Whole-Slide Imaging, Mutual Information Registration for Multiplex Immunohistochemistry and Immunofluorescence.

Multiplex immunohistochemistry/immunofluorescence (mIHC/mIF) is a developing technology that facilitates the evaluation of multiple, simultaneous protein expressions at single-cell resolution while preserving tissue architecture. These approaches have shown great potential for biomarker discovery, yet many challenges remain. Importantly, streamlined cross-registration of multiplex immunofluorescence images with additional imaging modalities and immunohistochemistry (IHC) can help increase the plex and/or improve the quality of the data generated by potentiating downstream processes such as cell segmentation. To address this problem, a fully automated process was designed to perform a hierarchical, parallelizable, and deformable registration of multiplexed digital whole-slide images (WSIs). We generalized the calculation of mutual information as a registration criterion to an arbitrary number of dimensions, making it well suited for multiplexed imaging. We also used the self-information of a given IF channel as a criterion to select the optimal channels to use for registration. Additionally, as precise labeling of cellular membranes in situ is essential for robust cell segmentation, a pan-membrane immunohistochemical staining method was developed for incorporation into mIF panels or for use as an IHC followed by cross-registration. In this study, we demonstrate this process by registering whole-slide 6-plex/7-color mIF images with whole-slide brightfield mIHC images, including a CD3 and a pan-membrane stain. Our algorithm, WSI, mutual information registration (WSIMIR), performed highly accurate registration allowing the retrospective generation of an 8-plex/9-color, WSI, and outperformed 2 alternative automated methods for cross-registration by Jaccard index and Dice similarity coefficient (WSIMIR vs automated WARPY, P < .01 and P < .01, respectively, vs HALO + transformix, P = .083 and P = .049, respectively). Furthermore, the addition of a pan-membrane IHC stain cross-registered to an mIF panel facilitated improved automated cell segmentation across mIF WSIs, as measured by significantly increased correct detections, Jaccard index (0.78 vs 0.65), and Dice similarity coefficient (0.88 vs 0.79).

Characterization of the tumor immune microenvironment in human papillomavirus-positive and -negative head and neck squamous cell carcinomas.

Approximately 15% of advanced head and neck squamous cell carcinomas (HNSCC) respond to anti-PD-(L)1 monotherapies. Tumor PD-L1 expression and human papillomavirus (HPV) status have been proposed as biomarkers to identify patients likely to benefit from these treatments. We aimed to understand the potential immune effects of HPV in HNSCC and to characterize additional potentially targetable immune-regulatory pathways in primary, treatment-naïve tumors. CD3, CD4, CD8, CD20, CD68, FoxP3, PD-1, PD-L2, LAG-3, IDO-1, and GITR cell densities were determined in 27 HNSCC specimens. IHC for PD-L1 assessed percentage of positive tumor cells and immune cells separately or as a combined positive score (CPS), and whether PD-L1 was expressed in an adaptive or constitutive pattern (i.e., PD-L1+ tumor cells juxtaposed to TILs or in the absence of TILs, respectively). HPV testing with p16 IHC was confirmed by HPV genotyping. When compared to HPV(-) tumors (n = 14), HPV+ tumors (n = 13) contained significantly higher densities of CD3+, CD4+, CD8+, CD20+, and PD-1+ cells (P < 0.02), and there was a trend towards increased density of FoxP3 + cells. PD-L1 expression patterns did not vary by tumor viral status, suggesting possible heterogeneous mechanisms driving constitutive vs adaptive PD-L1 expression patterns in HNSCC. IDO-1 expression was abundant (> 500 IDO-1+ cells/mm2 in 17/27 specimens) and was found on tumor cells as well as immune cells in 12/27 (44%) cases (range 5-80% tumor cells+). Notably, the studied markers varied on a per-patient basis and were not always related to the degree of T cell infiltration. These findings may inform therapeutic co-targeting strategies and raise consideration for a personalized treatment approach.

Marked Enteropathy in an Accelerated Macaque Model of AIDS.

