Strategies to relieve immunosuppression in pancreatic cancer

Comprehensive multi-omics profiling identifies novel molecular subtypes of pancreatic ductal adenocarcinoma

Pancreatic cancer, a highly fatal malignancy, is predicted to rank as the second leading cause of cancer-related death in the next decade. This highlights the urgent need for new insights into personalized diagnosis and treatment. Although molecular subtypes of pancreatic cancer were well established in genomics and transcriptomics, few known molecular classifications are translated to guide clinical strategies and require a paradigm shift. Notably, chronically developing and continuously improving high-throughput technologies and systems serve as an important driving force to further portray the molecular landscape of pancreatic cancer in terms of epigenomics, proteomics, metabonomics, and metagenomics. Therefore, a more comprehensive understanding of molecular classifications at multiple levels using an integrated multi-omics approach holds great promise to exploit more potential therapeutic options. In this review, we recapitulated the molecular spectrum from different omics levels, discussed various subtypes on multi-omics means to move one step forward towards bench-to-beside translation of pancreatic cancer with clinical impact, and proposed some methodological and scientific challenges in store.

Spatially restricted drivers and transitional cell populations cooperate with the microenvironment in untreated and chemo-resistant pancreatic cancer

Pancreatic ductal adenocarcinoma is a lethal disease with limited treatment options and poor survival. We studied 83 spatial samples from 31 patients (11 treatment-naïve and 20 treated) using single-cell/nucleus RNA sequencing, bulk-proteogenomics, spatial transcriptomics and cellular imaging. Subpopulations of tumor cells exhibited signatures of proliferation, KRAS signaling, cell stress and epithelial-to-mesenchymal transition. Mapping mutations and copy number events distinguished tumor populations from normal and transitional cells, including acinar-to-ductal metaplasia and pancreatic intraepithelial neoplasia. Pathology-assisted deconvolution of spatial transcriptomic data identified tumor and transitional subpopulations with distinct histological features. We showed coordinated expression of TIGIT in exhausted and regulatory T cells and Nectin in tumor cells. Chemo-resistant samples contain a threefold enrichment of inflammatory cancer-associated fibroblasts that upregulate metallothioneins. Our study reveals a deeper understanding of the intricate substructure of pancreatic ductal adenocarcinoma tumors that could help improve therapy for patients with this disease.

Deciphering the Crosstalk Between Myeloid-Derived Suppressor Cells and Regulatory T Cells in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease with rising incidence and a remarkable resistance to current therapies. The reasons for this therapeutic failure include the tumor's extensive infiltration by immunosuppressive cells such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). By using light sheet fluorescent microscopy, we identified here direct interactions between these major immunoregulatory cells in PDAC. The in vivo depletion of MDSCs led to a significant reduction in Tregs in the pancreatic tumors. Through videomicroscopy and ex vivo functional assays we have shown that (i) MDSCs are able to induce Treg cells in a cell-cell dependent manner; (ii) Treg cells affect the survival and/or the proliferation of MDSCs. Furthermore, we have observed contacts between MDSCs and Treg cells at different stages of human cancer. Overall our findings suggest that interactions between MDSCs and Treg cells contribute to PDAC immunosuppressive environment.

Cold Atmospheric Plasma-Treated PBS Eliminates Immunosuppressive Pancreatic Stellate Cells and Induces Immunogenic Cell Death of Pancreatic Cancer Cells

