Endoplasmic reticulum stress induced by gemcitabine/cannabinoid combination triggers autophagy in pancreatic cancer cells through a ROS mediated mechanism.

Gemcitabine (GEM) is currently the standard treatment for advanced pancreatic adenocarcinoma, one of the most aggressive human tumors, although it has a response rate of less than 20%. The purpose of this thesis was to improve GEM activity by addition of cannabinoids, a novel class of antitumor compounds. This work shows that GEM induces both CB1 and CB2 receptors by an NF-B-dependent mechanism and that its association with cannabinoids synergistically inhibits pancreatic adenocarcinoma cell growth and increases reactive oxygen species (ROS) induced by single treatments. This effect is prevented by the radical scavenger N-acetyl-L-cysteine and by the specific NF-B inhibitor BAY 11-7085, demonstrating that the induction of ROS by GEM/cannabinoids and of NF-B by GEM is required for the antiproliferative synergism. Neither apoptotic nor cytostatic mechanisms are responsible for the synergistic cell growth inhibition, which is strictly associated to the enhancement of endoplasmic reticulum stress and autophagic cell death. . Noteworthy, the antiproliferative synergism is stronger in GEM-resistant compared to GEM-sensitive pancreatic cancer cell lines and no synergism is observed in normal primary fibroblasts. The combined treatment strongly inhibits growth of human pancreatic tumor cells xenografted in nude mice without apparent toxic effects.