Expression of programmed death ligand 1 (PD-L1) is associated with poor prognosis in human breast cancer

Checkpoint Inhibitors and Their Application in Breast Cancer

Immune checkpoints are crucial for the maintenance of self-tolerance and for the modulation of immune responses in order to minimize tissue damage. Tumor cells take advantage of these mechanisms to evade immune recognition. A significant proportion of tumors, including breast cancers, can express co-inhibitory molecules that are important formediating the escape from T cell-mediated immune surveillance. The interaction of inhibitory receptors with their ligands can be blocked by specific molecules. Monoclonal antibodies (mAbs) directed against the cytotoxic T lymphocyte-associated antigen-4 (CTLA4) and, more recently, against the programmed cell death protein 1 (PD1), have been approved for the therapy of melanoma (anti-CTLA4 and anti-PD1 mAbs) and non-small cell lung cancer (anti-PD1 mAbs). Moreover, inhibition of PD1 signaling has shown extremely promising signs of activity in breast cancer. An increasing number of molecules directed against other immune checkpoints are currently under clinical development. In this review, we summarize the evidence supporting the implementation of checkpoint inhibition in breast cancer by reviewing in detail data on PD-L1 expression and its regulation. In addition, opportunities to boost anti-tumor immunity in breast cancer with checkpoint inhibitor-based immunotherapies alone and in combination with other treatment options will be discussed.

RAS/MAPK Activation Is Associated with Reduced Tumor-Infiltrating Lymphocytes in Triple-Negative Breast Cancer: Therapeutic Cooperation Between MEK and PD-1/PD-L1 Immune Checkpoint Inhibitors

PURPOSE

Tumor-infiltrating lymphocytes (TIL) in the residual disease (RD) of triple-negative breast cancers (TNBC) after neoadjuvant chemotherapy (NAC) are associated with improved survival, but insight into tumor cell-autonomous molecular pathways affecting these features are lacking.

EXPERIMENTAL DESIGN

We analyzed TILs in the RD of clinically and molecularly characterized TNBCs after NAC and explored therapeutic strategies targeting combinations of MEK inhibitors with PD-1/PD-L1-targeted immunotherapy in mouse models of breast cancer.

RESULTS

Presence of TILs in the RD was significantly associated with improved prognosis. Genetic or transcriptomic alterations in Ras-MAPK signaling were significantly correlated with lower TILs. MEK inhibition upregulated cell surface MHC expression and PD-L1 in TNBC cells both in vivo and in vitro. Moreover, combined MEK and PD-L1/PD-1 inhibition enhanced antitumor immune responses in mouse models of breast cancer.

CONCLUSIONS

These data suggest the possibility that Ras-MAPK pathway activation promotes immune-evasion in TNBC, and support clinical trials combining MEK- and PD-L1-targeted therapies. Furthermore, Ras/MAPK activation and MHC expression may be predictive biomarkers of response to immune checkpoint inhibitors.

RAS/MAPK Activation Is Associated with Reduced Tumor-Infiltrating Lymphocytes in Triple-Negative Breast Cancer: Therapeutic Cooperation Between MEK and PD-1/PD-L1 Immune Checkpoint Inhibitors

PURPOSE

Tumor-infiltrating lymphocytes (TIL) in the residual disease (RD) of triple-negative breast cancers (TNBC) after neoadjuvant chemotherapy (NAC) are associated with improved survival, but insight into tumor cell-autonomous molecular pathways affecting these features are lacking.

EXPERIMENTAL DESIGN

We analyzed TILs in the RD of clinically and molecularly characterized TNBCs after NAC and explored therapeutic strategies targeting combinations of MEK inhibitors with PD-1/PD-L1-targeted immunotherapy in mouse models of breast cancer.

RESULTS

Presence of TILs in the RD was significantly associated with improved prognosis. Genetic or transcriptomic alterations in Ras-MAPK signaling were significantly correlated with lower TILs. MEK inhibition upregulated cell surface MHC expression and PD-L1 in TNBC cells both in vivo and in vitro. Moreover, combined MEK and PD-L1/PD-1 inhibition enhanced antitumor immune responses in mouse models of breast cancer.

CONCLUSIONS

These data suggest the possibility that Ras-MAPK pathway activation promotes immune-evasion in TNBC, and support clinical trials combining MEK- and PD-L1-targeted therapies. Furthermore, Ras/MAPK activation and MHC expression may be predictive biomarkers of response to immune checkpoint inhibitors.

Diffuse high intensity PD-L1 staining in thymic epithelial tumors

INTRODUCTION

Blockade of the immune checkpoint programmed death receptor ligand-1 (PD-L1)/PD-1 pathway has well-established clinical activity across many tumor types. PD-L1 protein expression by immunohistochemistry is emerging as a predictive biomarker of response to these therapies. Here, we examine PD-L1 expression in a thymic epithelial tumor (TET) tissue microarray (TMA).

METHODS

The TMA contained 69 TETs and 17 thymic controls, with each case represented by triplicate cores. The TMA was stained with rabbit monoclonal antibody (clone 15; Sino Biological, Beijing, China) to human PD-L1. PD-L1 staining was scored based on intensity as follows: 0 = none, 1 = equivocal/uninterpretable, 2 = weak, and 3 = intermediate-strong. Those cases with all cores scoring three in the epithelial component were categorized as PD-L1 high and the remaining as PD-L1 low.

RESULTS

PD-L1 high scores were more frequent in TETs than in controls (68.1% versus 17.6%; p = 0.0036). PD-L1 scores and histology were significantly correlated, with higher intensity staining in World Health Organization (WHO). B2/B3/C TETs. Only 14.8% of TETs had PD-L1 staining of associated lymphocytes. In an adjusted analysis (age/sex), PD-L1 high TETs had a significantly worse overall survival (hazard ratio: 5.40, 95% confidence interval: 1.13-25.89; p = 0.035) and a trend for worse event-free survival (hazard ratio: 2.94, 95% confidence interval: 0.94-9.24; p = 0.064).

CONCLUSIONS

PD-L1 expression was present in all cases of TETs within the epithelial component but only in a minority in the lymphocytic component. TETs stained more intensely for PD-L1 than in controls, and PD-L1 high TETs were associated with more aggressive histology and worse prognosis. This study lends rationale to a clinical trial with anti-PD-1/PD-L1 therapy in this rare tumor type.

PD-L1 Expression and Survival among Patients with Advanced Non-Small Cell Lung Cancer Treated with Chemotherapy

BACKGROUND

Recent clinical trial results have suggested that programmed cell death ligand 1 (PD-L1) expression measured by immunohistochemistry may predict response to anti-programmed cell death 1 (PD-1) therapy. Results on the association between PD-L1 expression and survival among patients with advanced non-small cell lung cancer (NSCLC) treated with chemotherapy are inconsistent.

