Stiffness-induced cancer-associated fibroblasts are responsible for immunosuppression in a platelet-derived growth factor ligand-dependent manner

Pancreatic ductal adenocarcinoma (PDAC) is associated with a vast stromal reaction that arises mainly from cancer-associated fibroblasts (CAFs) and promotes both immune escape and tumor growth. Here, we used a mouse model with deletion of the activin A receptor ALK4 in the context of the KrasG12D mutation, which strongly drives collagen deposition that leads to tissue stiffness. By ligand-receptor analysis of single-cell RNA-sequencing data, we identified that, in stiff conditions, neoplastic ductal cells instructed CAFs through sustained platelet-derived growth factor (PDGF) signaling. Tumor-associated tissue rigidity resulted in the emergence of stiffness-induced CAFs (siCAFs) in vitro and in vivo. Similar results were confirmed in human data. siCAFs were able to strongly inhibit CD8+ T-cell responses in vitro and in vivo, promoting local immunosuppression. More importantly, targeting PDGF signaling led to diminished siCAF and reduced tumor growth. Our data show for the first time that early paracrine signaling leads to profound changes in tissue mechanics, impacting immune responses and tumor progression. Our study highlights that PDGF ligand neutralization can normalize the tissue architecture independent of the genetic background, indicating that finely tuned stromal therapy may open new therapeutic avenues in pancreatic cancer.

291 Pre-Operative Venepuncture: An Audit of The Trauma and Orthopaedic Department at The Royal Sussex County Hospital, Brighton

Background

NICE recommends that patients undergoing intermediate or minor elective surgery do not need routine coagulation or transfusion blood testing unless they are ASA 3+ or taking anticoagulation mediation, where testing may be considered. Currently there is no guidance for trauma patients.

Method

We identified all patients that underwent intermediate or minor trauma and orthopaedic surgery within a three-month period from December 2019- February 2020 at the RSCH. We excluded major trauma patients, patients taking anticoagulants and patients with complex admission or past medical history. Computer records were used to identify pre-operative investigations and admission history.

Results

843 patients met our inclusion criteria. In total, 92 clotting studies and 200 transfusion samples were taken preoperatively. The majority of tests were for patients undergoing ankle 130/292 (45%) or Tibia/Fibula 54/292 (18%) procedures. This equates to approximately 1168 blood tests per year. Based on the lab cost of £15.97 for a transfusion sample and £18 for a coagulation sample, this is a cost of approximately £19,616 each year on blood testing that is not indicated.

Discussion

We hope that by presenting these results we will help reduce the unnecessary time and financial burden of routine venipuncture in departments undertaking intermediate and minor surgery.

Arterial complications of pancreatitis: diagnostic and therapeutic role of radiology

Hemorrhage from pseudoaneurysm complicating pancreatitis is an infrequent but very severe condition. In most cases, acute, massive gastrointestinal bleeding is typical at onset, and prognosis of these cases is usually poor. Nine cases of arterial lesions secondary to pancreatic inflammation are presented, eight related to chronic pancreatitis and one to acute postoperative pancreatitis. Five patients were evaluated during emergency episodes because of acutely gastrointestinal bleeding (four cases), and pseudocyst acute bleeding (one case). Four patients were selectively evaluated: three had a history of self-limiting gastrointestinal hemorrhage, whereas one had experienced no episodes of gastrointestinal hemorrhage. Angiography was performed in all cases and was always diagnostic, even in the two cases of very small pseudoaneurysms. Transcatheter arterial blockade was attempted in five patients and failed to control the hemorrhage in one acutely bleeding patient because of irreversible shock. Two cases of pancreatic hemorrhage not related to a pseudocyst were effectively and permanently treated by embolization. A case of a pseudoaneurysm associated with a pseudocyst required surgery in addition to embolization for a definite treatment. Nevertheless, when a pseudoaneurysm or a pseudocyst hemorrhages acutely, transcatheter arterial blockade can control the hemorrhage and improve the hemodynamic status of the patient before surgery.