Enteropathy in HIV infection is not eliminated with combination antiretroviral therapy and is possibly linked to microbial translocation. We used a rapidly progressing SIV/pigtailed macaque model of HIV to examine enteropathy and microbial translocation. Histologic evidence of intestinal disease was observed in only half of infected macaques during late-stage infection (LSI). Combination antiretroviral therapy initiated during acute infection prevented intestinal disease. In the ileum and colon, enteropathy was associated with increased caspase-3 staining, decreased CD3+ T cells, and increased SIV-infected cells. CD3+ T cells were preserved in LSI animals without intestinal disease, and levels of CD3 staining in all LSI animals strongly correlated with the number of infected cells in the intestine and plasma viral load. Unexpectedly, there was little evidence of microbial translocation as measured by soluble CD14, soluble CD163, lipopolysaccharide binding protein, and microbial 16s ribosomal DNA. Loss of epithelial integrity indicated by loss of the tight junction protein claudin-3 was not observed during acute infection despite significantly fewer T cells. Claudin-3 was reduced in LSI animals with severe intestinal disease but did not correlate with increased microbial translocation. LSI animals that did not develop intestinal disease had increased T-cell intracytoplasmic antigen 1-positive cytotoxic T lymphocytes, suggesting a robust adaptive cytotoxic T-lymphocyte response may, in part, confer resilience to SIV-induced intestinal damage.

Splenic Damage during SIV Infection: Role of T-Cell Depletion and Macrophage Polarization and Infection.

The effects of HIV infection on spleen and its cellular subsets have not been fully characterized, particularly for macrophages in which diverse populations exist. We used an accelerated SIV-infected macaque model to examine longitudinal effects on T-cell and macrophage populations and their susceptibilities to infection. Substantial lymphoid depletion occurred, characterized by follicular burn out and a loss of CD3 T lymphocytes, which was associated with cellular activation and transient dysregulations in CD4/CD8 ratios and memory effector populations. In contrast, the loss of CD68 and CD163(+)CD68(+) macrophages and increase in CD163 cells was irreversible, which began during acute infection and persisted until terminal disease. Mac387 macrophages and monocytes were transiently recruited into spleen, but were not sufficient to mitigate the changes in macrophage subsets. Type I interferon, M2 polarizing genes, and chemokine-chemokine receptor signaling were up-regulated in spleen and drove macrophage alterations. SIV-infected T cells were numerous within the white pulp during acute infection, but were rarely observed thereafter. CD68, CD163, and Mac387 macrophages were highly infected, which primarily occurred in the red pulp independent of T cells. Few macrophages underwent apoptosis, indicating that they are a long-lasting target for HIV/SIV. Our results identify macrophages as an important contributor to HIV/SIV infection in spleen and in promoting morphologic changes through the loss of specific macrophage subsets that mediate splenic organization.

A Murine Viral Outgrowth Assay to Detect Residual HIV Type 1 in Patients With Undetectable Viral Loads.

BACKGROUND: Sensitive assays are needed for detection of residual human immunodeficiency virus (HIV) in patients with undetectable plasma viral loads to determine whether eradication strategies are effective. The gold standard quantitative viral outgrowth assay (QVOA) underestimates the magnitude of the viral reservoir. We sought to determine whether xenograft of leukocytes from HIV type 1 (HIV)-infected patients with undetectable plasma viral loads into immunocompromised mice would result in viral amplification. METHODS: Peripheral blood mononuclear cells or purified CD4(+) T cells from HIV or simian immunodeficiency virus (SIV)-infected subjects with undetectable plasma viral loads were adoptively transferred into NOD.Cg-Prkdc(scid)Il2rg(tm1Wjl)/SzJ (NSG) mice. The mice were monitored for viremia following depletion of human CD8(+) T cells to minimize antiviral activity. In some cases, humanized mice were also treated with activating anti-CD3 antibody. RESULTS: With this murine viral outgrowth assay (MVOA), we successfully amplified replication-competent HIV or SIV from all subjects tested, including 5 HIV-positive patients receiving suppressive antiretroviral therapy (ART) and 6 elite controllers or suppressors who were maintaining undetectable viral loads without ART, including an elite suppressor from whom we were unable to recover virus by QVOA. CONCLUSIONS: Our results suggest that the MVOA has the potential to serve as a powerful tool to identify residual HIV in patients with undetectable viral loads.