MATERIAL AND METHODS

We evaluated the relationship between PD-L1 expression and overall survival (OS) among 204 patients with advanced NSCLC treated at Aarhus University Hospital, Aarhus, Denmark, from 2007 to 2012. PD-L1 expression was measured using a prototype immunohistochemistry assay with the anti-PD-L1 22C3 antibody (Merck). PD-L1 strong positivity and weak positivity were defined to be traceable to the clinical trial version of the assay.

RESULTS

Twenty-five percent of patients had PD-L1 strong-positive tumors, and 50% had PD-L1 weak-positive tumors. No statistically significant association was found between PD-L1 expression and survival; adjusted hazard ratio of 1.34 (95% confidence interval, 0.88-2.03; median OS, 9.0 months) for the PD-L1 strong-positive group and 1.07 (0.74-1.55; median OS, 9.8 months) for the PD-L1 weak-positive group compared with the PD-L1-negative group (median OS, 7.5 months). No association was seen between PD-L1 expression and OS when PD-L1 expression levels were stratified by median or tertiles.

CONCLUSIONS

In concordance with previous studies, we found PD-L1 measured by immunohistochemistry to be frequently expressed in patients with advanced NSCLC. However, PD-L1 expression is not a strong prognostic marker in patients with advanced NSCLC treated with chemotherapy.

The immune microenvironment of breast ductal carcinoma in situ

The host immune response has a key role in breast cancer progression and response to therapy. However, relative to primary invasive breast cancers, the immune milieu of breast ductal carcinoma in situ (DCIS) is less understood. Here, we profile tumor infiltrating lymphocytes and expression of the immune checkpoint ligand programmed death ligand 1 (PD-L1) in 27 cases of DCIS with known estrogen receptor (ER), progesterone receptor, and human epidermal growth factor 2 (HER-2) expression using tissue microarrays. Twenty-four cases were pure DCIS and three had associated invasive ductal carcinoma. Tumors were stained by immunohistochemistry for PD-L1, as well as the lymphocyte markers CD3, CD4, CD8, FoxP3, and CD20. The expression of PD-L1 by DCIS carcinoma cells and tumor infiltrating lymphocytes was determined, and the average tumor infiltrating lymphocytes per high power field were manually scored. None of the DCIS cells expressed PD-L1, but 81% of DCIS lesions contained PD-L1+ tumor infiltrating lymphocytes. DCIS with moderate-diffuse tumor infiltrating lymphocytes was more likely to have PD-L1+ tumor infiltrating lymphocytes (P=0.004). Tumor infiltrating lymphocytes with high levels of PD-L1 expression (>50% cells) were seen only in triple-negative DCIS (P=0.0008), and PD-L1-tumor infiltrating lymphocytes were seen only in ER+/HER-2-DCIS (P=0.12). The presence of PD-L1+ tumor infiltrating lymphocytes was associated with a younger mean patient age (P=0.01). Further characterization of the DCIS immune microenvironment may identify useful targets for immune-based therapy and breast cancer prevention.

Mammaglobin-A is a target for breast cancer vaccination

We recently completed a phase 1 clinical trial demonstrating the safety of a mammaglobin-A DNA vaccine in patients with metastatic breast cancer. We are currently enrolling patients with early stage breast cancer in a phase 1b clinical trial. The mammaglobin-A DNA vaccine will be administered concurrently with neoadjuvant endocrine therapy, providing a unique opportunity to examine the impact of vaccination in the tumor microenvironment.

Immune regulation of canine tumour and macrophage PD-L1 expression

Expression of programmed cell death receptor ligand 1 (PD-L1) on tumor cells has been associated with immune escape in human and murine cancers, but little is known regarding the immune regulation of PD-L1 expression by tumor cells and tumor-infiltrating macrophages in dogs. Therefore, 14 canine tumor cell lines, as well as primary cultures of canine monocytes and macrophages, were evaluated for constitutive PD-L1 expression and for responsiveness to immune stimuli. We found that PD-L1 was expressed constitutively on all canine tumor cell lines evaluated, although the levels of basal expression were very variable. Significant upregulation of PD-L1 expression by all tumor cell lines was observed following IFN-γ exposure and by exposure to a TLR3 ligand. Canine monocytes and monocyte-derived macrophages did not express PD-L1 constitutively, but did significantly upregulate expression following treatment with IFN-γ. These findings suggest that most canine tumors express PD-L1 constitutively and that both innate and adaptive immune stimuli can further upregulate PD-L1 expression. Therefore the upregulation of PD-L1 expression by tumor cells and by tumor-infiltrating macrophages in response to cytokines such as IFN-γ may represent an important mechanism of tumor-mediated T-cell suppression in dogs as well as in humans.

Natural and therapy-induced immunosurveillance in breast cancer

The immunosurveillance theory postulates that tumors evolve and progress in an uncontrolled fashion only when anticancer immune responses fail. Natural immunosurveillance clearly influences human breast cancer (BC) progression because the prognosis of BC patients is dictated by the density, composition and activity of the tumor immune infiltrate at diagnosis. Moreover, chemotherapeutic and radiotherapeutic regimens commonly employed for the treatment of BC affect the tumor immune infiltrate, and accumulating data suggest that the clinical efficacy of these treatments is largely determined by T cell-dependent tumor-specific immune responses. In addition, the mechanism of action of targeted anticancer therapeutics, such as the erb-b2 receptor tyrosine kinase 2 (ERBB2)-targeting agent trastuzumab, involves the innate and adaptive arms of the immune system. In this Review, we discuss these findings as well as preliminary evidence indicating that immunotherapy constitutes a promising option for the treatment of BC. Moreover, we point out that the successful implementation of immunotherapy to BC management requires the optimization of current immunotherapeutic regimens and the identification of immunological biomarkers that enable improved risk stratification and the design of personalized, dynamic treatment plans.

Programmed death ligand 1 expression in triple-negative breast cancer is associated with tumour-infiltrating lymphocytes and improved outcome

AIMS

Triple-negative breast cancer (TNBC) patients generally have a poor outcome; there is a pressing need to identify more effective therapeutic strategies. Clinical trials targeting programmed death 1/programmed death ligand 1 (PD1/PDL1) in melanoma and non-small-cell lung cancer have reported high response rates, and tumoral PDL1 expression has been suggested as a potential biomarker to enrich for patient response to these treatments. There are only very limited data to date reporting the expression of PDL1 in TNBC.

METHODS AND RESULTS

PDL1 immunohistochemistry was performed on 161 primary TNBCs and assessed in the tumour as well as immune cells in the stromal compartment. PDL1 expression was very common in TNBC, expressed in the tumour cell membrane (64%), cytoplasm (80%) and stromal (93%) cellular compartments. Cytoplasmic tumoral expression of PDL1 was associated with a lower risk of breast cancer-specific death [hazard ratio (HR) 0.45, P = 0.035] while stromal PDL1 expression was associated with a lower rate of deaths from all causes (HR 0.305, P = 0.0042). Membranous expression of PDL1 was not associated with outcome. While both PDL1 expression and tumour-infiltrating lymphocytes were associated with a better outcome, only lymphovascular invasion and high tumour-infiltrating lymphocytes were independently prognostic for breast cancer-specific death.

