Background: Available medical therapies against pancreatic cancer are largely ineffective and have many side effects. Physiologically, vitamins K1 and K2 (VK) act as co-factors for γ-carboxylation of prothrombin and other coagulation factors. In previous studies, VK analogs have been found to be potent growth inhibitors of various cancer cells. We hypothesized that the well-tolerated and naturally occurring vitamins K1 and K2 may be useful against pancreatic cancer cell growth.Methods/Results: Four pancreas cancer cell lines were tested. Two of these ( MiaPaCa2 and PL5) were found to be sensitive to growth inhibition by exposure to VK1 or VK2 (defined as IC50 values of 100 μM or less). To address the mechanisms of this growth inhibition, we performed cell cycle and apoptosis studies using V2 (the more potent compound). We found VK induced caspase-dependent apoptosis in over 60% of cells in the sensitive lines at the calculated IC50 range. Further, this induction in apoptosis was effectively inhibited by apoptosis inhibitors. Accompanying apoptosis, a dose and time dependent induction of external signal-regulated kinase (ERK) phosphorylation occurred when sensitive lines were treated with either VK1 or VK2 at growth inhibitory doses. Simultaneous co-treatment of cells with a MEK1 inhibitor and VK prevented both the induction of ERK phosphorylation and the apoptosis, showing that the MAP kinase pathway is central for VK-mediated apoptosis in pancreatic cancer cells. Conclusions: These data show that natural non-toxic K vitamins can inhibit the growth of certain pancreatic cancer cell lines. These novel, safe and clinically-utilized agents initiate a caspase dependent apoptosis via the MAP kinase pathway and could potentially benefit patients with pancreatic cancer either as a single agent or in combination with chemotherapy for treatment or prevention of recurrence post resection.