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Background: Inflammatory breast cancer (IBC) is a rare but aggressive tumor type accounting for up to 10% of breast cancer deaths. One-third of IBCs express high PD-L1 that can be targeted by atezolizumab (Az). MEK inhibitor cobimetinib (Co) not only inhibits the RAS-MAPK pathway but can further enhance immune-mediated killing. Thus, we hypothesize that Az+Co may enhance the efficacy of chemotherapy in metastatic IBC (mIBC). We opened a trial to test this hypothesis with a comprehensive multi-omics biomarker assessment. Patients and Methods: In a single-center, open-label phase II study, cohort 1 received one cycle of Az+ Co, followed by four cycles of Az+Co+eribulin (E) to induce a maximum clinical response, followed by Az+Co maintenance. Pre and Post one cycle of Az+Co tumors were collected for immunohistochemistry (IHC), multiplex immunofluorescence (mIF), whole-exome sequencing (WES), and RNA sequencing (RNAseq). Blood was collected for circulating tumor DNA (ctDNA). Results: Seventeen patients were enrolled in cohort 1. Seven had PR, and three had SD as the best responses. Fourteen had pre, and six had pre/post tumors. The levels of PD-L1 expression at pre/post were not associated with responses. WES revealed the median tumor mutation burden at pre- was 9mt/Mb. More than 50% had TP53 and PI3K pathway mutations at pre. RTK-RAS and Notch pathways were altered in 4/9 cases. PRDM9 and DPY19L2 single-gene mutations were commonly noted in pre. No cancer-associated gene aberration, including potential biomarkers of anti-PDL1 agent response was associated with clinical outcomes. Transcriptomic gene set enrichment analysis demonstrated a greater degree of TNFa and TGFb signaling, Oxphos, angiogenesis, and epithelial-to-mesenchymal transition (EMT) processes in tumors from patients with poor response. Immune profiling by RNAseq revealed two responders to have elevated effector memory T cells, NK T cells, myeloid dendritic cells, and M1 macrophage signatures in pre-samples, but post-samples were not available. mIF confirmed a higher frequency of NK-T cells. The ctDNA analysis from serially collected blood samples is ongoing. Discussion: In this comprehensive multi-omics analysis of pre-and-post-Az+Co, we observed several novel findings, while conventional biomarkers for Az and Co did not correlate with clinical responses. EMT, Oxphos, Notch, and chronic inflammation pathways, which are not previously well reported, were observed in this IBC cohort. These markers warrant further validation to see if they carry significance as therapeutic targets in IBC. Citation Format: Bora Lim, Angela Alexander, Jie S. Willey, Huiming Sun, Suyu Liu, Anisha B. Patel, Edwin Roger Parra, Cara Haymaker, Luisa Solis Soto, Alejandra Serrano, Baohua Sun, Cibelle Freitas Pinto Lima, Auriole Tamegnon, Renganayaki K. Pandurengan, Dzifa Douse, Jessica Lan, Luthra Raja, Randy Chu, Mark Knafl, Scott E. Woodman, Haifeng Zhu, Katja Shulze, Katherine Fedenko, Walter Darbonne, Naoto T. Ueno, Vicente Valero. Biomarker analysis: Multi-omics elucidation of Cohort 1 from a phase II study of a triple combination of Atezolizumab + cobimetinib + eribulin in patients with metastatic inflammatory breast cancer. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-08-19.

Background Study of the geographic distribution of cellular populations and their interaction with malignant cells in non-small cell lung cancer (NSCLC) is essential to understand the roles of cellular populations and potentially design new therapeutic approaches. Material and Methods We studied 225 formalin-fixed, paraffin-embedded tumor tissue samples from patients with stage I-III NSCLC—142 adenocarcinomas and 83 squamous cell carcinomas—placed in tissue microarrays. Twenty-three markers were used, including T-cell, B-cell, immune checkpoint, and myeloid cell markers, placed in five multiplex immunofluorescence panels. We used dimensional data reduction and cellular spatial distribution to identify cell phenotypes and their cellular distribution across panels. In addition, we analyzed associations between cellular spatial distribution patterns and clinicopathologic variables, tumor mutational status, and outcomes. Results Overall, we observed two patterns of cellular distribution—unmixed and mixed—related to T-cells, B-cells, granulocytic cells, and macrophages, and we detected various cellular interactions between malignant and immunosuppressive cells and various associations between cell distribution and clinicopathologic characteristics. Cellular distribution patterns and the distance from various cell phenotypes to malignant cells were associated with recurrence-free survival and overall survival in univariate and multivariable analysis. Conclusions Diverse populations of tumor cells and tumor-associated immune cell phenotypes can be present in NSCLC samples. Spatial distribution is a new tool to better understand the tumor microenvironment and help select therapeutic interventions.

