Rapamycin Partially Mimics the Anticancer Effects of Calorie Restriction in a Murine Model of Pancreatic Cancer
Menée sur un modèle murin de cancer du pancréas, cette étude évalue l’intérêt de la rapamycine, un médicament immunosuppresseur, pour imiter l’effet anti-cancer d’une restriction calorique
Etiologic factors for pancreatic cancer, the fourth deadliest malignant neoplasm in the United States, include obesity and abnormal glucose metabolism. Calorie restriction (CR) and rapamycin each affect energy metabolism and cell survival pathways via inhibition of mammalian target of rapamycin (mTOR) signaling. Using a Panc02 murine pancreatic cancer cell transplant model in 45 male C57BL/6 mice, we tested the hypothesis that rapamycin mimics the effects of CR on pancreatic tumor growth. A chronic regimen of CR, relative to an ad libitum-fed control diet, produced global metabolic effects such as reduced body weight (20.6±1.6g vs. 29.3±2.3g; p<0.0001), improved glucose responsiveness, and decreased circulating levels of insulin-like growth factor (IGF)-1 (126±8ng/mL vs. 199±11ng/mL; p=0.0006) and leptin (1.14±0.2 ng/mL vs. 5.05±1.2 ng/mL; p=0.01). In contrast, rapamycin treatment (2.5mg/kg i.p. every other day, initiated in mice following 20 weeks of ad libitum control diet consumption), relative to control diet, produced no significant change in body weight, IGF-1 or leptin levels, but decreased glucose responsiveness. Pancreatic tumor volume was significantly reduced in the CR group (221±107mm3; p<0.001) and, to a lesser extent, the rapamycin group (374±206mm3; p=0.04) relative to controls (550±147mm3), and this differential inhibition correlated with expression of the proliferation marker Ki-67. Both CR and rapamycin decreased phosphorylation of mTOR, p70/S6K and S6 ribosomal protein, but only CR decreased phosphorylation of Akt, GSK-3β, ERK/MAPK, and STAT-3TYR705. These findings suggest rapamycin partially mimics the anticancer effects of calorie restriction on tumor growth in a murine model of pancreatic cancer.