We established an in-vitro model to study the mechanisms of bile reflux and cigarette smoking on the metabolic regulation of EAC. The bile acid, deoxycholic acid (DCA), is a main component of bile reflux and thought to be the most carcinogenic. Altering mitochondrial respiration revealed a decrease in ATP production and mitochondrial membrane potential with an unexpected increase in ROS. The expression of several metabolic genes were evaluated which revealed that uncoupling protein 2 (UCP2) was significantly repressed by CSC and DCA. UCP2 serves as a feedback mechanism to limit ROS in normal conditions; its reduction with CSC and DCA would explain an increase in ROS. The role of UCP2 in the progression of EAC cells revealed that the mitochondria or bioenergetics is quite relevant to the malignant progression of these cells. This project has been returned for revisions to the journal Oncotarget and our planned responses should be completed within 4 weeks. This project lead to evaluation of MOMP. These changes may be early events in apoptosis, so members of the Bcl-2 family were evaluated which revealed the upregulation of mitochondrial outer membrane proteins, Bak and Bax. MOMP occurs with the colocalization of Bak and Bax to the outer mitochondrial membrane. These proteins are thought to be terminal steps in apoptosis. However, at the doses in this model, no apoptosis or reduction in proliferation or viability occurred, therefore, CSC and DCA may induce MOMP but without apoptosis - a phenomenon called 'Minority MOMP'. In minority MOMP, the oncogenetic proteins are released and cause DNA damage and mutagenesis instead of apoptosis. We hypothesize that minority MOMP links CSC and DCA to EAC development and progression. While Bak and Bax may lead to minority MOMP, they may paradoxically 'prime' the mitochondria for apoptosis. These mechanisms and the evaluation with BH3 profiling is one of the major focuses in our laboratory.