Immune profiling is becoming a vital tool for identifying predictive and prognostic markers for translational studies. The study of the tumor microenvironment (TME) in paraffin tumor tissues such as malignant pleural mesothelioma (MPM) could yield insights to actionable targets to improve patient outcome. Here, we optimized and tested a new immune-profiling method to characterize immune cell phenotypes in paraffin tissues and explore the co-localization and spatial distribution between the immune cells within the TME and the stromal or tumor compartments. Tonsil tissues and tissue microarray (TMA) were used to optimize an automated nine-color multiplex immunofluorescence (mIF) panel to study the TME using eight antibodies: PD-L1, PD-1, CD3, CD8, Foxp3, CD68, KI67, and pancytokeratin. To explore the potential role of the cells into the TME with this mIF panel we applied this panel in twelve MPM cases to assess the multiple cell phenotypes obtained from the image analysis and well as their spatial distribution in this cohort. We successful optimized and applied an automated nine-color mIF panel to explore a small set of MPM cases. Image analysis showed a high degree of cell phenotype diversity with immunosuppression patterns in the TME of the MPM cases. Mapping the geographic cell phenotype distribution in the TME, we were able to identify two distinct, complex immune landscapes characterized by specific patterns of cellular distribution as well as cell phenotype interactions with malignant cells. Successful we showed the optimization and reproducibility of our mIF panel and their incorporation for comprehensive TME immune profiling into translational studies that could refine our ability to correlate immunologic phenotypes with specific patterns of cells distribution and distance analysis. Overall, this will improve our ability to understand the behavior of cells within the TME and predict new treatment strategies to improve patient outcome.

BackgroundHead and Neck Squamous Cell Carcinoma is the 8th leading cancer worldwide and it is associated with significant morbidity and mortality.1 2 Tumor microenvironment (TME) is dynamic and it plays an important role in head and neck carcinogenesis.3 4 Cytotoxic T-cells, immune checkpoint molecules such as programmed cell death 1 (PD-1), its ligand (PD-L1), and other checkpoints molecules have been described in these tumors.1 3 This study aimed to characterize the TME of oral squamous cell carcinoma (OSCC) and compare with their pathology features.MethodsFour microns thickness consecutives slides from representative OSCC (N=46) cases were stained and analyzed using 11 biomarkers (CK, CD3, CD8, CD68, PD1, PDL1, LAG3, TIM3, ICOS, VISTA, OX40) placed in two multiplex immunofluorescence panels to characterize the TME. For image analysis, the samples were divided in tumor, stroma and peritumoral compartment. Co-expression of markers (cell phenotypes) where analyzed as densities by mm2 in each compartment. For PD-L1 expression by malignant cells (CK+PD-L1+) we set up a cutoff of positive case as ≥ than 1%. Cell phenotypes were correlated with anatomopathological information retrieved from records such as tumor size, margin status, stage and perineural, lymphovascular, and bone invasion among others. Statistical analyses and plots were performed using SPSS and Graphpad prism8 software packages.ResultsWe found significant higher cell density for CK+PDL1+ (P= 0.038), CD3+PDL1+ (P= 0.027), CD3+CD8+PDL1+ (P=0.040) in female patients compared with the male population. Interestingly, smaller tumor size (≤ median, 25mm) showed higher densities of CD3+ (P= 0.006), CD3+CD8+ (P= 0.007), CD3+PDL1+ (P= 0.037), CD3+CD8+PDL1+ (P= 0.016), CD3+ICOS+ (P= 0.036), CD3+VISTA+ (P= 0.001), CD68+ (P= 0.001) and CD68+PD-L1+ (P= 0.008) than large tumors. Additionally, high cell density CD3+OX40+ (P= 0.011) was observed in tumors without margin invasion and high cell density for macrophages CD68+ (p= 0.005) in tumors without bone invasion. In ulcerative and infiltrative tumor pattern we observed higher cell density of CD3+PDL1+ (P= 0.020), CD3+CD8+PDL1+ (P=0.006) and CD3+OX40+ (P= 0.022) than non-ulcerate and no infiltrative pattern. Lastly, 58.7% of cases were PDL1+.ConclusionsOur findings of a diminished immune response in larger tumors might be correlated to their potential role in tumor aggressiveness and progression. Furthermore, high