CONCLUSION

While PDL1 expression is frequent in TNBC, it was not independently prognostic. There were differences in outcome depending on the cellular compartment of PDL1 expression. These data provide further impetus for investigating the utility of immune checkpoint therapies in TNBC, given the clinical significance of tumour-infiltrating lymphocytes (TILs) and PDL1 expression in this cohort.

PD-L1 (B7-H1) expression and the immune tumor microenvironment in primary and metastatic breast carcinomas

Programmed death ligand 1 (PD-L1) expression by tumor-infiltrating lymphocytes (TILs) and tumor cells in breast cancer has been reported, but the relationships between PD-L1 expression by TIL, carcinoma cells, and other immunologic features of the breast tumor microenvironment remain unclear. We therefore evaluated the interrelationships between tumor cell surface and TIL PD-L1 expression, lymphocyte subpopulations, and patterns of immune cell infiltration in cohorts of treatment-naive, primary breast cancers (PBCs) (n = 45) and matched PBC and metastatic breast cancers (MBC) (n = 26). Seventy-eight percent of untreated PBCs contained PD-L1(+) TILs, but only 21% had PD-L1(+) carcinoma cells. Carcinoma PD-L1 expression localized to the tumor invasive front and was associated with high tumor grade (P = .04). Eighty-nine percent of PD-L1(+) carcinomas contained brisk TIL infiltrates, compared to only 24% of PD-L1(-) carcinomas; this included CD3(+) (P = .02), CD4(+) (P = .04), CD8(+) (P = .002), and FoxP3(+) T cells (P = .02). PD-L1(+) PBCs were more likely to contain PD-L1(+) TIL than PD-L1(-) PBCs (P = .04). Peripheral lymphoid aggregates were present in 100% of PD-L1(+) compared to 41% of PD-L1(-) PBC (P < .001). No patient with PD-L1(+) PBC developed distant recurrence, compared to 15% of patients with PD-L1(-) PBC. For the matched PBC and MBC cohort, 2 patients (8%) had PD-L1(+) tumors, with 1 case concordant and 1 case discordant for carcinoma PD-L1 expression in the PBC and MBC. Our data support PD-L1 expression by tumor cells as a biomarker of active breast tumor immunity and programmed death 1 blockade as a therapeutic strategy for breast cancer.

CLINICAL SIGNIFICANCE OF PD-L1 EXPRESSION IN PARATHYROID CANCER

Introduction

Parathyroid carcinoma accounts for 0.5% to 5% of all cases of primary hyperparathyroidism and it is an exceedingly rare endocrine malignancy first described in 1933. Most experts recommend en bloc excision at initial surgery as the only chance for its cure. Both chemotherapy and radiotherapy have not been demonstrated to be beneficial in parathyroid carcinoma. Some patients have multiple recurrences or metastases. Therefore, new therapies are urgently needed. Inhibition of the interaction between Programmed Death Receptor 1 (PD-1) and Programmed Death Receptor Ligand 1 (PD-L1) enhances T-cell responses in vitro and mediates clinical antitumour activity.

Aim

We analysed the expression of PD-L1 in parathyroid cancer to evaluate its potential as target for immunotherapeutic strategy.

Subjects and methods

A cohort of 18 patients were diagnosed with primary or metastatic parathyroid cancer. Immunohistochemistry was performed in 18 formalin-fixed paraffin-embedded specimens using a rabbit monoclonal antibody. A 5% cut-off value was applied for PD-L1 positivity.

Results

The anti PD-L1 antibody showed a pre-dominantly membranous staining pattern in parathyroid cancer cells. Programmed Death Receptor Ligand-1 expression was found in 22.2% of all parathyroid carcinoma cases. There was no correlation between the expression of PD-L1 with lymph node metastasis, gender and age (P> 0.05).

Conclusion

This expression of PD-L1 in human parathyroid cancer suggests that patients with parathyroid cancer could profit from immunotherapeutic strategies using anti-PDL1 antibodies.

Programmed death 1 expression in the peritumoral microenvironment is associated with a poorer prognosis in classical Hodgkin lymphoma

Programmed cell death protein-1 (PD-1) inhibitor may be therapeutic in patients with relapsed or refractory classical Hodgkin's lymphoma (cHL). This study examined the prognostic significance of PD-1 and two PD-1 ligands (PD-L1 and PD-L2) in uniformly treated cHL. Diagnostic tissues from 109 cHL patients treated with a doxorubicin, bleomycin, vinblastine, and dacarbazine regimen were evaluated retrospectively by immunohistochemical analysis of PD-L1, PD-L2, and PD-1 expressions. The median follow-up time was 4.91 years (range, 0.17-17.33 years). Thirteen patients (11 %) expressed PD-1 protein in the peritumoral microenvironment, which was associated with poor overall survival (OS) (P = 0.017). PD-L1 or PD-L2 expression was not associated with OS. There was no correlation between PD-L1 and PD-1 expression or between PD-L2 and PD-1 expression. Multivariate analysis identified PD-1 protein as an independent prognostic factor for OS (P = 0.019). Subgroup analysis according to the Ann Arbor stage of cHL showed that PD-1 protein expression had a prognostic value in limited-stage cHL (P = 0.048). PD-1 is an independent prognostic factor in cHL and may allow the identification of a subgroup of patients with limited-stage cHL who require more intensive therapy and who may benefit from anti-PD-1 agents.

Prognostic value of programmed-death-1 receptor (PD-1) and its ligand 1 (PD-L1) in testicular germ cell tumors

BACKGROUND

Testicular germ cell tumors (TGCTs) belong to the most chemosensitive solid tumors; however, a small proportion of patients fail to be cured with cisplatin-based chemotherapy. Inhibitors of PD-1/PD-L1 pathways represent a new class of promising drugs in anticancer therapy. The aim of this study was to evaluate expression and prognostic value of PD-1 and PD-L1 in TGCTs.

PATIENTS AND METHODS

Surgical specimens from 140 patients with TGCTs (131 with primary testicular tumor and 9 with extragonadal GCTs) were included into the translational study. PD-1 and PD-L1 expression was detected in the tumor tissue by immunohistochemistry using monoclonal antibodies, scored by the multiplicative quickscore (QS) method, compared with their expression in normal testicular tissue and correlated with clinicopathological characteristics and clinical outcome.

