Pancreatic adenocarcinomas are among the most malignant forms of cancer and, therefore, it is of especial interest to set new strategies aimed at improving the prognostic of this deadly disease. The present study was undertaken to investigate the action of cannabinoids, a new family of potential antitumoral agents, in pancreatic cancer. We show that cannabinoid receptors are expressed in human pancreatic tumor cell lines and tumor biopsies at much higher levels than in normal pancreatic tissue. Studies conducted with MiaPaCa2 and Panc1 cell lines showed that cannabinoid administration (a) induced apoptosis, (b) increased ceramide levels, and (c) up-regulated mRNA levels of the stress protein p8. These effects were prevented by blockade of the CB2 cannabinoid receptor or by pharmacologic inhibition of ceramide synthesis de novo. Knockdown experiments using selective small interfering RNAs showed the involvement of p8 via its downstream endoplasmic reticulum stress–related targets activating transcription factor 4 (ATF-4) and TRB3 in Δ9-tetrahydrocannabinol–induced apoptosis. Cannabinoids also reduced the growth of tumor cells in two animal models of pancreatic cancer. In addition, cannabinoid treatment inhibited the spreading of pancreatic tumor cells. Moreover, cannabinoid administration selectively increased apoptosis and TRB3 expression in pancreatic tumor cells but not in normal tissue. In conclusion, results presented here show that cannabinoids lead to apoptosis of pancreatic tumor cells via a CB2 receptor and de novo synthesized ceramide-dependent up-regulation of p8 and the endoplasmic reticulum stress–related genes ATF-4 and TRB3. These findings may contribute to set the basis for a new therapeutic approach for the treatment of pancreatic cancer. (Cancer Res 2006; 66(13): 6748-55)
- Pancreatic cancer
- in vivo models
- endoplamic reticulum stress
- de novo synthesized ceramide
Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/).
M. Gironella and M. Lorente, as well as J.L. Iovanna and G. Velasco, contributed equally to this work. A. Carracedo did experiments of cell viability, Western blot, RNA isolation from cultured cells, real-time quantitative PCR, transfections with siRNA, quantification of ceramide levels, and experiments with s.c. and intrapancreatic tumor xenografts and contributed to experiment design, data analysis, and discussion. M. Gironella participated in the experiments with tumor xenografts, immunofluorescence, and RNA isolation from human tumor samples and participated in data analysis and discussion. M. Lorente did RNA isolation from tumor samples, real-time quantitative PCR analysis, transfections with siRNAs, TUNEL staining of tumor samples, and immunofluorescence experiments and participated in data analysis and discussion. S. Garcia processed tumor samples. M. Guzmán participated in experimental design, data analysis, and discussion, as well as critical reading of the manuscript. G. Velasco coordinated the general experimental design, data analysis, and discussion and wrote the manuscript. J.L. Iovanna participated in general experimental design, data analysis, and discussion, as well as critical reading of the manuscript.
- Received January 16, 2006.
- Revision received April 5, 2006.
- Accepted May 5, 2006.
- ©2006 American Association for Cancer Research.