Do programmed death 1 (PD-1) and its ligand (PD-L1) play a role in patients with non-clear cell renal cell carcinoma?

Association between PD-L1 Expression and the Prognosis and Clinicopathologic Features of Non-Clear Cell Renal Cell Carcinoma

PD-L1 is one of the two programmed cell death 1 (PD-1) ligands and a part of an immune checkpoint system (PD-1/PD-L1) with widespread clinical application. The aim of this study was to investigate PD-L1 expression and its association with clinicopathological and prognostic significance in non-clear cell renal cell carcinoma (non-ccRCC) patients. A total of 41 papillary (pRCC) and 20 chromophobe (chRCC) RCC tumors were examined for PD-L1 expression by immunohistochemistry in the cancer cells and tumor-infiltrating mononuclear cells (TIMCs). PD-L1 positivity was detected in 36.6% pRCC and 85.0% chRCC cancer cells, while PD-L1 positivity was observed in 73.2% pRCC and 50.0% chRCC TIMCs. PD-L1 positivity in both pRCC and chRCC tumor cells was not correlated with any of the examined clinicopathological features, while PD-L1 positivity in TIMCs was associated with the age of patients with pRCC. During follow-up, the death was documented among 6 patients with pRCC. Papillary RCC patients with PD-L1-positive tumor cells were significantly associated with an increased risk of death compared with patients with PD-L1-negative cancer cells. A similar trend was observed when comparing PD-L1 expression in TIMCs. However, no differences in overall survival for PD-L1-positive pRCC patients with compared to PD-L1-negative patients were observed in tumor cells or TIMCs.

Clinicopathologic Evaluation of CD80, CD86, and PD-L1 Expressions with Immunohistochemical Methods in Malignant Melanoma Patients

OBJECTIVE

Diagnostic and prognostic biomarkers for malignant melanoma are crucial for treatment and for developing targeted therapies. Malignant melanoma is a highly immunogenic tumor, and its regression, treatment, and prognostic evaluation are directly related to escape from immune destruction. Therefore, we aimed to determine the expression levels of CD80, CD86, and PD -L1 in malignant melanoma tissue samples by immunohistochemistry and to investigate the possible relationship between these proteins and the clinicopathological features in this study.

MATERIAL AND METHODS

Hematoxylin and eosin staining and immunohistochemical staining for CD80, CD86, and PD-L1 were evaluated for clinical data, survival, prognosis, tumor location, malignant melanoma subtypes, tumor size, and prognostic findings.

RESULTS

Higher survival rates were observed in patients with lower PD-L1 staining scores in the tumor. The 5-year survival was higher in patients with CD80-positive and CD86-positive biopsies. Mortality was lower in superficial spreading melanoma and Lentigo maligna melanoma types, whereas staining positivity of CD80 and CD86 was higher. Furthermore, a relationship between clinical stage and Breslow thickness ( < 2mm/≥2mm), tumor ulceration, lymph node metastasis, and CD80 and CD86 expression was also identified.

CONCLUSION

Our findings suggest that PD-L1, CD80, and CD86 expression are essential in malignant melanoma and could be used as prognostic markers.

