IL6 and pancreatic ductal adenocarcinoma: What is established in PDAC. Circulating interleukin-6 (IL-6), tumour necrosis factor (TNF), and interleukin-1 (IL-1) family cytokines are elevated in pancreatic ductal adenocarcinoma (PDAC) and correlate with cachexia and adverse host metabolic profiles [55,57,58].