Combination fluconazole/paroxetine treatment is neuroprotective despite ongoing neuroinflammation and viral replication in an SIV model of HIV neurological disease.

Effective combined antiretroviral therapy (cART) in HIV-infected patients has made HIV a treatable infection; however, debilitating HIV-associated neurocognitive disorders (HAND) can still affect approximately 50% of HIV-infected individuals even under cART. While cART has greatly reduced the prevalence of the most severe form of HAND, milder forms have increased in prevalence, leaving the total proportion of HIV-infected individuals suffering from HAND relatively unchanged. In this study, an in vitro drug screen identified fluconazole and paroxetine as protective compounds against HIV gp120 and Tat neurotoxicity. Using an accelerated, consistent SIV/macaque model of HIV-associated CNS disease, we tested the in vivo neuroprotective capabilities of combination fluconazole/paroxetine (FluPar) treatment. FluPar treatment protected macaques from SIV-induced neurodegeneration, as measured by neurofilament light chain in the CSF, APP accumulation in axons, and CaMKIIα in the frontal cortex, but did not significantly reduce markers of neuroinflammation or plasma or CNS viral loads. Since HIV and SIV neurodegeneration is often attributed to accompanying neuroinflammation, this study provides proof of concept that neuroprotection can be achieved even in the face of ongoing neuroinflammation and viral replication.

Entinostat, nivolumab and ipilimumab for women with advanced HER2-negative breast cancer: a phase Ib trial.

We report the results of 24 women, 50% (N = 12) with hormone receptor-positive breast cancer and 50% (N = 12) with advanced triple-negative breast cancer, treated with entinostat + nivolumab + ipilimumab from the dose escalation (N = 6) and expansion cohort (N = 18) of ETCTN-9844 ( NCT02453620 ). The primary endpoint was safety. Secondary endpoints were overall response rate, clinical benefit rate, progression-free survival and change in tumor CD8:FoxP3 ratio. There were no dose-limiting toxicities. Among evaluable participants (N = 20), the overall response rate was 25% (N = 5), with 40% (N = 4) in triple-negative breast cancer and 10% (N = 1) in hormone receptor-positive breast cancer. The clinical benefit rate was 40% (N = 8), and progression-free survival at 6 months was 50%. Exploratory analyses revealed that changes in myeloid cells may contribute to responses; however, no correlation was noted between changes in CD8:FoxP3 ratio, PD-L1 status and tumor mutational burden and response. These findings support further investigation of this treatment in a phase II trial.

Comparing and Correcting Spectral Sensitivities between Multispectral Microscopes: A Prerequisite to Clinical Implementation.

Multispectral, multiplex immunofluorescence (mIF) microscopy has been used to great effect in research to identify cellular co-expression profiles and spatial relationships within tissue, providing a myriad of diagnostic advantages. As these technologies mature, it is essential that image data from mIF microscopes is reproducible and standardizable across devices. We sought to characterize and correct differences in illumination intensity and spectral sensitivity between three multispectral microscopes. We scanned eight melanoma tissue samples twice on each microscope and calculated their average tissue region flux intensities. We found a baseline average standard deviation of 29.9% across all microscopes, scans, and samples, which was reduced to 13.9% after applying sample-specific corrections accounting for differences in the tissue shown on each slide. We used a basic calibration model to correct sample- and microscope-specific effects on overall brightness and relative brightness as a function of the image layer. We tested the generalizability of the calibration procedure and found that applying corrections to independent validation subsets of the samples reduced the variation to 2.9 ± 0.03%. Variations in the unmixed marker expressions were reduced from 15.8% to 4.4% by correcting the raw images to a single reference microscope. Our findings show that mIF microscopes can be standardized for use in clinical pathology laboratories using a relatively simple correction model.

