MHC Class II Expression Influences the Composition and Distribution of Immune Cells in the Metastatic Colorectal Cancer Microenvironment

Simple Summary

Extensive data exist regarding the importance of major histocompatibility complex (MHC) class I in the tumor microenvironment, but data on MHC class II (MHC-II) are lacking. Using multiplex immunohistochemistry and spatial modeling, we demonstrate that MHC-II expression impacts both the relationships of cells traditionally associated with T lymphocyte priming and spatial interactions of cytotoxic lymphocytes and tumor cells in colorectal cancer.

Abstract

Despite advances in therapy over the past decades, metastatic colorectal cancer (mCRC) remains a highly morbid disease. While the impact of MHC-I on immune infiltration in mCRC has been well studied, data on the consequences of MHC-II loss are lacking. Multiplex fluorescent immunohistochemistry (mfIHC) was performed on 149 patients undergoing curative intent resection for mCRC and stratified into high and low human leukocyte antigen isotype DR (HLA-DR) expressing tumors. Intratumoral HLA-DR expression was found in stromal bands, and its expression level was associated with different infiltrating immune cell makeup and distribution. Low HLA-DR expression was associated with increased intercellular distances and decreased population mixing of T helper cells and antigen-presenting cells (APC), suggestive of decreased interactions. This was associated with less co-localization of tumor cells and cytotoxic T lymphocytes (CTLs), which tended to be in a less activated state as determined by Ki67 and granzyme B expression. These findings suggest that low HLA-DR in the tumor microenvironment of mCRC may reflect a state of poor helper T-cell interactions with APCs and CTL-mediated anti-tumor activity. Efforts to restore/enhance MHC-II presentation may be a useful strategy to enhance checkpoint inhibition therapy in the future.

Multimodal Mapping of the Tumor and Peripheral Blood Immune Landscape in Human Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDA) is characterized by an immune-suppressive tumor microenvironment that renders it largely refractory to immunotherapy. We implemented a multimodal analysis approach to elucidate the immune landscape in PDA. Using a combination of CyTOF, single-cell RNA sequencing, and multiplex immunohistochemistry on patient tumors, matched blood, and non-malignant samples, we uncovered a complex network of immune-suppressive cellular interactions. These experiments revealed heterogeneous expression of immune checkpoint receptors in individual patient's T cells and increased markers of CD8+ T cell dysfunction in advanced disease stage. Tumor-infiltrating CD8+ T cells had an increased proportion of cells expressing an exhausted expression profile that included upregulation of the immune checkpoint TIGIT, a finding that we validated at the protein level. Our findings point to a profound alteration of the immune landscape of tumors, and to patient-specific immune changes that should be taken into account as combination immunotherapy becomes available for pancreatic cancer.

Abstract 3442: Multimodal mapping of the immune landscape in human pancreatic cancer

Background: Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer related death in the US. Unfortunately, recent clinical trials using immunotherapy targeting the highly immunosuppressive tumor microenvironment have showed disappointing results, as there is no method to predict which patients will respond to therapy. More recently, the development of single cell technology has allowed for in-depth profiling at the cellular level using small amounts of tissue, raising the potential to develop precision medicine tools at time of endoscopic fine needle biopsy.

Results: We performed single-cell RNA sequencing (scRNAseq) on endoscopic fine needle biopsies from 10 PDAC tumors at time of diagnostic endoscopic biopsy or 6 surgically resected tissues. We also sequenced 3 adjacent or normal pancreas tissues. We captured 8,521 cells from 3 surgical normal adjacent samples and 46,244 cells from PDAC tumors. Mapping of putative interactions between ligands and receptors demonstrated upregulation of key signaling pathways, including Hedgehog, NOTCH, and chemokine signaling within myeloid, epithelial, T, and NK cells. Differential expression analysis in cytotoxic CD8 T cells of PDA patients revealed increased expression of genes involved in T cell activation (GZMB, GZMA), exhaustion (GZMK, EOMES) as well as immune checkpoint pathway upregulation when compared to cytotoxic T cells in adjacent normal pancreatic tissue. Among the most significantly increased genes in CD8 T cells of PDAC tumor was the immune checkpoint TIGIT. Upon further analysis of the CD8 T cells, we found TIGIT was almost exclusively expressed in exhausted CD8 T cells, while other checkpoints such as PD-1 and LAG3 were equally distributed across effector and exhausted T cell populations. Interestingly, we were able to capture patient-specific heterogeneity of gene expression in T cells, suggesting the possibility of individualized T cell gene signatures present in PDAC tumors. We used mass cytometry and immunostaining to validate our transcript-based findings.