RESULTS

None of the GCTs exhibited PD-1 protein, although expression of PD-L1 was significantly higher in GCTs in comparison with normal testicular tissue (mean QS = 5.29 versus 0.32, P < 0.0001). Choriocarcinomas exhibit the highest level of PD-L1 with decreasing positivity in embryonal carcinoma, teratoma, yolk sac tumor and seminoma. PD-L1 expression was associated with poor prognostic features, including ≥3 metastatic sites, increased serum tumor markers and/or non-pulmonary visceral metastases. Patients with low PD-L1 expression had significantly better progression-free survival [hazard ratio (HR) = 0.40, 95% confidence interval (CI) 0.16-1.01, P = 0.008] and overall survival (HR = 0.43, 95% CI 0.15-1.23, P = 0.040) compared with patients with high PD-L1 expression.

CONCLUSIONS

In this translational study, we showed, for the first time, the prognostic value of PD-L1 expression in TGCTs and our data imply that the PD-1/PD-L1 pathway could be a novel therapeutic target in TGCTs.

A Perspective of Immunotherapy for Breast Cancer: Lessons Learned and Forward Directions for All Cancers

Immunotherapy for cancer has been a focus 50 years ago. At the time, this treatment was developed prior to cloning of the cytokines, no knowledge of regulatory T-cells, and very little information that mesenchymal stem cells (MSCs) (originally colony forming unit-fibroblasts [CFU-F]) could be licensed by the inflammatory microenvironment to suppress an immune response. Given the information available at that time, mononuclear cells from the peripheral blood were activated ex vivo and then replaced in the patients with tumor. The intent was to harness these activated immune cells to target the cancer cells. These studies did not lead to long-term responses because the activated cells when reinfused into the patients were an advantage to the resident MSCs, which can home the tumor and then become suppressive in the presence of the immune cells. The immune suppression caused by MSCs would also expand regulatory T-cells, resulting instead in tumor protection. As time progressed, these different fields converged into a new approach to use immunotherapy for cancer. This article discusses these approaches and also reviews chimeric antigen receptor in the context of future treatments for solid tumors, including breast cancer.

Clinicopathologic Significance and Prognostic Value of B7 Homolog 1 in Gastric Cancer: A Systematic Review and Meta-Analysis

Immunologic checkpoint marker B7 homolog 1 (B7-H1) plays a fundamental role in the initiation and progression of gastric cancer (GC); however, the clinicopathologic significance and prognostic value of B7-H1 in GC remains controversial. In this study, we aimed to assess their relationship through a meta-analysis.Medline/PubMed, EMBASE, the Cochrane Library databases, and Grey literature were searched up to August 10, 2015, for eligible studies of the association between B7-H1 expression and overall survival in GC. The hazard ratio and its 95% confidence interval (CI) were calculated from the included studies. Moreover, the odds ratio (OR) was also extracted to evaluate the association between the clinicopathologic parameters of participants and B7-H1 expression.Five studies involving 481 patients were included in the meta-analysis. The pooled results showed that positive B7-H1 expression was a negative predictor for overall survival with hazard ratio of 1.74 (95% CI: 1.40-2.17; Pheterogeneity = 0.146) in GC. Additionally, increased B7-H1 was found to be significantly associated with positive lymph node metastasis (OR = 2.61, 95% CI: 1.78-3.84; Pheterogeneity = 0.004) and poorer tumor stage (OR = 2.28, 95% CI: 1.39-3.74; Pheterogeneity = 0.006); however, higher B7-H1 expression was not significantly correlated with poorer tumor differentiation (OR = 1.29, 95% CI: 0.90-1.86; Pheterogeneity = 0.013) and bigger tumor size (OR = 1.18, 95% CI: 0.81-1.73; Pheterogeneity = 0.104).The meta-analysis suggested that B7-H1 could act as a significant biomarker in the poor prognosis of gastric carcinoma.

Prognostic significance of PD-L1 and PD-L2 in breast cancer

PD-L1 and PD-L2 constitute an important antitumor immune response. In breast cancer, their prognostic value is still to be defined. In this study, we investigate the correlation between PD-L1 and PD-L2 protein expressions with clinical and pathologic features and disease-free survival and overall survival. To assess PD-L1 and PD-L2 expressions, we conducted immunohistochemistry studies using a breast cancer tissue microarray encompassing a total of 192 breast cancer cases, stages I, II, and III, with detailed clinical and outcome data. PD-L1 expression was present in 56.6% (107/189), and PD-L2 expression was identified in 50.8% (97/191) of breast cancer cases. Younger age at diagnosis, lymph node positivity, negative estrogen receptor, and recurrence at distant sites were all associated with both PD-L1 and PD-L2 expressions. The presence of larger tumors was associated only with PD-L1 expression. In our study, PD-L1 expression was significantly associated with better overall survival (P = .04) in breast cancer patients. Despite its association with poor clinical and pathologic features, PD-L1 expression emerges as a positive prognostic biomarker in breast cancer. This survival result might be due to the presence of a strong antitumor immune response leading to PD-L1 expression.

Human Cancer Immunotherapy with PD-1/PD-L1 Blockade

The ligation of programmed cell death-1 (PD-1) to its ligands PD-L1 and PD-L2 counteracts T-cell activation, which is critical in immune tolerance. The persistent high expression of PD-1 and PD-L1 are also observed on tumor-infiltrating lymphocytes and various tumor cells, maintaining the highly suppressive microenvironment in tumor sites and promoting tumor malignancies. The blockade of PD-1 axis with PD-L2 fusion protein or monoclonal antibodies against either PD-1 or PD-L1 has been clinically evaluated in various tumor types. This short review summarizes the progress of PD-1 axis blockade in clinical trials to evaluate its effectiveness in the antitumor immunotherapy.

Clinicopathological and prognostic value of programmed death ligand-1 (PD-L1) in renal cell carcinoma: a meta-analysis

BACKGROUND

Recently, the association of immunological checkpoint marker programmed death ligand-1 (PD-L1) and the prognosis of various cancers has always been a research hotspot. The objective of this study is to assess the clinical value of PD-L1 as a novel prognostic biomarker of renal cell carcinoma (RCC).

METHODS

Medline/PubMed, EMBASE, the Cochrane Library databases and Grey literature were searched up to 30 March 2015 for eligible studies of the association between PD-L1 expression and cancer-specific survival (CSS) in RCC. The risk ratio (RR) and its 95% confidence interval (CI) were calculated from the included studies. Moreover, the odds ratio (OR) was also extracted to evaluate the association between the clinicopathological parameters of participants and PDL1 expression.

RESULTS

Five studies involving 1073 patients were included in the meta-analysis. The pooled results showed that positive/higher PD-L1 expression was a negative predictor for CSS with RR of 2.90 (95% CI: 1.64-5.13; Pheterogeneity. ≤ 0.001). Additionally, increased PD-L1 was found to be significantly associated with large tumor size (OR = 2.28, 95% CI: 1.61-3.23; Pheterogeneity. = 0.645), high TNM stage (OR = 4.37, 95% CI: 2.99-6.39; Pheterogeneity. = 0.676), poor nuclear grade (OR = 7.58, 95% CI: 5.26-10.92; Pheterogeneity. = 0.203) and present tumor necrosis (OR = 6.77, 95% CI: 4.73-9.71; Pheterogeneity. = 0.111) in renal cell carcinoma patients.