Increased Expression of PD-1 and PD-L1 in Patients With Laryngotracheal Stenosis.

OBJECTIVES: Laryngotracheal stenosis (LTS) is a fibrotic condition of the upper airway. Recent evidence suggests dysregulated host immunity plays a role in LTS development and progression. The programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) axis, targeted by paradigm-shifting immunotherapies for cancer treatment, has also recently been implicated in the pathogenesis of fibrotic pulmonary disease. However, a role for the PD-1/PD-L1 axis in the proximal airway fibrosis seen in LTS patients has not been explored. STUDY DESIGN: Controlled ex vivo study. METHODS: Expression of PD-1, PD-L1, CD4, and CD8 were evaluated using immunohistochemical staining of cricotracheal resection specimens from postintubation iatrogenic laryngotracheal stenosis (iLTS), idiopathic subglottic stenosis (iSGS) patients, and normal controls derived from rapid autopsy (n = 8 per group). Fibroblasts derived from iLTS scar were also treated with transforming growth factor beta 1 (TGFß1) and analyzed for PD-L1 expression by quantitative real-time polymerase chain reaction (n = 6). RESULTS: iLTS specimens exhibited increased expression of PD-1, PD-L1, and CD4 (all P < .0167) compared to controls, whereas iSGS specimens exhibited increased expression of PD-1 and CD4 (P < .0167) compared to controls. PD-1, PD-L1, and CD4 showed periepithelial patterns of expression in both disease cohorts. TGFß1 treatment of iLTS fibroblasts increased expression of PD-L1 (the cognate ligand for PD-1). CONCLUSION: Expression of both PD-1 and its ligand PD-L1 are significantly greater in patients with iLTS compared to controls, and PD-1 expression is also elevated in patients with iSGS. Given published evidence implicating the PD-1/PD-L1 axis in pulmonary fibrosis, this suggests a possible role for checkpoint inhibitors targeting the PD-1/PD-L1 axis for the treatment of LTS. LEVEL OF EVIDENCE: N/A Laryngoscope, 131:967-974, 2021.

Mismatch repair-deficient prostate cancer with parenchymal brain metastases treated with immune checkpoint blockade.

Parenchymal brain metastases from prostate cancer are unusual and are associated with poor prognosis. Given the rarity of this entity, little is known about its molecular and histologic characteristics. Here we describe a patient with metastatic castration-resistant, mismatch repair-deficient (dMMR) prostate cancer with parenchymal brain metastases. Analysis of a brain metastasis revealed MLH1 loss consistent with dMMR, yet few tumor-infiltrating lymphocytes (TILs). He was treated with immune checkpoint blockade (ICB) and exhibited an extra-central nervous system (CNS) systemic response but CNS progression. Subsequent assessment of a brain metastasis following ICB treatment surprisingly showed increased TIL density and depletion of macrophages, suggestive of an enhanced antitumor immune response. Post-treatment tumoral DNA sequencing did not reveal acquired mutations that might confer resistance to ICB. This is the first description of ICB therapy for a patient with prostate cancer with parenchymal brain metastases, with pre- and post-treatment immunogenomic analyses.

Quantitative Assessment of the Immune Microenvironment in Patients With Iatrogenic Laryngotracheal Stenosis.

