POLQ inhibition elicits an immune response in homologous recombination-deficient pancreatic adenocarcinoma via cGAS/STING signaling

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy that harbors mutations in homologous recombination-repair (HR-repair) proteins in 20%-25% of cases. Defects in HR impart a specific vulnerability to poly ADP ribose polymerase inhibitors and platinum-containing chemotherapy in tumor cells. However, not all patients who receive these therapies respond, and many who initially respond ultimately develop resistance. Inactivation of the HR pathway is associated with the overexpression of polymerase theta (Polθ, or POLQ). This key enzyme regulates the microhomology-mediated end-joining (MMEJ) pathway of double-strand break (DSB) repair. Using human and murine HR-deficient PDAC models, we found that POLQ knockdown is synthetically lethal in combination with mutations in HR genes such as BRCA1 and BRCA2 and the DNA damage repair gene ATM. Further, POLQ knockdown enhances cytosolic micronuclei formation and activates signaling of cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING), leading to enhanced infiltration of activated CD8+ T cells in BRCA2-deficient PDAC tumors in vivo. Overall, POLQ, a key mediator in the MMEJ pathway, is critical for DSB repair in BRCA2-deficient PDAC. Its inhibition represents a synthetic lethal approach to blocking tumor growth while concurrently activating the cGAS-STING signaling pathway to enhance tumor immune infiltration, highlighting what we believe to be a new role for POLQ in the tumor immune environment.

Single-cell RNA sequencing reveals the effects of chemotherapy on human pancreatic adenocarcinoma and its tumor microenvironment

The tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDAC) is a complex ecosystem that drives tumor progression; however, in-depth single cell characterization of the PDAC TME and its role in response to therapy is lacking. Here, we perform single-cell RNA sequencing on freshly collected human PDAC samples either before or after chemotherapy. Overall, we find a heterogeneous mixture of basal and classical cancer cell subtypes, along with distinct cancer-associated fibroblast and macrophage subpopulations. Strikingly, classical and basal-like cancer cells exhibit similar transcriptional responses to chemotherapy and do not demonstrate a shift towards a basal-like transcriptional program among treated samples. We observe decreased ligand-receptor interactions in treated samples, particularly between TIGIT on CD8 + T cells and its receptor on cancer cells, and identify TIGIT as the major inhibitory checkpoint molecule of CD8 + T cells. Our results suggest that chemotherapy profoundly impacts the PDAC TME and may promote resistance to immunotherapy.

Tumor infiltrating T cell states and checkpoint inhibitor expression in hepatic and pancreatic malignancies

Hepato-pancreatico-biliary (HPB) malignancies are difficult-to-treat and continue to to have a high mortality and significant therapeutic resistance to standard therapies. Immune oncology (IO) therapies have demonstrated efficacy in several solid malignancies when combined with chemotherapy, whereas response rates in pancreatic ductal adenocarcinoma (PDA) are poor. While promising in hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), there remains an unmet need to fully leverage IO therapies to treat HPB tumors. We therefore defined T cell subsets in the tumor microenvironment of HPB patients utilizing a novel, multiparameter flow cytometry and bioinformatics analysis. Our findings quantify the T cell phenotypic states in relation to checkpoint receptor expression. We demonstrate the presence of CD103⁺ tissue resident memory T cells (T_RM), CCR7⁺ central memory T cells, and CD57⁺ terminally differentiated effector cells across all HPB cancers, while the anti-tumor function was dampened by expression of multiple co-inhibitory checkpoint receptors. Terminally exhausted T cells lacking co-stimulatory receptors were more prevalent in PDA, whereas partially exhausted T cells expressing both co-inhibitory and co-stimulatory receptors were most prevalent in HCC, especially in early stage. HCC patients had significantly higher T_RM with a phenotype that could confer restored activation in response to immune checkpoint therapies. Further, we found a lack of robust alteration in T cell activation state or checkpoint expression in response to chemotherapy in PDA patients. These results support that HCC patients might benefit most from combined checkpoint therapies, whereas efforts other than cytotoxic chemotherapy will likely be necessary to increase overall T cell activation in CCA and PDA for future clinical development.

Corrigendum: Tumor infiltrating T cell states and checkpoint inhibitor expression in hepatic and pancreatic malignancies

[This corrects the article DOI: 10.3389/fimmu.2023.1067352.].

Abstract PR005: Primary results of PanCAN-SR1, a phase 1b study evaluating Gemcitabine, nab-Paclitaxel, Canakinumab, and Spartalizumab to target IL-1β and PD-1 in metastatic pancreatic cancer with correlative tissue and blood biomarker analysis

In preclinical work, the inflammatory cytokine IL-1β was shown to be upregulated in pancreatic cancer tumors and to contribute to activation of pancreatic stellate cells and immunosuppression (Das et al 2020). We conducted an open-label multicenter Phase Ib study evaluating gemcitabine, nab-paclitaxel, canakinumab (ACZ885), a high-affinity human anti-interleukin-1β (IL-1β) mAb, and spartalizumab (PDR001), a PD-1 mAb. Eligible subjects had previously untreated metastatic PDA and RECIST measurable disease. The primary objective was to confirm recommended phase II dose by evaluating the incidence of dose limiting toxicities (DLTs) in the first 56 days of dosing in at least 6 evaluable subjects utilizing a Bayesian logistic regression model. Subjects underwent baseline and on-study tissue and blood collection for correlative translational research. Results: 10 subjects were enrolled between Nov 2020 and Mar 2021. At the primary data cut off of May 23, 2021, 6 subjects were evaluable for DLT. There were no DLTs, the recommended Phase II dose was established as: gemcitabine (1000mg/m2 IV) day 1,8,15; nab-paclitaxel (125mg/m2 IV) day 1,8,15; canakinumab (250mg SC) day 1, spartalizumab (400mg IV) day 1; of each 28 day cycle. At the time of an updated database extraction on June 1, 2022, 2 subjects remain on study. Adverse events were consistent with those typically seen with chemotherapy. The most common Grade 3/4 AEs were neutropenia (60%) and anemia (50%), with no fatal AEs. One patient discontinued spartalizumab due to grade 3 pneumonitis. In preliminary efficacy analysis (n=10), there are 3 confirmed PRs, 5 subjects with stable disease, 2 subjects with progression as best response. Individual site data estimates that the 12 month OS rate is 60%; updated RR, PFS and OS data will be reported. Activation of CD8 T cells in peripheral blood and increased serum levels of IFN-induced chemokines CXCL9/10 were observed in both responder and non-responder patients. Using an in vitro suppression assay, we showed that baseline serum from responders could induce myeloid derived suppressor cells, an effect that was abrogated with treatment. Single cell transcriptional profiling, multiplex immunofluorescence and spatial transcriptomics also revealed treatment-dependent shifts in T cell activation state and myeloid cells in the tumors of patients experiencing clinical response. Conclusions: PanCAN-SR1 established the Phase II dose of canakinumab and spartalizumab with chemotherapy in first line metastatic PDA, based upon favorable benefit-risk assessment. Based on our comprehensive analysis of 10 patients treated with combination therapy including IL-1b blockade, we hypothesize that the definitive role of anti-IL-1b in human patients with pancreatic cancer is to reduce systemic immune suppression and to reduce immunosuppressive myeloid cell activation in the tumor. The clinical utility of targeting IL-1β in pancreatic cancer is being evaluated in a randomized Phase II/III study through the Precision Promise clinical trial network. NCT04581343.