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers with a low response to treatment and a five-year survival rate below 5%. The ineffectiveness of treatment is partly because of an immunosuppressive tumor microenvironment, which comprises tumor-supportive pancreatic stellate cells (PSCs). Therefore, new therapeutic strategies are needed to tackle both the immunosuppressive PSC and pancreatic cancer cells (PCCs). Recently, physical cold atmospheric plasma consisting of reactive oxygen and nitrogen species has emerged as a novel treatment option for cancer. In this study, we investigated the cytotoxicity of plasma-treated phosphate-buffered saline (pPBS) using three PSC lines and four PCC lines and examined the immunogenicity of the induced cell death. We observed a decrease in the viability of PSC and PCC after pPBS treatment, with a higher efficacy in the latter. Two PCC lines expressed and released damage-associated molecular patterns characteristic of the induction of immunogenic cell death (ICD). In addition, pPBS-treated PCC were highly phagocytosed by dendritic cells (DCs), resulting in the maturation of DC. This indicates the high potential of pPBS to trigger ICD. In contrast, pPBS induced no ICD in PSC. In general, pPBS treatment of PCCs and PSCs created a more immunostimulatory secretion profile (higher TNF-α and IFN-γ, lower TGF-β) in coculture with DC. Altogether, these data show that plasma treatment via pPBS has the potential to induce ICD in PCCs and to reduce the immunosuppressive tumor microenvironment created by PSCs. Therefore, these data provide a strong experimental basis for further in vivo validation, which might potentially open the way for more successful combination strategies with immunotherapy for PDAC.

Irreversible electroporation of locally advanced pancreatic cancer transiently alleviates immune suppression and creates a window for antitumor T cell activation

Purpose: Local tumor ablation through irreversible electroporation (IRE) may offer a novel therapeutic option for locally advanced pancreatic cancer (LAPC). It may also serve as a means of in vivo vaccination. To obtain evidence of the induction of systemic antitumor immunity following local IRE-mediated ablation, we performed an explorative immune monitoring study. Methods: In ten patients enrolled in a clinical trial exploring the safety, feasibility, and efficacy of percutaneous image-guided IRE in LAPC, we determined the frequency and activation state of lymphocytic and myeloid subsets in pre- and post-treatment peripheral blood samples using flow cytometry. Tumor-specific systemic T cell responses to the pancreatic cancer associated antigen Wilms Tumor (WT)1 were determined after in vitro stimulation in an interferon-y enzyme-linked immunospot assay (Elispot), at baseline and at 2 weeks and 3 months after IRE. Results: Our data showed a transient decrease in systemic regulatory T cells (Treg) and a simultaneous transient increase in activated PD-1⁺ T cells, consistent with the temporary reduction of tumor-related immune suppression after the IRE procedure. Accordingly, we found post-IRE boosting of a pre-existing WT1 specific T cell response in two out of three patients as well as the de novo induction of these responses in another two patients. There was a trend for these WT1 T cell responses to be related to longer overall survival (p = .055). Conclusions: These findings are consistent with a systemic and tumor-specific immune stimulatory effect of IRE and support the combination of percutaneous IRE with therapeutic immune modulation.

Pancreatic ductal adenocarcinoma: biological hallmarks, current status, and future perspectives of combined modality treatment approaches

Pancreatic ductal adenocarcinoma (PDAC) is a highly devastating disease with poor prognosis and rising incidence. Late detection and a particularly aggressive biology are the major challenges which determine therapeutic failure. In this review, we present the current status and the recent advances in PDAC treatment together with the biological and immunological hallmarks of this cancer entity. On this basis, we discuss new concepts combining distinct treatment modalities in order to improve therapeutic efficacy and clinical outcome - with a specific focus on protocols involving radio(chemo)therapeutic approaches.

Stromal biology and therapy in pancreatic cancer: ready for clinical translation?

Pancreatic ductal adenocarcinoma (PDA) is notoriously aggressive and hard to treat. The tumour microenvironment (TME) in PDA is highly dynamic and has been found to promote tumour progression, metastasis niche formation and therapeutic resistance. Intensive research of recent years has revealed an incredible heterogeneity and complexity of the different components of the TME, including cancer-associated fibroblasts, immune cells, extracellular matrix components, tumour vessels and nerves. It has been hypothesised that paracrine interactions between neoplastic epithelial cells and TME compartments may result in either tumour-promoting or tumour-restraining consequences. A better preclinical understanding of such complex and dynamic network systems is required to develop more powerful treatment strategies for patients. Scientific activity and the number of compelling findings has virtually exploded during recent years. Here, we provide an update of the most recent findings in this area and discuss their translational and clinical implications for basic scientists and clinicians alike.