CONCLUSION

The meta-analysis suggested that PD-L1 could act as a significant biomarker in the worse prognosis and adverse clinicopathologic features of renal cell carcinoma.

PD-L1 and HLA Class I Antigen Expression and Clinical Course of the Disease in Intrahepatic Cholangiocarcinoma

PURPOSE

More effective therapy is needed for intrahepatic cholangiocarcinoma (ICC). The encouraging clinical results obtained with checkpoint molecule-specific monoclonal antibodies (mAb) have prompted us to investigate whether this type of immunotherapy may be applicable to ICC. The aims of this study were to determine whether (i) patients mount a T-cell immune response to their ICC, (ii) checkpoint molecules are expressed on both T cells and tumor cells, and (iii) tumor cells are susceptible to recognition by cognate T cells.

EXPERIMENTAL DESIGN

Twenty-seven ICC tumors were analyzed for (i) lymphocyte infiltrate, (ii) HLA class I and HLA class II expression, and (iii) PD-1 and PD-L1 expression by T cells and ICC cells, respectively. The results of this analysis were correlated with the clinicopathologic characteristics of the patients investigated.

RESULTS

Lymphocyte infiltrates were identified in all tumors. PD-L1 expression and HLA class I antigen expression by ICC cells was observed in 8 and 11, respectively, of the 27 tumors analyzed. HLA class I antigen expression correlated with CD8(+) T-cell infiltrate. Furthermore, positive HLA class I antigen expression in combination with negative/rare PD-L1 expression was associated with favorable clinical course of the disease.

CONCLUSIONS

ICC patients are likely to mount a T-cell immune response against their own tumors. Defects in HLA class I antigen expression in combination with PD-L1 expression by ICC cells provide them with an immune escape mechanism. This mechanism justifies the implementation of immunotherapy with checkpoint molecule-specific mAbs in patients bearing ICC tumors without defects in HLA class I antigen expression.

Prognostic significance of tumor-infiltrating CD8+ and FOXP3+ lymphocytes in residual tumors and alterations in these parameters after neoadjuvant chemotherapy in triple-negative breast cancer: a retrospective multicenter study

Introduction

The status of tumor-infiltrating lymphocytes (TILs) has been recently proposed to predict clinical outcome of patients with breast cancer. We therefore studied the prognostic significance of CD8⁺ TILs and FOXP3⁺ TILs in residual tumors after neoadjuvant chemotherapy (NAC) and the alterations in these parameters before and after NAC in patients with triple-negative breast cancer (TNBC).

Methods

One hundred thirty-one TNBC patients who received NAC at three institutions were examined. CD8⁺ TIL and FOXP3⁺ TIL in residual tumors and biopsy specimens were evaluated by double-staining immunohistochemistry. The CD8⁺ TIL and FOXP3⁺ TIL status of the residual tumors was assessed, and the rates of their changes before and after NAC were calculated.

Results

TNBC patients with high CD8⁺ TIL levels or a high CD8/FOXP3 ratio in residual tumors had significantly better recurrence-free survival (RFS) and breast cancer-specific survival (BCSS) than patients with low values of these parameters. In multivariate analyses, CD8⁺ TIL exhibited strong prognostic significance for RFS, with a hazard ratio (HR) of 3.09 (95 % confidence interval (CI) 1.537–6.614, P=0.0013). The CD8/FOXP3 ratio was also significantly correlated with RFS (HR=2.07, 95 % CI 1.029–4.436, P=0.0412). TNBC with larger residual tumor size and positive lymph node status, which are known prognostic factors, was independently associated with worse RFS (P=0.0064 and P=0.0015, respectively). High CD8⁺ TIL levels were a markedly powerful indicator of improved BCSS, with an HR of 3.59 (95 % CI 1.499–9.581, P=0.0036). Nodal status was also associated with BCSS (P=0.0024). TNBC with a high rate of CD8⁺ TIL changes was associated with significantly better RFS compared with the low group (P=0.011). Higher rates of changes in the CD8/FOXP3 ratio were significantly correlated with both better RFS and BCSS compared with lower rates (P=0.011 and P=0.023, respectively).

Conclusions

This is the first study to demonstrate that high CD8⁺ TIL and a high CD8/FOXP3 ratio in residual tumors and increment of these parameters following NAC and accurately predict improved prognosis in TNBC patients with non-pathological complete response following NAC. These parameters could serve as a surrogate one for adjuvant treatment in patients with residual disease in the neoadjuvant setting.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0632-x) contains supplementary material, which is available to authorized users.

The PD1/PDL1 axis, a promising therapeutic target in aggressive breast cancers

Analysis of PDL1 mRNA expression in ∼5,500 breast cancers showed PDL1 upregulation in 38% of basal tumors and 38% of inflammatory breast cancers (IBC). Upregulation, associated with signs of strong cytotoxic local immune response, was associated with a better survival in the basal or triple-negative subtypes, and with a better pathological response to chemotherapy in these subtypes and IBC. Reactivation of dormant tumor-infiltrating lymphocytes (TILs) by PD1/PDL1-inhibitors represents a promising strategy in these aggressive tumors.

Relevance of tumor-infiltrating lymphocytes in breast cancer

While breast cancer has not been considered a cancer amenable to immunotherapeutic approaches, recent studies have demonstrated evidence of significant immune cell infiltration via tumor-infiltrating lymphocytes in a subset of patient tumors. In this review we present the current evidence highlighting the clinical relevance and utility of tumor-infiltrating lymphocytes in breast cancer. Retrospective and prospective studies have shown that the presence of tumor-infiltrating lymphocytes is a prognostic marker for higher responses to neoadjuvant chemotherapy and better survival, particularly in triple negative and HER2-positive early breast cancer. Further work is required to determine the immune subsets important in this response and to discover ways of encouraging immune infiltrate in tumor-infiltrating lymphocytes-negative patients.

Bidirectional crosstalk between PD-L1 expression and epithelial to mesenchymal transition: significance in claudin-low breast cancer cells

Background

The T-cell inhibitory molecule PD-L1 (B7-H1, CD274) is expressed on tumor cells of a subset of breast cancer patients. However, the mechanism that regulates PD-L1 expression in this group of patients is still not well-identified.

Methods

We have used loss and gain of function gene manipulation approach, multi-parametric flow cytometry, large scale gene expression dataset analysis and immunohistochemistry of breast cancer tissue sections.