Citation Format: Paul E. Oberstein, Osama Rahma, Nina Beri, Amy Stoll-D'Astice, Emily A. Kawaler, Igor Dolgalev, Gregor Werba, Victoire Cardo-Ruffino, Naïma Böllenrücher, Andressa Dias Costa, Saloney Nazeer, Matthew Squires, Jonathan Nowak, Dafna Bar-Sagi, Brian Wolpin, Diane M Simeone, Stephanie K Dougan. Primary results of PanCAN-SR1, a phase 1b study evaluating Gemcitabine, nab-Paclitaxel, Canakinumab, and Spartalizumab to target IL-1β and PD-1 in metastatic pancreatic cancer with correlative tissue and blood biomarker analysis [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr PR005.

Abstract PR010: Single-cell sequencing elucidates the effects of chemotherapy on cancer cell heterogeneity and the tumor microenvironment of human pancreatic adenocarcinoma

The tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDAC) is a complex ecosystem that drives tumor progression. Improving our understanding of the PDAC TME and its role in response to therapy via in-depth single cell characterization will have broad clinical implications for biomarker development and therapeutic design. In this study, we performed single-cell RNA sequencing on freshly collected human PDAC samples of primary (n=16) or metastatic (n=11) origin, either before (n=20) or after (n=7) chemotherapy. We found a heterogeneous mixture of basal and classical Moffitt cancer cell subtypes in all samples, along with distinct cancer-associated fibroblast (CAF) and tumor-associated macrophage (TAM) subpopulations. We identified the major CAF subpopulations as inflammatory CAFs (iCAFs) and myofibroblastic CAFs (myCAFs); within these subpopulations were a very few cells expressing immunogenic features which have previously been associated with antigen presenting CAFs (apCAFs). Tumor-associated macrophages (TAMs) could be categorized into two major subpopulations, C1QC+ TAMs or SPP1+ TAMs, each with distinct functional characteristics. For example, phagocytosis-associated gene sets were enriched in C1QC+ TAMs, while angiogenesis-associated gene sets were enriched in SPP1+ TAMs. Comparison of naïve and chemotherapy treated primary PDAC samples revealed that classical and basal-like cancer cells exhibited similar transcriptional responses to chemotherapy; this contrasts with some previous reports which posited a shift towards a basal-like transcriptional program among treated samples. We further noted that treated samples evinced fewer ligand-receptor interactions, particularly between TIGIT on CD8+ T cells and its ligand on cancer cells. We also identified TIGIT, not PD1, as the major inhibitory checkpoint molecule of CD8+ T cells in the PDAC TME. Altogether, our results suggest that chemotherapy impacts the PDAC TME and may further reduce response to immunotherapy.

Citation Format: Daniel Weissinger, Emily A. Kawaler, Gregor Werba, Ende Zhao, Despoina Kalfakakou, Surajit Dhara, Grace Oh, Xiaohong Jing, Nina Beri, Lauren Khanna, Tamas Gonda, Paul E. Oberstein, Cristina Hajdu, Cynthia Loomis, Adriana Heguy, Mara H. Sherman, Amanda W. Lund, Theodore H. Welling, Igor Dolgalev, Aristotelis Tsirigos, Diane M. Simeone. Single-cell sequencing elucidates the effects of chemotherapy on cancer cell heterogeneity and the tumor microenvironment of human pancreatic adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr PR010.

BTLA+CD200+ B cells dictate the divergent immune landscape and immunotherapeutic resistance in metastatic vs. primary pancreatic cancer

Response to cancer immunotherapy in primary versus metastatic disease has not been well-studied. We found primary pancreatic ductal adenocarcinoma (PDA) is responsive to diverse immunotherapies whereas liver metastases are resistant. We discovered divergent immune landscapes in each compartment. Compared to primary tumor, liver metastases in both mice and humans are infiltrated by highly anergic T cells and MHCII^loIL10⁺ macrophages that are unable to present tumor-antigen. Moreover, a distinctive population of CD24⁺CD44^-CD40^- B cells dominate liver metastases. These B cells are recruited to the metastatic milieu by Muc1^hiIL18^hi tumor cells, which are enriched >10-fold in liver metastases. Recruited B cells drive macrophage-mediated adaptive immune-tolerance via CD200 and BTLA. Depleting B cells or targeting CD200/BTLA enhanced macrophage and T-cell immunogenicity and enabled immunotherapeutic efficacy of liver metastases. Our data detail the mechanistic underpinnings for compartment-specific immunotherapy-responsiveness and suggest that primary PDA models are poor surrogates for evaluating immunity in advanced disease.

Cancer cell states recur across tumor types and form specific interactions with the tumor microenvironment

Transcriptional heterogeneity among malignant cells of a tumor has been studied in individual cancer types and shown to be organized into cancer cell states; however, it remains unclear to what extent these states span tumor types, constituting general features of cancer. Here, we perform a pan-cancer single-cell RNA-sequencing analysis across 15 cancer types and identify a catalog of gene modules whose expression defines recurrent cancer cell states including 'stress', 'interferon response', 'epithelial-mesenchymal transition', 'metal response', 'basal' and 'ciliated'. Spatial transcriptomic analysis linked the interferon response in cancer cells to T cells and macrophages in the tumor microenvironment. Using mouse models, we further found that induction of the interferon response module varies by tumor location and is diminished upon elimination of lymphocytes. Our work provides a framework for studying how cancer cell states interact with the tumor microenvironment to form organized systems capable of immune evasion, drug resistance and metastasis.

