Dicumarol is a naturally occurring anticoagulant obtained from sweet clover. Though such compounds as dicumarol have been utilized in cancer therapy, little is known about the mechanism of action of these drugs. Mitochondria have been hypothesized to be the site of prooxidant production during dicumarol treatment since dicumarol is thought to affect quinone-mediated electron transfer reactions leading to the production of superoxide (O2-), and hydrogen peroxide (H2O2). Dicumarol-induced oxidative stress could represent a difference between tumor cell and normal cell mitochondrial metabolism amenable to manipulations designed to improve cancer therapy. To gain a mechanistic understanding of dicumarol-induced oxidative stress in pancreatic cancer cells, the current proposal will test the hypothesis that mitochondrial production of reactive oxygen species (ROS) mediates the increased susceptibility of pancreatic cancer cells to dicumarol-induced metabolic oxidative stress, relative to normal human cells. We plan to test our hypothesis by pursuing the following three specific aims:
Specific Aim 1 : Determine if mitochondrial O2- and/or H2O2 mediate the cytotoxicity and metabolic oxidative stress seen with dicumarol treatment in pancreatic cancer cells. Transient transduction using adenoviral vectors to increase tumor cell expression of antioxidant enzymes will be used to determine the role of specific ROS in dicumarol-induced cytotoxicity and oxidative stress.
Specific Aim 2 : Determine if rho (0) human cancer cells, deficient in functional mitochondrial electron transport chains demonstrate altered susceptibility to dicumarol-induced cytotoxicity and oxidative stress, relative to parental rho (+) cells containing fully functional mitochondrial electron transport chains.
Specific Aim 3 : Determine using electron transport chain blockers if cancer cells (relative to normal human cells) demonstrate alterations in production of ROS by mitochondrial electron transport chain Complexes I, II, and/or III that could contribute to increased susceptibility to dicumarol-induced metabolic oxidative stress. If it could be rigorously demonstrated that dicumarol-induced preferential cytotoxicity and oxidative stress in human pancreatic cancer cells vs. normal human cell types was dependent on increased production of ROS by mitochondrial metabolism, the proposed experiments could provide evidence supporting the rational design of combined modality cancer therapy based on a fundamental difference between the biochemistry of oxidative metabolism in normal vs. pancreatic cancer cells. ? ? ?
