Purpose: Epithelial neoplasms of the appendix are difficult to study preclinically given their low incidence, frequent mucinous histology, and absence of a comparable organ in mice for disease modeling. Although surgery is an effective treatment for localized disease, metastatic disease has a poor prognosis as existing therapeutics borrowed from colorectal cancer have limited efficacy. Recent studies reveal that appendiceal cancer has a genomic landscape distinct from colorectal cancer and thus preclinical models to study this disease are a significant unmet need. Experimental Design: We adopted an ex vivo slice model that permits the study of cellular interactions within the tumor microenvironment. Mucinous carcinomatosis peritonei specimens obtained at surgical resection were cutoff using a vibratome to make 150-μm slices cultured in media. Results: Slice cultures were viable and maintained their cellular composition regarding the proportion of epithelial, immune cells, and fibroblasts over 7 days. Within donor specimens, we identified a prominent and diverse immune landscape and calcium imaging confirmed that immune cells were functional for 7 days. Given the diverse immune landscape, we treated slices with TAK981, an inhibitor of SUMOylation with known immunomodulatory functions, in early-phase clinical trials. In 5 of 6 donor samples, TAK981-treated slices cultures had reduced viability, and regulatory T cells (Treg). These data were consistent with TAK981 activity in purified Tregs using an in vitro murine model. Conclusions: This study demonstrates an approach to study appendiceal cancer therapeutics and pathobiology in a preclinical setting. These methods may be broadly applicable to the study of other malignancies.

Improvement of outcome in patients with pancreatic ductal adenocarcinoma (PDAC) requires exploration of novel therapeutic targets. Thus far, most studies of PDAC therapies, including those inhibiting small ubiquitin-like modifications (SUMOylation), have focused on PDAC epithelial cell biology, yet SUMOylation occurs in a variety of cell types. The mechanisms by which SUMOylation impacts PDAC in the context of its tumor microenvironment are poorly understood. We used clinically relevant orthotopic PDAC mouse models to investigate the effect of SUMOylation inhibition using a specific, clinical-stage compound, TAK-981. In contrast to its inhibition of PDAC cell proliferation in vitro, the survival benefit conferred by TAK-981 in vivo is dependent on the presence of T cells, suggesting that induction of adaptive antitumor immunity is an important antitumor effect of SUMOylation inhibition in vivo. To understand how this adaptive antitumor immunity is promoted, we investigated how SUMOylation inhibition in vivo alters major cell types/subtypes and their communications in the PDAC tumor microenvironment by performing transcriptomic analyses at single-cell resolution, which allowed mapping of cells in our orthotopic mouse model to cells in human PDAC tumors based on gene expression profiles. Findings are further validated by flow cytometry, immunofluorescence, IHC, western blots, and qPCR. The single-cell transcriptome dataset provided here suggests several combination strategies to augment adaptive immune responses that are necessary for durable disease control in patients with PDAC.

Background: Ovarian cancer is an immunologically cold tumor that is treated with surgery and a chemotherapy regimen of platinum agents with taxanes. Paradoxically, elevated levels of several immune markers are effective at predicting prognosis for patients with ovarian cancer, though it is not clear how chemotherapy might influence this. Chemotherapy elicits immunogenic cell death, yet tumor-controlling doses of chemotherapy are also immunotoxic. Objectives: To evaluate interactions of chemotherapy with the immune system, we studied the impact of chemotherapy in an aggressive mouse model of ovarian cancer developed within our lab. Methods: Using a single-cell transcriptomics sequencing approach, supported by flow cytometry, we evaluated the influence of a first-line therapy, cisplatin and docetaxel, and a second-line therapy, pegylated liposomal doxorubicin (PLD), on control of tumor growth and on tumor-associated immune populations of cells. Results: Both chemotherapy approaches were effective at controlling tumor growth and selectively depleted tumor cells from distinct transcriptional clusters. Both chemotherapies also resulted in relative increases in immune populations compared to untreated tumor-bearing mice, but immune populations from PLD-treated mice were more abundant and expressed a greater fraction of maturity-associated transcripts and increased proportions of tumor resident macrophage populations. PLD treatment selectively upregulated MHC class II on tumor cells, and this could be replicated in vitro across ovarian cancer cell lines and in patient tumor cells ex vivo. Conclusions: Altogether, the results support the notion that PLD has a greater capacity for immunopotentiation, which may be important to consider if immunotherapy approaches are adapted for ovarian tumors in the future.

Improvement of outcome in patients with pancreatic ductal adenocarcinoma (PDAC) requires exploration of novel therapeutic targets. Thus far, most studies of PDAC therapies, including those inhibiting small ubiquitin-like modifications (SUMOylation), have focused on PDAC epithelial cell biology, yet SUMOylation occurs in a variety of cell types. The mechanisms by which SUMOylation impacts PDAC in the context of its tumor microenvironment are poorly understood. We used clinically relevant orthotopic PDAC mouse models to investigate the effect of SUMOylation inhibition using a specific, clinical-stage compound, TAK-981. In contrast to its inhibition of PDAC cell proliferation in vitro, the survival benefit conferred by TAK-981 in vivo is dependent on the presence of T cells, suggesting that induction of adaptive antitumor immunity is an important antitumor effect of SUMOylation inhibition in vivo. To understand how this adaptive antitumor immunity is promoted, we investigated how SUMOylation inhibition in vivo alters major cell types/subtypes and their communications in the PDAC tumor microenvironment by performing transcriptomic analyses at single-cell resolution, which allowed mapping of cells in our orthotopic mouse model to cells in human PDAC tumors based on gene expression profiles. Findings are further validated by flow cytometry, immunofluorescence, IHC, western blots, and qPCR. The single-cell transcriptome dataset provided here suggests several combination strategies to augment adaptive immune responses that are necessary for durable disease control in patients with PDAC.

Supplementary Figure from An Ex Vivo Organotypic Culture Platform for Functional Interrogation of Human Appendiceal Cancer Reveals a Prominent and Heterogenous Immunological Landscape

Supplementary Figure from An Ex Vivo Organotypic Culture Platform for Functional Interrogation of Human Appendiceal Cancer Reveals a Prominent and Heterogenous Immunological Landscape