Systematic Review of Treatment of Metastatic Non-Clear Cell Renal Cell Carcinoma

Background: Metastatic and unresectable non-clear cell renal cell carcinoma comprises more than a quarter of kidney cancers but does not have standardized treatment. Non-clear renal carcinoma consists of a variety of diverse histologic subtypes, including papillary, chromophobe, collecting duct, translocation, and medullary histologies, many of which carry a poor prognosis. Many prospective clinical trials exclude these kidney cancers, and for most clinical trials of non-clear cell renal cell carcinoma, only a small number of patients are enrolled. Objective: To perform a systematic review of recently published and currently enrolling prospective clinical trials for advanced non-clear cell renal cell carcinoma. Methods: A systematic search of Pubmed and MEDLINE (Ovid) was conducted as per PRISMA guidelines to identify recent prospective clinical trials in non-clear cell renal cell carcinoma. To ensure a thorough search, terms not only included non-clear cell renal carcinoma but also molecular subtypes. A review of currently enrolling clinical trials was conducted on Clinicaltrials.gov and the EU Clinical Trials Register as well. Results: A total of 33 prospective clinical trials with published results and 10 currently enrolling clinicals trials were identified. About half (48.5%) of these studies were reported in 2020 or 2021, and 36.4% were in the first-line setting. Treatments investigated in these trials included mTOR inhibitors, VEGF- and MET-targeted tyrosine kinase inhibitors, immune checkpoint inhibitors, and combinatorial strategies. Outcomes from these data revealed a wide range of response rate and progression free survival, favoring TKIs and immune checkpoint inhibitors -based combination regimens. Conclusions: Novel targeted therapies and immunotherapies have changed the landscape of treatment for advanced non-clear cell renal cell carcinoma. Combination regimens may provide even further clinical benefit and warrant further investigation in larger, randomized prospective clinical trials.

PD-L1 Expression and Treatment Implications in Metastatic Clear Cell Renal Cell Carcinoma: A Systematic Review

BACKGROUND: Over the past decade, immune checkpoint inhibitors (ICIs) have increasingly become the standard of care for various advanced malignancies, including metastatic clear cell renal cell carcinoma (mccRCC). Most ICIs currently used in clinical practice inhibit the interaction between the programmed cell death protein-1 (PD-1) and programmed death ligand-1 (PD-L1) complex. A deeper understanding of this interaction and PD-L1 expression in tumors has led to more effective therapies in the treatment of advanced cancers, but the debate regarding the utility of PD-L1 as a biomarker continues. OBJECTIVE: We aimed to systematically evaluate the role of PD-L1 in mccRCC in terms of expression and treatment implications. METHODS: Following PRISMA guidelines, we performed a systematic literature search using PubMed and Embase through August 31, 2020. Titles and abstracts were screened to identify articles for full-text review. A hand search was also performed using Google Scholar and the bibliography to relevant studies. RESULTS: A total of 26 articles were identified, and relevant data were extracted and organized. The available information regarding PD-L1 expression in mccRCC from both prospective clinical trials and retrospective studies were summarized. We discussed the utility of PD-L1 as a predictive and prognostic biomarker in mccRCC, its association with other potential biomarkers, and the pattern and level of expression of PD-L1 in primary versus metastatic tumors. CONCLUSIONS: Although significant progress has been made, much more remains to be learned regarding the differences between PD-L1+ and PD-L1- ccRCC tumors, in terms of both the underlying biology and clinical responses to immunotherapy and other agents.

PD1/PD-L1 Axis in Uro-oncology

The immune system is important to control tumor development and progression in humans. However, tumor cells and cells of the tumor microenvironment can induce immune escape mechanisms including activation of immune checkpoints such as PD-1/PD-L1. Based on this knowledge, new immune therapies, including PD-1 and PD-L1 inhibition, have been developed and are already recommended as a standard treatment in metastatic bladder and kidney cancer patients. In addition to its role as a therapeutic target, PD-L1 seems to be a prognostic parameter although data are controversial. Only little is known about signaling pathways inducing PD-L1 expression in tumor cells on one hand and about its functional role for tumor cells itself. However, the understanding of the complex biological function of PD-L1 will improve therapeutic options in urological malignancies. This review is giving an overview of the current knowledge concerning the PD-1/PD-L1 axis in urological tumors including bladder, kidney, prostate, testicular and penile cancer.

Characterization of PD-1 and PD-L1 Expression in Papillary Renal Cell Carcinoma: Results of a Large Multicenter Study

BACKGROUND

Programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) play a decisive role as prognostic markers in clear-cell renal cell carcinoma (RCC). To date, the role of PD-1/PD-L1 as a prognostic marker in papillary RCC (pRCC) remains scarce.

PATIENTS AND METHODS

Patients' sample collection was a joint collaboration of the nationwide PANZAR consortium - a multicenter study. Medical history and tumor specimens were collected from 245 and 129 patients with pRCC types 1 and 2, respectively. Expression of PD-1 and PD-L1 was determined by immunohistochemistry in pRCC and tumor-infiltrating mononuclear cells.