Initial efficacy and biomarker analysis of a phase 1b study targeting IL-1β and PD-1 with chemotherapy in metastatic pancreatic cancer (PanCAN-SR1)

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Background: Pancreatic ductal adenocarcinoma (PDA) has been refractory to therapeutic targeting of the immune microenvironment. In preclinical work, IL-1β was upregulated in PDA tumors, and in mouse models, IL-1β expression led to activation of pancreatic stellate cells and immunosuppression. We hypothesize that blockade of IL-1β and PD-1 will result in significant alterations in immune and fibroblast subsets within the PDA microenvironment. Methods: We conducted an open-label multicenter Phase Ib study evaluating gemcitabine and nab-paclitaxel with canakinumab (ACZ885), a high-affinity human anti-interleukin-1β (IL-1β) mAb, and spartalizumab (PDR001), a mAb directed against human PD-1. 10 subjects with untreated metastatic PDA and RECIST measurable disease were enrolled. The primary objective was to identify a recommended phase II/III dose by evaluating the incidence of DLTs in the first 56 days. All subjects underwent baseline and on-study tissue and blood collection for extensive exploratory correlative studies. Secondary objectives including safety and tolerability and preliminary assessment of clinical activity. Results: 10 subjects were enrolled between November 2020 and March 2021. 6 out of 10 were evaluable for the dose confirmation. In the dose confirmation analysis there were no dose limiting toxicities (DLTs) and the recommended Phase II/III dose was established as; gemcitabine (1000 mg/m2 IV) and nab-paclitaxel (125 mg/m2 IV) on day 1,8,15; canakinumab (250 mg via subcutaneous injection) and spartalizumab (400 mg IV) on day 1; of each 28 day cycle. Adverse events were consistent with those seen with chemotherapy and were predominately hematologic. A preliminary efficacy analysis confirms 1 PR and 7 pts with SD. Two of the 7 pts have been treated for 11 and 12 cycles, respectively, without progression. Activation of CD8 T cells in peripheral blood and increased serum levels of IFN-induced chemokines CXCL9/10 were observed in patient samples. Using an in vitro suppression assay, we showed that baseline serum, from patients deriving clinical benefit, could induce myeloid derived suppressor cells, but that this effect was abrogated with treatment. Single cell transcriptional profiling also revealed treatment-dependent shifts in T cell activation state and myeloid cells in the tumors of patients experiencing clinical benefit. Conclusions: In this Phase Ib study, we established the Phase II/III dose of canakinumab and spartalizumab with chemotherapy in first line metastatic PDA. Translational studies suggest putative biomarkers that may help identify responding pts. This novel combination is being evaluated in a randomized Phase II/III study through the Precision Promise clinical trial network. Clinical trial information: NCT04581343.

Impact of preoperative biliary drainage on 30 Day outcomes of patients undergoing pancreaticoduodenectomy for malignancy

BACKGROUND

Preoperative biliary drainage (PBD) has been advocated to address the plethora of physiologic derangements associated with cholestasis. However, available literature reports mixed outcomes and is based on largely outdated and/or single-institution studies.

METHODS

Patients undergoing PBD prior to pancreaticoduodenectomy (PD) for periampullary malignancy between 2014-2018 were identified in the ACS-NSQIP pancreatectomy dataset. Patients with PBD were propensity-score-matched to those without PBD and 30-day outcomes compared.

RESULTS

8,970 patients met our inclusion criteria. 4,473 with obstruction and PBD were matched to 829 with no preoperative drainage procedure. In the non-jaundiced cohort, 711 stented patients were matched to 2,957 without prior intervention. PBD did not influence 30-day mortality (2.2% versus 2.4%) or major morbidity (19.8% versus 20%) in patients with obstructive jaundice. Superficial surgical site infections (SSIs) were more common with PBD (6.8% versus 9.2%), however, no differences in deep or organ-space SSIs were found. Patients without obstruction prior to PBD exhibited a 3-fold increase in wound dehiscence (0.5% versus 1.5%) additionally to increased superficial SSIs.

CONCLUSION

PBD was not associated with an increase in 30-day mortality or major morbidity but increased superficial SSIs. PBD should be limited to symptomatic, profoundly jaundiced patients or those with a delay prior to PD.

Intrahepatic microbes govern liver immunity by programming NKT cells

The gut microbiome shapes local and systemic immunity. The liver is presumed to be a protected sterile site. As such, a hepatic microbiome has not been examined. Here, we showed a liver microbiome in mice and humans that is distinct from the gut and is enriched in Proteobacteria. It undergoes dynamic alterations with age and is influenced by the environment and host physiology. Fecal microbial transfer experiments revealed that the liver microbiome is populated from the gut in a highly selective manner. Hepatic immunity is dependent on the microbiome, specifically Bacteroidetes species. Targeting Bacteroidetes with oral antibiotics reduced hepatic immune cells by ~90%, prevented APC maturation, and mitigated adaptive immunity. Mechanistically, our findings are consistent with presentation of Bacteroidetes-derived glycosphingolipids to NKT cells promoting CCL5 signaling, which drives hepatic leukocyte expansion and activation, among other possible host-microbe interactions. Collectively, we reveal a microbial - glycosphingolipid - NKT - CCL5 axis that underlies hepatic immunity.

The PrEDICT-DGE score as a simple preoperative screening tool identifies patients at increased risk for delayed gastric emptying after pancreaticoduodenectomy

BACKGROUND

Morbidity after Pancreaticoduodenectomy (PD) has remained unchanged over the past decade. Delayed Gastric Emptying (DGE) is a major contributor with significant impact on healthcare-costs, quality of life and, for malignancies, even survival. We sought to develop a scoring system to aid in easy preoperative identification of patients at risk for DGE.

METHODS

The ACS-NSQIP dataset from 2014 to 2018 was queried for patients undergoing PD with Whipple or pylorus preserving reconstruction. 15,154 patients were analyzed using multivariable logistic regression to identify risk factors for DGE, which were incorporated into a prediction model. Subgroup analysis of patients without SSI or fistula (primary DGE) was performed.

RESULTS

We identified 9 factors independently associated with DGE to compile the PrEDICT-DGE score: Procedures (Concurrent adhesiolysis, feeding jejunostomy, vascular reconstruction with vein graft), Elderly (Age>70), Ductal stent (Lack of biliary stent), Invagination (Pancreatic reconstruction technique), COPD, Tobacco use, Disease, systemic (ASA>2), Gender (Male) and Erythrocytes (preoperative RBC-transfusion). PrEDICT-DGE scoring strongly correlated with actual DGE rates (R² = 0.95) and predicted patients at low, intermediate, and high risk. Subgroup analysis of patients with primary DGE, retained all predictive factors, except for age>70 (p = 0.07) and ASA(p = 0.30).