cell density of macrophages on tumor bone invasion may suggest an immune suppressive M2 response supported by the presence of PDL1+ expression. All these results can be the first approach for the development of a treatment based of immune interception.AcknowledgementsThis study was supported by a strategic alliance between the Translational Molecular Pathology-Immunoprofiling las (TMP-IL) at the Department Translational Molecular Pathology, the University of Texas MD Anderson Cancer Center and the Université Claude Bernard Lyon, Centre de Recherche en Cancérologie de Lyon and the Department of Translational Medicine, Centre Léon Bérard, Lyon, France. The authors would acknowledge ITMO Cancer 2020, ”Formation à la Recherche Fondamentale et Translationnelle en Cancérologie” (JB); CLARA 2020 ”Soutien à la mobilité des jeunes chercheurs en oncologie, N° CVPPRCAN000198” (JB); Fondation de France 2020 ”Aide à la mobilité international de médecins et pharmaciens, N° 00112162” (JB); Ligue contre le cancer 2021, comité de Saône-et-Loire (PS); 2017-INCa-DGOS-Inserm_12563: INCa SIRIC-LYriCAN INCa-DGOS-Inserm_12563 (PS)ReferencesCohen EEW, Bell RB, Bifulco CB, Burtness B, Gillison ML, Harrington KJ, et al. The society for immunotherapy of cancer consensus statement on immunotherapy for the treatment of squamous cell carcinoma of the head and neck (HNSCC). J Immunother Cancer 2019;7(1):184. Bouaoud J, Foy JP, Tortereau A, Michon L, Lavergne V, Gadot N, et al. Early changes in the immune microenvironment of oral potentially malignant disorders reveal an unexpected association of M2 macrophages with oral cancer free survival. Oncoimmunology 2021;10(1):1944554.Mei Z, Huang J, Qiao B, Lam AK. Immune checkpoint pathways in immunotherapy for head and neck squamous cell carcinoma. Int J Oral Sci 2020;12(1):16.Yokota T, Homma A, Kiyota N, Tahara M, Hanai N, Asakage T, et al. Immunotherapy for squamous cell carcinoma of the head and neck. Jpn J Clin Oncol 2020;50(10):1089–96.Ethics ApprovalThe study was conducted in accordance with all applicable laws, rules, and requests of French and European government authorities. Written informed consent was obtained from all patients and the study was approved by the Centre Leon Bérard institutional review board (Lyon, France). Samples were obtained from the CRB Centre Léon Bérard (n°BB-0033-00050) which is quality certified according NFS96-900 French standard and ISO 9001 for clinical trials.

Multiplex immunofluorescence (mIF) has arisen as an important tool for immuno-profiling tumor tissues. We updated our manual protocol into an automated protocol that allows the use of up to seven markers in five mIF panels to apply to formalin-fixed paraffin-embedded tumor tissues. Using a tyramide signal amplification system, we optimized five mIF panels that included cytokeratin to characterize malignant cells (MCs), immune checkpoint markers (i.e., PD-L1, B7-H3, B7-H4, IDO-1, VISTA, LAG3, ICOS, TIM3, and OX40), tumor-infiltrating lymphocytic markers (i.e., CD3, CD8, CD45RO, granzyme B, PD-1, and FOXP3), and markers to characterize myeloid-derived suppressor cells (i.e., CD68, CD66b, CD14, CD33, Arg-1, and CD11b). To determine analytical reproducibility and the impact of those panels for immuno-profiling tumor tissues, we performed an exploratory analysis in a set of non–small cell lung cancer (NSCLC) samples. The slides were scanned, and the different cell phenotypes were quantified by simultaneous co-localizations with the markers using image analysis software. Comparison between the time points of staining showed high analytical reproducibility. The analysis of NSCLC cases showed an immunosuppressive microenvironment with PD-L1/PD-1 expression as a predominant axis. Interestingly, high density of MCs expressing B7-H4 was correlated with recurrence. Unexpectedly, MCs expressing OX40 were also detected, and those cells were a closer distance to CD3+T-cells than were MCs expressing other immune checkpoints. Two different cellular patterns of spatial distribution were determined according the CD3 distribution, and the predominant pattern was related with active immunosuppressive interaction with MCs. Our study shows that these five mIF panels can identify multiple targets in a single cell with high reproducibility. The study of different cell populations and their spatial relationship can open new ideas for therapeutic approaches.