RESULTS

Of 374 pRCC specimens, 204 type 1 and 97 type 2 were evaluable for PD-1 and PD-L1 expression analysis. In total, PD-1 and PD-L1 expression were found in 8 (4.9%) of 162 and 12 (7.2%) of 166 evaluable pRCC type 1 specimens. Comparably, PD-1 and PD-L1 expression were found in 2 (2.4%) of 83 and 5 (6.2%) of 81 evaluable pRCC type 2 specimens. Hardly any clinically relevant associations between PD-1 and PD-L1 positivity and clinicopathologic or clinical courses were observed, neither in pRCC type 1 nor type 2.

CONCLUSION

The analysis of a large pRCC cohort from a multicenter consortium revealed no impact of PD-1/PD-L1 expression on prognosis in patients with pRCC with predominantly limited disease status, neither for type 1 nor type 2. However, the impact of PD-1 and PD-L1 in more advanced pRCC disease needs further elucidation.

Association between PD-L1 Expression and the Prognosis and Clinicopathologic Features of Renal Cell Carcinoma: A Systematic Review and Meta-Analysis

The expression of programmed cell death-ligand 1 (PD-L1) and its correlation with the prognosis and clinicopathologic features of renal cell carcinoma (RCC) remain controversial to date. Concerning this issue, we had conducted a meta-analysis of relevant studies searched in the Web of Science, PubMed, EMBASE, and Cochrane Library databases. The Newcastle-Ottawa quality assessment scale was applied to assess the quality of the included studies. The hazard ratio (HR) and its corresponding 95% confidence intervals (CIs) were collected by Stata 12.0 and used for the results of overall survival (OS) and disease-free survival (DFS). A total of 1,644 patients in 8 studies were included in this meta-analysis. Results showed that PD-L1 expression significantly correlated with OS (HR = 1.98, 95% CI: 1.22-3.22, Z = 2.77, p = 0.006) and DFS (HR = 3.70, 95% CI: 2.07-6.62, Z = 4.40, p = 0.0001) in ccRCC. Subgroup analysis indicated that PD-L1 expression significantly correlated with the lymph-gland transfer ratio (HR = 2.45, 95% CI: 1.02-5.92, Z = 1.99, p = 0.05) and tumor necrosis (HR = 6.05, 95% CI: 3.78-9.67, Z = 7.51, p < 0.00001). This meta-analysis suggests that PD-L1 expression is a valuable prognostic tool for patients with ccRCC. Subgroup analyses demonstrated that it was helpful for screening patients with RCC who need anti-PD-1/PD-L1 treatment and support them to benefit from such immune-targeted therapy.

The prevalence and prognostic and clinicopathological value of PD-L1 and PD-L2 in renal cell carcinoma patients: a systematic review and meta-analysis involving 3,389 patients

Background

The research of the prognostic and clinicopathologic values of programmed cell death ligand 1/2 (PD-L1/2) in renal cell carcinoma (RCC) patients has been mired by a dearth of studies and considerable controversy. We thus conducted a systematic review and meta-analysis to report the prevalence and prognostic and clinicopathological value of programmed cell death ligand 1 (PD-L1) and programmed cell death-legend 2 (PD-L2) in RCC patients.

Methods

The PubMed, Cochrane Library, EMBASE databases were searched to find human studies limited to English language literature published through October 1, 2019. Using random or fixed effects models, hazard ratios (HRs) and 95% confidence intervals (CIs) were evaluated to explore the prognostic value of PD-Ls expression, while odds ratios (ORs) and 95% CIs were evaluated to investigate clinicopathological parameters. The protocol of the study was registered in PROSPERO (CRD42019135199).