CONCLUSION

PrEDICT-DGE scoring accurately identifies patients at high risk for DGE and can help guide perioperative management.

The biological underpinnings of therapeutic resistance in pancreatic cancer

In this review, Beatty et al. discuss recent advances in our understanding of the biological underpinnings of pancreatic ductal adenocarcinoma (PDAC) and dissect therapeutic targets that are intrinsic to PDAC and those that are defined by noncancer cells, including stromal cells, immune cells, and microbes.

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer-related mortality in the United States and has only recently achieved a 5-yr survival rate of 10%. This dismal prognosis reflects the remarkable capacity of PDAC to effectively adapt to and resist therapeutic intervention. In this review, we discuss recent advances in our understanding of the biological underpinnings of PDAC and their implications as targetable vulnerabilities in this highly lethal disease.

Video-Assisted Thoracoscopic Surgery Lung Resection in United States Veterans: Trends and Outcomes versus Thoracotomy

BACKGROUND

 Video-assisted thoracoscopic surgery (VATS) offers reduced morbidity compared with open thoracotomy (OT) for pulmonary surgery. The use of VATS over time has increased, but at a modest rate in civilian populations. This study examines temporal trends in VATS use and compares outcomes between VATS and OT in the Veterans Health Administration (VHA).

METHODS

 Patients who underwent pulmonary surgery (wedge or segmental resection, lobectomy, or pneumonectomy) at Veterans Affairs centers from 2008 to 2018 were retrospectively identified using the Veterans Affairs Surgical Quality Improvement Project database. The cohort was divided into OT and VATS and propensity score matched, taking into account the type of pulmonary resection, preoperative diagnosis, and comorbidities. Thirty-day postoperative outcomes were compared. The prevalence of VATS use and respective complications over time was also analyzed.

RESULTS

 A total of 16,895 patients were identified, with 5,748 per group after propensity matching. VATS had significantly lower rates of morbidity and a 2-day reduction in hospital stay. Whereas 76% of lung resections were performed open in 2008, nearly 70% of procedures were performed using VATS in 2018. While VATS was associated with an 8% lower rate of major complications compared with thoracotomy in 2008, patients undergoing VATS lung resection in 2018 had a 58% lower rate of complications (p < 0.001).

CONCLUSIONS

 VATS utilization at VHA centers has become the predominant technique used for pulmonary surgeries over time. OT patients had more complications and longer hospital stays compared with VATS. Over the study period, VATS patients had increasingly lower complication rates compared with open surgery.

Presenting Symptomatology of Mediastinal Masses and Its Effect on Surgical Outcomes

OBJECTIVE

Mediastinal masses are commonly encountered by the thoracic surgeon. Few studies have reported on the frequency and characteristics of symptoms at presentation. The primary objective of this study is to determine how often patients present with symptoms from a mediastinal mass. The secondary objective is to determine if the presence of symptoms has an effect on outcomes after surgery.

METHODS

A retrospective review of an institutional database was performed. All patients who underwent surgical resection of a mediastinal mass from 2013 to 2019 were included in the analysis. Medical records were reviewed for the presence or absence of symptoms preoperatively, and these cohorts were compared. Multivariable analysis was performed, adjusting for clinical variables to assess for differences between these cohorts.

RESULTS

70 patients underwent surgery for a mediastinal mass. The average age was 49.2 years, and 46 patients (65.7%) presented with symptoms. There were no significant differences in demographics between the symptomatic and asymptomatic groups. The most common symptom was dyspnea in 18 patients (22%), followed by chest pain (15 patients, 19%) and dysphagia (8 patients, 10%). When comparing symptomatic and asymptomatic patients, symptomatic patients had a larger tumor size (5.8 cm vs 3.8 cm, P = .04) and a longer length of stay (2.0 days vs 1.2 days, P = .02).

CONCLUSIONS

The majority of patients with mediastinal masses present with symptoms, with the most common symptom being dyspnea. Symptomatic patients are more likely to have a larger tumor and tend to have a longer length of hospital stay postoperatively compared to asymptomatic patients.

Impact of Trainee Involvement on Video-Assisted Thoracoscopic Lobectomy for Cancer

BACKGROUND

Previous literature in other surgical disciplines regarding the impact of resident and fellow involvement on operative time and outcomes has yielded mixed results. The impact of trainee involvement on minimally invasive thoracic surgery is unknown. This study compared risk-adjusted differences in operative time and outcomes of video-assisted thoracoscopic lobectomy for cancer between cases performed with and without residents and fellows involved.

METHODS

All patients undergoing elective video-assisted thoracoscopic lobectomy for cancer between 2008 and 2018 were identified in the Veterans Affairs Surgical Quality Improvement Program database. Patients were stratified into 2 cohorts: cases with residents and fellows involved, and cases performed only by attending surgeons. Primary outcomes included operative time, postoperative hospital length of stay, and composite 30-day morbidity and mortality. Secondary outcomes included factors associated with high and low trainee operative autonomy.

RESULTS

A total of 3678 patients met study inclusion criteria. In all, 1780 cases were performed with residents and fellows involved (median postgraduate year, 5; interquartile range, 4-7). Multivariate analysis showed that operative time was significantly shorter in resident- and fellow-involved cases compared with attending-only cases (mean [SD], 3.6 [1.4] versus 3.8 [1.6] hours; P < .001). There were no significant differences in composite 30-day morbidity and mortality (16.0% versus 17.1%; adjusted odds ratio = 0.93; 95% confidence interval, 0.77-1.11; P = .40) or length of stay. Substratification of trainees by postgraduate year resulted in similar findings. Cases performed in July through October and those in the Northeastern United States were associated with low autonomy.

CONCLUSIONS

Current training paradigms in thoracic surgery are safe, and the involvement of motivated and skilled trainees with appropriate supervision may benefit operative duration.