Results

Induction of epithelial to mesenchymal transition (EMT) in human mammary epithelial cells upregulated PD-L1 expression, which was dependent mainly on the activation of the PI3K/AKT pathway. Interestingly, gene expression signatures available from large cohort of breast tumors showed a significant correlation between EMT score and the PD-L1 mRNA level (p < 0.001). Strikingly, very strong association (p < 0.0001) was found between PD-L1 expression and claudin-low subset of breast cancer, which is known to have high EMT score. On the protein level, significant correlation was found between PD-L1 expression and standard markers of EMT (p = 0.005) in 67 breast cancer patients. Importantly, specific downregulation of PD-L1 in claudin-low breast cancer cells showed signs of EMT reversal as manifested by CD44 and Vimentin downregulation and CD24 upregulation.

Conclusions

We have demonstrated a bidirectional effect between EMT status and PD-L1 expression especially in claudin-low subtype of breast cancer cells. Our findings highlights the potential dual benefit of anti-PD-L1 particularly in this subset of breast cancer patients that will likely benefit more from anti-PD-L1 targeted therapy as well as in monitoring biological changes upon treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0421-2) contains supplementary material, which is available to authorized users.

Frequent PD-L1 expression in testicular germ cell tumors

BACKGROUND

Many testicular germ cell cancers are curable despite metastatic disease, but about 10-15% of patients fail cisplatin-based first-line treatment. Immunotherapy is considered as additional treatment approach for these patients. Inhibition of the interaction between Programmed Death Receptor 1 (PD-1) and Programmed Death Receptor Ligand 1 (PD-L1) enhances T-cell responses in vitro and mediates clinical antitumour activity. We analysed the expression of PD-L1 in testicular germ cell tumours to evaluate its potential as target for immunotherapeutic strategies.

METHODS

Immunohistochemistry was performed in 479 formalin-fixed paraffin-embedded specimens using a rabbit monoclonal antibody (E1L3N). The tissue microarray consisted of 208 pure seminomas, 121 non-seminomas, 20 intratubular germ cell neoplasia unclassified (IGCNU) and 20 specimens of non-neoplastic testicular tissue.

RESULTS

Programmed Death Receptor Ligand-1 expression was found in 73% of all seminomas and in 64% of all non-seminomas. None of 20 IGCNU and none of 20 normal tissue specimens exhibited PD-L1 expression. PD-L1 positive stromal cells were only detected in seminomas, but not in non-seminomas. The anti PD-L1 antibody showed a pre-dominantly membranous staining pattern in testicular tumour cells, as well as expression in stromal cells.

CONCLUSIONS

This frequent expression of PD-L1 in human testicular germ cell tumours suggests that patients with testicular germ cell tumours could profit from immunotherapeutic strategies using anti-PD1 and anti-PDL1 antibodies.

Immunosuppressive Mechanisms of Malignant Gliomas: Parallels at Non-CNS Sites

The central nervous system (CNS) possesses powerful local and global immunosuppressive capabilities that modulate unwanted inflammatory reactions in nervous tissue. These same immune-modulatory mechanisms are also co-opted by malignant brain tumors and pose a formidable challenge to brain tumor immunotherapy. Routes by which malignant gliomas coordinate immunosuppression include the mechanical and functional barriers of the CNS; immunosuppressive cytokines and catabolites; immune checkpoint molecules; tumor-infiltrating immune cells; and suppressor immune cells. The challenges to overcoming tumor-induced immunosuppression, however, are not unique to the brain, and several analogous immunosuppressive mechanisms also exist for primary tumors outside of the CNS. Ultimately, the immune responses in the CNS are linked and complementary to immune processes in the periphery, and advances in tumor immunotherapy in peripheral sites may therefore illuminate novel approaches to brain tumor immunotherapy, and vice versa.

PD-L1 protein expression in breast cancer is rare, enriched in basal-like tumours and associated with infiltrating lymphocytes

BACKGROUND

Expression of programmed death ligand 1 (PD-L1) in solid tumours has been shown to predict whether patients are likely to respond to anti-PD-L1 therapies. To estimate the therapeutic potential of PD-L1 inhibition in breast cancer, we evaluated the prevalence and significance of PD-L1 protein expression in a large collection of breast tumours.

PATIENTS AND METHODS

Correlations between CD274 (PD-L1) copy number, transcript and protein levels were evaluated in tumours from 418 patients recruited to the METABRIC genomic study. Immunohistochemistry was used to detect PD-L1 protein in breast tumours in tissue microarrays from 5763 patients recruited to the SEARCH population-based study (N = 4079) and the NEAT randomised, controlled trial (N = 1684).

RESULTS

PD-L1 protein data was available for 3916 of the possible 5763 tumours from the SEARCH and NEAT studies. PD-L1 expression by immune cells was observed in 6% (235/3916) of tumours and expression by tumour cells was observed in just 1.7% (66/3916). PD-L1 was most frequently expressed in basal-like tumours. This was observed both where tumours were subtyped by combined copy number and expression profiling [39% (17/44) of IntClust 10 i.e. basal-like tumours were PD-L1 immune cell positive; P < 0.001] and where a surrogate IHC-based classifier was used [19% (56/302) of basal-like tumours were PD-L1 immune cell positive; P < 0.001]. Moreover, CD274 (PD-L1) amplification was observed in five tumours of which four were IntClust 10. Expression of PD-L1 by either tumour cells or infiltrating immune cells was positively correlated with infiltration by both cytotoxic and regulatory T cells (P < 0.001). There was a nominally significant association between PD-L1 and improved disease-specific survival (hazard ratio 0.53, 95% confidence interval 0.26-1.07; P = 0.08) in ER-negative disease.

CONCLUSIONS

Expression of PD-L1 is rare in breast cancer, markedly enriched in basal-like tumours and is correlated with infiltrating lymphocytes. PD-L1 inhibition may benefit the 19% of patients with basal-like tumours in which the protein is expressed.

NEAT CLINICALTRIALSGOV

NCT00003577.

Inhibitory receptors as targets for cancer immunotherapy

Inhibitory receptors expressed on T cells control immune responses while limiting autoimmunity. However, tumors can hijack these "checkpoints" for protection from immune attack. Tumor-specific T cells that exhibit an exhausted, unresponsive phenotype express high levels of inhibitory receptors including CTLA4, PD1, and LAG3, among others. Intratumoral regulatory T cells promote immunosuppression and also express multiple inhibitory receptors. Overcoming this inhibitory receptor-mediated immune tolerance has thus been a major focus of recent cancer immunotherapeutic developments. Here, we review how boosting the host's immune system by blocking inhibitory receptor signaling with antagonistic mAbs restores the capacity of T cells to drive durable antitumor immune responses. Clinical trials targeting the CTLA4 and PD1 pathways have shown durable effects in multiple tumor types. Many combinatorial therapies are currently being investigated with encouraging results that highlight enhanced antitumor immunogenicity and improved patient survival. Finally, we will discuss the ongoing identification and dissection of novel T-cell inhibitory receptor pathways, which could lead to the development of new combinatorial therapeutic approaches.