Results

After pooling all 16 eligible studies comprising 3,389 patients, we found that the overall prevalence of PD-L1 and PD-L2 in RCC patients was 27% and 39%, respectively. Furthermore, PD-L1 over-expression was a strong negative predictor for overall survival (OS), disease-free survival/progression-free survival (DFS/PFS), and cancer-specific survival (CSS) in renal cell carcinoma patients (HR =2.86, 95% CI: 1.83–4.47, P<0.001; HR =2.64, 95% CI: 1.99–3.52, P<0.001; HR =2.78, 95% CI: 2.17–3.56, P<0.001). Meanwhile, PD-L2 over-expression was only a weak negative predictor for CSS (HR =1.66, 95% CI: 1.05–2.65, P<0.05). Subgroup analysis showed that Caucasians had worse OS (HR =3.60, 95% CI: 1.77–7.33, P<0.001), PFS (HR =3.56, 95% CI: 2.44–5.18, P<0.001), and CSS (HR =3.13, 95% CI: 2.37–4.14, P<0.001) than Asians. PD-L1 was a strong indicator for worse prognosis (P<0.05 for all), while PD-L2 over-expression was only associated with sarcomatoid features (presence vs. absence, OR =1.80, 95% CI: 1.13–2.86, P=0.014). Notably, PD-L1 overexpression was more prevalent in women (male vs. female, OR =0.68, 95% CI: 0.51–0.90, P=0.006).

Conclusions

Higher PD-L1 expression is more closely associated with poor prognosis and more advanced clinicopathological features in RCC patients than PD-L2, especially in women and Caucasian patients. PD-L2 was a weak negative predictor of poor CSS of RCC and was not a prompt for the metastasis of RCC.

[Chromophobe renal cell carcinoma-diagnosis and prognosis]

Chromophobe renal cell carcinoma is one of four malignant kidney tumor subtypes. Due to its morphological variance in clinical pathological routine diagnostics, this subtype can cause certain difficulties. The tumor can be mistaken for more aggressive or benign tumors. In both cases the consequences of misdiagnosis regarding treatment decisions can be serious. Due to the morphological variance of the tumor, it has not yet been possible to develop a generally accepted, prognostically convincing graduation scheme. The aim is to improve the quality of diagnostics and estimation of prognosis for this subtype of tumor in order to optimize patient care.

The Interplay between Inflammation, Anti-Angiogenic Agents, and Immune Checkpoint Inhibitors: Perspectives for Renal Cell Cancer Treatment

Treatment options for metastatic renal cell carcinoma (RCC) have been expanding in the last years, from the consolidation of several anti-angiogenic agents to the approval of immune checkpoint inhibitors (ICIs). The rationale for the use of immunomodulating agents derived from the observation that RCC usually shows a diffuse immune-cell infiltrate. ICIs target Cytotoxic T Lymphocytes Antigen 4 (CTLA-4), programmed death 1 (PD-1), or its ligand (PD-L1), showing promising therapeutic efficacy in RCC. PD-L1 expression is associated with poor prognosis; however, its predictive role remains debated. In fact, ICIs may be a valid option even for PD-L1 negative patients. The establishment of valid predictors of treatment response to available therapeutic options is advocated to identify those patients who could benefit from these agents. Both local and systemic inflammation contribute to tumorigenesis and development of cancer. The interplay of tumor-immune status and of cancer-related systemic inflammation is pivotal for ICI-treatment outcome, but there is an unmet need for a more precise characterization. To date, little is known on the role of inflammation markers on PD-1 blockade in RCC. In this paper, we review the current knowledge on the interplay between inflammation markers, PD-1 axis, and anti-angiogenic agents in RCC, focusing on biological rationale, implications for treatment, and possible future perspectives.

Prognostic value of PD-L1 expression for surgically treated localized renal cell carcinoma: implications for risk stratification and adjuvant therapies

Background:

We aimed to evaluate the prognostic role of programmed-death receptor ligand (PD-L1) in a multinational cohort of patients with localized renal cell carcinoma (RCC).

Methods:

Formalin-fixed paraffin-embedded blocks of 1017 patients from the Latin American Renal Cancer Group were analyzed. Tissue microarrays were immunostained for PD-L1 using a commercially available monoclonal antibody. Expression of PD-L1 in ⩾5% tumor cells was considered positive. PD-1 expression in immune cells was also assessed. All cases were reviewed twice based on antibody expression and compared with a positive control. Cox proportional hazard regression models were used to identify predictors of recurrence-free survival (RFS) and overall survival (OS).

