role of immune checkpoint inhibitors in BCBM.

Inhibition of formyl peptide receptor 1 reduces the efficacy of anticancer chemotherapy against carcinogen-induced breast cancer

The loss-of-function mutation of formyl peptide receptor 1 (FPR1) has a negative impact on the progression-free and overall survival of breast cancer patients treated with anthracycline-based adjuvant chemotherapy. This effect may be attributed to the fact that chemotherapy-induced antitumor immunity requires FPR1 and that such anticancer immune responses are responsible for the long-term effects of chemotherapy. Here, we investigated the possible contribution of FPR1 to the efficacy of a combination of mitoxantrone (MTX) and cyclophosphamide (CTX) for the treatment of hormone-induced breast cancer. Breast cancer induced by a combination of medroxyprogesterone acetate (MPA) and 7,12-Dimethylbenz[a]anthracene (DMBA) could be successfully treated with MTX plus CTX in thus far that tumor growth was retarded and overall survival was extended (as compared to vehicle-only treated controls). However, the therapeutic efficacy of the combination therapy was completely abolished when FPR1 receptors were blocked by means of cyclosporin H (CsH). Future genetic studies on neoadjuvant chemotherapy-treated breast cancers are warranted to validate these findings at the clinical level.

MUC1 Vaccines, Comprised of Glycosylated or Non-Glycosylated Peptides or Tumor-Derived MUC1, Can Circumvent Immunoediting to Control Tumor Growth in MUC1 Transgenic Mice

It remains challenging to produce decisive vaccines against MUC1, a tumor-associated antigen widely expressed by pancreas, breast and other tumors. Employing clinically relevant mouse models, we ruled out such causes as irreversible T-cell tolerance, inadequate avidity, and failure of T-cells to recognize aberrantly glycosylated tumor MUC1. Instead, every tested MUC1 preparation, even non-glycosylated synthetic 9mer peptides, induced interferon gamma-producing CD4⁺ and CD8⁺ T-cells that recognized glycosylated variants including tumor-associated MUC1. Vaccination with synthetic peptides conferred protection as long as vaccination was repeated post tumor challenge. Failure to revaccinate post challenge was associated with down-regulated tumor MUC1 and MHC molecules. Surprisingly, direct admixture of MUC1-expressing tumor with MUC1-hyperimmune T-cells could not prevent tumor outgrowth or MUC1 immunoediting, whereas ex vivo activation of the hyperimmune T-cells prior to tumor admixture rendered them curative. Therefore, surrogate T-cell preactivation outside the tumor bed, either in culture or by repetitive vaccination, can overcome tumor escape.

CCR 20th Anniversary Commentary: Triple-Negative Breast Cancer in 2015—Still in the Ballpark

The research article by Dent and colleagues, which was published in the August 1, 2007, issue of Clinical Cancer Research, provided a clinical description of metastatic progression of triple-negative breast cancers. Finding successful treatment strategies for women with triple-negative breast cancer remains a challenge.

Trial Watch: Immunomodulatory monoclonal antibodies for oncological indications

Immunomodulatory monoclonal antibodies (mAbs) differ from their tumor-targeting counterparts because they exert therapeutic effects by directly interacting with soluble or (most often) cellular components of the immune system. Besides holding promise for the treatment of autoimmune and inflammatory disorders, immunomodulatory mAbs have recently been shown to constitute a potent therapeutic weapon against neoplastic conditions. One class of immunomodulatory mAbs operates by inhibiting safeguard systems that are frequently harnessed by cancer cells to establish immunological tolerance, the so-called "immune checkpoints." No less than 3 checkpoint-blocking mAbs have been approved worldwide for use in oncological indications, 2 of which during the past 12 months. These molecules not only mediate single-agent clinical activity in patients affected by specific neoplasms, but also significantly boost the efficacy of several anticancer chemo-, radio- or immunotherapies. Here, we summarize recent advances in the development of checkpoint-blocking mAbs, as well as of immunomodulatory mAbs with distinct mechanisms of action.

Classification of current anticancer immunotherapies

During the past decades, anticancer immunotherapy has evolved from a promising therapeutic option to a robust clinical reality. Many immunotherapeutic regimens are now approved by the US Food and Drug Administration and the European Medicines Agency for use in cancer patients, and many others are being investigated as standalone therapeutic interventions or combined with conventional treatments in clinical studies. Immunotherapies may be subdivided into "passive" and "active" based on their ability to engage the host immune system against cancer. Since the anticancer activity of most passive immunotherapeutics (including tumor-targeting monoclonal antibodies) also relies on the host immune system, this classification does not properly reflect the complexity of the drug-host-tumor interaction. Alternatively, anticancer immunotherapeutics can be classified according to their antigen specificity. While some immunotherapies specifically target one (or a few) defined tumor-associated antigen(s), others operate in a relatively non-specific manner and boost natural or therapy-elicited anticancer immune responses of unknown and often broad specificity. Here, we propose a critical, integrated classification of anticancer immunotherapies and discuss the clinical relevance of these approaches.