Everolimus and mycophenolate mofetil sensitize human pancreatic cancer cells to gemcitabine in vitro: a novel adjunct to standard chemotherapy?

BACKGROUND/AIMS: Gemcitabine improves survival in pancreatic adenocarcinoma. A variety of drugs have been tested to potentiate gemcitabine treatment for pancreatic cancer cells. Two major immunosuppressive drugs, mycophenolate mofetil (MMF) and everolimus (RAD001) have been shown to exert an anti-tumoral effect, but their ability to sensitize human pancreatic cell lines during gemcitabine treatment remains unclear. We examined the effects of everolimus and MMF on gemcitabine-treated MiaPaCa and Panc-1 cell lines. METHODS: MiaPaCa and Panc-1 human pancreatic tumor cell lines were subjected to everolimus (0.001-1 microg/ml) or MMF (0.1-100 microg/ml) treatment in combination with gemcitabine (1-10(6) nM). Western blot analysis was performed for Panc-1 cells in the presence or absence of TGF-beta1 and different treatments: 0.1-100 muicro/ml MMF and 0.1-100 microg/ml everolimus. The antiproliferative effect of the treatment was assessed by BrdU test. The results were evaluated by two-way analysis of variance followed by post-hoc tests, and nonlinear regression analysis for dose-response rates. RESULTS: As expected, standard treatment doses of gemcitabine decreased proliferation dose-dependently. Everolimus increased the actual EC(50) response to gemcitabine treatment (1-10(3) nM) to as much as 83.1 and 82.1% in MiaPaCa and Panc-1 cell lines, respectively. Likewise, concomitant administration with MMF altered the EC(50) of gemcitabine treatment in MiaPaCa cell lines to values between 76.8 and 85.2% for doses of >or=1 microg/ml. Even the minor dose of MMF (0.1 microg/ml) increased the antiproliferative effect of gemcitabine by 43.5% for MiaPaCa and 42.4% for Panc-1 cells. In addition, treatment of Panc-1 cells with MMF (0.1-100 microg/ml) dose-dependently inhibited TGF-beta1-induced collagen expression. CONCLUSION: We found an overadditive antiproliferative effect of both MMF and everolimus in gemcitabine-treated MiaPaCa and Panc-1 cells in vitro, and an additional inhibitory effect of MMF on TGF-beta1-induced collagen type I expression. Interestingly, both the sensitizing effect of pancreatic cancer cells to gemcitabine treatment and the inhibition of collagen type I expression could be achieved by clinically feasible doses of everolimus and MMF. The use of these drugs is promising as a novel adjunct to standard chemotherapy.