Conclusion: Overall, we have successfully performed robust in-depth profiling using single-cell sequencing of PDAC tumors from fine needle biopsies. TIGIT, but not other immune checkpoints, correlates with T cells exhaustion in tumors, revealing an important biological function of this relatively understudied checkpoint. Analysis of our results identified patient-specific heterogeneity of key signaling pathways in different cell compartments of PDAC tumors that have to potential to be leveraged for precision medicine.

Citation Format: Nina Steele, Eileen Carpenter, Samantha Kemp, Veerin Sirihorachai, Stephanie The, Lawrence Delrosario, Jenny Lazarus, El-ad Amir, Valerie Gunchick, Carlos Espinoza, Samantha Bell, Lindsey Harris, Valerie Irizarry-Negron, Dan Paglia, Justin Macchia, Fatima Lima, Angel Ka Yan Chu, Heather Schofield, Erik Jan Wamsteker, Richard Kwon, Allison Schulman, Anoop Prabhu, Ryan law, Arjun Sondhi, Katelyn Donahue, Hari Nathan, Clifford Cho, Michelle Anderson, Vaibhav Sahai, Costas Lyssiotis, Benjamin Allen, Arvind Rao, Weiping Zou, Filip Bednar, Timothy Frankel, Marina Pasca di Magliano. Multimodal mapping of the immune landscape in human pancreatic cancer [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 3442.

Interleukin 22 Signaling Regulates Acinar Cell Plasticity to Promote Pancreatic Tumor Development in Mice

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy that invades surrounding structures and metastasizes rapidly. Although inflammation is associated with tumor formation and progression, little is known about the mechanisms of this connection. We investigate the effects of interleukin (IL) 22 in the development of pancreatic tumors in mice.

METHODS

We performed studies with Pdx1-Cre;LSL-KrasG12D;Trp53+/-;Rosa26EYFP/+ (PKCY) mice, which develop pancreatic tumors, and PKCY mice with disruption of IL22 (PKCY Il22-/-mice). Pancreata were collected at different stages of tumor development and analyzed by immunohistochemistry, immunoblotting, real-time polymerase chain reaction, and flow cytometry. Some mice were given cerulean to induce pancreatitis. Pancreatic cancer cell lines (PD2560) were orthotopically injected into C57BL/6 mice or Il22-/-mice, and tumor development was monitored. Pancreatic cells were injected into the tail veins of mice, and lung metastases were quantified. Acini were collected from C57BL/6 mice and resected human pancreata and were cultured. Cell lines and acini cultures were incubated with IL22 and pharmacologic inhibitors, and protein levels were knocked down with small hairpin RNAs. We performed immunohistochemical analyses of 26 PDACs and 5 nonneoplastic pancreas specimens.