Targeting Piezo1 unleashes innate immunity against cancer and infectious disease

Piezo1 is a mechanosensitive ion channel that has gained recognition for its role in regulating diverse physiological processes. However, the influence of Piezo1 in inflammatory disease, including infection and tumor immunity, is not well studied. We postulated that Piezo1 links physical forces to immune regulation in myeloid cells. We found signal transduction via Piezo1 in myeloid cells and established this channel as the primary sensor of mechanical stress in these cells. Global inhibition of Piezo1 with a peptide inhibitor was protective against both cancer and septic shock and resulted in a diminution in suppressive myeloid cells. Moreover, deletion of Piezo1 in myeloid cells protected against cancer and increased survival in polymicrobial sepsis. Mechanistically, we show that mechanical stimulation promotes Piezo1-dependent myeloid cell expansion by suppressing the retinoblastoma gene Rb1 We further show that Piezo1-mediated silencing of Rb1 is regulated via up-regulation of histone deacetylase 2. Collectively, our work uncovers Piezo1 as a targetable immune checkpoint that drives immunosuppressive myelopoiesis in cancer and infectious disease.

Arterial, but Not Venous, Reconstruction Increases 30-Day Morbidity and Mortality in Pancreaticoduodenectomy

BACKGROUND

Vascular reconstruction during pancreaticoduodenectomy is increasingly utilized to improve pancreatic cancer resectability. However, few multi-institutional studies have evaluated the morbidity and mortality of arterial and venous reconstruction during this procedure.

METHODS

A retrospective analysis was performed utilizing the targeted pancreas module of the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) for pancreaticoduodenectomy from 2014 to 2015. Demographics, comorbidities, and 30-day outcomes for patients who underwent venous or arterial reconstruction and both were compared to no reconstruction.

RESULTS

A total of 3002 patients were included in our study: 384 with venous reconstruction, 52 with arterial, 81 with both, and 2566 without. Compared to patients without reconstruction, those who underwent venous reconstruction had more congestive heart failure (1.8% vs 0.2%, P < 0.01), those with arterial reconstruction had higher rates of pulmonary disease (11.5% vs. 4.5%, P = 0.02), and neoadjuvant chemotherapy was more common in both venous (34% vs 12%, P < 0.01) and arterial reconstruction (21% vs 12%, P = 0.04). In multivariable analysis, there was no increase in morbidity or mortality following venous reconstruction. However, arterial reconstruction was associated with increased 30-day mortality with an odds ratio (OR): 6.7, 95%; confidence interval (CI): 1.8-25. Morbidity was increased as represented with return to the operating room (OR: 4.5, 95%; CI: 1.5-15), pancreatic fistula (OR: 4.4, 95%; CI: 1.7-11), and reintubation (OR: 3.9, 95%; CI: 1.1-14).

CONCLUSIONS

Venous reconstruction during pancreaticoduodenectomy does not increase perioperative morbidity or mortality and should be considered for patients previously considered to be unresectable or those where R0 resection would otherwise not be possible due to venous involvement. Careful consideration should be made prior to arterial reconstruction given the significant increase in perioperative complications and death within 30 days.

Increased serum concentrations of soluble ST2 predict mortality after burn injury

Background:

Large burn injuries induce a systemic response in affected patients. Soluble ST2 (sST2) acts as a decoy receptor for interleukin-33 (IL-33) and has immunosuppressive effects. sST2 has been described previously as a prognostic serum marker. Our aim was to evaluate serum concentrations of sST2 and IL-33 after thermal injury and elucidate whether sST2 is associated with mortality in these patients.

Methods:

We included 32 burn patients (total body surface area [TBSA] >10%) admitted to our burn intensive care unit and compared them to eight healthy probands. Serum concentrations of sST2 and IL-33 were measured serially using an enzyme-linked immunosorbent assay (ELISA) technique.

Results:

The mean TBSA was 32.5%±19.6%. Six patients (18.8%) died during the hospital stay. Serum analyses showed significantly increased concentrations of sST2 and reduced concentrations of IL-33 in burn patients compared to healthy controls. In our study cohort, higher serum concentrations of sST2 were a strong independent predictor of mortality.

Conclusions:

Burn injuries cause an increment of sST2 serum concentrations with a concomitant reduction of IL-33. Higher concentrations of sST2 are associated with increased in-hospital mortality in burn patients.

The Pancreatic Cancer Microbiome Promotes Oncogenesis by Induction of Innate and Adaptive Immune Suppression

We found that the cancerous pancreas harbors a markedly more abundant microbiome compared with normal pancreas in both mice and humans, and select bacteria are differentially increased in the tumorous pancreas compared with gut. Ablation of the microbiome protects against preinvasive and invasive pancreatic ductal adenocarcinoma (PDA), whereas transfer of bacteria from PDA-bearing hosts, but not controls, reverses tumor protection. Bacterial ablation was associated with immunogenic reprogramming of the PDA tumor microenvironment, including a reduction in myeloid-derived suppressor cells and an increase in M1 macrophage differentiation, promoting TH1 differentiation of CD4⁺ T cells and CD8⁺ T-cell activation. Bacterial ablation also enabled efficacy for checkpoint-targeted immunotherapy by upregulating PD-1 expression. Mechanistically, the PDA microbiome generated a tolerogenic immune program by differentially activating select Toll-like receptors in monocytic cells. These data suggest that endogenous microbiota promote the crippling immune-suppression characteristic of PDA and that the microbiome has potential as a therapeutic target in the modulation of disease progression.Significance: We found that a distinct and abundant microbiome drives suppressive monocytic cellular differentiation in pancreatic cancer via selective Toll-like receptor ligation leading to T-cell anergy. Targeting the microbiome protects against oncogenesis, reverses intratumoral immune tolerance, and enables efficacy for checkpoint-based immunotherapy. These data have implications for understanding immune suppression in pancreatic cancer and its reversal in the clinic. Cancer Discov; 8(4); 403-16. ©2018 AACR.See related commentary by Riquelme et al., p. 386This article is highlighted in the In This Issue feature, p. 371.

NLRP3 signaling drives macrophage-induced adaptive immune suppression in pancreatic carcinoma

The tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDA) is characterized by immune tolerance, which enables disease to progress unabated by adaptive immunity. However, the drivers of this tolerogenic program are incompletely defined. In this study, we found that NLRP3 promotes expansion of immune-suppressive macrophages in PDA. NLRP3 signaling in macrophages drives the differentiation of CD4+ T cells into tumor-promoting T helper type 2 cell (Th2 cell), Th17 cell, and regulatory T cell populations while suppressing Th1 cell polarization and cytotoxic CD8+ T cell activation. The suppressive effects of NLRP3 signaling were IL-10 dependent. Pharmacological inhibition or deletion of NLRP3, ASC (apoptosis-associated speck-like protein containing a CARD complex), or caspase-1 protected against PDA and was associated with immunogenic reprogramming of innate and adaptive immunity within the TME. Similarly, transfer of PDA-entrained macrophages or T cells from NLRP3-/- hosts was protective. These data suggest that targeting NLRP3 holds the promise for the immunotherapy of PDA.