T-cell exhaustion in the tumor microenvironment

T-cell exhaustion was originally identified during chronic infection in mice, and was subsequently observed in humans with cancer. The exhausted T cells in the tumor microenvironment show overexpressed inhibitory receptors, decreased effector cytokine production and cytolytic activity, leading to the failure of cancer elimination. Restoring exhausted T cells represents an inspiring strategy for cancer treatment, which has yielded promising results and become a significant breakthrough in the cancer immunotherapy. In this review, we overview the updated understanding on the exhausted T cells in cancer and their potential regulatory mechanisms and discuss current therapeutic interventions targeting exhausted T cells in clinical trials.

Antagonists of PD-1 and PD-L1 in Cancer Treatment

The PD-1 pathway, comprising the immune cell co-receptor Programmed Death 1 (PD-1) and its ligands, PD-L1 (B7-H1) and PD-L2 (B7-DC), mediates local immunosuppression in the tumor microenvironment. Drugs designed to block PD-1 or PD-L1 "release the brakes" on anti-tumor immunity and have demonstrated clinical activity in several types of advanced cancers, validating this pathway as a target for cancer therapy. Two such drugs have recently been approved to treat melanoma and lung cancers, and regulatory approvals in first- and second-line settings for additional cancer types are anticipated. The manageable safety profile of PD-1/PD-L1 blocking drugs identifies them as suitable for outpatient administration and the development of combinatorial therapies. Ongoing studies aim to identify biomarkers to guide patient selection, which would further improve the risk:benefit ratio for these drugs.

Prognostic and predictive value of PDL1 expression in breast cancer

Expression of programmed cell death receptor ligand 1 (PDL1) has been scarcely studied in breast cancer. Recently PD1/PDL1-inhibitors have shown promising results in different carcinomas with correlation between PDL1 tumor expression and responses. We retrospectively analyzed PDL1 mRNA expression in 45 breast cancer cell lines and 5,454 breast cancers profiled using DNA microarrays. Compared to normal breast samples, PDL1 expression was upregulated in 20% of clinical samples and 38% of basal tumors. High expression was associated with poor-prognosis features (large tumor size, high grade, ER-negative, PR-negative, ERBB2-positive status, high proliferation, basal and ERBB2-enriched subtypes). PDL1 upregulation was associated with biological signs of strong cytotoxic local immune response. PDL1 upregulation was not associated with survival in the whole population, but was associated with better metastasis-free and overall specific survivals in basal tumors, independently of clinicopathological features. Pathological complete response after neoadjuvant chemotherapy was higher in case of PDL1 upregulation (50% versus 21%). In conclusion, PDL1 upregulation, more frequent in basal breast cancers, was associated with increased T-cell cytotoxic immune response. In this aggressive subtype, upregulation was associated with better survival and response to chemotherapy. Reactivation of dormant tumor-infiltrating lymphocytes by PDL1-inhibitors could represent promising strategy in PDL1-upregulated basal breast cancer.

Breast Cancer Update 2014 - Focus on the Patient and the Tumour

The therapy for patients with breast cancer has developed markedly in the past ten years. Our understanding of the molecular biology of tumours and the characteristics of the patients has shaped the recent advances. In this review we present the latest knowledge about the therapy for breast cancer. There are new tests and options not only in the field of anti-HER2 therapy but also in the management of triple negative and hormone receptor-positive patients. Comprehension of prognosis and therapeutic response to chemotherapies is little by little helping to define patient groups who will not respond to chemotherapy or who do not need treatment because their prognosis is extremely good. In the field of anti-HER2 therapy, work is continuing on the development of drugs suitable for and able to overcome trastuzumab resistance. For hormone receptor-positive cancers, we now have a better understanding of which therapy groups will benefit from which anti-endocrine drugs, and which will be able to overcome a possible resistance (treatment of the PI3K pathways, inhibition of the cell cycle). Molecular tests are still being evaluated with regard to the clinical situations in which they may have the greatest relevance for therapeutic decision-making; however, evidence is also increasing as to the fields in which good predictions for the prognosis can be obtained. On the whole, more work is needed to promote our understanding of the new developments in diagnostics and therapy and to involve both physicians and patients equally in the procedures.

Prognostic significance of programmed cell death 1 (PD-1) or PD-1 ligand 1 (PD-L1) Expression in epithelial-originated cancer: a meta-analysis

The expression of programmed cell death 1 (PD-1) and its ligand (PD-L1) has been observed in various epithelial-originated malignancies. However, whether the expression of PD-L1 on tumor cells or the expression of PD-1 on tumor-infiltrating lymphocytes (TILs) is associated with patients' survival remains controversial.Electronic databases were searched for eligible literatures. Data of hazard ratio (HR) for overall survival (OS) with 95% confidence interval (CI) according to the expression status of PD-L1 or PD-1 evaluated by immunohistochemistry were extracted. The outcomes were synthesized based on random-effects model. Subgroup analyses were proposed.Twenty-nine studies covering 12 types of epithelial-originated malignancies involving 7319 patients (2030/3641 cases for PD-L1 positive/negative, 505/1143 cases for PD-1 positive/negative) with available data of the outcome stratified by PD-L1/PD-1 status were enrolled. Epithelial-originated cancer patients with positive expression of PD-L1 on tumor tissues were associated with significantly poorer OS when compared to those with negative expression of PD-L1 (HR 1.81, 95% CI 1.33-2.46, P < 0.001). Similarly, patients with PD-1 positive expression on TILs had significantly shorter OS than the PD-1 negative group (HR 2.53, 95% CI 1.22-5.21, P = 0.012). In analyses of PD-L1, all subgroups showed consistent trends toward unfavorable prognoses of patients with positive PD-L1 expression, regardless of antibodies and evaluation cutoffs. Subgroup analyses on PD-1 were not available due to limited data.PD-L1 or PD-1 expression status is a significant prognostic factor in epithelial-originated malignancies.

Human cancer immunotherapy with antibodies to the PD-1 and PD-L1 pathway

The programmed death 1 (PD-1) receptor and its ligands programmed death ligand 1 (PD-L1) and PD-L2, members of the CD28 and B7 families, play critical roles in T cell coinhibition and exhaustion. Overexpression of PD-L1 and PD-1 on tumor cells and tumor-infiltrating lymphocytes, respectively, correlates with poor disease outcome in some human cancers. Monoclonal antibodies (mAbs) blockading the PD-1/PD-L1 pathway have been developed for cancer immunotherapy via enhancing T cell functions. Clinical trials with mAbs to PD-1 and PD-L1 have shown impressive response rates in patients, particularly for melanoma, non-small-cell lung cancer (NSCLC), renal cell carcinoma (RCC), and bladder cancer. Further studies are needed to dissect the mechanisms of variable response rate, to identify biomarkers for clinical response, to develop small-molecule inhibitors, and to combine these treatments with other therapies.

