Neoadjuvant chemotherapy is associated with suppression of the B cell-centered immune landscape in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is typically diagnosed at advanced stages and associated with early distant metastasis and poor survival. Besides clinical factors, the tumor microenvironment (TME) emerged as a crucial determinant of patient survival and therapy response in many tumors, including PDAC. Thus, the presence of tumor-infiltrating lymphocytes and the formation of tertiary lymphoid structures (TLS) is associated with longer survival in PDAC. Although neoadjuvant therapy (NeoTx) has improved the management of locally advanced tumors, detailed insight into its effect on various TME components is limited. While a remodeling towards a proinflammatory state was reported for PDAC-infiltrating T cells, the effect of NeoTx on B cell subsets, including plasma cells, and TLS formation is widely unclear. We thus investigated the frequency, composition, and spatial distribution of PDAC-infiltrating B cells in primary resected (PR) versus neoadjuvant-treated patients using a novel multiplex immunohistochemistry panel. The NeoTx group displayed significantly lower frequencies of pan B cells, GC B cells, plasmablasts, and plasma cells, accompanied by a reduced abundance of TLS. This finding was supported by bulk RNA-sequencing analysis of an independent fresh frozen tissue cohort, which revealed that major B cell pathways were downregulated in the NeoTx group. We further observed that plasma cells frequently formed aggregates that localized close to TLS and that TLS+ patients displayed significantly higher plasma cell frequencies compared to TLS- patients in the PR group. Additionally, high densities of CD20+ intratumoral B cells were significantly associated with longer overall survival in the PR group. While CD20+ B cells held no prognostic value for NeoTx patients, an increased frequency of proliferating CD20+Ki67+ B cells emerged as an independent prognostic factor for longer survival in the NeoTx group. These results indicate that NeoTx differentially affects PDAC-infiltrating immune cells and may have detrimental effects on the existing B cell landscape and the formation of TLS. Gaining further insight into the underlying molecular mechanisms is crucial to overcome the intrinsic immunotherapy resistance of PDAC and develop novel strategies to improve the long-term outcome of PDAC patients.

CD38 promotes hematopoietic stem cell dormancy

A subpopulation of deeply quiescent, so-called dormant hematopoietic stem cells (dHSCs) resides at the top of the hematopoietic hierarchy and serves as a reserve pool for HSCs. The state of dormancy protects the HSC pool from exhaustion throughout life; however, excessive dormancy may prevent an efficient response to hematological stresses. Despite the significance of dHSCs, the mechanisms maintaining their dormancy remain elusive. Here, we identify CD38 as a novel and broadly applicable surface marker for the enrichment of murine dHSCs. We demonstrate that cyclic adenosine diphosphate ribose (cADPR), the product of CD38 cyclase activity, regulates the expression of the transcription factor c-Fos by increasing the release of Ca2+ from the endoplasmic reticulum (ER). Subsequently, we uncover that c-Fos induces the expression of the cell cycle inhibitor p57Kip2 to drive HSC dormancy. Moreover, we found that CD38 ecto-enzymatic activity at the neighboring CD38-positive cells can promote human HSC quiescence. Together, CD38/cADPR/Ca2+/c-Fos/p57Kip2 axis maintains HSC dormancy. Pharmacological manipulations of this pathway can provide new strategies to improve the success of stem cell transplantation and blood regeneration after injury or disease.

Immunotheranostic target modules for imaging and navigation of UniCAR T-cells to strike FAP-expressing cells and the tumor microenvironment

BACKGROUND

Chimeric antigen receptor (CAR) T-cells are a promising approach in cancer immunotherapy, particularly for treating hematologic malignancies. Yet, their effectiveness is limited when tackling solid tumors, where immune cell infiltration and immunosuppressive tumor microenvironments (TME) are major hurdles. Fibroblast activation protein (FAP) is highly expressed on cancer-associated fibroblasts (CAFs) and various tumor cells, playing an important role in tumor growth and immunosuppression. Aiming to modulate the TME with increased clinical safety and effectiveness, we developed novel small and size-extended immunotheranostic UniCAR target modules (TMs) targeting FAP.