Local Blockade of Interleukin 10 and C-X-C Motif Chemokine Ligand 12 with Nano-Delivery Promotes Antitumor Response in Murine Cancers

In many cancers, the tumor microenvironment (TME) is largely immune suppressive, blocking the antitumor immunity and resulting in immunotherapy resistance. Interleukin 10 (IL-10) is a major player controlling the immunosuppressive TME in different murine tumor models. Increased IL-10 production suppresses intratumoral dendritic cell production of interleukin 12, thereby limiting antitumor cytotoxic T-cell responses and activation of NK cells during therapy. We engineered, formulated, and delivered genes encoding an IL-10 protein trap to change immunosuppressive TME, which could enhance antitumor immunity. Additionally, to achieve stronger and long-term therapeutic efficacy in a pancreatic cancer model, we targeted C-X-C motif chemokine ligand 12 (CXCL12), a key factor for inhibiting T-cell tumor infiltration, and simultaneously delivered an IL-10 trap. Following three injections of the lipid-protamine-DNA (LPD) nanoparticles loaded with trap genes (IL-10 trap and CXCL12 trap), we found tumor growth reduction and significantly prolonged survival of the host compared to control groups. Furthermore, the combination trap gene treatment significantly reduced immunosuppressive cells, such as M2 macrophages, MDSCs, and PD-L1⁺ cells, and activated immunosuppressive tolerogenic dendritic cells, NK cells, and macrophages intratumorally. We have also shown that, when effectively delivered to the tumor, the IL-10 trap gene alone can inhibit triple-negative breast cancer growth. This strategy may allow clinicians and researchers to change the immunosuppressive microenvironment in the tumor with either a single therapeutic agent or in combination with other immunotherapies to prime the immune system, preventing cancer invasion and prolonging patient survival.

The critical roles of activated stellate cells-mediated paracrine signaling, metabolism and onco-immunology in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant diseases worldwide. It is refractory to conventional treatments, and consequently has a documented 5-year survival rate as low as 7%. Increasing evidence indicates that activated pancreatic stellate cells (PSCs), one of the stromal components in tumor microenvironment (TME), play a crucial part in the desmoplasia, carcinogenesis, aggressiveness, metastasis associated with PDAC. Despite the current understanding of PSCs as a "partner in crime" to PDAC, detailed regulatory roles of PSCs and related microenvironment remain obscure. In addition to multiple paracrine signaling pathways, recent research has confirmed that PSCs-mediated tumor microenvironment may influence behaviors of PDAC via diverse mechanisms, such as rewiring metabolic networks, suppressing immune responses. These new activities are closely linked with treatment and prognosis of PDAC. In this review, we discuss the recent advances regarding new functions of activated PSCs, including PSCs-cancer cells interaction, mechanisms involved in immunosuppressive regulation, and metabolic reprogramming. It's clear that these updated experimental or clinical studies of PSCs may provide a promising approach for PDAC treatment in the near future.

Efficacy of vaccination with tumor-exosome loaded dendritic cells combined with cytotoxic drug treatment in pancreatic cancer

Pancreatic cancer (PaCa) has a dismal prognosis and adjuvant immunotherapy frequently is of low efficacy due to immunosuppressive features of PaCa and PaCa-stroma. We here explored, whether the efficacy of vaccination with tumor-exosome (TEX)-loaded dendritic cells (DC) can be improved by combining with drugs affecting myeloid-derived suppressor cells (MDSC). Experiments were performed with the UNKC6141 PaCa line. UNKC6141 TEX-loaded DC were weekly intravenously injected, mice additionally receiving Gemcitabine (GEM) and/or ATRA and/or Sunitinib (Sun). UNKC6141 grow aggressively after subcutaneous and orthotopic application and are consistently recovered in peripheral blood, bone marrow, lung and frequently liver. Vaccination with DC-TEX significantly prolonged the survival time, the efficacy of DC-TEX exceeding that of the cytotoxic drugs. However, ATRA, Sun and most efficiently GEM, sufficed for a pronounced reduction of MDSC including tumor-infiltrating MDSC, which was accompanied by a decrease in migrating and metastasizing tumor cells. When combined with DC-TEX vaccination, a higher number of activated T cells was recovered in the tumor and the survival time was prolonged compared with only DC-TEX vaccinated mice. As ATRA, GEM and Sun affect MDSC at distinct maturation and activation stages, a stronger support for DC-TEX vaccination was expected by the drug combination. Intrapancreatic tumor growth was prevented beyond the death of control mice. However, tumors developed after a partial breakdown of the immune system by the persisting drug application. Nonetheless, in combination with optimized drug tuning to prevent MDSC maturation and activation, vaccination with TEX-loaded DC appears a most promising option in PaCa therapy.

