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Ex vivo patient-derived tumor slices (PDTS) are currently limited by short-term viability in culture. Here, we show how bioengineered hydrogels enable the identification of key matrix parameters that significantly enhance PDTS viability compared to conventional culture systems. As demonstrated using single-cell RNA sequencing and high-dimensional flow cytometry, hydrogel-embedded PDTS tightly preserved cancer, cancer-associated fibroblast, and various immune cell populations and subpopulations in the corresponding original tumor. Cell-cell communication networks within the tumor microenvironment, including immune checkpoint ligand-receptor interactions, were also maintained. Remarkably, our results from a co-clinical trial suggest hydrogel-embedded PDTS may predict sensitivity to immune checkpoint inhibitors (ICIs) in head and neck cancer patients. Further, we show how these longer term-cultured tumor explants uniquely enable the sampling and detection of temporal evolution in molecular readouts when treated with ICIs. By preserving the compositional heterogeneity and complexity of patient tumors, hydrogel-embedded PDTS provide a valuable tool to facilitate experiments targeting the tumor microenvironment. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) is the sixth most common cancer and the second leading cause of cancer worldwide. Despite approvals of several therapeutics to treat advanced HCC in the past few years, the impact of anti-angiogenic treatment on HCC patient overall survival remains limited. This suggests there may be alternative, perfusion-independent roles of endothelial cells that support tumor progression. Thus, we leveraged a well-defined hydrogel system to establish co-culture models to mimic and characterize the angiocrine crosstalk between HCC and endothelial cells in vitro. Co-cultures of HCC cell lines or patient-derived xenograft organoids with endothelial cells exhibited the upregulation of MCP-1, IL-8 and CXCL16, suggesting that the HCC-endothelial interactions established in our models recapitulate known angiocrine signaling. Additionally, by subjecting co-cultures and mono-cultures to RNA sequencing, transcriptomic analysis revealed an upregulation in the expression of genes associated with tumor necrosis factor (TNF) signaling, such as that of chemokines, suggesting that endothelial cells induce HCC cells to generate an inflammatory microenvironment by recruiting immune cells. Finally, HCC-endothelial angiocrine crosstalk in the co-culture models polarized macrophages towards a pro-inflammatory and pro-angiogenic phenotype, paralleling a tumor-associated macrophage subset previously reported in HCC. Together, these findings suggest that these HCC-endothelial co-culture models may serve as important models to understand and target the interplay between angiogenesis and the immune milieu. [ABSTRACT FROM AUTHOR]