292 Ex vivo profiling of PD-1 blockade using an organotypic tissue slice model in solid tumors

BackgroundTumor explant models provide a powerful ex vivo tool to evaluate complex biological mechanisms in a controlled environment. Ex vivo models retain much of the original tumor biology, heterogeneity, and tumor microenvironment, and therefore provide a useful preclinical platform and functional approach to assess drug responses rapidly and directly.MethodsTo explore mechanisms of resistance to cancer immunotherapy, we established an organotypic tissue slice Air-Liquid Interface (ALI) ex vivo system utilizing surgical tumor specimens from patients to assess the impact of the clinically utilized anti-PD-1 antibody nivolumab (OPDIVO). In the present study, we built a real-world patient cohort comprised of six tumor types: non-small cell lung cancer, melanoma, pancreatic ductal adenocarcinoma, breast cancer, prostate cancer, and colorectal cancer. We assessed tissue morphology, histology, PD-L1 IHC (CPS and TPS), CD8 T cell topology, proliferation in the tumor and stromal compartments, and secretome profiling.ResultsOur tumor slice model highly recapitulated features of the original tumor, including tumor architecture, immune phenotypes, and the prognostic markers. To identify responses to aPD-1 treatment, we compared baseline values for the cultured tumor slices with values at different timepoints post treatment. Secretome profiling of tissue explant supernatants using a panel of 94 analytes, revealed alterations to cytokines produced in the tumor microenvironment in response to aPD-1 treatment. We found that soluble expression patterns were associated with T-cell patterns (inflamed, excluded and desert) and PD-L1 score (CPS and TPS) in tumor tissues. These cytokines mediate critical functions across the immune cell cycle. Ongoing efforts to characterize T cell activation, exhaustion, tumor intrinsic responses and microenvironment composition using Imaging Mass Cytometry will be presented.ConclusionsIn this study, we demonstrated the feasibility of using fresh, surgically resected human tumors to test aPD-1 responses in an ex vivo system. Further, this model system has the potential to drive discovery and translational efforts by evaluating mechanisms of resistance to cancer immunotherapy and evaluate new single agent or combination therapies in the ex vivo setting.

Nivolumab Reduces PD1 Expression and Alters Density and Proliferation of Tumor Infiltrating Immune Cells in a Tissue Slice Culture Model of Renal Cell Carcinoma

Background: In the treatment of clear cell renal cell carcinoma (ccRCC), nivolumab is an established component of the first-line therapy with a favorable impact on progression free survival and overall survival. However, treatment-related adverse effects occur and, to date, there is no approved predictive biomarker for patient stratification. Thus, the aim of this study was to establish an ex vivo tissue slice culture model of ccRCC and to elucidate the impact of nivolumab on tumor infiltrating immune cells. Methods: Fresh tumor tissue of ccRCC was treated with the immune checkpoint inhibitor nivolumab using ex vivo tissue slice culture (TSC). After cultivation, tissue slices were formalin-fixed, immunohistochemically stained and analyzed via digital image analysis. Results: The TSC model was shown to be suitable for ex vivo pharmacological experiments on intratumoral immune cells in ccRCC. PD1 expression on tumor infiltrating immune cells was dose-dependently reduced after nivolumab treatment (p < 0.01), whereas density and proliferation of tumor infiltrating T-cells and cytotoxic T-cells were inter-individually altered with a remarkable variability. Tumor cell proliferation was not affected by nivolumab. Conclusions: This study could demonstrate nivolumab-dependent effects on PD1 expression and tumor infiltrating T-cells in TSC of ccRCC. This is in line with results from other scientific studies about changes in immune cell proliferation in peripheral blood in response to nivolumab. Thus, TSC of ccRCC could be a further step to personalized medicine in terms of testing the response of individual patients to nivolumab.

Glioblastoma Tissue Slice Tandem-Cultures for Quantitative Evaluation of Inhibitory Effects on Invasion and Growth

Glioblastomas (GBMs) are the most malignant brain tumors and are essentially incurable even after extensive surgery, radiotherapy, and chemotherapy, mainly because of extensive infiltration of tumor cells into the adjacent normal tissue. Thus, the evaluation of novel drugs in malignant glioma treatment requires sophisticated ex vivo models that approach the authentic interplay between tumor and host environment while avoiding extensive in vivo studies in animals. This paper describes the standardized setup of an organotypic brain tissue slice tandem-culture system, comprising of normal brain tissue from adult mice and tumor tissue from human glioblastoma xenografts, and explore its utility for assessing inhibitory effects of test drugs. The microscopic analysis of vertical sections of the slice tandem-cultures allows for the simultaneous assessment of (i) the invasive potential of single cells or cell aggregates and (ii) the space occupying growth of the bulk tumor mass, both contributing to malignant tumor progression. The comparison of tissue slice co-cultures with spheroids vs. tissue slice tandem-cultures using tumor xenograft slices demonstrates advantages of the xenograft tandem approach. The direct and facile application of test drugs is shown to exert inhibitory effects on bulk tumor growth and/or tumor cell invasion, and allows their precise quantitation. In conclusion, we describe a straightforward ex vivo system mimicking the in vivo situation of the tumor mass and the normal brain in GBM patients. It reduces animal studies and allows for the direct and reproducible application of test drugs and the precise quantitation of their effects on the bulk tumor mass and on the tumor’s invasive properties.