METHODS

The specific binding and functionality of the αFAP-scFv TM and the size-extended αFAP-IgG4 TM were assessed using 2D and 3D in vitro models as well as in vivo. Their specific tumor accumulation and diagnostic potential were evaluated using PET studies after functionalization with a chelator and suitable radionuclide.

RESULTS

The αFAP-scFv and -IgG4 TMs effectively and specifically redirected UniCAR T-cells using 2D, 3D, and in vivo models. Moreover, a remarkably high and specific accumulation of radiolabeled FAP-targeting TMs at the tumor site of xenograft mouse models was observed.

CONCLUSIONS

These findings demonstrate that the novel αFAP TMs are promising immunotheranostic tools to foster cancer imaging and treatment, paving the way for a more convenient, individualized, and safer treatment of cancer patients.

Guidelines for visualization and analysis of DC in tissues using multiparameter fluorescence microscopy imaging methods

This article is part of the Dendritic Cell Guidelines article series, which provides a collection of state-of-the-art protocols for the preparation, phenotype analysis by flow cytometry, generation, fluorescence microscopy, and functional characterization of mouse and human dendritic cells (DC) from lymphoid organs and various non-lymphoid tissues. Here, we provide detailed procedures for a variety of multiparameter fluorescence microscopy imaging methods to explore the spatial organization of DC in tissues and to dissect how DC migrate, communicate, and mediate their multiple functional roles in immunity in a variety of tissue settings. The protocols presented here entail approaches to study DC dynamics and T cell cross-talk by intravital microscopy, large-scale visualization, identification, and quantitative analysis of DC subsets and their functions by multiparameter fluorescence microscopy of fixed tissue sections, and an approach to study DC interactions with tissue cells in a 3D cell culture model. While all protocols were written by experienced scientists who routinely use them in their work, this article was also peer-reviewed by leading experts and approved by all co-authors, making it an essential resource for basic and clinical DC immunologists.

Prognostic impact of the post-treatment T cell composition and spatial organization in soft tissue sarcoma patients treated with neoadjuvant hyperthermic radio(chemo)therapy

Soft tissue sarcomas (STS) form a heterogeneous group of tumors sharing a mesenchymal origin. Despite good local control of the disease, the occurrence of distant metastases often limits survival of STS patients with localized, high-risk tumors of the extremities. Accumulating evidence suggests a central role for the tumor immune microenvironment in determining the clinical outcome and response to therapy. Thus, it has been reported that STS patients with a high immune signature and especially presence of B cells and tertiary lymphoid structures display improved overall survival and response to checkpoint inhibitor treatment. Here, we explored the effect of curative multimodal therapy on the T cell landscape of STS using multiplex immunohistochemistry. We analyzed the phenotype, frequency, and spatial distribution of STS-infiltrating CD8⁺ T cells by staining for CD8, 4-1BB, Granzyme B, Ki67, PD-1, and LAG-3 as well as CD3⁺ T helper cells using a panel consisting of CD3, T-bet, GATA3, RORγT, FoxP3, and Ki67. All patients received neoadjuvant radiotherapy plus locoregional hyperthermia with or without chemotherapy. While the treatment-naïve biopsy sample allows an analysis of baseline T cell infiltration levels, both intra- and peritumoral areas of the matched resected tissue were analyzed to assess composition and spatial distribution of the T cell compartment and its therapeutic modulation. Generally, post-treatment tissues displayed lower frequencies of CD3⁺ and CD8⁺ T cells. Association with clinical data revealed that higher post-treatment frequencies of peritumoral and intratumoral CD3⁺ T cells and intratumoral PD-1⁺ CD8⁺ T cells were significantly associated with improved disease-free survival (DFS), while these densities had no prognostic significance in the biopsy. Upon spatial analysis, a high ratio of intratumoral to peritumoral CD8⁺ T cells emerged as an independent prognostic marker for longer DFS. These results indicate that the STS T cell landscape is altered by multimodal therapy and may influence the clinical outcome of patients. An enhanced understanding of the STS immune architecture and its modulation by neoadjuvant therapy may pave the way towards novel treatment modalities and improve the long-term clinical outcome of STS patients.

