In this study, we evaluated the effects of vitamin E δ-tocotrienol (DT3) and aspirin on Wnt signaling in human colon cancer stem cells (CCSCs) and in the prevention of adenoma formation in APCmin/+ mice. We found that knockdown of the adenomatous polyposis coli (APC) gene led to subsequent activation of Wnt signaling in colon epithelial cells (NCM460-APCsiRNA) and induction of β-catenin and its downstream target proteins c-MYC, cyclin D1, and survivin. When aspirin and DT3 were combined, cell growth and survival were inhibited and apoptosis was induced in colon epithelial cells and in CCSCs. However, DT3 and/or aspirin had little or no effect on control normal colon epithelial cells (NCM460-NCsiRNA). The induction of apoptosis was directly related to activation of caspase 8 and cleavage of BID to truncated BID. In addition, DT3 and/or aspirin-induced apoptosis was associated with cleaved PARP, elevated levels of cytosolic cytochrome c and BAX, and depletion of anti-apoptotic protein BCl-2 in CCSCs. The combination of aspirin and DT3 inhibited the self-renewal capacity, Wnt/β-catenin receptor activity, and expression of β-catenin and its downstream targets c-MYC, cyclin D1 and survivin in CCSCs. We also found that treatment with DT3 alone or combined with aspirin significantly inhibited intestinal adenoma formation and Wnt/ β-catenin signaling and induced apoptosis, compared to vehicle, in APCmin/+ mice. Our study demonstrated a rationale for further investigation of the combination of DT3 and aspirin for colorectal cancer prevention and therapy.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers in the world. Therefore, new therapeutic options are urgently needed to improve the survival of PDAC patients. Protein kinase G (PKG) conducts the interlude of cGMP signaling which is important for healthy as well as for cancer cells. DT3 is a specific inhibitor of PKG, and it has been shown to possess an anti-tumor cytotoxic activity in vitro. The main aim of this work was to investigate anti-tumor effects of DT3 upon PDAC in vivo.Expression of PKG was assessed with real-time PCR analysis in the normal and tumor pancreatic cells. In vitro cell viability, proliferation, apoptosis, necrosis, migration, and invasion of the murine PDAC cell line Panc02 were assessed after DT3 treatment. In vivo anti-tumor effects of DT3 were investigated in the murine Panc02 orthotopic model of PDAC. Western blot analysis was used to determine the phosphorylation state of the proteins of interest.Functional PKGI is preferentially expressed in PDAC cells. DT3 was capable to reduce viability, proliferation, and migration of murine PDAC cells in vitro. At the same time, DT3 treatment did not change the viability of normal epithelial cells of murine liver. In vivo, DT3 treatment reduced the tumor volume and metastases in PDAC-bearing mice, but it was ineffective to prolong the survival of the tumor-bearing animals. In addition, DT3 treatment decreased phosphorylation of GSK-3, P38, and CREB in murine PDAC.Inhibition of PKG could be a potential therapeutic strategy for PDAC treatment which should be carefully validated in future pre-clinical studies.