Adjuvant combination therapy with gemcitabine and autologous γδ T-cell transfer in patients with curatively resected pancreatic cancer

BACKGROUND AIMS

The outcome for pancreatic cancer after surgery remains highly unsatisfactory, and development of more effective therapies is urgently needed. Therefore, we conducted a phase I clinical study of a novel combination of gemcitabine (GEM) and autologous γδ T-cell therapy for patients with curatively resected pancreatic cancer (University Hospital Medical Information Clinical Trials Registry identifier 000000931).

METHODS

From July 2008 to December 2012, 56 consenting patients were recruited. After preliminary testing of γδ T-cell proliferative capacity, 28 patients were eligible to receive combined GEM plus γδ T-cell therapy.

RESULTS

During treatment, most of the adverse events observed were due to GEM, including myelosuppression and gastrointestinal disorders. No severe adverse events were obviously related to the γδ T-cell therapy. To evaluate clinical efficacy, patients receiving combined therapy (Group A, n = 28) were compared with those receiving GEM alone (Group B, n = 20). No significant differences were observed between the two groups in recurrence-free survival or overall survival. However, we found that, relative to progressing patients, more γδ T-cells were detectable in the blood of recurrence-free patients after only two injections (P < .0388) and more so five injections (P < .0175). Patients with >15% peripheral γδ T-cells after two injections and >20% after five injections had a chance of a more favorable clinical outcome. Accumulation of γδ T cells was positively related to the quality of the infused products, with those having >80% γδ T cells being optimal.

DISCUSSION

High quality of the γδ T-cell product is crucial to achieve a high percentage of γδ T cells in the blood and to achieve better clinical outcome.

Wilms’ tumor 1 (WT1)-targeted cancer vaccines to extend survival for patients with pancreatic cancer

Despite novel chemotherapy treatments, pancreatic ductal adenocarcinoma (PDA) remains a lethal disease. New targeted cancer vaccines may represent a viable option for patients with PDA. The Wilms’ tumor 1 (WT1) antigen is one of the most widely expressed tumor-associated antigens in various types of tumors, including PDA. Recent reports have indicated that WT1-targeted cancer vaccines for patients with PDA mediated a potent antitumor effect when combined with chemotherapy in preclinical and clinical studies. This review summarizes the early-phase clinical trials of WT1-targeted cancer vaccines (peptide vaccines and dendritic cell-based vaccines) for PDA. Moreover, we will discuss future strategies for PDA treatments using WT1-specific cancer vaccines combined with immune checkpoint therapies to maximize the clinical effectiveness of PDA treatments.

Randomized Phase 2 Trial of the Oncolytic Virus Pelareorep (Reolysin) in Upfront Treatment of Metastatic Pancreatic Adenocarcinoma

Pelareorep causes oncolysis in tumor cells with activated Ras. We hypothesized that pelareorep would have efficacy and immunomodulatory activity in metastatic pancreatic adenocarcinoma (MPA) when combined with carboplatin and paclitaxel. A randomized phase 2 study (NCT01280058) was conducted in treatment-naive patients with MPA randomized to two treatment arms: paclitaxel/carboplatin + pelareorep (Arm A, n = 36 evaluable patients) versus paclitaxel/carboplatin (Arm B, n = 37 evaluable patients). There was no difference in progression-free survival (PFS) between the arms (Arm A PFS = 4.9 months, Arm B PFS = 5.2 months, P = 0.6), and Kirsten rat sarcoma viral oncogene (KRAS) status did not impact outcome. Quality-adjusted Time without Symptoms or Toxicity analysis revealed that the majority of PFS time was without toxicity or progression (4.3 months). Patient immunophenotype appeared important, as soluble immune biomarkers were associated with treatment outcome (fractalkine, interleukin (IL)-6, IL-8, regulated on activation, normal T cell expressed and secreted (RANTES), and vascular endothelial growth factor (VEGF)). Increased circulating T and natural killer (NK)-cell subsets were also significantly associated with treatment outcome. Addition of pelareorep was associated with higher levels of 14 proinflammatory plasma cytokines/chemokines and cells with an immunosuppressive phenotype (Tregs, cytotoxic T lymphocyte associated protein 4 (CTLA4)(+) T cells). Overall, pelareorep was safe but does not improve PFS when administered with carboplatin/paclitaxel, regardless of KRAS mutational status. Immunologic studies suggest that chemotherapy backbone improves immune reconstitution and that targeting remaining immunosuppressive mediators may improve oncolytic virotherapy.