VISTA Ligation Reduces Antitumor T-Cell Activity in Pancreatic Cancer

Immunotherapy has shown promising results in multiple solid tumors and hematological malignancies. However, pancreatic ductal adenocarcinoma (PDAC) has been largely refractory to current clinical immunotherapies. The V-domain Ig suppressor of T-cell activation (VISTA) inhibits T-cell effector function and maintains peripheral tolerance. Here, we determine VISTA expression in nontumorous pancreatic (n = 5) and PDAC tissue using immunohistochemistry (n = 76) and multiplex immunofluorescence staining (n = 67). Additionally, VISTA expression on tumor-infiltrating immune cells and matched blood samples (n = 13) was measured with multicolor flow cytometry. Further, the effect of recombinant VISTA on T-cell activation was investigated in vitro, and VISTA blockade was tested in an orthotopic PDAC mouse model in vivo. PDAC showed significantly higher VISTA expression compared to that of a nontumorous pancreas. Patients with a high density of VISTA-expressing tumor cells had reduced overall survival. The VISTA expression of CD4⁺ and CD8⁺ T cells was increased after stimulation and particularly after a coculture with tumor cells. We detected a higher level of proinflammatory cytokine (TNFα and IFNγ) expression by CD4⁺ and CD8⁺ T cells, which was reversed with the addition of recombinant VISTA. A VISTA blockade reduced tumor weights in vivo. The VISTA expression of tumor cells has clinical relevance, and its blockade may be a promising immunotherapeutic strategy for PDAC.

Abstract 926: Genomics-based personalized oncology of advanced thymic epithelial tumors

Introduction: Thymic epithelial tumors (TETs) are very rare. Thymoma A and AB have a better prognosis than more aggressive thymoma B, thymic carcinoma (TC) and neuroendocrine tumors of the thymus (NET). While previous efforts such as TCGA have mainly characterized thymomas (Radovich et al., Cancer Cell 2018), the molecular landscape of TCs and NETs is still elusive.

Patients and Methods: Between 03/2014 and 07/2020, we enrolled 44 TET patients (27 TCs, 11 thymomas, 6 NETs) in a prospective observational study (MASTER) conducted by the National Center for Tumor Diseases (NCT) Heidelberg, NCT Dresden and the German Cancer Consortium (DKTK). MASTER applied whole genome/exome sequencing (WGS, n=22; WES, n=22), transcriptome (n=40) and germline analysis to inform therapy recommendations by a dedicated molecular tumor board (MTB). We systematically gathered follow-up data to evaluate outcome and compared progression-free survival (PFS) of the first treatment according to an MTB recommendation (PFS2) to the last prior systemic treatment (PFS1) in each patient (PFS ratio).

Results: Tumor mutational burden (TMB) was low (median=0.99 mutations/Mb, range 0.08-3.48) but higher than in TCGA (p<0.05). TMB was higher in TCs than in thymoma (p<0.05). Most frequently mutated genes were TP53 (30%), CYLD (16%), SETD2 (14%) and KIT (14%). Germline analysis revealed (likely) pathogenic germline alterations in 25% of patients (MUTYH, n=3; BRCA1, n=2; BRCA2, BAP1, CHEK2, FANCA, TP53, MEN1, n=1). A comprehensive analysis of candidate biomarkers of homologous recombination repair (HRR) defects revealed a subgroup of TET patients with a rationale for PARP inhibitor therapy. Unsupervised clustering of RNA sequencing data mainly revealed clustering that correlated with WHO classification. Additionally, TCs clustered in two subgroups that we identified as immunologically hot and cold tumors using immunohistochemistry validation. Overall survival of patients with hot tumors was significantly longer (p<0.05). The MTB recommended therapies for 42 patients (95%), which were implemented in 24 cases (57%). Five patients had a PFS2 > 6 months and a PFS ratio > 1.3. The best outcome was achieved using imatinib in a patient with a KIT mutation (p.W557R). After progression, the MTB recommended ponatinib based on a secondary KIT mutation (p.V654A). The patient was still on ponatinib when the observation period ended.