In contrast to the curative effect of allogenic stem cell transplantation in acute myeloid leukemia via T cell activity, only modest responses are achieved with checkpoint-blockade therapy, which might be explained by T cell phenotypes and T cell receptor (TCR) repertoires. Here, we show by paired single-cell RNA analysis and TCR repertoire profiling of bone marrow cells in relapsed/refractory acute myeloid leukemia patients pre/post azacytidine+nivolumab treatment that the disease-related T cell subsets are highly heterogeneous, and their abundance changes following PD-1 blockade-based treatment. TCR repertoires expand and primarily emerge from CD8+ cells in patients responding to treatment or having a stable disease, while TCR repertoires contract in therapy-resistant patients. Trajectory analysis reveals a continuum of CD8+ T cell phenotypes, characterized by differential expression of granzyme B and a bone marrow-residing memory CD8+ T cell subset, in which a population with stem-like properties expressing granzyme K is enriched in responders. Chromosome 7/7q loss, on the other hand, is a cancer-intrinsic genomic marker of PD-1 blockade resistance in AML. In summary, our study reveals that adaptive T cell plasticity and genomic alterations determine responses to PD-1 blockade in acute myeloid leukemia., The response rate of relapsed/refractory acute myeloid leukemia patients to PD-1 checkpoint blockade is low and unpredictable. Authors here show by single cell RNA sequencing, T cell receptor profiling and genomic analysis that the phenotypes and repertoire of CD8 + T cells and loss of chromosome 7/7q are important determinants of response.

In the development of a multiplex immunofluorescence (IF) platform and the optimization and validation of new multiplex IF panels using a tyramide signal amplification system, several technical requirements are important for high-quality staining, analysis, and results. The aim of this review is to discuss the basic requirements for performing multiplex IF tyramide signal amplification (TSA) in formalin-fixed, paraffin-embedded cancer tissues to support translational oncology research. Our laboratory has stained approximately 4000 formalin-fixed, paraffin-embedded tumor samples using the multiplex IF TSA system for immune profiling of several labeled biomarkers in a single slide to elucidate cancer biology at a protein level and identify therapeutic targets and biomarkers. By analyzing several proteins in thousands of cells on a single slide, this technique provides a systems-level view of various processes in various tumor tissues. Although this technology shows high flexibility in cancer studies, it presents several challenges when applied to study different histology cancers. Our experience shows that adequate antibody validation, staining optimization, analysis strategies, and data generation are important steps for generating quality results. Tissue management, fixation procedures, storage, and cutting can also affect the results of the assay and must be standardized. Overall, this method is reliable for supporting translational research given a precise, step-by-step approach.

BackgroundOral squamous cell carcinomas (OSCC) prognosis remains poor. While AJCC TNM 8th edition has slightly improved patients‘ stratification with regard to prognostic, innovative approaches to are still needed. As in other tumor types, tumor immune microenvironment (TiME) might represent an opportunity to improve prognostic assessment.MethodsTiME landscape of 47 HPV-negative OSCC was analyzed using multiplex immunofluorescence (mIF). Markers for tumor cells (PanCK), tumor infiltrating lymphocytes (CD3, CD8), macrophages (CD68), inhibitory (PD-1, PD-L1, TIM3, LAG3, VISTA) or stimulatory (OX40, ICOS) immune checkpoints (ICP) were studied. Regions of interest (ROI), 5 in the tumor core and 5 at the invasion front, were subjected to cell markers identification and quantification (scoring) as well as tissue compartmentalization to divide them in tumor-epithelial and tumor-stroma compartments, respectively. A total of 20 cell phenotypes were defined based on previous work (CK+, CK+PD-L1+, CD3+, CD3+CD8+, CD3+PD-1+, CD3+CD8+PD-1+, CD3+PD-L1+, CD3+CD8+PD-L1+, CD3+PD-L1+PD-1+, CD3+CD8+PD-L1+PD-1+, CD68+, CD68+PD-L1+, CK+OX40+, CD3+VISTA+, CD3+ICOS+, CD3+LAG3+, CD3+OX-40+, CD3+TIM3+). Results were correlated with clinical features including disease-specific survival (DSS) using the Kaplan-Meier