OBJECTIVE: Iatrogenic laryngotracheal stenosis (iLTS) is characterized by fibroinflammatory narrowing of the upper airway and is most commonly caused by intubation injury. Evidence suggests a key role for CD4 T cells in its pathogenesis. The objective of this study is to validate emerging multiplex immunofluorescence (mIF) technology for use in the larynx and trachea while quantitatively characterizing the immune cell infiltrate in iLTS. In addition to analyzing previously unstudied immune cell subsets, this study aims to validate previously observed elevations in the immune checkpoint PD-1 and its ligand PD-L1 while exploring their spatial and cellular distributions in the iLTS microenvironment. STUDY DESIGN: Controlled ex vivo cohort study. SETTING: Tertiary care center. METHODS: mIF staining was performed with formalin-fixed, paraffin-embedded slides from 10 patients with iLTS who underwent cricotracheal resection and 10 control specimens derived from rapid autopsy for CD4, CD8, CD20, FoxP3, PD-1, PD-L1, and cytokeratin. RESULTS: There was greater infiltration of CD4+ T cells, CD8+ T cells, CD20+ B cells, FoxP3+CD4+ Tregs, and FoxP3+CD8+ early effector T cells in the submucosa of iLTS specimens as compared with controls (P < .05 for all). PD-1 was primarily expressed on T cells and PD-L1 predominantly on CD4+ cells and "other" cells. CONCLUSION: This study leverages the power of mIF to quantify the iLTS immune infiltrate in greater detail. It confirms the highly inflammatory nature of iLTS, with CD4+ cells dominating the immune cell infiltrate; it further characterizes the cellular and spatial distribution of PD-1 and PD-L1; and it identifies novel immunologic targets in iLTS.

Prognostic Implications of the Immune Tumor Microenvironment in Patients With Pancreatic and Gastrointestinal Neuroendocrine Tumors.

OBJECTIVES: The aim of this study was to characterize the tumor microenvironment of patients with gastroenteropancreatic neuroendocrine tumors relative to progression-free survival (PFS). METHODS: Immune profiling for CD3, CD8, programmed death-1/programmed death-ligand 1, and indoleamine 2,3-dioxygenase expression in 2 cohorts of gastroenteropancreatic neuroendocrine tumors: patients with short PFS (<4 years, n = 12) versus long PFS (≥4 years, n = 14) after surgery. Immune infiltrates in the tumor and interface were quantified. Programmed death-ligand 1 expression was determined within the tumor, stroma, and interface. RESULTS: Patients with shorter PFS had larger tumors (P = 0.02), mostly in the pancreas (P = 0.04). We observed a higher mean expression of CD3+, CD8+, programmed death-1+ cells, and indoleamine 2,3-dioxygenase at the interface compared with the tumor: log 10 mean differences 0.56 (95% confidence interval [CI], 0.43-0.68; P < 0.0001), 0.45 (95% CI, 0.32-0.59; P = 0.0002), 0.50 (95% CI, 0.40-0.61; P < 0.0001), and 0.24 (95% CI, 0.03-0.46; P = 0.046), respectively. Patients with longer PFS had higher intratumoral CD3+ T cells, log 10 mean difference 0.38 (95% CI, 0.19-0.57; P = 0.004). Programmed death-ligand 1 expression tended to be higher among patients with shortened PFS (odds ratio, 2.00; 95% CI, 0.68-5.91). CONCLUSIONS: Higher intratumoral CD3+ T-cell infiltrate was associated with longer PFS after resection.

Multi-institutional TSA-amplified Multiplexed Immunofluorescence Reproducibility Evaluation (MITRE) Study.