Depletion of FAP+ cells reduces immunosuppressive cells and improves metabolism and functions CD8+T cells within tumors

The tumor stroma, which is essential to support growth and metastasis of malignant cells, provides targets for active immunotherapy of cancer. Previous studies have shown that depleting fibroblast activation protein (FAP)-expressing stromal cells reduces tumor progression and concomitantly increases tumor antigen (TA)-specific T cell responses. However the underlying pathways remain ill defined. Here we identify that immunosuppressive cells (ISCs) from tumor-bearing mice impose metabolic stress on CD8⁺T cells, which is associated with increased expression of the co-inhibitor PD-1. In two mouse melanoma models, depleting FAP⁺ stroma cells from the tumor microenvironment (TME) upon vaccination with an adenoviral-vector reduces frequencies and functions of ISCs. This is associated with changes in the cytokine/chemokine milieu in the TME and decreased activity of STAT6 signaling within ISCs. Decreases in ISCs upon FAP⁺stromal cell depletion is associated with reduced metabolic stress of vaccine-induced tumor infiltrating CD8⁺T cells and their delayed progression towards functional exhaustion, resulting in prolonged survival of tumor-bearing mice.

On the analysis of clonogenic survival data: Statistical alternatives to the linear-quadratic model

Background

The most frequently used method to quantitatively describe the response to ionizing irradiation in terms of clonogenic survival is the linear-quadratic (LQ) model. In the LQ model, the logarithm of the surviving fraction is regressed linearly on the radiation dose by means of a second-degree polynomial. The ratio of the estimated parameters for the linear and quadratic term, respectively, represents the dose at which both terms have the same weight in the abrogation of clonogenic survival. This ratio is known as the α/β ratio. However, there are plausible scenarios in which the α/β ratio fails to sufficiently reflect differences between dose-response curves, for example when curves with similar α/β ratio but different overall steepness are being compared. In such situations, the interpretation of the LQ model is severely limited.

Methods

Colony formation assays were performed in order to measure the clonogenic survival of nine human pancreatic cancer cell lines and immortalized human pancreatic ductal epithelial cells upon irradiation at 0-10 Gy. The resulting dataset was subjected to LQ regression and non-linear log-logistic regression. Dimensionality reduction of the data was performed by cluster analysis and principal component analysis.

Results

Both the LQ model and the non-linear log-logistic regression model resulted in accurate approximations of the observed dose-response relationships in the dataset of clonogenic survival. However, in contrast to the LQ model the non-linear regression model allowed the discrimination of curves with different overall steepness but similar α/β ratio and revealed an improved goodness-of-fit. Additionally, the estimated parameters in the non-linear model exhibit a more direct interpretation than the α/β ratio. Dimensionality reduction of clonogenic survival data by means of cluster analysis was shown to be a useful tool for classifying radioresistant and sensitive cell lines. More quantitatively, principal component analysis allowed the extraction of scores of radioresistance, which displayed significant correlations with the estimated parameters of the regression models.

Conclusions

Undoubtedly, LQ regression is a robust method for the analysis of clonogenic survival data. Nevertheless, alternative approaches including non-linear regression and multivariate techniques such as cluster analysis and principal component analysis represent versatile tools for the extraction of parameters and/or scores of the cellular response towards ionizing irradiation with a more intuitive biological interpretation. The latter are highly informative for correlation analyses with other types of data, including functional genomics data that are increasingly beinggenerated.