Conclusion: We demonstrate that comprehensive molecular analysis provides clinically relevant information in a subgroup of TET patients. Thymoma, TCs, and NETs present with different molecular characteristics. Distinction between immunologically hot and cold TCs may have value for risk stratification and therapeutic strategies. PARP inhibition could be a potential new treatment option in a small subgroup of TETs. Molecular testing of KIT, germline analysis and genetic counseling should be recommended for all patients with advanced TETs.

Citation Format: Lino Möhrmann, Lysann Rostock, Małgorzata Oleś, Arne Jahn, Marie Arlt, Nagarajan Paramasivam, Korinna Jöhrens, Luise Rupp, Marc Schmitz, Daniela Richter, Sebastian Uhrig, Martina Fröhlich, Barbara Hutter, Jennifer Hüllein, Elena E. Wolf, Dorothea Hanf, Laura Gieldon, Simon Kreutzfeldt, Christoph E. Heilig, Veronica Teleanu, Daniel B. Lipka, Andreas Mock, Ivan Jelas, Damian T. Rieke, Marcel Wiesweg, Melanie Boerries, Anna L. Illert, Alexander Desuki, Thomas Kindler, Angela M. Krackhardt, C. Benedikt Westphalen, Heidrun Grosch, Leonidas Apostolidis, Albrecht Stenzinger, Irina A. Kerle, Christoph Heining, Daniel Hübschmann, Evelin Schröck, Stefan Fröhling, Hanno Glimm. Genomics-based personalized oncology of advanced thymic epithelial tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 926.

Deficiency for SAMHD1 activates MDA5 in a cGAS/STING-dependent manner

Defects in nucleic acid metabolizing enzymes can lead to spontaneous but selective activation of either cGAS/STING or RIG-like receptor (RLR) signaling, causing type I interferon-driven inflammatory diseases. In these pathophysiological conditions, activation of the DNA sensor cGAS and IFN production are linked to spontaneous DNA damage. Physiological, or tonic, IFN signaling on the other hand is essential to functionally prime nucleic acid sensing pathways. Here, we show that low-level chronic DNA damage in mice lacking the Aicardi-Goutières syndrome gene SAMHD1 reduced tumor-free survival when crossed to a p53-deficient, but not to a DNA mismatch repair-deficient background. Increased DNA damage did not result in higher levels of type I interferon. Instead, we found that the chronic interferon response in SAMHD1-deficient mice was driven by the MDA5/MAVS pathway but required functional priming through the cGAS/STING pathway. Our work positions cGAS/STING upstream of tonic IFN signaling in Samhd1-deficient mice and highlights an important role of the pathway in physiological and pathophysiological innate immune priming.

Peri- and intraoperative EEG signatures in newborns and infants

OBJECTIVE

The electroencephalographic derived indices have been developed for adult patients, however these monitors have not been validated for infants.

METHODS

Frontal EEGs were recorded in 115 infants aged <1 year [0-3-months (N = 27), 4-6-months (N = 30), 7-9-months (N = 29) and 10-12-months (N = 29)] who received general anaesthesia with sevoflurane. Total power (µV²) and relative β-, α-, θ-, δ-power (%) were analyzed. Additionally, in 20 EEGs event marker were added (baseline, loss of consciousness, intraoperative situation, extubation) to assess perioperative EEG dynamics.