BACKGROUND: Emerging data suggest predictive biomarkers based on the spatial arrangement of cells or coexpression patterns in tissue sections will play an important role in precision immuno-oncology. Multiplexed immunofluorescence (mIF) is ideally suited to such assessments. Standardization and validation of an end-to-end workflow that supports multisite trials and clinical laboratory processes are vital. Six institutions collaborated to: (1) optimize an automated six-plex assay focused on the PD-1/PD-L1 axis, (2) assess intersite and intrasite reproducibility of staining using a locked down image analysis algorithm to measure tumor cell and immune cell (IC) subset densities, %PD-L1 expression on tumor cells (TCs) and ICs, and PD-1/PD-L1 proximity assessments. METHODS: A six-plex mIF panel (PD-L1, PD-1, CD8, CD68, FOXP3, and CK) was rigorously optimized as determined by quantitative equivalence to immunohistochemistry (IHC) chromogenic assays. Serial sections from tonsil and breast carcinoma and non-small cell lung cancer (NSCLC) tissue microarrays (TMAs), TSA-Opal fluorescent detection reagents, and antibodies were distributed to the six sites equipped with a Leica Bond Rx autostainer and a Vectra Polaris multispectral imaging platform. Tissue sections were stained and imaged at each site and delivered to a single site for analysis. Intersite and intrasite reproducibility were assessed by linear fits to plots of cell densities, including %PDL1 expression by TCs and ICs in the breast and NSCLC TMAs. RESULTS: Comparison of the percent positive cells for each marker between mIF and IHC revealed that enhanced amplification in the mIF assay was required to detect low-level expression of PD-1, PD-L1, FoxP3 and CD68. Following optimization, an average equivalence of 90% was achieved between mIF and IHC across all six assay markers. Intersite and intrasite cell density assessments showed an average concordance of R2=0.75 (slope=0.92) and R2=0.88 (slope=0.93) for breast carcinoma, respectively, and an average concordance of R2=0.72 (slope=0.86) and R2=0.81 (slope=0.68) for NSCLC. Intersite concordance for %PD-L1+ICs had an average R2 value of 0.88 and slope of 0.92. Assessments of PD-1/PD-L1 proximity also showed strong concordance (R2=0.82; slope=0.75). CONCLUSIONS: Assay optimization yielded highly sensitive, reproducible mIF characterization of the PD-1/PD-L1 axis across multiple sites. High concordance was observed across sites for measures of density of specific IC subsets, measures of coexpression and proximity with single-cell resolution.

Spatial UMAP and Image Cytometry for Topographic Immuno-oncology Biomarker Discovery.

Multiplex immunofluorescence (mIF) can detail spatial relationships and complex cell phenotypes in the tumor microenvironment (TME). However, the analysis and visualization of mIF data can be complex and time-consuming. Here, we used tumor specimens from 93 patients with metastatic melanoma to develop and validate a mIF data analysis pipeline using established flow cytometry workflows (image cytometry). Unlike flow cytometry, spatial information from the TME was conserved at single-cell resolution. A spatial uniform manifold approximation and projection (UMAP) was constructed using the image cytometry output. Spatial UMAP subtraction analysis (survivors vs. nonsurvivors at 5 years) was used to identify topographic and coexpression signatures with positive or negative prognostic impact. Cell densities and proportions identified by image cytometry showed strong correlations when compared with those obtained using gold-standard, digital pathology software (R2 > 0.8). The associated spatial UMAP highlighted "immune neighborhoods" and associated topographic immunoactive protein expression patterns. We found that PD-L1 and PD-1 expression intensity was spatially encoded-the highest PD-L1 expression intensity was observed on CD163+ cells in neighborhoods with high CD8+ cell density, and the highest PD-1 expression intensity was observed on CD8+ cells in neighborhoods with dense arrangements of tumor cells. Spatial UMAP subtraction analysis revealed numerous spatial clusters associated with clinical outcome. The variables represented in the key clusters from the unsupervised UMAP analysis were validated using established, supervised approaches. In conclusion, image cytometry and the spatial UMAPs presented herein are powerful tools for the visualization and interpretation of single-cell, spatially resolved mIF data and associated topographic biomarker development.

Analysis of multispectral imaging with the AstroPath platform informs efficacy of PD-1 blockade.

Next-generation tissue-based biomarkers for immunotherapy will likely include the simultaneous analysis of multiple cell types and their spatial interactions, as well as distinct expression patterns of immunoregulatory molecules. Here, we introduce a comprehensive platform for multispectral imaging and mapping of multiple parameters in tumor tissue sections with high-fidelity single-cell resolution. Image analysis and data handling components were drawn from the field of astronomy. Using this "AstroPath" whole-slide platform and only six markers, we identified key features in pretreatment melanoma specimens that predicted response to anti-programmed cell death-1 (PD-1)-based therapy, including CD163+PD-L1- myeloid cells and CD8+FoxP3+PD-1low/mid T cells. These features were combined to stratify long-term survival after anti-PD-1 blockade. This signature was validated in an independent cohort of patients with melanoma from a different institution.

PD-L1 Expression in Pediatric Low-Grade Gliomas Is Independent of BRAF V600E Mutational Status.