method and a multivariate Cox model. A multivariate general linear model (GLM) was built to test the specific association of each variable with a given cell density by correcting the possible confusion due to other variables.ResultsImmune cells densities were significantly higher overall in the stroma. The intra-tumor stroma showed a significant enrichment of in CD3+PD-1+ T cells compared to peri-tumor stroma. None of the clinical or pathological (resection margin, tumor stage, lymph node invasion, perineural invasion) was significantly associated with DSS. In contrast, the following cell phenotypes in the tumor invasion front were strongly associated with a poor DSS, including CD3+PD-L1+ (P-value= 0.004), CD3+PD1+PD-L1+ (P-value= 0.02) and CD3+OX40+ (P-value= 0.02) T cells as well as CD3+CD8+PD-1+ (P-value= 0.048), CD3+CD8+PD-L1+ (P-value= 0.008) and CD3+CD8+PD1+PD-L1+ (P-value= 0.01) cytotoxic T cells. In the tumor core, CD68+PD-L1- macrophages (P-value= 0.06) were marginally associated with better DSS. Using a GLM, we found that tumor from smoker-drinker patients and/or with pN+, were significantly more infiltrated by PD-1- and/or PD-L1-positive immune cells. On the other hand, floor of mouth and gingiva-mandibular OSCC were significantly less infiltrated than others.ConclusionsThe prognostic value of PD-1+ and/or PD-L1+ cells in the invasion front of resected OSCC was remarkable, underlying the importance of this area when studying the TiME. Incorporating TiME analysis in the invasion front may improve prognostic evaluation of patients treated for OSCC, especially in the context of immunotherapy.AcknowledgementsThis study was supported by a strategic alliance between the Translational Molecular Pathology-Immunoprofiling las (TMP-IL) at the Department Translational Molecular Pathology, the University of Texas MD Anderson Cancer Center and the Université Claude Bernard Lyon, Centre de Recherche en Cancérologie de Lyon and the Department of Translational Medicine, Centre Léon Bérard, Lyon, France. The authors would acknowledge ITMO Cancer 2020, ”Formation à la Recherche Fondamentale et Translationnelle en Cancérologie” (JB); CLARA 2020 ”Soutien à la mobilité des jeunes chercheurs en oncologie, N° CVPPRCAN000198” (JB); Fondation de France 2020 ”Aide à la mobilité international de médecins et pharmaciens, N° 00112162” (JB); Ligue contre le cancer 2021, comité de Saône-et-Loire (PS); 2017-INCa-DGOS-Inserm_12563: INCa SIRIC-LYriCAN INCa-DGOS-Inserm_12563 (PS)Ethics ApprovalThe study was conducted in accordance with all applicable laws, rules, and requests of French and European government authorities. Written informed consent was obtained from all patients and the study was approved by the Centre Leon Bérard institutional review board (Lyon, France). Samples were obtained from the CRB Centre Léon Bérard (n°BB-0033-00050) which is quality certified according NFS96-900 French standard and ISO 9001 for clinical trials.ConsentWritten informed consent was obtained from all patients and the study was approved by the Centre Leon Bérard institutional review board (Lyon, France)

Introduction: Tertiary lymphoid structures (TLS) are ectopic lymphoid structures organized in a nodular pattern secondary to chronic inflammation. The presence of TLS has been associated with efficacious response to immune checkpoint blockade in a wide array of tumor types, including Non-Small Cell Lung Carcinoma (NSCLC). At early stages of NSCLC, TLS are observed in up to 70% of primary tumors where they are also associated with effective anti-tumor immune-responses and response to anti-PD-1 therapy. Despite complete surgical resection, however, up to 50% of patients with early stage NSCLC will eventually relapse. A systematic histomorphologic analysis of TLS and their association with relapse has not been well characterized. Design: Serial sections from Formalin-Fixed Paraffin-Embedded (FFPE) tissue specimens from 33 patients with stage I NSCLC were obtained (23 adenocarcinomas and 10 squamous cell carcinomas). Slides were stained with hematoxylin and eosin (H&E), immunohistochemistry for Vimentin, and 2 multiplex immunofluorescence (mIF) panels (Panel 1: cytokeratin (CK), CD3, CD8, CD68, PD-1, PD-L1 and DAPI Panel 2: CK, CD3 CD8, CD45RO, FOXP3, Granzyme B and DAPI). TLS were classified based on the H&E and Vimentin analysis into lymphoid aggregates (LA), immature TLS (iTLS), and mature TLS (mTLS). Morphometric analysis (number, area, and distance