Abstract 1057: PDX models of solid cancer express distinct cytokine profiles in humanized mice relating to their tumor infiltrating lymphocyte landscape

Model selection is one critical step in anti-cancer drug development. In the advent of immune modulatory compounds being part of most of the oncology drug development pipelines, the available preclinical models have to be characterized with respect to those assets. In the current study we analyzed 26 PDX models covering a broad range of solid cancer entities with regard to the phenotypic characteristics in a humanized environment. Well established PDX models from six different entities (breast, colon, renal, pancreatic, NSCL cancer and glioblastoma) were implanted subcutaneously into immune-compromised mice substituted with CD34+ hematopoietic stem cells (hu-mice). Tumor characterization included: tumor growth curves, take rates, human immune cell infiltrates of tumor (=TILs), peripheral blood, spleen and bone marrow (determined by flow cytometry, FC, and IHC) and secretion of human cytokines in murine serum (determined by cytokine array & Luminex based technology). Those data were compared to equivalent data-sets in non-humanized mice. The analysis of TILs revealed a large bandwidth of immune cell infiltration in the respective model ranging from 94% huCD45+ cells (renal cancer RXF 2773) to 3.54% huCD45+ (NSCLC LXFA 1041). Based on the percentage and of huCD4+ cell engraftment and the ratio of their subtypes (memory vs naive) in untreated tumors the models were grouped into high (=hot), medium and low (=cold) infiltrated tumor models. The infiltration rate was stable across different experiments and specific for one distinct model. IHC analyses confirmed infiltration rates in tumor tissue determined by FC for CD45+, CD4+ and CD8+ cells. Furthermore, the models previously defined as “hot” or “cold” expressed distinct cytokine profiles in serum of tumor bearing mice. Amongst other cytokines, hot tumors secreted high levels of IL-17A, IL-18 BPa, MMP-9, Osteopontin, CD31, TIM-3 and YKL-40. In contrast, levels of GDF-15 and Lipocalin-2 were down regulated in those models compared to their cold counterpart. Of note, neither the amount nor the composition of human immune cell populations in peripheral blood of those mice was suitable to conclude on the amount of TILs in the respective model. Further validation of the cytokine profiles using immune modulating compounds on hot as well as cold PDX models are currently underway. Taken together, the characterization of PDX models with respect to their TIL composition facilitates model selection for innovative drugs in the immune-oncology field. The possibility to discriminate hot vs cold tumors by a minimal-invasive method like serum analysis of cytokine expression profile as potential biomarker will help to characterize the complete PDX collection of more than 500 models but will as well serve as additional read-out in preclinical I-O studies. Citation Format: Eva Oswald, Dorothee Lenhard, Stefanie Schmitt, Anna Edinger, Anne Lohr, Volker Knauff, Anke Behnke, Anne-Lise Peille, Julia Schuler. PDX models of solid cancer express distinct cytokine profiles in humanized mice relating to their tumor infiltrating lymphocyte landscape [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1057.