To evaluate a potential relationship between BRAF V600E mutation and PD-L1 expression, we examined the expression of PD-L1 in pediatric high- and low-grade glioma cell lines as well as a cohort of pediatric low-grade glioma patient samples. Half of the tumors in our patient cohort were V600-wildtype and half were V600E mutant. All tumors expressed PD-L1. In most tumors, PD-L1 expression was low (<5%), but in some cases over 50% of cells were positive. Extent of PD-L1 expression and immune cell infiltration was independent of BRAF V600E mutational status. All cell lines evaluated, including a BRAF V600E mutant xenograft, expressed PD-L1. Transient transfection of cell lines with a plasmid expressing mutant BRAF V600E had minimal effect on PD-L1 expression. These findings suggest that the PD-1 pathway is active in subsets of pediatric low-grade glioma as a mechanism of immune evasion independent of BRAF V600E mutational status. Low-grade gliomas that are unresectable and refractory to traditional therapy are associated with significant morbidity and continue to pose a treatment challenge. PD-1 pathway inhibitors may offer an alternative treatment approach. Clinical trials will be critical in determining whether PD-L1 expression indicates likely therapeutic benefit with immune checkpoint inhibitors.

Neoadjuvant Nivolumab for Patients With Resectable Merkel Cell Carcinoma in the CheckMate 358 Trial.

PURPOSE: Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer commonly driven by the Merkel cell polyomavirus (MCPyV). The programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) immunosuppressive pathway is often upregulated in MCC, and advanced metastatic MCC frequently responds to PD-1 blockade. We report what we believe to be the first trial of anti-PD-1 in the neoadjuvant setting for resectable MCC. METHODS: In the phase I/II CheckMate 358 study of virus-associated cancer types, patients with resectable MCC received nivolumab 240 mg intravenously on days 1 and 15. Surgery was planned on day 29. Tumor regression was assessed radiographically and microscopically. Tumor MCPyV status, PD-L1 expression, and tumor mutational burden (TMB) were assessed in pretreatment tumor biopsies. RESULTS: Thirty-nine patients with American Joint Committee on Cancer stage IIA-IV resectable MCC received ≥ 1 nivolumab dose. Three patients (7.7%) did not undergo surgery because of tumor progression (n = 1) or adverse events (n = 2). Any-grade treatment-related adverse events occurred in 18 patients (46.2%), and grade 3-4 events in 3 patients (7.7%), with no unexpected toxicities. Among 36 patients who underwent surgery, 17 (47.2%) achieved a pathologic complete response (pCR). Among 33 radiographically evaluable patients who underwent surgery, 18 (54.5%) had tumor reductions ≥ 30%. Responses were observed regardless of tumor MCPyV, PD-L1, or TMB status. At a median follow-up of 20.3 months, median recurrence-free survival (RFS) and overall survival were not reached. RFS significantly correlated with pCR and radiographic response at the time of surgery. No patient with a pCR had tumor relapse during observation. CONCLUSION: Nivolumab administered approximately 4 weeks before surgery in MCC was generally tolerable and induced pCRs and radiographic tumor regressions in approximately one half of treated patients. These early markers of response significantly predicted improved RFS. Additional investigation of these promising findings is warranted.

The Society for Immunotherapy of Cancer statement on best practices for multiplex immunohistochemistry (IHC) and immunofluorescence (IF) staining and validation.

OBJECTIVES: The interaction between the immune system and tumor cells is an important feature for the prognosis and treatment of cancer. Multiplex immunohistochemistry (mIHC) and multiplex immunofluorescence (mIF) analyses are emerging technologies that can be used to help quantify immune cell subsets, their functional state, and their spatial arrangement within the tumor microenvironment. METHODS: The Society for Immunotherapy of Cancer (SITC) convened a task force of pathologists and laboratory leaders from academic centers as well as experts from pharmaceutical and diagnostic companies to develop best practice guidelines for the optimization and validation of mIHC/mIF assays across platforms. RESULTS: Representative outputs and the advantages and disadvantages of mIHC/mIF approaches, such as multiplexed chromogenic IHC, multiplexed immunohistochemical consecutive staining on single slide, mIF (including multispectral approaches), tissue-based mass spectrometry, and digital spatial profiling are discussed. CONCLUSIONS: mIHC/mIF technologies are becoming standard tools for biomarker studies and are likely to enter routine clinical practice in the near future. Careful assay optimization and validation will help ensure outputs are robust and comparable across laboratories as well as potentially across mIHC/mIF platforms. Quantitative image analysis of mIHC/mIF output and data management considerations will be addressed in a complementary manuscript from this task force.