to nearest malignant cell) of intratumoral (IT) and peritumoral (PT) TLS was performed. mIF slides were scanned and IT representative areas were selected for cell densities and percentage quantification of immune-phenotypes. Morphometric analysis of TLSs was correlated with clinical outcomes, and tumor infiltrating immune cells. Results: Patients who recurred had fewer IT mTLS (1.8 vs 6; p=0.02) and smaller area of mTLS (64541.7μm2 vs 149870.5 μm2; p=0.004) compared with patients who did not recurr.The cell density of IT antigen-experienced cytotoxic T-lymphocytes (CTLs), regulatory T-cells, memory CTLs, and memory CTLs expressing FOXP3 were inversely correlated with the mTLS area (r=-0.6, p≤0.02). Antigen-experienced CTLs (r=-0.61; p≤0.05) and non-CTLs (r=-0.63; p≤0.05) were inversely correlated with the number of IT mTLS. Conclusion: Detailed morphometric analysis of mTLS offers relevant prognostic information for recurrence at stage I of NSCLC. mTLSs are associated with reduced IT infiltration by PD-1+ TILs. Taken together, germinal center development in mTLSs might convey a protective immune response due to immuno-dominant neoantigen presentation. Supported in part by CPRIT RP160668 grant and UT Lung SPORE. Citation Format: Rossana Natalia Lazcano Segura, Andre Catao, Luisa M. Solis, Mei Jiang, Auriole Tamegnon, Junya Fujimoto, Jaime Rodriguez-Canales, Chi-Wan B. Chow, Carmen Behrens, Neda Kalhor, Annika Weissferdt, John Heymach, Stephen Swisher, Boris Sepesi, Jack Lee, Cesar Moran, Andrew Futreal, Jianjun Zhang, Edwin R. Parra, Ignacio I. Wistuba, Michael T. Tetzlaff, Alejandro Francisco-Cruz. Tertiary lymphoid structures features associate with outcome in non-small cell lung carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 399.

Introduction: Imaging mass cytometry (IMC) enables highly multiplexed assessment of more than 30 proteins at a time for the quantification of cell phenotypes within the tumor microenvironment of formaldehyde fixed-paraffin embedded (FFPE) tumor tissue. This methodology provides a deep understanding of the immune-contexture while preserving their spatial information in regards to malignant cells. We report a detailed workflow for optimization of a 27-plex immune-oncology (IO) panel, immune-phenotyping, and spatial analysis of tumor tissue. Methods: IO-panel includes 27 antibodies targeting lymphoid (CD3e, CD4, CD8a, CD19, CD45RO, LAG3, ICOS, Granzyme-B), myeloid (CD11b, CD14, CD33, CD68, CSF1R, IDO-1), immune-regulatory (HLA-DR, OX-40, VISTA, TIM-3, CD73, B7-H3), epithelial (Cytokeratin), proliferative (Ki-67), and constitutive (GAPDH, NaKATPase, Vimentin, aSMA, Histone H3) markers that were selected by singlet automated chromogenic immunohistochemistry (IHC) staining. BSA-free formulation from the same clones of antibodies were isotope-metal conjugated and manual indirect immunofluorescence (IF) staining was used to confirm the stability of metal-tagged antibodies. The optimization by singlet-IF and multiplexed-IMC staining was performed with normal and malignant tissues (4mm core TMA with tonsil, placenta, prostate, breast carcinoma, ovarian carcinoma, and endometrioid carcinoma tissues). All images from IHC (HALO software), indirect IF (InForm software), and IMC (MCD viewer software) slides were evaluated by two pathologists. Cell densities and spatial analysis of a breast carcinoma core was performed using HALO software. Results: All antibodies included in the panel were individually optimized by IHC under the same protocol conditions. A significant correlation of optimal antibody concentrations where observed across the different staining techniques (IHC vs IF, r=0.51; IHC vs IMC, r= 0.54; IF vs IMC, r=0.992; all p values Conclusions: IMC is a powerful platform for highly multiplexed detection of protein and cell phenotypes quantification in FFPE samples. Our developed IMC panel and digital image analysis of tissues allow the quantification of immune cells and spatial analysis of the tumor tissue microenvironment. Citation Format: Pedro Rocha, Luisa Solis, Edwin Parra, Ou Shi, Barbara Mino, Vidya C. Sinha, Amanda Rinkenbaugh, Auriole Tamegnon, Mak Duncan, Wei Lu, Mei Jiang, Lakshimi Kakarala, Jared K. Burks, Helen Piwnica-Worms, Cara Haymacker, Michael Teztlaff, Ignacio Wistuba, Alejandro Francisco-Cruz. Immuno-oncology panel optimization for imaging mass cytometry and digital image analysis of tumor tissues [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2679.