Results:

A total of 738 cases with complete follow up met criteria. Median age was 57 [interquartile range (IQR): 49–64] years, and median follow up was 34 (IQR: 15–62.9) months. Median tumor size was 5 cm (IQR: 3.0–7.5 cm). Approximately 8.2% and 7.6% of tumors were PD-L1 and programmed cell-death 1 (PD-1) positive, respectively. PD-L1 and PD-1 positivity were significantly associated with higher tumor stage (both p < 0.001), and presence of tumor necrosis and lymphovascular multivariable analyses; PD-L1 positivity was found as a predictor of worse RFS [hazard ratio (HR) = 2.08, p = 0.05] and OS (HR = 2.61, p = 0.02).

Conclusions:

PD-L1 positivity was significantly associated with worse outcomes for patients with localized RCC at intermediate follow up. This marker may help stratify patients for stricter surveillance after surgical treatment and provide a basis for checkpoint-inhibitor therapy in the adjuvant setting.

Implications of Programmed Death Ligand-1 Positivity in Non-Clear Cell Renal Cell Carcinoma

The purpose of this study was to assess the prognostic value of programmed death ligand-1 (PD-L1) positivity in a non-clear cell renal cell carcinoma (non-ccRCC) cohort. PD-L1 expression was evaluated by immunohistochemistry (IHC) using formalin-fixed paraffin-embedded (FFPE) specimens from 45 non-ccRCC patients with available tissue. PD-L1 positivity was defined as ≥1% of staining. Histopathological characteristics and oncological outcomes were correlated to PD-L1 expression. Cancer-specific survival (CSS) and recurrence-free survival (RFS) stratified by PD-L1 status were estimated using the Kaplan-Meier method. Median age was 58 years and median follow-up was 40 months. Non-ccRCC subtypes included sarcomatoid (n = 9), rhabdoid (n = 6), medullary (n = 2), Xp11.2 translocation (n = 2), collecting duct (n = 1), papillary type I (n = 11), and papillary type II (n = 14). PD-L1 positivity was noted in nine (20%) patients. PD-L1 positivity was significantly associated with higher Fuhrman nuclear grade (P = 0.048) and perineural invasion (P = 0.043). Five-year CSS was 73.2 and 83% for PD-L1 positive and negative tumors, respectively (P = 0.47). Five-year RFS was 55.6 and 61.5% for PD-L1 positive and negative tumors, respectively (P = 0.58). PD-L1 was expressed in a fifth of non-ccRCC cases and was associated with adverse histopathologic features. Expression of biomarkers such PD-L1 may help better risk-stratify non-ccRCC patients to guide treatment decisions and follow-up strategies.

Prognostic and clinicopathological significance of PD-L1 in patients with renal cell carcinoma: a meta-analysis based on 1863 individuals

The prognostic significance of PD-L1 in renal cell carcinoma (RCC) had been investigated in previous studies; however, the results remain controversial. The primary aim of this meta-analysis was to investigate the prognostic and clinicopathological significance of the PD-L1 expression in patients with RCC. Relevant literature was identified form PubMed, Embase, Web of Science and Cochrane library, which compared the prognostic significance between PD-L1 expression and RCC. Hazard ratios (HRs) for survival outcomes and odds ratios (ORs) for clinical parameters associated with PD-L1 were extracted from eligible studies. Heterogeneity was assessed using the I² value. The fixed-effects model was used if there was no evidence of heterogeneity; otherwise, the random-effects model was used. Publication bias was evaluated using Begg's funnel plots and Egger's regression test. A total of 1863 patients from ten eligible studies were analyzed. The results showed that PD-L1 expression is associated with poor overall survival in clear cell RCC (ccRCC) (HR = 2.76, 95%CI: 2.25-3.38, I² = 14.4%, P < 0.001) and non-clear cell RCC (non-ccRCC) (HR = 2.77, 95%CI: 1.62-4.72, I² = 28.8%, P < 0.001). In addition, PD-L1 expression was found to be significantly associated with primary tumor stage (OR = 1.76, 95%CI: 1.39-2.23; I² = 56.3%), regional lymph node involvement (OR = 2.10, 95%CI: 1.48-2.98; I² = 14.9%), distant metastases (OR = 2.69, 95%CI: 2.05-3.54; I² = 0.0%), nuclear grade (OR = 1.72, 95%CI: 1.32-2.23; I² = 79.4%) and histologic tumor necrosis (OR = 2.25, 95%CI: 1.59-3.18; I² = 66.1%) in patients with RCC. The outcome stability was confirmed by sensitivity analysis. Both the Begg's funnel plot test (P = 0.276) and the Egger's (P = 0.388) verified that there was no publication bias within the included studies. This study suggests that PD-L1 expression is correlated with poor prognosis and advanced clinicopathological features in RCC patients.