Multiple Immune-Suppressive Mechanisms in Fibrolamellar Carcinoma.

Fibrolamellar carcinoma (FLC) is a rare type of liver cancer that affects adolescents and young adults. The most effective treatment for FLC is surgical resection, but no standardized systemic therapy exists for patients with recurrent or unresectable FLC. As a first step to understand the immune microenvironment of FLC, we investigated targetable immune-checkpoint pathways, PD-1, PD-L1, B7-H3, IDO-1, and LAG3, in relation to CD8+ cytotoxic T-lymphocyte density. Thirty-two FLC tumor specimens were analyzed using IHC staining for PD-L1, CD8, PD-1, IDO, LAG3, and B7-H3. Sixty-three percent of FLC cases demonstrated membranous PD-L1 expression on tumor cells, and almost 70% of cases demonstrated PD-L1+ tumor-infiltrating lymphocytes and tumor-associated macrophages (TIL/TAM). Myeloid-derived cells appeared to be a major component of PD-L1+ tumor-infiltrating immune cells. Forty percent of the cases showed B7-H3 expression in the tumor zone, with 91% cases showing B7-H3 expression in TILs and TAMs. IDO and PD-1 expression was highest in the tumor interface zone. B7-H3 or IDO expression on tumor cells significantly correlated with higher CD8+ T-cell density. In conclusion, a high proportion of FLC cases showed robust expression of PD-1, PD-L1, B7-H3, and IDO in an adaptive immune-resistance pattern. Our findings provide further basis for targeting these different immune-checkpoint axes in FLC.

Intratumoral Adaptive Immunosuppression and Type 17 Immunity in Mismatch Repair Proficient Colorectal Tumors.

PURPOSE: Approximately 10% of patients with mismatch repair-proficient (MMRp) colorectal cancer showed clinical benefit to anti-PD-1 monotherapy (NCT01876511). We sought to identify biomarkers that delineate patients with immunoreactive colorectal cancer and to explore new combinatorial immunotherapy strategies that can impact MMRp colorectal cancer. EXPERIMENTAL DESIGN: We compared the expression of 44 selected immune-related genes in the primary colon tumor of 19 patients with metastatic colorectal cancer (mCRC) who responded (n = 13) versus those who did not (n = 6) to anti-PD-1 therapy (NCT01876511). We define a 10 gene-based immune signature that could distinguish responder from nonresponder. Resected colon specimens (n = 14) were used to validate the association of the predicted status (responder and nonresponder) with the immune-related gene expression, the phenotype, and the function of tumor-infiltrating lymphocytes freshly isolated from the same tumors. RESULTS: Although both IL17Low and IL17High immunoreactive MMRp colorectal cancers are associated with intratumor correlates of adaptive immunosuppression (CD8/IFNγ and PD-L1/IDO1 colocalization), only IL17Low MMRp tumors (3/14) have a tumor immune microenvironment (TiME) that resembles the TiME in primary colon tumors of patients with mCRC responsive to anti-PD-1 treatment. CONCLUSIONS: The detection of a preexisting antitumor immune response in MMRp colorectal cancer (immunoreactive MMRp colorectal cancer) is not sufficient to predict a clinical benefit to T-cell checkpoint inhibitors. Intratumoral IL17-mediated signaling may preclude responses to immunotherapy. Drugs targeting the IL17 signaling pathway are available in clinic, and their combination with T-cell checkpoint inhibitors could improve colorectal cancer immunotherapy.See related commentary by Willis et al., p. 5185.