Dectin 1 activation on macrophages by galectin 9 promotes pancreatic carcinoma and peritumoral immune tolerance

The progression of pancreatic oncogenesis requires immune-suppressive inflammation in cooperation with oncogenic mutations. However, the drivers of intratumoral immune tolerance are uncertain. Dectin 1 is an innate immune receptor crucial for anti-fungal immunity, but its role in sterile inflammation and oncogenesis has not been well defined. Furthermore, non-pathogen-derived ligands for dectin 1 have not been characterized. We found that dectin 1 is highly expressed on macrophages in pancreatic ductal adenocarcinoma (PDA). Dectin 1 ligation accelerated the progression of PDA in mice, whereas deletion of Clec7a-the gene encoding dectin 1-or blockade of dectin 1 downstream signaling was protective. We found that dectin 1 can ligate the lectin galectin 9 in mouse and human PDA, which results in tolerogenic macrophage programming and adaptive immune suppression. Upon disruption of the dectin 1-galectin 9 axis, CD4⁺ and CD8⁺ T cells, which are dispensable for PDA progression in hosts with an intact signaling axis, become reprogrammed into indispensable mediators of anti-tumor immunity. These data suggest that targeting dectin 1 signaling is an attractive strategy for developing an immunotherapy for PDA.

Abstract A08: Dectin-1 signaling drives pancreatic oncogenesis by promoting adaptive immune suppression

Progression of pancreatic oncogenesis requires immune-suppressive inflammation in cooperation with oncogenic mutations. However, the drivers of intra-tumoral immune tolerance are uncertain. Dectin-1 is an innate immune receptor critical in anti-fungal immunity, but its role in sterile inflammation and oncogenesis is not well-defined. Further, non-pathogen-derived ligands for Dectin-1 have not been characterized. We found that Dectin-1 is highly expressed on myeloid cells in pancreatic ductal adenocarcinoma (PDA). Moreover, Dectin-1 ligation accelerates PDA, whereas Dectin-1 deletion, or blockade of its downstream signaling, was highly protective. We show that Dectin-1 ligates the lectin Galectin-9 in the PDA tumor microenvironment (TME) leading to macrophage-induced adaptive immune suppression. Upon interruption of the Dectin-1–Galectin-9 axis, CD4+ and CD8+ T cells – which are dispensable to PDA progression in hosts with an intact signaling axis – become reprogrammed into indispensable mediators of anti-tumor immunity. These data suggest that Dectin-1 and Galectin-9 are novel and attractive targets for PDA immunotherapy.

Citation Format: Donnele Daley, Neha Akkad, Navyatha Mohan, Atsuo Ochi, Gregor Werba, Vishnu Mani, Rocky Barilla, Constantinos Zambirinis, Mautin Hundeyin, Ki Buom Lee, Steven Chang, Ding Wang, Lawrence Gardener, Beatrix Ueberheide, George Miller. Dectin-1 signaling drives pancreatic oncogenesis by promoting adaptive immune suppression. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr A08.

Abstract B20: The necrosome promotes pancreatic Oncogenesis via CXCL1 and mincle-induced immune Suppression

Neoplastic pancreatic epithelial cells are widely believed to die via Caspase 8-dependantapoptotic cell death and chemotherapy is thought to further promote tumor apoptosis. Conversely, disruption of apoptosis is a basic modality cancer cells exploit for survival. However, the role of necroptosis, or programmed necrosis, in pancreatic ductal adenocarcinoma (PDA) is uncertain. There are a multitude of potential inducers of necroptosis in PDA including ligation of TNFR1, CD95, TRAIL receptors, Toll-like receptors, ROS, and Chemotherapeutics. We doscovered that the principal components of the necrosome, RIP1 and RIP3, are highly expressed in PDA and are further upregulated by chemotherapy. Blockade of the necrosome in vitro promoted cancer cell proliferation and induced an aggressive oncogenic phenotype. However, belying these findings, in vivo RIP3 deletion or RIP1 inhibition was protective against oncogenic progression and was associated with the development of a highly immunogenic myeloid and T cell infiltrate. The immune-suppressive tumor microenvironment (TME) associated with intact RIP1/RIP3 signaling was in-part contingent on necroptosis-induced CXCL1 expression whereas CXCL1 blockade was protective against PDA. Moreover, we found that cytoplasmic SAP130 was expressed in PDA in a RIP1/RIP3-dependent manner, and Mincle – its cognate receptor – was upregulated in tumor-infiltrating myeloid cells. Mincle ligation by SAP130 promoted oncogenesis whereas Mincle deletion was protective and phenocopied the immunogenic reprogramming of the TME characteristic of RIP3 deletion. Cellular depletion experiments suggested that whereas inhibitory macrophages promote tumorigenesis in PDA, they lose their immune-suppressive effects in the context of RIP3 or Mincle deletion. As such, T cells which are dispensable to PDA progression in hosts with intact RIP3 or Mincle signaling become reprogrammed into indispensable mediators of anti-tumor immunity in absence of RIP3 or Mincle. Our work describes parallel networks of necroptosis-induced CXCL1 and Mincle signaling which critically promote macrophage-induced adaptive immune suppression enabling PDA progression.

Citation Format: Lena Seifert, Gregor Werba, Shaun Tiwari, Ly Nancy Ngoc Giao, Dalia Alqunaibit, Sara Alothman, Donnele Daley, Mautin Hundeyin, Vishnu R. Mani, Rocky Barilla, George Miller.{Authors}. The necrosome promotes pancreatic Oncogenesis via CXCL1 and mincle-induced immune Suppression. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B20.

Radiation Therapy Induces Macrophages to Suppress T-Cell Responses Against Pancreatic Tumors in Mice

BACKGROUND & AIMS

The role of radiation therapy in the treatment of patients with pancreatic ductal adenocarcinoma (PDA) is controversial. Randomized controlled trials investigating the efficacy of radiation therapy in patients with locally advanced unresectable PDA have reported mixed results, with effects ranging from modest benefit to worse outcomes compared with control therapies. We investigated whether radiation causes inflammatory cells to acquire an immune-suppressive phenotype that limits the therapeutic effects of radiation on invasive PDAs and accelerates progression of preinvasive foci.