RESULTS

We observed increased expression of IL22 and the IL22 receptor (IL22R) in the pancreas compared with other tissues in mice; IL22 increased with pancreatitis and tumorigenesis. Flow cytometry indicated that the IL22 was produced primarily by T-helper 22 cells. PKCY Il22-/-mice did not develop precancerous lesions or pancreatic tumors. The addition of IL22 to cultured acinar cells increased their expression of markers of ductal metaplasia; these effects of IL22 were prevented with inhibitors of Janus kinase signaling to signal transducer and activator of transcription (STAT) (ruxolitinib) or mitogen-activated protein kinase kinase (MEK) (trametinib) and with STAT3 knockdown. Pancreatic cells injected into Il22-/- mice formed smaller tumors than those injected into C57BL/6. Incubation of IL22R-expressing PDAC cells with IL22 promoted spheroid formation and invasive activity, resulting in increased expression of stem-associated transcription factors (GATA4, SOX2, SOX17, and NANOG), and increased markers of the epithelial-mesenchymal transition (CDH1, SNAI2, TWIST1, and beta catenin); ruxolitinib blocked these effects. Human PDAC tissues had higher levels of IL22, phosphorylated STAT3, and markers of the epithelial-mesenchymal transition than nonneoplastic tissues. An increased level of STAT3 in IL22R-positive cells was associated with shorter survival times of patients.

CONCLUSIONS

We found levels of IL22 to be increased during pancreatitis and pancreatic tumor development and to be required for tumor development and progression in mice. IL22 promotes acinar to ductal metaplasia, stem cell features, and increased expression of markers of the epithelial-mesenchymal transition; inhibitors of STAT3 block these effects. Increased expression of IL22 by PDACs is associated with reduced survival times.

Development of Injectable Amniotic Membrane Matrix for Postmyocardial Infarction Tissue Repair

Ischemic heart disease represents the leading cause of death worldwide. Heart failure following myocardial infarction (MI) is associated with severe fibrosis formation and cardiac remodeling. Recently, injectable hydrogels have emerged as a promising approach to repair the infarcted heart and improve heart function through minimally invasive administration. Here, a novel injectable human amniotic membrane (hAM) matrix is developed to enhance cardiac regeneration following MI. Human amniotic membrane is isolated from human placenta and engineered to be a thermoresponsive, injectable gel around body temperature. Ultrasound-guided injection of hAM matrix into rat MI hearts significantly improves cardiac contractility, as measured by ejection fraction (EF), and decrease fibrosis. The results of this study demonstrate the feasibility of engineering as an injectable hAM matrix and its efficacy in attenuating degenerative changes in cardiac function following MI, which may have broad applications in tissue regeneration.

Abstract A08: Human preadipocytes promote pancreatic cancer cellular growth in a diabetes-specific manner

Objective: Type 2 diabetes mellitus (DM) is a known risk factor for pancreatic ductal adenocarcinoma (PDAC), but the mechanisms underlying this association remain poorly understood. Multiple reports implicate adipocytes and preadipocytes as putative promoters of PDAC in humans and mice. To test whether preadipocytes regulate PDAC tumorigenic functions in the context of DM, we explored the effects of conditioned media (CM) prepared from preadipocytes from nondiabetic (NDM) and DM patients on PDAC cells.

Methods: Preadipocytes were isolated from omental adipose tissue obtained from NDM and DM patients undergoing bariatric surgery. Serum-free conditioned media was prepared from these preadipocytes cultured in vitro for 72 hours. Sphere assays using T3M4 and Capan1 PDAC lines were performed in the presence or absence of conditioned media, and sphere surface area was measured over 2-3 weeks. Modifications of the sphere assays, including boiling of conditioned media as well as addition of neutralizing antibodies or recombinant proteins, were implemented. A proteome profiler array was used to identify differences in cytokine composition between CM from DM and NDM. A phospho-kinome array was used to identify differentially activated signaling pathways when PDAC cells were treated with NDM and DM conditioned media.

Results: Conditioned media from human DM preadipocytes, compared to media from NDM preadipocytes, increased PDAC cell sphere surface area in both T3M4 and Capan1 cell lines. Sphere surface area correlated directly with hemoglobin A1c (HbA1c) but not sex or body mass index of the human subjects from which preadipocytes were derived. Boiling of preadipocyte supernatants abrogated their pro-growth effects. Proteome profiler array analysis identified different proteins that were differentially expressed by DM and NDM preadipocytes, among which chitinase-3-like protein 1 (CHI3L1) and interleukin-6 (IL-6) were increased over 2-fold in DM relative to NDM preadipocyte supernatants. Neutralizing antibody to human CHI3L1 and IL-6 attenuated the increase in PDAC sphere surface area in response to DM preadipocyte conditioned media in a dose-dependent manner. Recombinant human CHI3L1 and IL-6 enhanced the growth of PDAC cells when they were exposed to NDM conditioned media. Phospho-kinome analysis demonstrated that treatment of PDAC cells with DM-derived conditioned media increased activation of inflammation-associated signal transduction pathways.