Evaluation of programmed cell death protein 1 (PD-1) expression as a prognostic biomarker in patients with clear cell renal cell carcinoma

Programmed cell death protein 1 (PD-1) immune checkpoint inhibitors have shown activity in patients with advanced renal cell carcinoma (RCC). However, the role of PD-1 expression in tumor-infiltrating lymphocytes (TILs) as a biomarker for poor outcome is not clear. In this study, we evaluated the prognostic value of TIL PD-1 expression in patients with clear cell RCC (ccRCC). 82 patients who underwent nephrectomy for localized or metastatic ccRCC and followed up for at least four years were searched from our database and retrospectively enrolled. Their fixed primary tumor specimens were stained with anti-PD-1 (NAT105). The specimens were classified as negative or positive for PD-1 expression, and the positive specimens were further scored in 10% increments. 37 (45.12%) patients were negative (<1% stained), 26 (31.71%) patients were low (<10 and 10%), and 19 (23.17%) patients were high (20-50%) for PD-1 expression. The prognostic value of TIL PD-1 expression was evaluated by univariate Cox proportional hazards regression on overall and recurrence-free survivals. Higher TIL PD-1 expression was not associated with increased risk of death (P = 0.336) or with increased risk of recurrence (P = 0.572). Higher primary tumor stage was associated with increased risk of recurrence (P = 0.003), and higher Fuhrman nuclear grade was associated with increased risk of death (P <0.001) and with increased risk of recurrence (P <0.001). Our study shows that TIL PD-1 expression by immunohistochemistry (IHC) does not correlate with poor clinical outcome in patients with ccRCC and is inferior to established prognosticating tools.

Systemic Therapy for Non-Clear Cell Renal Cell Carcinoma

Treatment options for metastatic clear cell renal cell carcinoma (ccRCC) have evolved markedly over the past decade, with multiple targeted therapies approved for the disease. In contrast, little improvement has been made in the management of metastatic non-clear cell RCC (nccRCC). Non-clear cell disease is an umbrella term that encompasses multiple biologically distinct entities, including but not limited to papillary, chromophobe, and sarcomatoid RCC. To date, prospective studies have largely explored treatments for ccRCC (e.g., VEGF- and mTOR-directed therapies) in trials that aggregate non-clear cell histologies. However, the studies do not acknowledge the varying biology of each non-clear cell subtype. Emerging studies in nccRCC should examine individual histologies and apply biologically relevant therapies. An example of this is SWOG 1500, a randomized phase II study that will compare a VEGF-inhibitor to one of three MET-directed therapies in patients with metastatic papillary RCC. Until the biologic diversity of nccRCC is appreciated, outcomes are likely to remain dismal.