METHODS

We investigated the effects of radiation therapy in p48(Cre);LSL-Kras(G12D) (KC) and p48(Cre);LSLKras(G12D);LSL-Trp53(R172H) (KPC) mice, as well as in C57BL/6 mice with orthotopic tumors grown from FC1242 cells derived from KPC mice. Some mice were given neutralizing antibodies against macrophage colony-stimulating factor 1 (CSF1 or MCSF) or F4/80. Pancreata were exposed to doses of radiation ranging from 2 to 12 Gy and analyzed by flow cytometry.

RESULTS

Pancreata of KC mice exposed to radiation had a higher frequency of advanced pancreatic intraepithelial lesions and more foci of invasive cancer than pancreata of unexposed mice (controls); radiation reduced survival time by more than 6 months. A greater proportion of macrophages from radiation treated invasive and preinvasive pancreatic tumors had an immune-suppressive, M2-like phenotype compared with control mice. Pancreata from mice exposed to radiation had fewer CD8(+) T cells than controls, and greater numbers of CD4(+) T cells of T-helper 2 and T-regulatory cell phenotypes. Adoptive transfer of T cells from irradiated PDA to tumors of control mice accelerated tumor growth. Radiation induced production of MCSF by PDA cells. A neutralizing antibody against MCSF prevented radiation from altering the phenotype of macrophages in tumors, increasing the anti-tumor T-cell response and slowing tumor growth.

CONCLUSIONS

Radiation treatment causes macrophages murine PDA to acquire an immune-suppressive phenotype and disabled T-cell-mediated anti-tumor responses. MCSF blockade negates this effect, allowing radiation to have increased efficacy in slowing tumor growth.

The necrosome promotes pancreatic oncogenesis via CXCL1 and Mincle-induced immune suppression

Neoplastic pancreatic epithelial cells are widely believed to die via Caspase 8-dependant apoptotic cell death and chemotherapy is thought to further promote tumor apoptosis¹. Conversely, disruption of apoptosis is a basic modality cancer cells exploit for survival^2,3. However, the role of necroptosis, or programmed necrosis, in pancreatic ductal adenocarcinoma (PDA) is uncertain. There are a multitude of potential inducers of necroptosis in PDA including ligation of TNFR1, CD95, TRAIL receptors, Toll-like receptors, ROS, and Chemotherapeutics^4,5. Here we report that the principal components of the necrosome, RIP1 and RIP3, are highly expressed in PDA and are further upregulated by chemotherapy. Blockade of the necrosome in vitro promoted cancer cell proliferation and induced an aggressive oncogenic phenotype. By contrast, in vivo RIP3 deletion or RIP1 inhibition was protective against oncogenic progression and was associated with the development of a highly immunogenic myeloid and T cell infiltrate. The immune-suppressive tumor microenvironment (TME) associated with intact RIP1/RIP3 signaling was in-part contingent on necroptosis-induced CXCL1 expression whereas CXCL1 blockade was protective against PDA. Moreover, we found that cytoplasmic SAP130 was expressed in PDA in a RIP1/RIP3-dependent manner, and Mincle – its cognate receptor – was upregulated in tumor-infiltrating myeloid cells. Mincle ligation by SAP130 promoted oncogenesis whereas Mincle deletion was protective and phenocopied the immunogenic reprogramming of the TME characteristic of RIP3 deletion. Cellular depletion experiments suggested that whereas inhibitory macrophages promote tumorigenesis in PDA, they lose their immune-suppressive effects in the context of RIP3 or Mincle deletion. As such, T cells which are dispensable to PDA progression in hosts with intact RIP3 or Mincle signaling become reprogrammed into indispensable mediators of anti-tumor immunity in absence of RIP3 or Mincle. Our work describes parallel networks of necroptosis-induced CXCL1 and Mincle signaling which critically promote macrophage-induced adaptive immune suppression enabling PDA progression.

Abstract A145: Radiation therapy induces tumor-promoting immune suppression in the microenvironment of pancreatic carcinoma

Radiation therapy (RT) has shown marginal efficacy in patients with pancreatic ductal adenocarcinoma (PDA). Two of the past three randomized controlled trials investigating the efficacy of RT for patients with locally advanced unresectable PDA have shown a statistically significant worse survival by 40% or more for patients receiving RT. We postulated that RT reprograms inflammatory cells within the tumor microenvironment to an immune suppressive phenotype limiting the efficacy of RT in invasive PDA and accelerating disease progression in surrounding pre-invasive foci. We found that RT markedly accelerates the progression of pre-invasive PDA in a dose-dependent manner and reduces animal survival by more than 6 months. In both invasive and pre-invasive PDA, RT reprograms immunogenic macrophages towards an immune-suppressive M2 phenotype resulting in CD8 T cell scarcity and Th2 and Treg differentiation of CD4 T cells. Moreover, adoptive transfer of T cells harvested from RT-treated tumors accelerates tumor growth in recipient hosts. We show that M-CSF blockade concurrent with RT prevents immune-suppressive macrophage and T cell reprogramming and markedly enhances the efficacy of RT in PDA. These data suggest that targeting macrophage reprogramming can unleash the utility of RT for PDA.

Citation Format: Lena Tomkötter, Gregor Werba, Susanna Nguy, Sara Alothman, Dalia Alqunaibit, Shaun Tiwari, Nancy Ngoc Giao Ly, Donnele Daley, Atsuo Ochi, Rocky Barilla, Alejandro Torres-Hernandez, Ilenia Pellicciotta, Kevin Du, George Miller. Radiation therapy induces tumor-promoting immune suppression in the microenvironment of pancreatic carcinoma. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A145.

Dectin-1 Regulates Hepatic Fibrosis and Hepatocarcinogenesis by Suppressing TLR4 Signaling Pathways

Dectin-1 is a C-type lectin receptor critical in anti-fungal immunity, but Dectin-1 has not been linked to regulation of sterile inflammation or oncogenesis. We found that Dectin-1 expression is upregulated in hepatic fibrosis and liver cancer. However, Dectin-1 deletion exacerbates liver fibro-inflammatory disease and accelerates hepatocarcinogenesis. Mechanistically, we found that Dectin-1 protects against chronic liver disease by suppressing TLR4 signaling in hepatic inflammatory and stellate cells. Accordingly, Dectin-1(-/-) mice exhibited augmented cytokine production and reduced survival in lipopolysaccharide (LPS)-mediated sepsis, whereas Dectin-1 activation was protective. We showed that Dectin-1 inhibits TLR4 signaling by mitigating TLR4 and CD14 expression, which are regulated by Dectin-1-dependent macrophage colony stimulating factor (M-CSF) expression. Our study suggests that Dectin-1 is an attractive target for experimental therapeutics in hepatic fibrosis and neoplastic transformation. More broadly, our work deciphers critical cross-talk between pattern recognition receptors and implicates a role for Dectin-1 in suppression of sterile inflammation, inflammation-induced oncogenesis, and LPS-mediated sepsis.