Conclusions: Preadipocyte-PDAC cell crosstalk regulates PDAC cell growth in a DM-specific and CHI3L1 and IL-6-dependent manner. These results suggest that the positive clinical correlation between DM and PDAC may be mediated by preadipocytes expressing higher levels of CHI3L1 and IL-6. Preadipocytes CHI3L1 and IL-6 represent targets for further research directed towards developing novel therapies for PDAC based on manipulation of the tumor microenvironment.

Citation Format: Lawrence Delrosario, Carmen Flesher, Nicki Baker, Jenny Lazarus, Mirna Perusina-Lanfranca, Robert O'Rourke, Timothy Frankel. Human preadipocytes promote pancreatic cancer cellular growth in a diabetes-specific manner [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr A08.

Mathematical Modeling of the Metastatic Colorectal Cancer Microenvironment Defines the Importance of Cytotoxic Lymphocyte Infiltration and Presence of PD-L1 on Antigen Presenting Cells

BACKGROUND

Although immune-based therapy has proven efficacious for some patients with microsatellite instability (MSI) colon cancers, a majority of patients receive limited benefit. Conversely, select patients with microsatellite stable (MSS) tumors respond to checkpoint blockade, necessitating novel ways to study the immune tumor microenvironment (TME). We used phenotypic and spatial data from infiltrating immune and tumor cells to model cellular mixing to predict disease specific outcomes in patients with colorectal liver metastases.

METHODS

Formalin fixed paraffin embedded metastatic colon cancer tissue from 195 patients were subjected to multiplex immunohistochemistry (mfIHC). After phenotyping, the G-function was calculated for each patient and cell type. Data was correlated with clinical outcomes and survival.

RESULTS

High tumor cell to cytotoxic T lymphocyte (TC-CTL) mixing was associated with both a pro-inflammatory and immunosuppressive TME characterized by increased CTL infiltration and PD-L1+ expression, respectively. Presence and engagement of antigen presenting cells (APC) and helper T cells (Th) were associated with greater TC-CTL mixing and improved 5-year disease specific survival compared to patients with a low degree of mixing (42% vs. 16%, p = 0.0275). Comparison of measured mixing to a calculated theoretical random mixing revealed that PD-L1 expression on APCs resulted in an environment where CTLs were non-randomly less associated with TCs, highlighting their biologic significance.

CONCLUSION

Evaluation of immune interactions within the TME of metastatic colon cancer using mfIHC in combination with mathematical modeling characterized cellular mixing of TCs and CTLs, providing a novel strategy to better predict clinical outcomes while identifying potential candidates for immune based therapies.

Optimization, Design and Avoiding Pitfalls in Manual Multiplex Fluorescent Immunohistochemistry

Microenvironment evaluation of intact tissue for analysis of cell infiltration and spatial organization are essential in understanding the complexity of disease processes. The principle techniques used in the past include immunohistochemistry (IHC) and immunofluorescence (IF) which enable visualization of cells as a snapshot in time using between 1 and 4 markers. Both techniques have shortcomings including difficulty staining poorly antigenic targets and limitations related to cross-species reactivity. IHC is reliable and reproducible, but the nature of the chemistry and reliance on the visible light spectrum allows for only a few markers to be used and makes co-localization challenging. Use of IF broadens potential markers but typically relies on frozen tissue due to the extensive tissue autofluorescence following formalin fixation. Flow cytometry, a technique that enables simultaneous labeling of multiple epitopes, abrogates many of the deficiencies of IF and IHC, however, the need to examine cells as a single cell suspension loses the spatial context of cells discarding important biologic relationships. Multiplex fluorescent immunohistochemistry (mfIHC) bridges these technologies allowing for multi-epitope cellular phenotyping in formalin fixed paraffin embedded (FFPE) tissue while preserving the overall microenvironment architecture and spatial relationship of cells within intact undisrupted tissue. High fluorescent intensity fluorophores that covalently bond to the tissue epitope enables multiple applications of primary antibodies without worry of species specific cross-reactivity by secondary antibodies. Although this technology has been proven to produce reliable and accurate images for the study of disease, the process of creating a useful mfIHC staining strategy can be time consuming and exacting due to extensive optimization and design. In order to make robust images that represent accurate cellular interactions in-situ and to mitigate the optimization period for manual analysis, presented here are methods for slide preparation, optimizing antibodies, multiplex design as well as errors commonly encountered during the staining process.