Assessing Tumor-Infiltrating Lymphocytes in Solid Tumors: A Practical Review for Pathologists and Proposal for a Standardized Method from the International Immuno-Oncology Biomarkers Working Group: Part 2: TILs in Melanoma, Gastrointestinal Tract Carcinomas, Non-Small Cell Lung Carcinoma and Mesothelioma, Endometrial and Ovarian Carcinomas, Squamous Cell Carcinoma of the Head and Neck, Genitourinary Carcinomas, and Primary Brain Tumors

Assessment of the immune response to tumors is growing in importance as the prognostic implications of this response are increasingly recognized, and as immunotherapies are evaluated and implemented in different tumor types. However, many different approaches can be used to assess and describe the immune response, which limits efforts at implementation as a routine clinical biomarker. In part 1 of this review, we have proposed a standardized methodology to assess tumor-infiltrating lymphocytes (TILs) in solid tumors, based on the International Immuno-Oncology Biomarkers Working Group guidelines for invasive breast carcinoma. In part 2 of this review, we discuss the available evidence for the prognostic and predictive value of TILs in common solid tumors, including carcinomas of the lung, gastrointestinal tract, genitourinary system, gynecologic system, and head and neck, as well as primary brain tumors, mesothelioma and melanoma. The particularities and different emphases in TIL assessment in different tumor types are discussed. The standardized methodology we propose can be adapted to different tumor types and may be used as a standard against which other approaches can be compared. Standardization of TIL assessment will help clinicians, researchers and pathologists to conclusively evaluate the utility of this simple biomarker in the current era of immunotherapy.

PD-L1 and immune escape: insights from melanoma and other lineage-unrelated malignancies

One of the major breakthroughs in oncology in the past decade has been the research and development of immune checkpoint inhibitors. Since the discovery of the PD-1/PD-L1 axis as a key mediator in peripheral self-tolerance and the subsequent discovery of its role promoting immune escape in cancers, the PD-1/PD-L1 pathway has produced considerable excitement from both a scientific and therapeutic standpoint. The past decade has seen an explosion in the number of clinical trials utilizing anti-PD-1/PD-L1 therapy. Notably, pathologists have played a critical role in the development of these trials, and in guiding the use of anti-PD-1/PD-L1 therapies in FDA-approved clinical settings. Analysis of tissue biopsies has been increasingly used to predict patients with which cancers are most likely to benefit from these new therapies. However, many open questions remain in a rapidly changing therapeutic and scientific landscape. In this review, we describe the basic functioning of the PD-1/PD-L1 axis in normal biology, how it is coopted by cancers to promote immune escape, and then review the literature regarding the prognostic value of tumoral PD-L1 expression on its own before discussing recent therapeutic advances, and the emerging role for pathologists in predicting response to anti-PD-1/PD-L1 therapies. Special attention is given to melanoma and non-small cell lung cancer, malignancies that have seen the broadest applications of anti-PD-L1/PD-1 therapies.

Prognostic impact of PD-1 and its ligands in renal cell carcinoma

Programmed death-1 receptor (PD-1) and programmed death-1 receptor-ligand (PD-L1) have been suggested to play a role as prognostic markers in clear cell renal cell carcinoma (ccRCC). The association between PD-L1 and prognosis seems to be more robust than for PD-1. Further, preliminary analyses suggest that neither PD-1 nor its ligands play a role as prognostic markers in non-clear cell RCC, while the prognostic role of PD-L2 in ccRCC as well as in non-clear cell RCC remains unclear.

PD-L2: A prognostic marker in chromophobe renal cell carcinoma?

In the context of cancer immunotherapy, PD-1 as well as PD-L1 has been widely studied in renal cell carcinoma (RCC). PD-1 and PD-L1 play a significant role as prognostic markers in clear cell renal cell carcinoma. In contrast, little is known about PD-L2 expression patterns in RCC, especially in rarer subtypes. The aim of this study was to evaluate the prevalence, distribution and prognostic impact of PD-L2 expression in chromophobe (ch)RCC. Eighty-one patients who underwent renal surgery due to chRCC were retrospectively evaluated. Tumor specimens were analyzed for PD-L2 expression by immunohistochemistry. Expression data were associated with clinicopathological parameters and overall survival (OS). Twenty-three (28.4%) patients showed a PD-L2 > median (PD-L2 high) staining intensity. No significant association between clinicopathological parameters and PD-L2 expression was identified. A significant difference between 5- and 10-year OS in dependence of PD-L2 expression was found (PD-L2 low 96.4 and 87.7% vs. PD-L2 high 87.1 and 56%; log rank, p = 0.029). However, in multivariate analysis PD-L2 expression failed to be proofed as an independent prognostic factor. In conclusion, to our knowledge this is the first study evaluating the prognostic impact of PD-L2 in a considerably large cohort of chRCC. Our results showed a significant diminished OS in dependence of PD-L2 expression. This implicates that PD-L2 might play a role as prognostic marker in chRCC demanding further evaluation.

