Midazolam exhibits antitumour and anti-inflammatory effects in a mouse model of pancreatic ductal adenocarcinoma

Background: Anaesthesia and perioperative management contribute to long-term outcomes of patients with cancer, including pancreatic ductal adenocarcinoma. We assessed the antitumour, anti-inflammatory, and analgesic effects of midazolam on LSL-Kras^G12D/+;Trp53^flox/flox;Pdx-1^cre/+ transgenic mice with pancreatic ductal adenocarcinoma. Methods: Six-week-old transgenic mice were administered midazolam 30 mg kg⁻¹ day⁻¹ p.o. (n=13); midazolam 30 mg kg⁻¹ day⁻¹ with 1-(2-chlorophenyl)-N-methyl-N(1-methylpropyl)-3-isoquinoline carboxamide (PK11195) 3 mg kg⁻¹ day⁻¹ i.p., a peripheral benzodiazepine receptor antagonist (n=10); or vehicle (water; n=14) until the humane endpoint. Cancer-associated pain was evaluated using hunching score and mouse grimace scale. Tumour stage and immuno-inflammatory status were determined histopathologically. Anti-proliferative and apoptotic potentials of midazolam were investigated using mouse pancreatic ductal adenocarcinoma cell lines. Results: Midazolam significantly inhibited tumour size and proliferative index of Ki-67 and cyclins in pancreatic ductal adenocarcinoma, which was blocked by administration of PK11195. Local myeloperoxidase⁺ tumour-associated neutrophils, arginase-1⁺ M2-like tumour-associated macrophages, and CD11b⁺Ly-6G⁺ polymorphonuclear myeloid-derived suppressor cells were reduced by midazolam, which was antagonised by administration of PK11195. Hunching and mouse grimace scale were improved by midazolam, whereas the scores increased with midazolam+PK11195 treatment. Plasma pro-inflammatory cytokines, such as interleukin-6 and CC chemokine ligand (CCL)2, CCL3, and CCL5, were reduced by midazolam, whereas these cytokines increased with PK11195. Midazolam inhibited pancreatic ductal adenocarcinoma proliferation through downregulation of cyclins and cyclin-dependent kinases and induced apoptosis in vitro. Conclusions: These results suggest that midazolam inhibits pancreatic ductal adenocarcinoma proliferation and local infiltration of tumour-associated neutrophils, tumour-associated macrophages, and polymorphonuclear myeloid-derived suppressor cells, thereby inhibiting pancreatic ductal adenocarcinoma progression.