RESULTS

Newborns show a mean relative δ-power at 80% in intraoperative EEG compared to infants (10-12 months) showing 47.5%. Relative β-power and α-power are low in newborns (mean 3.2% and 4.6%; respectively), with a marked increase in the older infants (4-6 months) (mean 10.9% and 14.4%; respectively). EEG dynamic in newborns from baseline (relative δ-power of 88%) to the intraoperative situation (80.5%) are discrete. In contrast infants >6-months have a strong reduction of relative δ-power from baseline to the intraoperative situation, which corresponds to an increase of faster frequencies.

CONCLUSIONS

Age dependent perioperative EEG signatures can be demonstrated in infants younger than one year.

SIGNIFICANCE

We demonstrate significant differences in EEG readouts between newborns and infants which questions our monitoring systems in paediatric anaesthesia.

Hepatocellular Carcinoma Surveillance in a Cohort of Chronic Hepatitis C Virus-Infected Patients with Cirrhosis

BACKGROUND

Six-monthly hepatocellular carcinoma (HCC) screening in cirrhotic patients has been recommended since 2011. HCC prognosis is associated with diagnosis at an early stage. We examined the prevalence and correlates of 6-monthly HCC surveillance in a cohort of HCV-infected cirrhotic patients.

METHODS

Data were obtained from the medical records of patients receiving care from four hospitals between January 2011 and December 2016. Frequencies and logistic regression were conducted.

RESULTS

Of 2,933 HCV-infected cirrhotic patients, most were ≥ 60 years old (68.5%), male (62.2%), White (65.8%), and had compensated cirrhosis (74.2%). The median follow-up period was 3.5 years. Among these patients, 10.9% were consistently screened 6 monthly and 21.4% were never screened. Patients with a longer history of cirrhosis (AOR = 0.86, 95% CI = 0.80-0.93) were less likely to be screened 6 monthly while decompensated cirrhotic patients (AOR = 1.39, 95% CI = 1.06-1.81) and cirrhotic patients between 18 and 44 years (AOR = 2.01, 95% CI = 1.07-3.74) were more likely to be screened 6 monthly compared to compensated cirrhotic patients and patients 60 years and older respectively. There were no significant differences by race, gender, or insurance type.

CONCLUSION

The prevalence of consistent HCC surveillance remains low despite formalized recommendations. One in five patients was never surveilled. Patients with a longer history of cirrhosis were less likely to be surveilled consistently despite their greater HCC risk. Improving providers' knowledge about current HCC surveillance guidelines, educating patients about the benefits of consistent HCC surveillance, and systemic interventions like clinical reminders and standing HCC surveillance protocols can improve guideline-concordant surveillance in clinical practice.

Fluorescence Excitation Spectrum, Lifetimes and Photoisomerization of Jet-Cooled Conformers of 1,1´-bi(benzocyclobutylidene)

First measurements of fluorescence excitation spectra of the recently synthesized rigid stilbene analogue 1,1´-bi(benzocyclobutylidene) in asupersonic jet expansion show that, in contrast to the parent compound, both the

Chlorinated hydrocarbon insecticides in Colorado beef cattle serum--a pilot environmental monitoring system

A pilot project was initiated to test an existing animal disease surveillance system for use in monitoring environmental pollutants. Eleven chlorinated hydrocarbon insecticides were assayed to provide an indication of environmental contamination. A total of 241 bovine serum samples from 53 Colorado beef ranches was tested; 123 samples (51%) were found to contain detectable concentrations of 1 or more of 11 chlorinated hydrocarbons. There were a total of 203 occurrences of a compound being found at a level exceeding the detection limit. Heptachlor, heptachlor epoxide, lindane, and oxychlordane were the insecticides detected most frequently in bovine sera. This pilot study supports the use of domestic food-producing animals as sentinels of environmental contamination with insecticides.