PD-1/PD-L1 expression in chromophobe renal cell carcinoma: An immunological exception?

Immune checkpoint inhibitors targeting the inhibitory cross talk between tumor and immune cells have been approved for therapy in renal cell carcinoma (RCC). In contrast to clear cell RCC, little is known on PD-1/PD-L1 expression patterns in rarer RCC subtypes. The aim of this study was to evaluate the prevalence, distribution and prognostic impact of PD-1 and PD-L1 expression in chromophobe (ch)RCC. Patients who underwent renal surgery due to chRCC were retrospectively evaluated. Tumor specimen was analyzed for PD-1 and PD-L1 expression by immunohistochemistry. Expression data were correlated with clinic-pathological parameters including patient survival. Eighty-one chRCC patients were eligible for analysis, thereof 25 (30.9 %) and 11 (13.6 %) patients were positive for PD-1⁺ tumor-infiltrating mononuclear cells (TIMCs) and tumoral PD-L1⁺ expression, respectively. No significant associations were found for PD-1⁺ TIMC or tumoral PD-L1⁺ expression and clinical attributes. In addition, no differences in 5- and 10-year overall survival for PD-1^- TIMC compared to PD-1⁺ TIMC (90.5 and 72.2 vs. 100 and 75 %; p = 0.41) and for PD-L1^- tumors compared to PD-L1⁺ tumors (91.9 and 76.4 vs. 100 and 50 %; p = 0.48) were observed. In conclusion, to our knowledge this is the first study to evaluate the prognostic impact of PD-1 and PD-L1 in chRCC. PD-L1 does seem to be expressed in a minority of all chRCC, likewise only a minority of chRCC was infiltrated by PD-1-positive inflammatory cells. Neither PD-1⁺ TIMC nor tumoral PD-L1⁺ expression was associated with parameters of aggressiveness or survival.

Intratumoral expression of programmed death ligand 1 (PD-L1) in patients with clear cell renal cell carcinoma (ccRCC)

The immunological checkpoints of programmed death 1 and its ligand (PD-L1) are currently in focus as novel therapeutic targets in renal cell carcinoma (RCC). The aim of this study was to evaluate the prognostic association of PD-L1 expression in clear cell (cc) RCC with clinical parameters, tumor aggressiveness and overall survival (OS). Patients who underwent renal surgery due to RCC between 1994 and 2003 were retrospectively evaluated. Tumor specimens were analyzed for PD-L1 expression by immunohistochemistry. One hundred and seventy-seven ccRCC patients were eligible for analysis, in which 140 (79.1 %) were negative and 37 (20.9 %) were positive for PD-L1 expression. PD-L1 positivity was associated with female gender (p = 0.001), lymph node metastasis (p = 0.004), distant metastasis (p = 0.002), higher AJCC stage (p = 0.004), as well as advanced disease (pT3/4 and/or N+ and/or M1) (p < 0.001). Kaplan-Meier analysis revealed a significantly diminished 5- and 10-year overall survival of 46.7 and 28.3 % for PD-L1(+) compared to PD-L1(-) tumors with 66 and 53.4 % (p = 0.005), respectively. Univariate analysis showed a significant negative association of OS with PD-L1 positivity [p = 0.005; HR: 2 (95 % CI 1.2-3.3)], even though PD-L1 positivity only tends to predict independently the OS using multivariate analyses [p = 0.066; HR: 1.6 (95 % CI 0.98-2.7)]. PD-L1 expression in ccRCC is associated with parameters of aggressiveness, as well as with poor OS, even though PD-L1 status was not identified as a significant independent prognostic parameter. However, further studies in larger cohorts are warranted.