Dietary fat stimulates pancreatic cancer growth and promotes fibrosis of the tumor microenvironment through the cholecystokinin receptor.

The gastrointestinal peptide cholecystokinin (CCK) is released from the duodenum in response to dietary fat to aid in digestion, and plasma CCK levels are elevated with the consumption of high-fat diets. CCK is also a trophic peptide for the pancreas and has also been shown to stimulate growth of pancreatic cancer. In the current investigation, we studied the influence of a diet high in saturated fat on the growth of pancreatic cancer in syngeneic murine models before the mice became obese to exclude the confounding factors associated with obesity. The high-fat diet significantly increased growth and metastasis of pancreatic cancer compared with the control diet, and the stimulatory effect was blocked by the CCK-receptor antagonist proglumide. We then selectively knocked out the CCK receptor on the pancreatic cancer cells using clustered regularly interspaced short palindromic repeats technology and showed that without CCK-receptors, dietary fat was unable to stimulate cancer growth. We next demonstrated that dietary fat failed to influence pancreatic cancer xenograft growth in genetically engineered CCK peptide knockout mice. The tumor-associated fibrosis that is so prevalent in the pancreatic cancer microenvironment was significantly decreased with CCK-receptor antagonist therapy because fibroblasts also have CCK receptors. The CCK-receptor antagonist proglumide also altered tumor metalloprotease expression and increased tumor suppressor genes by a PCR array. Our studies confirm that a diet high in saturated fat promotes growth of pancreatic cancer and the action is mediated by the CCK-receptor pathway. NEW & NOTEWORTHY Diets high in long-chain saturated fats promote growth of pancreatic cancer independent of obesity. The mechanism through which dietary fat promotes cancer is mediated through the cholecystokinin (CCK) receptor pathway. Therapy with a CCK-receptor antagonist altered the tumor microenvironment by reducing fibrosis, increasing cluster of differentiation 8+ lymphocytes, increasing tumor suppressor genes, and thus decreasing metastases. Use of CCK-receptor antagonist therapy with standard chemotherapy for pancreatic cancer may improve response by altering the tumor microenvironment.