Date of Graduation
12-2014
Document Type
Thesis (MS)
Program Affiliation
Cancer Biology
Degree Name
Masters of Science (MS)
Advisor/Committee Chair
John V. Heymach, M.D., Ph.D.
Committee Member
Gary E. Gallick, Ph.D.
Committee Member
Varsha V. Gandhi, Ph.D.
Committee Member
Faye M. Johnson, M.D., Ph.D.
Committee Member
Dennis Hughes, M.D., Ph.D.
Abstract
Lung cancer is the second most frequent cancer in United States, which represents about 13.5% of new cancer cases every year. It accounts for about 27.2% of all cancer related deaths, which is more than the sum of deaths caused by prancretic, breast and colorectal. On average, only about 16% of lung cancer patients survive beyond 5 years. LKB1 is the third most mutated gene in lung cancer. It has been shown that LKB1 is mutated in at least 15% to 30% of NSCLC. Tumor with LKB1 mutation is associated with poor differentiation, high metastasis and worse response to chemotherapy. The development of targeted therapies has greatly improved the prognosis of a small subtype of lung cancer. However, there is no targeted therapy for this subtype and less effective chemotherapy is still being used as the first line treatment.
In normal cells, LKB1 regulates cellular energy by balancing energy production and consumption. Because tumor cells need vast amounts of energy for their growth, they must adapt alternative strategies to amplify their energy production. During low energy condition in normal cells, LKB1 signals cellular proteins to decrease energy consumption, often resulting in decreased cell growth. However, in LKB1 deficient tumor cells, there is no signal to slow down cell growth. As such, these tumor cells have a disrupted balance between energy consumption and production, and LKB1 deficient tumor cells are able to escape the normal growth inhibitory signals, resulting in unrestricted cell growth. I hypothesize that targeting cellular pathways regulating energy production in LKB1 deficient NSCLC will inhibit the growth of these tumor cells. 8-chloroadenosine (8-Cl-Ado) is a compound which depletes cellular ATP. In this study, we have identified that 8-Cl-Ado is a potential therapeutic agent for targeting tumors with LKB1 deficiency. To determine the role of LKB1 and 8-Cl-Ado in cellular metabolism, we generated isogenic cell lines with either LKB1 stable re-constitution or knockdown. Cells with LKB1 re-constitution showed decreased sensitivity to 8-Cl-Ado. Similarly, cells with LKB1 stable knockdown displayed increased sensitivity to 8-Cl-Ado. Additionally, analysis on cellular ATP and reactive oxygen species (ROS) levels showed that 8-Cl-Ado caused a greater reduction in ATP and increase in ROS in LKB1 deficient cells compared to cells with wild-type LKB1. Furthermore, a metabolic study demonstrated that LKB1 deficiency is associated with reduction in mitochondrial membrane potential. It also results in a phenotype with increased anaerobic respiration but decreased oxidative phosphorylation. These findings indicate that LKB1 can regulate the balance between anaerobic and aerobic respiration. This shifts cells toward a less efficient energy production mechanism, rendering a potential vulnerability of LKB1 deficient NSCLC to metabolic disruption.
Keywords
LKB1, AMPK, ATP, ROS, Energy stress, NSCLC