A phase II trial of two durations of Bevacizumab added to neoadjuvant gemcitabine for borderline and locally advanced pancreatic cancer

BACKGROUND

We report the results of a phase II trial of adding the anti-ascular endothelial growth factor (VEGF) bevacizumab to gemcitabine neoadjuvant chemotherapy for patients with borderline and unresectable non-metastatic pancreatic cancer.

PATIENTS AND METHODS

Patients were assigned to one of the two treatment arms. Both groups received 1,000 mg/m(2) gemcitabine on days 1, 8, and 15 of a 4-week cycle for a total of four cycles. Group 1 received 5 mg/kg bevacizumab for six weeks (three doses), every second week, starting at week 6 of gemcitabine therapy. Group 2 received 5 mg/kg bevacizumab for 12 weeks (six doses), every second week, starting at week 1 of gemcitabine therapy. The objective of the present study was to assess the rate of complete radical resection and overall survival.

RESULTS

A total of 30 patients were enrolled: 19 patients had unresectable and 11 patients had borderline-resectable pancreatic cancer. Eleven patients (37%) underwent resection. The median overall survival of patients who underwent tumor resection was 13 months (95% confidence interval=11-15 months).

CONCLUSION

In general, adding bevacizumab to neoadjuvant gemcitabine does not improve outcomes for patients with locally advanced pancreatic cancer. However, in individual cases, surgery is consequently possible and prolonged survival may be observed.

Phosphorylation of STAT3 correlates with HER2 status, but not with survival in pancreatic ductal adenocarcinoma

Activation of signal-transcriptional factor signal transducer and activator of transcription 3 (STAT3) is associated with more aggressive behaviour in a variety of human malignancies. As selective STAT3 inhibitors exist, this protein might represent a novel therapeutic target. Although STAT3 seems to play an important role in progression of pancreatic ductal carcinoma (PDAC), only few data on this subject exist. The aim of our study was the investigation of STAT3 activation and its correlation with its possible regulator HER2. Expression of tyrosine-705 phosphorylated STAT3 (pSTAT3) was determined immunohistochemically in 79 PDACs. HER2 status assessed by immunohistochemistry and double colour silver in situ hybridization was available from a previous study. PSTAT3 expression was seen in 33 (41.8%) patients. Six patients were scored as HER2 positive having strong correlation with pSTAT3 expression (p = 0.004, Fisher's exact test). No association of pSTAT3 expression with patients' age, tumour staging and grading, perineural invasion of tumour cells or survival time was seen. pSTAT3 is frequently expressed in PDAC. Nevertheless, its immediate clinical relevance seems to be low. However, further research needs to determine whether STAT3 status in PDAC is predictive for the response to novel targeting therapies.

Anti-thymocyte globulin induces neoangiogenesis and preserves cardiac function after experimental myocardial infarction

Rationale

Acute myocardial infarction (AMI) followed by ventricular remodeling is the major cause of congestive heart failure and death in western world countries.

Objective

Of relevance are reports showing that infusion of apoptotic leucocytes or anti-lymphocyte serum after AMI reduces myocardial necrosis and preserves cardiac function. In order to corroborate this therapeutic mechanism, the utilization of an immunosuppressive agent with a comparable mechanism, such as anti-thymocyte globulin (ATG) was evaluated in this study.

Methods and Results

AMI was induced in rats by ligation of the left anterior descending artery. Initially after the onset of ischemia, rabbit ATG (10 mg/rat) was injected intravenously. In vitro and in vivo experiments showed that ATG induced a pronounced release of pro-angiogenic and chemotactic factors. Moreover, paracrine factors released from ATG co-incubated cell cultures conferred a down-regulation of p53 in cardiac myocytes. Rats that were injected with ATG evidenced higher numbers of CD68+ macrophages in the ischemic myocardium. Animals injected with ATG evidenced less myocardial necrosis, showed a significant reduction of infarct dimension and an improvement of post-AMI remodeling after six weeks (infarct dimension 24.9% vs. 11.4%, p<0.01). Moreover, a higher vessel density in the peri-infarct region indicated a better collateralization in rats that were injected with ATG.

Conclusions

These data indicate that ATG, a therapeutic agent successfully applied in clinical transplant immunology, triggered cardioprotective effects after AMI that salvaged ischemic myocardium by down-regulation of p53. This might have raised the resistance against apoptotic cell death during ischemia. The combination of these mechanisms seems to be causative for improved cardiac function and less ventricular remodeling after experimental AMI.

Intravenous and intramyocardial injection of apoptotic white blood cell suspensions prevents ventricular remodelling by increasing elastin expression in cardiac scar tissue after myocardial infarction

Congestive heart failure developing after acute myocardial infarction (AMI) is a major cause of morbidity and mortality. Clinical trials of cell-based therapy after AMI evidenced only a moderate benefit. We could show previously that suspensions of apoptotic peripheral blood mononuclear cells (PBMC) are able to reduce myocardial damage in a rat model of AMI. Here we experimentally examined the biochemical mechanisms involved in preventing ventricular remodelling and preserving cardiac function after AMI. Cell suspensions of apoptotic cells were injected intravenously or intramyocardially after experimental AMI induced by coronary artery ligation in rats. Administration of cell culture medium or viable PBMC served as controls. Immunohistological analysis was performed to analyse the cellular infiltrate in the ischaemic myocardium. Cardiac function was quantified by echocardiography. Planimetry of the infarcted hearts showed a significant reduction of infarction size and an improvement of post AMI remodelling in rats treated with suspensions of apoptotic PBMC (injected either intravenously or intramoycardially). Moreover, these hearts evidenced enhanced homing of macrophages and cells staining positive for c-kit, FLK-1, IGF-I and FGF-2 as compared to controls. A major finding in this study further was that the ratio of elastic and collagenous fibres within the scar tissue was altered in a favourable fashion in rats injected with apoptotic cells. Intravenous or intramyocardial injection of apoptotic cell suspensions results in attenuation of myocardial remodelling after experimental AMI, preserves left ventricular function, increases homing of regenerative cells and alters the composition of cardiac scar tissue. The higher expression of elastic fibres provides passive energy to the cardiac scar tissue and results in prevention of ventricular remodelling.