Spatial and phenotypic immune profiling of metastatic colon cancer

Paramount to the efficacy of immune checkpoint inhibitors is proper selection of patients with adequate tumor immunogenicity and a robust but suppressed immune infiltrate. In colon cancer, immune-based therapies are approved for patients with DNA mismatch repair (MMR) deficiencies, in whom accumulation of genetic mutations results in increased neoantigen expression, triggering an immune response that is suppressed by the PD-L1/PD-1 pathway. Here, we report that characterization of the microenvironment of MMR-deficient metastatic colorectal cancer using multiplex fluorescent immunohistochemistry (mfIHC) identified increased infiltration of cytotoxic T lymphocytes (CTLs), which were more often engaged with epithelial cells (ECs) and improved overall survival. A subset of patients with intact MMR but a similar immune microenvironment to MMR-deficient patients was identified and found to universally express high levels of PD-L1, suggesting that they may represent a currently untreated, checkpoint inhibitor-responsive population. Further, PD-L1 expression on antigen-presenting cells (APCs) in the tumor microenvironment (TME) resulted in impaired CTL/EC engagement and enhanced infiltration and engagement of Tregs. Characterization of the TME by mfIHC highlights the interconnection between immunity and immunosuppression in metastatic colon cancer and may better stratify patients for receipt of immunotherapies.

Distraction Osteogenesis of Multiple Ribs for the Treatment of Acquired Thoracic Dystrophy

Acquired thoracic dystrophy is a complication associated with early open repair of pectus excavatum resulting from extensive cartilage resection. The condition can cause serious functional and physiologic impairments, including cardiac compression and restrictive pulmonary function. We describe a 17-year-old boy with acquired thoracic dystrophy after Ravitch repair of pectus excavatum during infancy, whom we treated with distraction osteogenesis. The patient had a marked deformity of the chest wall and general hypoplasia of the central portion of the ribcage, with resultant symptomatic dyspnea on exertion and reduced pulmonary function. After osteotomies and distraction osteogenesis of bilateral ribs 4-8 using customized distraction devices, he had improved thoracic contour, resolution of dyspnea, and decreased restrictive pulmonary symptoms. This case suggests that distraction osteogenesis, already used extensively in craniomaxillofacial and orthopedic surgery, may be a novel method for management of this condition.

Discrete microstructural cues for the attenuation of fibrosis following myocardial infarction

Chronic fibrosis caused by acute myocardial infarction (MI) leads to increased morbidity and mortality due to cardiac dysfunction. We have developed a therapeutic materials strategy that aims to mitigate myocardial fibrosis by utilizing injectable polymeric microstructures to mechanically alter the microenvironment. Polymeric microstructures were fabricated using photolithographic techniques and studied in a three-dimensional culture model of the fibrotic environment and by direct injection into the infarct zone of adult rats. Here, we show dose-dependent down-regulation of expression of genes associated with the mechanical fibrotic response in the presence of microstructures. Injection of this microstructured material into the infarct zone decreased levels of collagen and TGF-β, increased elastin deposition and vascularization in the infarcted region, and improved functional outcomes after six weeks. Our results demonstrate the efficacy of these discrete anti-fibrotic microstructures and suggest a potential therapeutic materials approach for combatting pathologic fibrosis.