The CD28-B7 Family in Anti-Tumor Immunity: Emerging Concepts in Cancer Immunotherapy

The interactions between B7 molecules and CD28-family receptors are crucial in the regulation of adaptive cellular immunity. In cancer, the aberrant expression of co-inhibitory B7 molecules has been attributed to reduced anti-tumor immunity and cancer immune evasion, prompting the development of cancer therapeutics that can restore T cell function. Murine tumor models have provided significant support for the targeting of multiple immune checkpoints involving CTLA-4, PD-1, ICOS, B7-H3 and B7-H4 during tumor growth, and clinical studies investigating the therapeutic effects of CTLA-4 and PD-1 blockade have shown exceptionally promising results in patients with advanced melanoma and other cancers. The expression pattern of co-inhibitory B7 ligands in the tumor microenvironment has also been largely correlated with poor patient prognosis, and recent evidence suggests that the presence of several B7 molecules may predict the responsiveness of immunotherapies that rely on pre-existing tumor-associated immune responses. While monotherapies blocking T cell co-inhibition have beneficial effects in reducing tumor burden, combinatorial immunotherapy targeting multiple immune checkpoints involved in various stages of the anti-tumor response has led to the most substantial impact on tumor reduction. In this review, we will examine the contributions of B7- and CD28-family members in the context of cancer development, and discuss the implications of current human findings in cancer immunotherapy.

The PD-1/PD-L1 pathway: biological background and clinical relevance of an emerging treatment target in immunotherapy

INTRODUCTION

The co-inhibitory receptor programmed death 1 (PD-1) and its ligands are key regulators in a wide spectrum of immune responses and play a critical role in autoimmunity and self-tolerance as well as in cancer immunology. Emerging evidence suggests that cancer cells might use the PD-1/PD-ligand (PD-L) pathway to escape anti-tumor immunity. Based on this evidence, early phase human clinical trials targeting the PD-1/PD-L pathway are currently underway for multiple human cancers.

AREAS COVERED

The role of the PD-1/PD-L pathway in autoimmune disease, viral infections as well as in malignant neoplasms is discussed and an overview of the existing therapeutics as well as the results of clinical trials targeting this pathway in cancer is given.

EXPERT OPINION

The PD-1/PD-L pathway represents an important mechanism of immune evasion for malignant neoplasms. Early clinical trials indicate effectiveness of PD-1/PD-L pathway blockade in several solid cancers. However, greater insight into the exact mechanisms by which tumors are able to evade anti-tumor immunity is needed to increase clinical effectiveness, for example by combination blockade of diverse co-inhibitory receptors.

Programmed cell death 1 (PD-1) and its ligand (PD-L1) in common cancers and their correlation with molecular cancer type

Cancer cells expressing PD-1 ligands (PD-L1/PD-L2) inhibit immune-modulatory T-cell activation facilitating disease progression. Preliminary clinical trials exploring interruption of PD-1/PD-L1 signaling showed benefit in several cancer types. We analyzed the distribution of PD-1-positive tumor-infiltrating lymphocytes (TIL) and cancer cells' expression of PD-L1 in a molecularly profiled cohort of 437 malignancies (380 carcinomas, 33 sarcomas, and 24 melanomas). We showed that the presence of PD-1(+) TILs significantly varied among cancer types (from 0% in extraskeletal myxoid chondrosarcomas to 93% in ovarian cancer), and was generally associated with the increased number of mutations in tumor cells (P = 0.029). Cancer cell expression of PD-L1 varied from absent (in Merkel cell carcinomas) to 100% (in chondro- and liposarcomas), but showed the inverse association with the number of detected mutations (P = 0.004). Both PD-1 and PD-L1 expression were significantly higher in triple-negative breast cancers (TNBC) than in non-TNBC (P < 0.001 and 0.017, respectively). Similarly, MSI-H colon cancers had higher PD-1 and PD-L1 expression than the microsatellite stable tumors (P = 0.002 and 0.02, respectively). TP53-mutated breast cancers had significantly higher PD-1 positivity than those harboring other driver mutations (e.g., PIK3CA; P = 0.002). In non-small cell lung cancer, PD-1/PD-L1 coexpression was identified in 8 cases (19%), which lacked any other targetable alterations (e.g., EGFR, ALK, or ROS1). Our study demonstrated the utility of exploring the expression of two potentially targetable immune checkpoint proteins (PD-1/PD-L1) in a substantial proportion of solid tumors, including some aggressive subtypes that lack other targeted treatment modalities.

Standard of care and promising new agents for triple negative metastatic breast cancer

Triple negative breast cancer (TNBC) is a cluster of heterogeneous diseases, all of them sharing the lack of expression of estrogen and progesterone receptors and HER2 protein. They are characterized by different biological, molecular and clinical features, including a poor prognosis despite the increased sensitivity to the current cytotoxic therapies. Several studies have identified important molecular features which enable further subdivision of this type of tumor. We are drawing from genomics, transcription and translation analysis at different levels, to improve our knowledge of the molecular alterations along the pathways which are activated during carcinogenesis and tumor progression. How this information should be used for the rational selection of therapy is an ongoing challenge and the subject of numerous research studies in progress. Currently, the vascular endothelial growth factor (VEGF), poly (ADP-ribose) polymerase (PARP), HSP90 and Aurora inhibitors are most used as targeting agents in metastatic setting clinical trials. In this paper we will review the current knowledge about the genetic subtypes of TNBC and their different responses to conventional therapeutic strategies, as well as to some new promising molecular target agents, aimed to achieve more tailored therapies.

Immune checkpoint inhibitors in clinical trials

Immunology-based therapy is rapidly developing into an effective treatment option for a surprising range of cancers. We have learned over the last decade that powerful immunologic effector cells may be blocked by inhibitory regulatory pathways controlled by specific molecules often called "immune checkpoints." These checkpoints serve to control or turn off the immune response when it is no longer needed to prevent tissue injury and autoimmunity. Cancer cells have learned or evolved to use these mechanisms to evade immune control and elimination. The development of a new therapeutic class of drugs that inhibit these inhibitory pathways has recently emerged as a potent strategy in oncology. Three sets of agents have emerged in clinical trials exploiting this strategy. These agents are antibody-based therapies targeting cytotoxic T-lymphocyte antigen 4 (CTLA4), programmed cell death 1 (PD-1), and programmed cell death ligand 1 (PD-L1). These inhibitors of immune inhibition have demonstrated extensive activity as single agents and in combinations. Clinical responses have been seen in melanoma, renal cell carcinoma, non-small cell lung cancer, and several other tumor types. Despite the autoimmune or inflammatory immune-mediated adverse effects which have been seen, the responses and overall survival benefits exhibited thus far warrant further clinical development.